Menu
▾
▴
#634 MDS: TIPC DROPPABLE usage
MDS uses RDM (Reliable DatagraM) type of TIPC sockets.
The default setting of DEST_DROPPABLE for RDM sockets is True. This means that TIPC is allowed to SILENTLY discard messages at congestion at the receiving node. We can see this happen with a collocated application using TIPC at the same IMPORTANCE. The consequence seen is often that IMM sync fails and immnd on many nodes exit. Or amfnd gets out of sync with messages and exits.
The difference of RDM and DGRAM sockets is basically the default value of SRC_DROPPABLE which is False for RDM. This means that on the sending node a send can fail due to link congestion. For RDM socket this will be returned to the client whereas for DGRAM it will not. Today I guess MDS just logs that this happened and return and error to the client.
Please comment/discuss!
See https://sourceforge.net/p/opensaf/tickets/654/
The Linux TIPC 2.0 Programmer's Guide in section 1.5.7. Multicast Message Delivery mention that.
The TIPC currently does not permit an application to send a multicast message with the "destination droppable" setting disabled.
Consequently, TIPC will never try to return an undeliverable multicast message to its sender.
so if we set destination droppable disabled , multicast is not permitted
I experimented setting TIPC_DEST_DROPPABLE=off in multicast_demo and observed that multicast is working
As if The Opensaf using multicast , it is not allowed to set TIPC_DEST_DROPPABLE=off