Re: [Wrapper-user] how to prevent 2 instances of the same service running on 2 servers

[Leif M. <le...@ta...>]

Martyn,
    You would have to modify the shell script a bit.  But you could 
place the pid file
mentioned in the shell script on the network share.  You would have to 
change the
logic a bit however as the file is currently ignored if the process in 
the pid file does
not exist.  It wouldn't exist on the other machine of course.

Cheers,
Leif

Martynas Brijunas wrote:
> Hi Leif,
>
> thank you for your answer.
>
> The processes are started manually by an operator. Or they can be
> started automatically on one server, and manually on another. So that
> would eliminate the problem of a power outage you mentioned.
>
> I was hoping that by detecting an existing PID file (for example, on a
> network share), the wrapper would refuse to start on another server,
> until this original PID file is removed.
>
> Martyn
>
>
> 2006/7/10, Leif Mortenson <le...@ta...>:
>   
>> Martyn,
>>    The problem is that you are talking about two physical machines.
>> The Wrapper has
>> features do this within a single machine.  But not for multiple
>> machines.  You will need to
>> implement a startup class which say attempts to open a socket to the
>> other machine.  If
>> it connects, it knows the other server is running and shuts down.   If
>> it fails to connect then
>> it can assume it opens its own server socket to listen for connections.
>>
>>    This is not fail proof however.  You need to account for cases where
>> both servers come
>> up at pretty much the same instant.  Say after a power outage or
>> something.   Maybe make
>> server a the master.  It will always try to run.  Server B will try to
>> start but then poll Server
>> A and always shutdown if it finds it.  Something like that.
>>
>>    But like was already said, I don't think this is really under the
>> scope of the wrapper
>> unless I am missing what you are trying to say.
>>
>> Cheers,
>> Leif
>>
>> Martynas Brijunas wrote:
>>     
>>> Hi Martin,
>>>
>>> thank you for your reply. I think i explained the problem not very clearly.
>>>
>>> Server A: process AAA is running
>>> Server B: process AAA must not be running if it is running on Server
>>> A, otherwise it can.
>>>
>>> How to ensure that when it is running on Server A, it cannot be
>>> started on Server B? And vice versa: when it is running on Server B,
>>> it cannot be started on Server A.
>>>
>>> Is it possible to emply PIDs or anchor files for this purpose?
>>>
>>> Thanks,
>>> Martyn
>>>
>>> 2006/7/7, Martin Gazak <ma...@mi...>:
>>>
>>>       
>>>> Hallo,
>>>> this seems not to be a task for Java Service Wrapper - try to look for
>>>> example at www.linux-ha.org (Linux/Unix environment only, but seems to
>>>> be your case), you may achieve also failover of the service (including
>>>> the IP failover).
>>>>
>>>>
>>>>
>>>> Martynas Brijunas wrote:
>>>>
>>>>         
>>>>> Hi,
>>>>>
>>>>> we have 2 servers that have the same wrapper services for failover
>>>>> reasons. Only one instance of each server can run at any given time.
>>>>> Is there a way to prevent an accidental start of a service in 2
>>>>> locations? I thought of employing a PID file on a network share, but
>>>>> not sure if that would work.
>>>>>
>>>>> Thank you.
>>>>>
>>>>>