File Release Notes and Changelog
Release Name: 0.97
Notes:
----------------------------------------------------------------------
DIET Agents Platform, Version 0.97
----------------------------------------------------------------------
* INTRODUCTION
DIET Agents is a multi-agent platform in Java. A bottom-up design is
used to ensure that the platform is lightweight, scalable, robust,
adaptive and extensible. It is especially suitable for rapidly
developing peer-to-peer prototype applications and/or adaptive,
distributed applications that use bottom-up, nature-inspired
techniques.
* SYSTEM REQUIREMENTS
- A Java Runtime Environment, Java 1.4 or higher.
Note: The dependency on features introduced after Java 1.2 is quite
minimal. Therefore, without too much effort it is possible to modify
the source code so that it is compatible with Java 1.2, should this
be necessary.
- Any Operating System supporting the above Java runtime environment.
* CONTENTS
The complete DIET Agents software distribution is contained in two zip
files:
* diet-agents-0_97.zip
This is the main release file. It contains the DIET Agents
source code, as well as the binary Java archive file.
* diet-agents-api-0_97.zip
This is an auxiliary file. It contains the DIET Agents API
documentation. The documentation is not included in the main
release file as it is relatively large and can be automatically
generated from the source code using the "javadoc" tool. For
your convenience, however, it is available for download as well.
Together, they contain the following files:
README.txt This file.
COPYING.txt Contains the licensing terms.
CHANGES.txt Contains a history of changes.
diet-agents-0_97.jar
Contains the compiled Java files.
src/ Contains the Java source files.
doc/ Contains the API documentation.
* LICENSE
The DIET Agents software has been released as Open Source under the
GNU General Public License. See COPYING.txt for details.
* RUNNING THE SAMPLE APPLICATIONS
You can start by running the sample applications. Make sure that the
classpath includes the "jar" file. Here is an example command line:
java -classpath diet-agents-0_97.jar com.btexact.diet.app.sorting.SortingApp
This works if you have a Java Runtime Environment installed, the Java
interpreter is accessible as "java", it supports the "-classpath"
argument for setting the classpath, and you are in the directory that
contains the DIET Agents "jar" file. If you experience any problems,
try asking your local Java guru for help.
* THE WEB SITE
For more help about using the DIET Agents platform, please visit the
DIET Agents website at http://diet-agents.sourceforge.net. The website
includes additional resources, such as tutorials, FAQs and mailing
lists.
* CONTACT DETAILS
The DIET Agents platform has been developed within the Intelligent
Systems Lab and the Pervasive ICT Research Centre at BT. Please visit
the DIET Agents website at http://diet-agents.sourceforge.net for
details on how to contact us. If all else fails, try contacting the
members of the DIET Agents team at the following postal address:
Pervasive ICT Research Centre, BT, Adastral Park, Martlesham Heath,
Ipswich, IP5 3RE, England.
Changes:
======================================================================
DIET Agents Platform
======================================================================
----------------------------------------------------------------------
Version 0.97, 14 Mar 2005
----------------------------------------------------------------------
- core: Added AddressParser interface.
- core.imp: BasicWorld provides #getAddressParser method to support
parsing of addresses. The parsing methods that used to be in
BasicWorldAddress have been removed.
Compatibility alert: If you used the parsing methods in
BasicWorldAddress, you should now use the parser provided by the
BasicWorld class. E.g.:
BasicWorldAddress.getEnvironmentAddress("04a4a-0bdbd@:4000/env1") ->
BasicWorld.getParser().parseEnvironmentAddress("04a4a-0bdbd@:4000/env1")
- core: Added AgentCreator interface. It is implemented by both Environment
and EnvironmentImp.
- app.shared: Added #createAgentCreatorWithRetry method to BasicApp.
- arc.remote: Added ClientListener support to MasterMirrorJob. This can
be used to track changes to its clients, so that for instance the
mirror can terminate after it has served its purpose.
- arc.remote: Added MirrorFactory interface and BasicMirrorFactory
implementation. These can be used to let agents easily create Mirror
agents when they require remote communication.
- app.running: Updated to use mirror factories.
- app.mirrorchat: Updated to use mirror factories.
----------------------------------------------------------------------
Version 0.96, 23 Dec 2004
----------------------------------------------------------------------
Changes with respect to Version 0.95:
- arc.jobs: Fixed bug in DatagramTransceiverJob. It incorrectly
decoded some client IDs in UDP packets.
- core.imp: Changed ThreadPool so that each executor has a unique name
(useful for debugging).
- core.imp.event: Added RunAdapter.
- core.imp: Renamed WorldAddressImp to BasicWorldAddress.
- core: Moved WorldImp, EnvironmentImp and EnvironmentNameClashException
from core.imp package to core package.
- core.imp: Entirely separated world, environment, agent and
connection-end models from their implementations. As a result,
listeners do not need a "cookie" at all anymore (which used to be
necessary for access protection).
Compatibility alert: Listeners now need to be added to the models
directly, instead of to their core implementations. So instead
using "world.addWorldListener(l)" to add listeners, you should now
use "world.getModel().addWorldListener(l)".
- core.model: New package for world, environment, agent and connection-
end models. There is now also an abstract class for each of the
models, which provides the event listening infrastructure (this can
be useful for more advanced visualisation tools)
Compatibility alert: If you are referring to these models in your
code, you need to change the import statements accordingly.
- core.model.event: New package for events generated by models. All
the listener and event classes used to be in the core.imp.event
package.
Compatibility alert: If you have written your own listeners that
observe core events, you need to change the import statements to
importing the listener interfaces and events from this new package.
- util: Added ToStringFormatter and BasicToStringFormatter helper
classes, which are helpful for generating developer-friendly
#toString output.
- core.imp: BasicAgent now has a #toString that generates detailed
output of the agent's state.
Compatibility alert: If you have created your own agent classes, it
is recommended that you override the #variablesToString method
accordingly.
- arc: Many classes including jobs, event managers and schedulers now
implement a #toString method that generates detailed output.
Compatibility alert: If you have created your own jobs or event
managers, it is recommended that you override the #variablesToString
method accordingly.
- app.lookup: This application used to be app.job, but renamed it to
LookupApp as this better reflects what it does (and it makes place
for the new JobApp). Also improved functionality. Added different
ways of generating requests (by default, all data items are now
found more quickly). Added listener for dumping full agent #toString
output once for each agent type. Extended the API documentation.
Made various improvements to the jobs that are used.
- arc.visit: Fixed silly bug in AbstractAgentVisitorGuide. It would
throw a NullPointerException when there were no listeners.
- diet.util: Moved the BufferWithRejection interface and classes that
implement it from the diet.core.imp package to the general utilities
packages. Also renamed the classes while doing so:
BufferWithRejection -> Buffer
ArrayBufferWithRejection -> ArrayBuffer
LinkedBufferWithRejection -> LinkedBuffer
Finally, renamed some of the methods to be similar to that of
the java.util.Queue interface (for clarity).
Compatibility alert: Most agents and jobs never directly accessed
these buffers, but if they do, they should be updated accordingly.
- diet.util: Added #canRejectElements method to Buffer. This is
particularly useful for jobs that want to enforce that the agent
should not reject any disconnection events.
- diet.arc.remote: Changed MessageChannelProviderJob and
MasterMirrorJob so that they require a disconnection buffer with
infinite capacity. This makes the jobs simpler and more efficient.
Removed the #missedDisconnections methods accordingly.
- diet.core.imp: To reflect the changes to the buffers, the parameters
that configure the buffer capacities in BasicAgent.Params have been
renamed accordingly (to avoid confusion between #size and
#getCapacity).
Compatibility alert: If you changed these parameters from their
default values, you have to update your code to reflect the new
parameter names.
- diet.arc.remote: Improved implementation of
MessageChannelProviderJob and MessageChannelEventManager. This fixes
a few minor bugs, which could occur under high load (when events
could be rejected).
- diet.arc.remote: Added the ability to limit the number of listening
and active channels to MessageChannelProviderJob. See the
#setMaxListeningChannels and #setMaxActiveChannels methods.
- diet.arc: Added EventManagerContainer. This can be used to wrap
multiple event managers as if they are one. It is useful for
atomically adding and removing a group of event managers.
- diet.arc: Added a #removeEventManager method to EventManagingAgent,
Also changed implementation of #addEventManager so that adding and
removing are symmetrical. Updated AgentGuts accordingly.
Compatibility alert: If you previously added a chain of event
managers with one call to #addEventManager, you should now wrap
them in an EventManagerContainer first.
- diet.arc.jobs: Added #start and #terminate to DatagramEventManager
to enable graceful shutdown. Implemented #startUp and #closeDown
DatagramTransceiverJob accordingly.
- diet.util: Added IntegerGenerator interface, together with two
implementations (ConstantIntegerGenerator and
UniformRandomIntegerGenerator). For an example use, this
diet.arc.jobs.AbstractDelayJob (and subclasses).
- diet.arc.jobs: Added AbstractDelayJob, DelegatingDelayJob and
TerminatingDelayJob.
- diet.arc.jobs: Removed ScheduledRandomWalkJob, as it is not necessary
anymore.
Compatibility alert: If you used this, you should now use a
normal RandomWalkJob wrapped inside a DelegatingDelayJob.
- diet.arc: Added #isJobActive method to JobMonitor. All job managers
in the ARC layer have been updated accordingly. Added #isActive
method to job that uses this new functionality.
Compatibility alert: If your classes implement this interface, you
should now implement this method as well (see API for details).
- diet.arc: ScheduleEvent now implements Comparable.
- diet.arc.jobs: Improved implementation of jobs to properly obey
startup/shutdown contract. I.e. on closedown each job now makes sure
that any event managers it added are removed again, and also that
all schedule events it scheduled are disabled. In particular, the
following jobs have been updated: AlarmClockJob, ExternalControlJob,
MessageOrderingJob and SchedulerJob.
- diet.arc.jobs: Added RepeatJob and RepeatLimiterJob.
- diet.app.job: New application to demonstrate basic jobs in the
ARC layer. (The application that used to be JobApp has been
renamed to LookupApp).
- diet.core.imp: BasicWorld#getEnvironments now returns the
environments in the order in which they were added (it used to be an
arbitrary order).
- diet.arc: Added different modes of execution to SerialJobManager:
reset on start-up, loop on completion and single job execution. The
new capabilities are demonstrated in the new JobApp.
- core.imp.event: Changed SocketManagerListener. The "socketOpenFailed
event has been split into two, to more clearly indicated why the
socket could not be opened. The new "socketOpenRejected" event means
that the world did not attempt to open the socket because it has
reached its local socket limit. The "socketOpenFailed" event now
means that it attempted to open the socket, but that this somehow
failed.
Compatibility alert: If you implement the SocketManagerListener
interface, you need to update your code accordingly.
- arc.listeners: Added SocketRejectionDumper.
- arc.jobs.ResourceConstrainJob: Changed implementation so that it
does not anymore switch in the charging environment itself. Instead
it fires a property event with the account.
- arc.util.resource: Added ResourceAccountCapture utility class, for
grabbing the accounts of agents.
- app.resource: Added EnvironmentSwitcher listener which switches in
a charging environment for all agents that support an account.
----------------------------------------------------------------------
Version 0.95, 1 Nov 2004
----------------------------------------------------------------------
Changes with respect to Version 0.94:
- core.imp.net: Now using socket factories (which enables use of SSL
sockets).
- util.net: Added ConfigurableServerSocketFactory generic helper
class.
- app.shared: Added support for SSL sockets, using "--use-ssl-socket"
commandline argument. See the online FAQ for some help about using
SSL.
- app.shared: Can now control for each monitor/listener if it outputs to
stderr or to stdout, using new "--toggle-stdout" and "--toggle-stderr"
options.
- app.shared: Removed support for lock monitors (only useful for kernel
developers, and even then rarely used).
- app.shared: Added support for creation of UDP transceiver agents (under
commandline control).
- app.shared: Made it more suitable for subclassing. E.g. #createWorld now
throws an exception, instead of calling System.exit on failure. Also
split createAgents into several helper methods.
Compatibility alert: #createWorld now throws an IOException, which must
be declared or caught if you call this method directly.
- arc: Fixed silly bug in ConnectionSharingConnectionManager (disconnection
events were forwarded to handleConnection).
- arc.jobs: DatagramEventManager now maintains the maximum size of packet
it has sent as a property. This is useful to emperically establish what
the maximum packet size should be in certain applications.
- arc: ExternalControl#invokeLater now returns a boolean to indicate if
agents has (obtained) a thread for handling the action.
- core: Added ability to lock an agent. This makes it possible to
stop a dormant agent from being awoken. See #lock, #unlock and #isLocked
in AgentImp and BasicAgent.
- core.imp: Changed serialisation of state in BasicAgent so that an agent
can be serialised while it is still hosted.
- core.imp: Made ConnectionEnd serialisable. However, after
deserialisation the connection is always disabled so it is only
useful for maintaining the address and the context associated with
the connection.
- core.imp: Added ability to queue tasks to ThreadPool. This way, if
there are temporarily no threads are available, tasks can be
executed as soon as threads become available.
- core.imp: Changed BasicAgent so that it can now accept events even
if it cannot be directly given a thread (as long as it will
eventually get one).
- app.shared: Added "max-queue-for-threads" commandline option to
configure whether or not agents can be queued for threads.
- arc.visit: Added new package providing support for "visiting" a
collection of agents. This can be used to apply an action
(e.g. backing up state) to a group of agents in a thread-safe
manner. It supports various ways of visiting agents. Most
importantly, agents can be visited synchronously or asynchronously.
The accompagnying arc.visit.event package provides an event listener
infrastructure.
- util: Added ReadWriteAccess interface that can be used to manage
concurrent reading/writing of data. Also provided LazyCopyOnWrite
class as one specific implementation.
- arc: Added ExternalControlCapture helper class.
- app.persistentsorting: Added new application to demonstrate (one
way) of using agent persistence. It extends the sorting application
so that linker agents can be stored to file, either synchronously or
asynchronously.
- app.sorting: Improved Linker and Crawler behaviour to make it more
robust.
- core: Using customised serialisation (to make it slightly more
lightweight) for the following classes: Tag, AgentIdentity,
AgentAddress, EnvironmentAddress, WorldAddressImp.
- core.imp: Bug fix. Changed serialisation of BasicAgent so that on
deserialisation the event count of the external event portal is
always zero. This prevents a simple DOS attack, but also avoids
inconsistent state when new events arrive while the agent is being
serialised.
[compatibility alert]: It is now the responsibility of event
handlers that use the external event portal to re-signal any events
they have when they are deserialised. Event handlers should also
never serialise a reference to the external event portal, as it is
replaced on deserialisation. To uncover bugs, the
ExternalEventPortal has therefore been changed so that it is not
Serializable anymore.
- arc: Updated BasicExternalControl so it resignal events when it is
being deserialised (as is now required). Prevented serialisation of
DatagramEventManager and MessageChannelEventManager as it is not
clear if serialisation makes sense here and/or how it should be
done.
- arc.remote: Fixed bug in MasterMirrorJob. Before this, it could
throw a ConcurrentModificationException in its #handleMessage.
- arc.remote: Fixed bug in MasterMirrorJob. It now properly handles a
disconnection initiated by the message channel provider (which is
unlikely, but can happen when there are too many incoming packets).
- arc.remote: Fixed bug in MessageChannelProviderJob that could
lead to a ClassCastException in #disconnect.
- core.imp.net: Fixed bug in SocketManager that could prevent sockets
from being closed after they had been idle for too long.
----------------------------------------------------------------------
Version 0.94, 29 Jun 2004
----------------------------------------------------------------------
Changes with respect to Version 0.93:
- core.imp.net.SocketManager: Fixed a socket connection bug, so that
an attempt to connect to an unreachable world times out after a
specified period. Furthermore, sockets to other worlds can now be
set-up while an attempt is in progess to set-up a socket to a world.
- core.imp.net: Generalised SocketManager (and related classes) so
that it is not specifically for agent migration between worlds
anymore:
- WorldAccessSocket has been removed, and its functionality has been
taken over by the SocketManager.
- Added DataPacket, DataPacketHandler and
DataPacketHandlerException.
- core.imp.WorldAddressImp: Changed to use InetSocketAddress (instead
of internal "int" representation).
- Changed output of socket related errors so that it is optional
instead of always going to System.err:
- core.imp.event: Added SocketErrorListener and corresponding
Event.
- core.imp.net: Updated SocketHandler and SocketManager to fire
"error" events.
- arc.listeners: Added SocketErrorEventDumper and Tracker.
- app.shared: Updated TestApp to support dumping of socket-error
events, and also dumping of all socket events.
- arc.remote: Added messages channels as a method of remote
communication. See MessageChannelProviderJob for details.
- arc.remote: Created "Mirrors" as a method of remote communication.
See MasterMirrorJob for details.
- app.chat, app.channelchat, app.mirrorchat: Created chat demo
applications. The "chat" application provides the basic chat
functionality, but only allows local chatting. The other two
applications extend the basic application to enable remote chatting
(i.e. between users on different computers). One uses "Message
Channels" for remote communication, the other uses "Mirror" agents.
- arc.shared: Added support for creation of agents on startup, with a
default number of creation attempt per agent, and a specified delay
to wait on failure.
- app.running: Created "running" sample application. It demonstrates
the convenience of using Mirrors for remote communication, and allows
experimenting with the automatic mirror connection liveness tests.
- core.imp.BasicAgent: Added "set" convenience methods to Params
member class. This for instance allows the following syntax:
env.createAgent(MyAgent.PROTOTYPE,
new MyAgent.Params().setFriendlyName("Harry"));
Also added ability to reject incoming messages and/or connections on
agent creation.
- arc.jobs: Added new MigrateJob, providing agents with the ability to
migrate (once) on start-up.
- core.WorldAddress: Removed dumpWrite method from interface. It is not
really useful in an interface, as the complimentary dumpRead cannot be
provided.
- core: Removed #dumpWrite and #dumpRead methods from AgentIdentity,
AgentAddress, EnvironmentAddress and WorldAddress. These methods are
now only in the Tag class, as it would be less efficient to achieve
the same elsewhere. The reason that the methods have been removed
from the other classes is that it unnecessarily contaminated the
API, and that it never worked properly anyway, as many classes could
not offer a #dumpRead method (as it depends on the particular
WorldAddress that is used).
[compatiblity alert]: If you were using these methods, you should
now instead do the writing to and reading from streams directly,
potentially by way of helper dumper objects.
- arc: Added DaemonJobManager.
- app.shared.BasicApp: Made initialisation methods more consistent.
Renamed #addListeners() to #createMonitors(), and removed
#addListeners(BasicAppArgumentParser). Renamed #setupWorld to
#createWorld. Renamed #fillWorld to #createAgents, and changed
method argument from BasicEnvironment[] to EnvironmentImp[].
[compatibility alert]: You will need to update your applications
accordingly (simply rename the methods). The compiler will issue an
error if you are still overriding or calling the old methods.
- arc.shared: Added support for various event counters. Using the
command line arguments, you can now count environment, agent and
connection events.
- core.imp: Fixed minor bug in BasicEnvironment to do with event
generation. It could happen that an agent creation/arrived event
was generated after an agent had already received a connection.
- app.job: Improved implementation, in particular that of
HandleDataNotificationJob and HandleDataRequestJob. These now better
cope with disconnections, so that connections are always destroyed,
even in the face of missed messages and/or disconnection events.
connections.
- core.imp: Made BufferWithRejection an interface. BasicAgent now uses
LinkedBufferWithRejection, allowing buffers of "infinite" capacity.
Note: It is strongly discouraged to use an unlimited capacity for
the message and connection event buffers, except for debugging. Only
for the disconnection event buffer does it for certain types of
agent make sense to have an unlimited capacity.
- arc: Fixed minor bug in SerialJobManager (so that it terminates when
it should).
- app.shared: Added ability to explicitly specify the internet address
for the world (using the "--host" argument). This is useful on machines
where the automatic detection of the host address fails (e.g. when it
resolves to the loopback address).
----------------------------------------------------------------------
Version 0.93, 7 Jan 2004
----------------------------------------------------------------------
Changes with respect to Version 0.92:
- arc.jobs: Fixed bug in DatagramTransceiverJob, and added short-cut
for sending "local" messages.
- arc: Fixed silly bug ConnectionSharingJobManager.
- Update package API comments (in package.html files) by replacing
infohabitant by agent everywhere (to reflect changes introduced in
Version 0.91).
- core.imp: Minor change to reporting of "run crashed" events in
BasicAgent so that it better copes with listeners that throw runtime
exceptions.
- core.imp: Added #isOwner method to ConnectionEnd.
- core.imp: Changed WorldFactory and World so that all worlds
generated by the factory use the same cookie (this can be useful
for visualising two "remote" worlds in a single VM).
- arc.listeners: Made output stream for event dumpers configurable (it
used to always go to System.err which is still the default).
- core.imp: Added new WorldModel, WorldImp, EnvironmentModel,
EnvironmentImp, AgentModel, ConnectionEndModel interfaces. These are
strictly for use by visualisation/debugging classes. These new interfaces
make it, amongst others, easier to filter and to replay of events.
- core.imp: Made AgentGuardian and ConnectionEnd package protected.
This is possible now that the model interfaces are used.
[compatiblity alert]: Any class that refers to AgentGuardian should
now probably refer to it as "AgentModel" but occassionally as
"Environment". Any class that refers to ConnectionEnd should now
probably refer to it as "ConnectionEndModel" but occassionally as
"Connection".
- core.imp: Renamed World to BasicWorld as this is more consistent given
the new model interfaces.
[compatiblity alert]: Where you create a "World" directly you should
now construct a "BasicWorld" instead. On the other hand, you are
refering to an existing world, you can problably change the type of
the reference to "WorldModel" or "WorldImp".
- core.imp.event: Updated the event classes to refer to the new model
interfaces.
- core.imp.event: Cleaned up "AgentEvent" class. Some superfluous
member variables have been removed (as they could be determined in
other ways).
[compatiblity alert]:
Instead of getNearConnectionEnd() use getConnectionEnd(). Instead of
getFarConnectionEnd() use getConnectionEnd().getOtherConnectionEnd(c).
Instead of getInitiatingAgent() and getPassiveAgent() use
didNearAgentInitiate() instead together with either
getConnectionEnd().getAgent(c) or
getConnectionEnd().getOtherConnectionEnd(c).getAgent(c).
- core.imp.event: Cleaned up "ConnectionEndEvent" class. Some
superfluous member variables have been removed (as they could be
determined in other ways).
[compatiblity alert]:
Instead of getSender() and getReceiver() use the context in which
the event was fired to get the sender/receiver. For "messageSent",
"messageAccepted" and "messageRejected" events, the sender is
getConnectionEnd().getAgent(c). For "messageReceived" events the
sender is getConnectionEnd().getOtherConnectionEnd(c).getAgent(c).
- core.imp.event: Removed toString support from events. This has now been
moved to the event dumpers in arc.listeners.
- core.imp: Added limit on number of agents to BasicEnvironment, and
added corresponding AgentLimitReachedException.
- app.shared: Added "--max-agents-per-env" argument to BasicApp to
configure maximum number of agents per environment.
- core: Made AgentIdentity "Comparable".
- arc: Fixed bug in AbstractMultiJobManager and ParallelJobManager to
prevent IndexOutOfBoundsException when last job removes itself.
- arc: Added "InterdependentJobManager".
- arc: Renamed JobManager to JobMonitor.
- app.sorting: Fixed bug in Linker, which was introduced in Version 0.92.
----------------------------------------------------------------------
Version 0.92, 25 Sep 2003
----------------------------------------------------------------------
Changes with respect to Version 0.91:
- core.imp: Created WorldFactory (and corresponding event listeners).
This can be used to attach visualisers and simular tools to the
platform. There was no good way of doing this after World had been
changed so that it was not a Singleton anymore.
- app.sorting: Fixed bug in Linker, which could leave connections
open when messages are rejected (due to system overload).
- arc.services: Fixed Mirror implementation to reflect change in
AgentIdentity. Since Version 0.91 the name tag and family tag
must always be non-null. Whereas the old implementation of the
Mirror sometimes used a null name tag.
----------------------------------------------------------------------
Version 0.91, 12 Sep 2003
----------------------------------------------------------------------
Changes with respect to Version 0.90:
- core.imp: Changed the order in which BasicInfohabitant handles
external events in its #handleExternalEvent method. The order is now
connection events first, then messages, and finally disconnection
events.
- arc: Changes to jobs and job managers so that a job's guts are unset
when a job is removed.
- arc: Added #getJobManager method to Job.
- arc: Added ConnectionSharingJobManager, an advanced job that lets
multiple jobs handle the same connection(s).
- core.imp: Made TerminateRunException a Singleton (for efficiency).
- core: Moved ConnectionDisabledException,
InfohabitantIdentityClashException and InfohabitantNotFoundException
from core package to core.imp package.
[compatibility alert]: If you catch these exceptions (probably not,
as typically you catch a more general base exception), you may need
to update the import statements.
- core.imp: ConnectionEnd#send now explicitely declares the specific
exceptions it throws (instead of general ConnectionException).
- arc.jobs: Added ScheduledRandomWalkJob.
- Cleaned up code by removing all unused variables and import statements.
- Changed all identifiers based on the term of "Infohabitant" to use
"Agent" instead.
Renamed classes:
BasicInfohabitant -> BasicAgent
EventManagingInfohabitant -> EventManagingAgent
IndexedInfohabitantGuardian -> IndexedAgentGuardian
InfohabitantAddress -> AgentAddress
Infohabitant -> Connection
InfohabitantCreationException -> AgentCreationException
InfohabitantEvent -> AgentEvent
InfohabitantEventCounter -> AgentEventCounter
InfohabitantEventDumper -> AgentEventDumper
InfohabitantEventTracker -> AgentEventTracker
InfohabitantGuardian -> AgentGuardian
InfohabitantGuts -> AgentGuts
InfohabitantIdentity -> AgentIdentity
InfohabitantIdentityClashException -> AgentIdentityClashException
InfohabitantImp -> AgentImp
InfohabitantInitialisationException -> AgentInitialisationException
InfohabitantListener -> AgentListener
InfohabitantLockMonitor -> AgentLockMonitor
InfohabitantNotFoundException -> AgentNotFoundException
InfohabitantRejectedDumper -> AgentRejectedDumper
JobInfohabitant -> JobAgent
Note: "Infohabitant" has been renamed to "Connection" instead of
"Agent" or something similar, as "Connection" best describes what
the class represents.
Renamed methods:
addInfohabitant -> addAgent
addInfohabitantListener -> addAgentListener
fireInfohabitantArrivalFailed -> fireAgentArrivalFailed
fireInfohabitantArrived -> fireAgentArrived
fireInfohabitantCreated -> fireAgentCreated
fireInfohabitantCreationFailed -> fireAgentCreationFailed
fireInfohabitantDeparted -> fireAgentDeparted
fireInfohabitantDepartureFailed -> fireAgentDepartureFailed
fireInfohabitantDestroyed -> fireAgentDestroyed
getInfohabitantAddress -> getAgentAddress
getInfohabitant -> getAgent
getInfohabitantGuardian -> getAgentGuardian
getInfohabitantIdentity -> getAgentIdentity
getInfohabitantImp -> getAgentImp
getInitiatingInfohabitant -> getInitiatingAgent
getNumInfohabitantArrivalFailed -> getNumAgentArrivalFailed
getNumInfohabitantArrived -> getNumAgentArrived
getNumInfohabitantCreated -> getNumAgentCreated
getNumInfohabitantCreationFailed -> getNumAgentCreationFailed
getNumInfohabitantDeparted -> getNumAgentDeparted
getNumInfohabitantDepartureFailed -> getNumAgentDepartureFailed
getNumInfohabitantDestroyed -> getNumAgentDestroyed
getPassiveInfohabitant -> getPassiveAgent
infohabitantArrivalFailed -> agentArrivalFailed
infohabitantArrived -> agentArrived
infohabitantCreated -> agentCreated
infohabitantCreationFailed -> agentCreationFailed
infohabitantDeparted -> agentDeparted
infohabitantDepartureFailed -> agentDepartureFailed
infohabitantDestroyed -> agentDestroyed
infohabitantIn -> agentIn
infohabitantOut -> agentOut
removeInfohabitantListener -> removeAgentListener
removeInfohabitant -> removeAgent
setInfohabitantGuardian -> setAgentGuardian
setInfohabitantGuts -> setAgentGuts
Renamed variables:
All relevant member variables as well local variables have been
renamed. E.g. "ihab" has been changed to "agent", "infohabitant"
to "agent" as well, etc.
Affected API and text:
The API, text that is outputted, and commandline arguments have
been updated as well.
[compatibility alert]: Nearly all software built on top of the
platform will be affected by these changes. However, there is a
conversion script available to automatically upgrade code that
uses Version 0.90 to use Version 0.91.
----------------------------------------------------------------------
Version 0.90, 5 Aug 2003
----------------------------------------------------------------------
Changes with respect to Version 0.52:
- Changed package root from "org.ist_uie.diet" to "com.btexact.diet"
[compabitility alert]: Conversion script can be used to update old code.
- Updated all file headers. They are now combined with class header, and
not separate anymore.
- core: Renamed CommunicationPacket to Message, and renamed its #getMessage
method to #getText. Also, in core.imp, renamed Message to MessageEvent.
[compabitility alert]: Conversion script can be used to update old code.
- core: Renamed methods in Environment interface: #connectMeAsPeer changed
to #connectMe, #migrateMeTo changed to #migrateMe.
[compabitility alert]: Conversion script can be used to update old code.
- core.imp: Changed World so that it is not a singleton anymore, but
just a normal class. This allows multiple worlds per JVM. This is in
particular useful when running multiple applets in a browser.
- core: Removed the Context interface. Infohabitant#setContext now takes
any Object.
[compabitility alert]: Need to update old code accordingly, which
mostly involved removing "implements Context" in class declaration.
- core: Changed the #disconnect method in Infohabitant so that it does
not throw an exception anymore, but returns a boolean flag instead.
This avoids the need for double nest try statements.
[compabitility alert]: Need to update old code yourself, but changes
are straightforward.
- arc: Renamed JobIhab to JobInfohabitant.
[compabitility alert]: Conversion script can be used to update old code.
- app.sorting: Removed use of SortingInfohab baseclass.
- app.shared: Renamed DemoApp to BasicApp.
[compabitility alert]: Conversion script can be used to update old code.
- arc.util.directory: Removed this package. It was there to illustrate
an idea (that you can use a Yellow pages approach in DIET), but not
actually used in practise.
- arc.util.bundle: Removed this package. It is still too much "work in
progress" to be included in public release.
- arc.services: Removed Handle. This method of remote communication
has not been sufficiently used and tested. If we want to support it,
it would need to be rewritten.
- arc.services.middleman: Removed this package. Functionality to
specialised to be in platform.
- app: Removed the following outdated sample applications:
"directory", "handle" and "multicast".
----------------------------------------------------------------------
Version 0.52, 3 Jul 2003
----------------------------------------------------------------------
Changes with respect to Version 0.51:
- Changed DatagramTransceiverJob so that local client ID is always in
[1...65536] range.
- util: Added Operator interface.
- arc: Split MultiJobManager into interface (with the same name) and
abstract implementation (AbstractMultiJobManager).
- arc: Improved iteration in ParallelJobManager. It now iterates in
ascending order, and implements strict checks to prevent concurrent
modification. The implementation is fast and memory efficient, but
therefore not as concise and easily re-usable.
- arc: Updated ExternalControlJob so that it directly returns an
external control (which, however, still cannot be fully used until
the infohabitant has started up). Also changed BasicExternalControl
and ExternalControlEventManager to enable this.
----------------------------------------------------------------------
Version 0.51, 26 March 2003
----------------------------------------------------------------------
Changes with respect to Version 0.50-ext1:
- core.imp: Added #fireAllProperties method to InfohabitantGuardian
that takes a specific property listener as an argument.
[compatibility alert]: It is recommended that property listeners
always use this new method, instead of #fireAllProperties provided
by BasicInfohabitant.
- core.imp: Updated API to support concept of "persistent" and
"volatile" properties.
- arc: Fixed bug in BasicExternalControl. It prevented migrated
infohabitants in zombies app from giving up their thread.
- app.primes: Disabled output from infohabitants. Output can now be
generated by way of a dedicated listener, the PrimeMasterDumper.
- arc.jobs: Added DatagramEventManager, which can be used by
infohabitants to manage their own datagram socket. Updated
DatagramTranceiverJob to use this new event manager.
- core.imp: Fixed loophole in InfohabitantGuardian which (in theory)
could allow an infohabitant to own more that its allowed number of
connections (by accessing it from multiple threads).
- core.imp: Fixed security loophole in BasicInfohabitant (by using
separate "guardian" member variable and new "ALIVE" state bit).
This prevents the infohabitant from inserting its own proxy object.
Doing so would allow thread-hijacking because the guardian's method
are called from the "kernel" parts of the infohabitant.
- core.imp: Removed EnvironmentImp interface. It is not needed anymore
now BasicInfohabitant directly references its infohabitant guardian.
- core: Removed #isHostingMe method from Environment, which had been
deprecated for a while already.
- core(.imp): Replaced Debug.assertTrue statements with more specific
exceptions. Proper assertions now throw a RuntimeException. For some
checks IllegalStateException and IllegalArgumentException are thrown
instead.
- core.imp: Removed empty "freeze" and "defrost" placeholder methods
from BasicEnvironment.
- core.imp: Updated NameClashException to include the name of the
other environment that caused the name clash (as it is not
necessarily the same as the name of the environment that was being
added).
- core(.imp): Renamed various exceptions to have more consistent
names. In particular, IdentityClashException became
InfohabitantIdentityClashException. TargetNotFoundException became
InfohabitantNotFoundException. NameClashException became
EnvironmentNameClashException. Also changed public exception member
variables of to protected (and added accessor methods instead).
[compatibility alert]: If you caught these specific exceptions, you
need to update your code accordingly.
- arc.jobs: Renamed DatagramTranceiverJob to DatagramTransceiverJob.
[compatibility alert]: If you used this job, you need to update your
code accordingly.
- arc.services: Added DatagramTransceiver infohabitant (which simply
uses DatagramTransceiverJob).
- util.listeners: Moved entire package to "arc.listeners", because this
is where they belong. The classes in "util" are stand-alone utilities
not specific to DIET, whereas these listeners are really DIET ARC
components.
[compatibility alert]: If you are using these generic listeners, you
need to change your import statements accordingly.
- core.imp.net: Made version of serialisation protocol that is used
configurable (to enable optional compatibility with Java 1.1).
Updated DemoApp as well to support this.
- core.imp.net: Added #signalAboutToSend method to SocketHandler to
prevent socket from terminating just before an infohabitant is going
to be sent across it. Also improved synchronisation of SocketHandler
in general.
----------------------------------------------------------------------
Version 0.50-ext1, 28 January 2003
----------------------------------------------------------------------
Changes with respect to Version 0.50:
- core.imp: Added public #getThreadPool(Object cookie) to BasicEnvironment.
(Not sure if we should keep this method, it may be gone again in a future
release).
- core.imp: Added #waitForExecutor to ThreadPool.
- arc.util: Added ExecutorThread.
- arc.jobs: Fixed DatagramTranceiverJob. Although it compiled, the
first implementation did not actually run properly.
- core: Fixed minor bugs in Tag (only occur when there are "unused
bits").
- app.shared: Added output-level commandline argument.
- app.sorting: Disabled output from infohabitants. It is now generated
by dedicated listeners which can be disabled using the new
output-level commandline argument.
- core.imp.event: Added PropertyAdapter.
- core: Added #awake method to InfohabitantImp interface.
- arc: Added ExternalControl interface, and BasicExternalControl
implementation. Updated ExternalControlEventManager to use the
latter.
- arc.jobs: Added ExternalControlJob, which enables external control
over an infohabitant.
- app.zombie: New sample application that demonstrates how
infohabitants can be controlled externally (e.g. by way of a GUI).
----------------------------------------------------------------------
Version 0.50, 23 September 2002
----------------------------------------------------------------------
Changes with respect to Version 0.41-ext1:
- core: Changed the various dumpRead and dumpWrite methods to use
DataInput and DataOutput instead of DataInputStream and
DataOutputStream.
- core.imp: Created EventPortal interface. As a result, the old
EventPortal class has been renamed to ExternalEventPortal.
- core.imp: Removed the BasicEventHandler and related event handling
interfaces from the core.
[compatibility alert]: If you used these interfaces (which you
probably didn't anyway) rewrite your code accordingly.
- core.imp: Made "external_events" in BasicInfohabitant private to
prevent potential for thread hijacking.
[compatibility alert]: Infohabitant that directly refer to this
member variable, should now use getExternalEventPortal().
- core.imp: Better handling of events portal on migration in
BasicInfohabitant. To do so, added #signalEventsDropped method to
ExternalEventPortal, and let BufferWithRejection#clear() return the
number of rejected elements.
- core.imp: Changed serialisation of BasicInfohabitant so that the
event portal is not stored, only the number of pending events.
- arc: Added new class InfohabitantGuts that provides access to the
interal parts of BasicInfohabitant (which are by default protected).
Access includes the event portal, the environment, the buffers used
for connections, messages and disconnections. Also allows provides
access to the event manager.
- arc: Updated Job to use new InfohabitantGuts. Its
#setInfohabitantImp and #getInfohabitantImp methods have been replaced
by #setInfohabitantGuts.
[compatibility alert]: If you have written your own jobs, these need
to be updated to use guts.
- arc: Added #missedConnections, #missedMessages and
#missedDisconnections methods to Job interface. Of these,
missedDisconnections is the most useful, as it can be used to discard
state associated with an infohabitant that has (maybe unexpectedly)
disconnected. Updated JobIhab, ParallelJobManager and SerialJobManager
accordingly.
- arc: Merged EventPortal and EventHandler into EventManager
interface. Event managers have been designed so that they can be
cascaded, and each event manager is responsible for dealing with
a specific type of event. Updated Guts and JobIhab accordingly.
- arc: Added EventManagingInfohabitant. An intermediate Infohabitant
between BasicInfohabitant and JobIhab.
- arc: Added AbstractEventManager and BasicEventManager. These are
both abstract classes. The first is useful for writing any event
manager. The second is more specific, and is intended to be a
base class for very simple event managers.
- arc: Added SchedulerEventManager to provide scheduling functionality
to infohabitants. This functionality used to be provided by
SchedulePortal, which has now disappeared.
[compatibility alert]: Infohabitants that used to use
SchedulePortal should now use a SchedulerEventManager as a
Scheduler. To do so, the infohabitant needs to subclass
EventManagingInfohabitant, and use addEventManager to install the
event manager (this will automatically handle the schedule events
and external events, so there is no need to do so explicitely).
- arc: Added ExternalControlEventManager, a pluggable
event manager that allows other threads to specify actions to be
executed by the infohabitant.
- arc: Moved many packages and classes to different location:
- arc.jobs: New package for reusable behaviours.
- arc.util: New package, so far only containing subpackages with
functionality for occasional use.
- arc.util.resource: Used to be arc.services.resource.
- arc.util.directory: Used to be arc.services.directory.
- arc.services.middleman: Used to be arc.services.middleware.
- arc.services.schedule: This old package has entirely disappeared.
[compatibility alert]: You may need to change import statements
accordingly.
- arc.jobs: Added DatagramTranceiverJob, which offers service provider
capabilities that can be used to send/receive UDP packets.
- arc.jobs: Added AlarmClockJob, which can "wake up" infohabitants at
a specified future time. Useful for infohabitants that want to use
scheduling, yet want to be able to give up their thread. Added
corresponding AlarmClock infohabitant in arc.services.
- arc.jobs: Added MessageOrderingJob, which allows infohabitants to
handle message according to a priority associated with each message.
An early implementation of this class used to be in app.priority
package.
- arc.util.bundle: Created utility classes that support the sharing
of data objects between infohabitants in the same environment.
Subject to change.
- arc.util.retry: Created basic utility classes for failure handling.
Basic backoff strategies are included, recommended components for
use with scheduling and job infrastructure. Expect further
RetryActions and RetryStrategies in next release. Subject to change.
- arc: Made ScheduleEvents Runnable. They are now always handled by
running them. As a result, removed the ScheduleEventHandler interface.
[compatibility alert]: Code that uses scheduling should be updated
by adding a run method to all schedule events. This should make the
code simpler, because schedule events do not need to be handled
explicitely anymore.
- arc: Improved Scheduler interface (is has now more methods for
accessing the schedule events).
- arc: Improved SchedulerJob to use AlarmClock instead of
SchedulerIhab.
- arc: Modified SchedulerEventManager to use SortedList for maintaining
events (it should be more efficient now).
- arc: Changed ParallelJobManager such that it now always copes properly
when one or more of its child jobs finish.
- arc.util.ressource: Renamed ResourceEnvironment to
ChargingEnvironment. Renamed ResourceInfohabitantRegister to
EnvironmentRentCollector.
- arc.util.resource: Entirely re-engineered ChargingEnvironment and
EnvironmentRentCollector to remove dependence on specific
conserved resources and to eliminate requirement for EnvironmentListener
approach to support resource constrained infohabitants. Resource
constraints can now be plugged into JobIhab, by giving it a
ResourceConstrainJob. Added EnvironmentPrices as a basis for pluggable
charging policies for ResourceEnvironments.
See package for current support. Subject to change.
- util: Improved SortedList interface by adding #addFromFront and
#addFromBack methods. These allow control over placement of objects
that are equal (according to their order).
- util.listeners: Added ThreadMonitor which can monitor thread use by
infohabitants.
- app.helloworldjob: Added job-based implementation of classic "hello
world" application (see app.helloworld for a lower level
implementation of the same application, which does not use jobs).
- app.shared: Added support for monitor thread to demo app. Added
support for running (periodic) actions. Added optional automatic
termination of demo app after specified time. Added optional
automatic creation of alarm clock service providers.
- app.priority: Changed from non-job based implementation to completely
use jobs.
- app.*: Changed all applications to reflect updated job
infrastructure, schedule infrastructure and other changes in the
ARC layer.
----------------------------------------------------------------------
Version 0.41-ext1, 13 August 2002
----------------------------------------------------------------------
Changes with respect to Version 0.41:
- app.schedule: Changed ScheduleExampleIhab to subclass
ConfigurableJobIhab to enable more flexible parameterisation.
Further simplified ScheduleExampleIhab. Now does not
implement Scheduler, but rather provides a getScheduler()
convenience method. Modified direct descendants to match.
- app.mirror, app.resource, app.schedule: Inserted getScheduler()
call, since Scheduler is now pluggable in ScheduleExampleIhab.
- util: Added SortedList interface and corresponding
LinkedSortedList implemention. These maintain a list of objects,
some of which can be "equal" or can have the same "order". For
instance useful for ordering prioritised messages.
- app.priority: Created sample application to demonstrate prioritised
message handling.
- arc.services.middleware: Added middleware functionality to
facilitate services among users. The services provided by the
middleware include: registering user information, searching
information resources for users and organising users into
communities of interests.
- app.communities: Created "communities" application to demonstrate the
technology of "self-organising communities" and demonstrate how DIET
can be used in a simulated distributed information system.
----------------------------------------------------------------------
Version 0.41, 22 May 2002
----------------------------------------------------------------------
Changes with respect to Version 0.40-ext1:
- core: Fixed non-fatal bug in String construction of Tag.
- core: Changed the local identifier of environment addresses from a
string to an integer value. This has the advantage that every
environment address can be represented in a fixed number of bytes.
This is, amongst others, useful when it is used as part of fixed
size UDP datagram packets.
[compatibility alert] Only applications that directly refer to the
environments local name are affected. However, most applications
should not do so anyway, and it should be straightforward to update
any affected code. Each environment still has a name associated with
it (see the new BasicEnvironment#getFriendlyName() method) that is
used to generate the integer identifier. You can still use the
friendly name to specify neighbourhood links as well.
- core: Added extra methods to facilitate navigation of the DIET
hierarchy by debugging and visualisation tools. See:
ConnectionEnd#getOtherConnectionEnd(Object),
ConnectionEnd#getInfohabitantGuardian(Object),
InfohabitantGuardian#getEnvironment(Object).
- core.imp: Changed serialisation of BasicInfohabitant so that its
buffers are not stored, only their size.
- util.listeners: Added ConnectionEndEventCounter,
InfohabitantEventCounter and EnvironmentEventCounter listeners.
Useful for basic debugging.
- core.imp.net: Removed bug in sockets that would cause distributed
applications to run out of memory eventually (amongst others).
- core.imp and core.imp.event: Added #infohabitantDepartureFailed
method to EnvironmentListener interface. Updated BasicEnvironment
to generate this event.
[compatibility alert] Any listeners that implement the
EnvironmentListener interface need to be updated.
- util.listeners: Updated all listeners that were affected by the
above change to the EnvironmentListener interface.
- core.imp.net: Removed bug in sockets that could leave sockets that
failed to be set up properly to linger.
- arc.services: Updated CarrierJob so that it can wait for a reply.
- arc: Changed Job Management infrastructure to increase flexibility.
Further developments expected.
- arc: Changed ConfigurableJobIhab to play nicer in releasing Thread.
- arc: Changed SingleJobIhab to support invokeLater(...) call,
allowing other threads to insert runnables to carry out
operations in the infohabitant's thread (e.g. initiated by
GUI control).
- arc: Added RandomFactory for convenient generation of multiple
distint random number generators.
- arc: Added RandomWalkJob.
- app: Changed System.out to System.err in multiple locations.
Where possible, these console debugging outputs will be replaced
by debugging listeners controlled by the command line in
app.shared.DemoApp.
- app: Changed demonstrators to reflect changes in Job infrastructure.
- app.selfheal: Added code for management of self-healing peer
network. This automates the management of DIET neighbourhoods
through exchange of Peer addresses between DIET environments. At
present this is a naively implemented but functional version. Future
versions which are more easily parameterised can be expected.
- app.helloworld: Created basic "hello world" application to
demonstrate simplicity of composing DIET applications and encourage
adoption of DIET as mobile process toolkit.
----------------------------------------------------------------------
Version 0.40-ext1, 15 Feb 2002
----------------------------------------------------------------------
Changes with respect to Version 0.40:
- core: Added "awake" method to BasicInfohabitant.
- core: Removed synchronization of Environment methods in
InfohabitantGuardian.
- core and core.imp: Added ability to generate address objects from
text strings. See WorldAddressImp#getEnvironmentAddress(String),
WorldAddressImp#getInfohabitantAddress(String) and
WorldAddressImp#WorldAddressImp(String).
- util: Renamed Debug#assert methods to Debug#assertTrue. This is
necessary because "assert" has become a reserved keyword in Java
1.4. To maintain compatibility with earlier Java versions, the new
Java "assert" feature is not yet used, nice though it is.
----------------------------------------------------------------------
Version 0.40, 25 Jan 2002
----------------------------------------------------------------------
Changes with respect to Version 0.30:
- core: Fixed synchronization bug in InfohabitantGuardian. When two
connected infohabitant's detach from their environments
simultaneously there was the potential to get into an invalid state,
resulting in an exception. This has been fixed.
- core: Added "infohabitantCreationFailed" and
"infohabitantArrivalFailed" methods to EnvironmentListener.
[compatibility alert] If you have implemented EnvironmentListeners
yourself, you may have to update them to incorporate the new
methods.
- core: Added "runResumeFailed" and "runCrashed" methods to
RunListener.
[compatibility alert] If you have implemented RunListeners yourself,
you may have to update them to incorporate the new methods.
- util.listeners: Added "InfohabitantRejectedDumper",
"RunFailedDumper" and "RunCrashedDumper" for logging failure
events. The first two listeners log events that are typically due to
a lack of threads. They are therefore useful to analyse the system
when it is (nearly) overloaded. The "RunCrashedDumper" dumps a
message whenever an infohabitant terminated abnormally, i.e. because
a runtime exception occured. As this is typically due to programming
errors and you want to be aware of those, this dumper is enabled by
default in DemoApp. However, when you are confident that your
application is running fine, you can disable it to reduce the extra
overload (at least a few bytes per infohabitant) it imposes on the
system.
- app.shared: Added support in DemoApp for the above additional event
dumpers.
- core: Used finer granularity of synchronisation in BasicEnvironment.
- core: Reduced memory used by BasicInfohabitant by eliminating two
member variables (threadpool and run_watcher). Also changed when
run events are fired, which is now synchronized by "state_lock"
(so that it the infohabitant's state can be checked to ensure
that infohabitants do not cheat by spuriously firing events).
- core: Fixed synchronization bug in BasicInfohabitant, which occured
after the above change had been made. The "state_lock" was
inadvertently initialised at the field declaration. Due to the
prototype mechanism for creating infohabitants, this meant that
multiple infohabitants could be using the same lock which could lead
to dead-locks.
- util.listeners: Added "InfohabitantLockMonitor" and
"EnvironmentLockMonitor" for analysing multi-threading
synchronisation.
- util: Added "LockMonitor" and "LockMonitorObserver" for analysing
multi-threading synchronisation.
- core: Removed "RunWatcher", added "Executor" and "EnvironmentImp"
interfaces.
- core: Reduced memory used by BasicInfohabitant by eliminating two
member variables (threadpool and run_watcher). Also changed when
run-events are fired (now within state_lock).
- core: Used finer granularity of synchronisation in BasicEnvironment.
- core: Added "infohabitantCreationFailed" and
"infohabitantArrivalFailed" methods to EnvironmentListener.
[compatibility alert] If you have implemented your own
EnvironmentListener, you may have to update them to incorporate the
new methods.
- core: Added "runFailed" method to RunListener.
[compatibility alert] If you have implemented RunListeners yourself,
you may have to update them to incoorporate the new method.
- core: Fixed synchronization bug in InfohabitantGuardian. When two
connected infohabitant's detach from their environments
simultaneously there was the potential to get into an invalid state,
resulting in an exception. This has been fixed.
- arc: Added 'Job' infrastructure ; a foundation for plug and play
Infohabitant behaviours. This helps to simplify the programming
of behaviour a great deal, and promotes re-use. In this way,
the implementation of common behaviours can be shared between
multiple infohabitants without being restricted to subclassing.
This is a provisional version of the Job infrastructure, and
is likely to change over time in response to user comments.
- arc: Modified Carrier to exploit Job infrastructure.
- arc: Modified SchedulerIhab with Dynamic backoff algorithm to
minimise contention when running large populations of infohabitants
with Schedules.
- arc.services.schedule : Added Scheduler interface and
ScheduleEventServer object. Now possible to achieve plug and play
scheduling either via SchedulePortal or via SchedulerJob (which
handles interactions with external scheduler). ScheduleEventServer
permits Jobs and other components to subscribe to ScheduleEvents
where needed.
- app.shared: Added support in DemoApp for lock monitors. Added
control of max owned connections.
- app.job: Added JobApp to demonstrate new Job and Scheduling
functionality.
- app.schedule: Modified ScheduleExampleIhab to demonstrate
use of SchedulerJob, and improve performance.
----------------------------------------------------------------------
Version 0.30, 26 Jun 2001
----------------------------------------------------------------------
Changes with respect to Version 0.20-ext1:
- core.imp.event.net package: The platform now supports remote
migration, i.e. infohabitants can now migrate to a different DIET
worlds. A DIET world is in a different Java VM, and potentially, a
different computer. The implementation uses sockets. See the
API documentation with this package for details.
[compatibility alert] If you have any infohabitants that migrate,
you should make sure that they can be properly serialised. I.e. all
objects that it should carry across to the destination VM should be
serialisable. All member variables that cannot/should not be taken
across should be marked "transient". Potentially extend
BasicInfohabitant#startUp/closeDown or
BasicInfohabitant#readObject/writeObject to perform additional
preparation before and recovery after migration.
- core: The address classes have changed slightly. The
EnvironmentAddress empty interface has become a concrete
class. Instead, there is now an empty WorldAddress interface. As a
result core.imp.EnvironmentAddressImp has disappeared, but there is
now a core.imp.WorldAddressImp class.
Also fixed bug in InfohabitantAddress. It now has a proper "equals"
and "hashCode" method. (sorry Harold!)
- core: All core components that can potentially be carried by a
migrating infohabitant are now Serializable. This excludes classes
that are specific to a VM, such as the ConnectionEnd and
InfohabitantGuardian proxies. As a result, infohabitants cannot take
these with them when they migrate. They can, however, take
infohabitant addresses and environments addresses with them.
In a next release we will probably provide an ARC-layer component
that makes it easier for infohabitants to maintain relevant
connection history.
- core.imp.BasicInfohabitant: Merged various boolean member variables
a into single "state" byte.
[compatibility alert] To (temporarily) reject any messages or
connections you should now use respectively the #setAcceptMessages
or #setAcceptConnections method. The "protected" boolean flags that
used to control this have now disappeared.
- core.imp.BasicInfohabitant: Removed potential deadlock (it could
occur when it simultaneously tried to migrate while its connections
where updated)
core.RunWatcher: This new interface was added to avoid the above
deadlock efficiently. The interface is not relevant to application
developers.
- core.imp.BasicInfohabitant: The #handleDisconnection,
#handleDisconnection and #handleMessage methods now return a boolean
flag to signal if the method processed the event. This makes it easier
to extend the behaviour of an existing infohabitant. Changed the
MessageHandler, ConnectionHandler and DisconnectionHandler interfaces
accordingly.
[compatibility alert] Infohabitants that override any of these
methods should be modified to reflect these changes. This is very
straightforward, see for instance the
app.primes.PrimeChecker#handleMessage implementation.
- core.imp.EventPortal: Returning from #waitForEvent without a timeout
does not automatically decrease the number of pending events. This
now needs to be done explicitely by calling #signalEventHandled when
an event is retrieved from its buffer. It was taken for granted in the
previous implementation that returning from the method would always
be associated with the handling of an external event, and hence the event
counter could be decremented. With the inclusion of internal events
(such as scheduling), and other future developments, it is best that
this counter is manipulated explicitly.
[compatibility alert] Infohabitants that extend the
#handleExternalEvent method need to be changed such that the external
events portal is signalled when an event has been retrieved from its
event buffer. See the implementation of
BasicInfohabitant#handleExternalEvent for details.
- core.imp.event.EnvironmentEvent: The event now contains the
infohabitant's parent when it is used to signal infohabitant
creation.
- core.imp.event: Added listeners and events for remote communication
events. See SocketHandlerEvent, SocketHandlerListenert,
SocketManagerEvent and SocketManagerListener for details.
- util.listeners: Added event dumpers and trackers for remote communication
events. See SocketHandlerEventDumper, SocketHandlerEventTracker,
SocketManagerEventDumper and SocketManagerEventTracker for details.
These new dumpers can be activated by the demo application command line
using "--show-events socket-handler" and "--show-events socket-manager".
- app.shared: Extended command line control for the demo
application. From the command line you can now also completely
configure all the environments in the world, and how they are
linked. Environments in different worlds may be connected in
open-ended ways. The command line argument parser may be further
extended to provide application-specific control.
[compatibility alert] Many of the methods that were used to set up
the worlds, the environments and their links have been changed. Much
of the functionality can now be controlled from the command line.
However, it is recommended that all applications by default create a
suitable world (especially when the application require multiple
environments). This should be done by overriding the
DemoAppArgumentParser#setDefaultEnvironmentsAndLinks method.
- arc.resource.ConservedResource: Security hole closed to prevent
negative values of ConservedResource as a means of acquiring
positive ConservedResources.
- arc.resource: Added various classes that provide a basic
resource accounting implementation. The ResourceEnvironment class is
a surrogate environment which charges its infohabitant for
environmental services. The ResourceIhab is an interface which
should be implemented by infohabitants which can be charged for
their use of environmental services. The
ResourceInfohabitantRegister is a listener which controls
registration and charging of ResourceIhabs in a given world. The
UserIhab is an infohabitant with protected access to the creation of
conserved resources which are accepted by the ResourceEnvironment.
- arc.services.Mirror: Automatic mirror tidyup on destruction of
client. Special command protocol introduced and 128 bit security for
Carriers. Tested across multiple virtual machines
- arc.services.ScheduleIhab: New scheduling functionality allows
delegation of schedule to specialist SchedulerIhab, allowing thread
to be released, and resources minimised for infohabitants which
execute rarely.
- arc.services.Handle: New infohabitant providing an alternative way
for remote communication. The current implementation is an initial
one. We plan to extend it significantly in upcoming releases.
- arc.services.directory: New package that provides a basic directory
for yellow-pages infohabitant look-up.
- app.migrate: Extended application to run on multiple VMs. The
behaviour of the Migrator infohabitant has been changed to better
so that it tests the new functionality better. Also added extensive
command line control. Added API documentation explaining how to
run the application on multiple DIET worlds.
- app.mirror: Added command line control. Users now subclass from
ScheduleExampleIhab, allowing schedule delegation, and self-destruct
to demonstrate Mirror tidyup. Tested with multiple virtual machines
and serialisation.
- app.resource: New application to demonstrate Resource Accounting
implementation of DIET Core. Tested with multiple virtual machines
and serialisation.
- app.schedule: Now contains command line control. Demonstrates thread
minimisation behaviour through reactivity and schedule
delegation. Provides example ihab for subclassing.
[compatibility alert] Infohabitants which previously subclassed
from ScheduleExampleIhab will require some mods, in particular if
they override #doRun, #update, #handleEvent, #handleExternalEvent or
reference schedule_portal directly.
- app.directory: New application demonstrating how the newly added
ARC directory can be used.
- app.handle: New application that uses the new Handle infohabitant
for remote communications.
- app.sorting: Minor modifications to reflect changes in core.
- app.primes: Minor modifications to reflect changes in core.
----------------------------------------------------------------------
Version 0.20-ext1, 23 Apr 2001
----------------------------------------------------------------------
Changes with respect to Version 0.20:
- core.imp.BasicInfohabitant: Fixed synchronisation bug that sometimes
caused a deadlock (only the MirrorApp sample application was
affected by this bug)
- arc.SchedulePortal: Removed superfluous debugging code. There was
still an assert statement that checked if the sequence of events was
in the right order, which reduced the performance of the scheduler,
especially for large numbers of events.
----------------------------------------------------------------------
Version 0.20, 17 Apr 2001
----------------------------------------------------------------------
Changes with respect to Version 0.15:
- Added ARC "CarrierPigeon" service. Basic migrator with message,
targeting individuals in remote environments, and delivering
messages. Placeholder methods for experimentation with different
failure handling strategies.
- Added ARC "Mirror" service. This makes communication transparent to
individuals in different environments, and is intended to be very
easy to initiate. An infohabitant is created 'representing' each
participant in the opposite participant's environment. Several
different forms of targeting are available, (by family tag, by
identity, limited numbers of clients). An infohabitant can mirror
itself (as a means of creating a presence in a remote environment),
or mirror another (as a means of interacting with them without
migrating to their environment). The implementation of this class
represents a classic use of the Context object.
- Added ARC "Multicast" service. In addition to the glorified 'for
loop' which is characteristic of multicast, convenience classes have
been provided for shielding infohabitants from the complexities of
handling multiple transactions. This is another demonstration of the
use of contexts.
- Added ARC scheduling functionality. The Scheduler allows an
infohabitant to timetable events whilst still responding to incoming
connection, message and disconnection notifications. A
thread-efficient schedule delegation mechanism is currently under
test for future releases.
- Added ARC ConservedResource abstract baseclass. This class is
intended to provide an uncheatable conserved resource. Access to the
creation can be controlled for a given subclass. Once a
ConservedResource object has been created, it may be separated into
smaller parts, or recombined with another ConservedResource object
of the same class but it is not possible to modify the total amount
of the conserved resource, without the privileged access to
creation.
- Provided "shared.DemoApp" as a base class for DIET applications. All
demo applications currently subclass from it. It allows you to
configure certain properties from the commandline. Amongst others,
you can control quite specifically which events are dumped to
standard error output. Try invoking applications with a "--help"
argument for full details on their options.
- Added "PrimesApp" demo application. It demonstrates how to handle
complex messages dependencies using a single thread. It is
definitely useful to take a look at the source code for PrimeMaster.
It's also good to experiment with various parameters. Use the
command-line arguments to do so!
- Added "MirrorApp" demo application. This demonstrates the use of the
Mirror infohabitant as a means of communicating with remote
infohabitants. The mirror infohabitant hides the details of the use
of Carrier Pigeon infohabitants (another new utility in the core).
The application shows a simple interaction between Service Users and
Service Providers, who both use mirrors to try to find each other
across three environments.
- Added "ScheduleApp" demo application. This demonstrates the use of
the SchedulePortal in a quality of service context.
- Added "MulticastApp" demo application. The simplicity of using
multicast in this implementation is best understood by looking at
the code. Simple text output shows a single user initating a
multicast, and handling the responses which come back.
- Added various general utility classes to the "diet.util" package.
Several are, for instance, used for handling command-line arguments.
- Improved "SortingApp" and "MigrateApp" applications to handle
command-line arguments and to support properties. Try running them
with "--help" to see what all options are. You could for instance
run the "MigrateApp" with respectively "--dont-share-threads" and
"--share-threads" and observe the difference.
- Added property support to infohabitants. Properties allow debug and
visualisation tools to give you an idea what goes on inside
infohabitants. A property has a name and can have any value. To
support properties in your infohabitants you have to fire a property
event whenever you change them. You should also implement the
fireAllProperties method so that it is possible to determine the
current values of all properties. See the various demo infohabitants
(e.g. sorting.Trigger) for details.
- Increased the types of event that are generated by the
"RunListener". It, for instance, now also signals when infohabitants
temporarily give up their thread, and subsequently resume execution.
- Various improvements to BasicInfohabitant. Dormant infohabitants now
also awake when they receive disconnection events. It does not
maintain any listeners anymore (these have all been moved to its
InfohabitantGuardian). Its internal state now better reflects the
events generated by the run listener (see #isAwake() and #isHosted()).
- Extended Environment interface to include various event firing
methods. As opposed to the existing methods these are not methods
corresponding to services provided by the environment, but methods
that infohabitants use to implement their commitments to the
environment. BasicInfohabitant already ensures that these are
obeyed, so you should never need to invoke these methods when
implementing your own infohabitant.
- Added various additional "Tracker" and "EventDumper" listeners
to "util.listeners".
- Fixed some problems with line-breaks.
- [compatibility alert] Renamed BasicInfohabitant#isRunning() to
isAwake()
- [compatibility alert] Added "cookie" arguments to some of the
"removeListener" methods in InfohabitantGuardian.
- [compatibility alert] Moved "run listener" support from
BasicInfohabitant to InfohabitantGuardian.
----------------------------------------------------------------------
Version 0.15, 17 Jan 2001
----------------------------------------------------------------------
Changes with respect to Version 0.14:
- core.imp.BasicInfohabitant: Added notification of "disconnection"
events. See #handleDisconnection and related methods.
- core.imp.BasicInfohabitant: Added #handleExternalEvent method.
- core.Tag: Added #getBit method.
- core.Environment: [compatibility alert] Removed ability to connect
to entirely arbitrary infohabitants.
Suprising as it may seem, removing this method actually makes the
platform more powerful. It means that you can completely limit the
access to (the ability to connect to) an infohabitant to a specific
group of infohabitants (typically only the one that created it, but
possibly more). This can be used in various ways.
- [compatibility alert] Added "cookie protection" mechanism to
prevent infohabitants from using listener functionality.
- core.imp.BasicEnvironment: [compatibility alert] Added "World"
argument to constructor.
- core.imp.BasicInfohabitant: Made event buffers private (for security
reasons)
- core.imp.ConnectionEnd: Removed connection near end/far end bug.
- core.imp.BasicInfohabitant: Reset event portal and
message/connection buffers after migration.
----------------------------------------------------------------------
Version 0.14, 17 Nov 2000
----------------------------------------------------------------------
Changes with respect to Version 0.13:
- [compatibility alert] Renamed "handleNewConnection" in
BasicInfohabitant to "handleConnection"
- [compatibility alert] Removed "Context" from "handleMessage" in
BasicInfohabitant. The context can simply directly be retrieved from
the sender.
- Added #getMyAddress method to Environment, and corresponding
#getAddress method to BasicInfohabitant.
- Removed "Context" parameter from InfohabitantImp #receive method
(and renamed #receive to #acceptMessage).
- Added #setAcceptConnections(boolean) and
#setAcceptMessages(boolean) to BasicInfohabitant.
- Added get methods to InfohabitantAddress (note: the set methods have
disappeared again, because it's better if objects of this class are
immutable).
- Removed "name clash" bug in BasicEnvironment.
- Added string constructor for Tag.
----------------------------------------------------------------------
Version 0.13, 9 Nov 2000
----------------------------------------------------------------------
Changes with respect to Version 0.11:
- Implemented World listeners, Environment listeners, Infohabitant
listeners, ConnectionEnd listeners and Neighbourhood listeners.
- Provided basic "event dumper" implementations for all these
listeners. These can be found in org.ist_uie.diet.util.debug
and can be used for very basic debugging.
- Updated SortingApp and MigrateApp. These now use the
event dumpers for visualisation (and the old visualisation code
has been removed from the infohabitant classes).
- Infohabitants can now limit the number of connections they
can simultaniously support. See InfohabitantImp#getMaxConnections
- Changed BasicInfohabitant#handleMessage arguments. It now also
uses CommunicationPacket.
- Added Environment#isHostingMe method.
- Renamed EnvironmentRegistry class to World.
- Added InfohabitantImp#getFriendlyName. This provides a
human-readable name that is useful for debugging.
- BasicEnvironment now automatically registers itself with the
world.
----------------------------------------------------------------------
Version 0.12, 6 Nov 2000
----------------------------------------------------------------------
Changes with respect to Version 0.11:
- Initial support for observers (see org.ist_uie.diet.core.imp.event)
- [compabitility alert] Renamed "InfohabitantProxy" to "ConnectionEnd"
- [compabitility alert] Renamed "EnvironmentProxy" to
"InfohabitantGuardian"
- The send and receive methods now use "CommunicationPacket"s.
----------------------------------------------------------------------
Version 0.11, 3 Nov 2000
----------------------------------------------------------------------
Changes with respect to Version 0.10:
- Added support for multiple environments (including neighbourhoods
and migrating from one to another).
- Added basic migration demo application.
- A few minor differences, most of which I've mentioned yesterday.
(eh?....)
----------------------------------------------------------------------
Version 0.10, 23 Oct 2000
----------------------------------------------------------------------
Initial release containing:
- core package: This defines core layer functionality. It provides all
the basic functionality (managing infohabitants and their
connections), but is not yet complete. It does not yet provide
support for multiple environments, nor does it yet provide
visualisation hooks. This will be added soon.
- core.imp package: Basic implementation of core layer. It's
worthwhile to check out the public classes. Do not bother with the
other, non-public classes unless you really want to. These classes
only embody specific implementation details and they are not used
outside the kernel.
- app.sorting package: Sample sorting application. The sample
application has been used to test the core layer and demonstrates
how to use the architecture. The output is still very boring and
basic (eventually there will be some fancier visualisation), but do
not let this put you off. The application is quite interesting. It
is definitely worthwhile to understand what it is doing and how it
does it, as it's very much bottom up and only uses very simple
infohabitants to achieve some interesting behaviour (sorting). Read
the API documentation for the "sorting" classes to find out more
about the application and its three types of infohabitant.
To get a feel of what the sample application does, it is useful to
experiment with different parameter settings. This currently
requires changing the static constants in BasicApp.java and
compiling the file again. It may be interesting to change the output
level to get an idea of how many messages are being sent
(LIMITED_OUTPUT), or to even see all messages in detail
(VERBOSE_OUTPUT). It is also interesting to decrease the amount that
the Trigger infohabitants sleep, to cause the system to overload
(infohabitants will then produce messages faster than they can
handle it) without letting it actually break down. Other
possibilities are: increasing the number of Linker infohabitants,
reducing the timeout of the Crawler, etc.
