Bug 54045 - ReplicatedMap don't like TcpFailureDetector in static configuration
ReplicatedMap don't like TcpFailureDetector in static configuration
Product: Tomcat 6
Classification: Unclassified
Component: Cluster
PC All
: P2 major (vote)
: default
Assigned To: Tomcat Developers Mailing List
Depends on:
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Reported: 2012-10-23 16:03 UTC by F.Arnoud
Modified: 2013-02-15 20:27 UTC (History)
0 users


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Description F.Arnoud 2012-10-23 16:03:53 UTC
Tribes stack using:
* TcpPingInterceptor
* TcpFailureDetector
* MessageDispatchInterceptor
* StaticMembershipInterceptor
Do not work well in static cluster.

First side (ie one thread):
* call to TcpFailureDetector.heartbeat()
* call to checkMembers(false)
* call to performBasicCheck() in synchronized(membership)
* in performBasicCheck, for a missing static node:
*   add "missing" member to membership with membership.memberAlive(m)
*   check it with memberAlive(m)
*   remove it since if it doesn't exist

Second side (ie another thread):
* some call to channel.getMembers() like what the done by AbstractReplicatedMap
* this call will call the TcpFailureDetector.getMembers()
* this one could return a wrong value since it can contains unavailable nodes

* synchronize on membership isn't use by TcpFailureDetector in getMember(), getMembers(), hasMembers(), neither in Membership equivalent method (maybe because it's too heavy to lock every thread while the TcpFailureDetector check if node are alive).

It must not be an issue for AbstractReplicatedMap since with or without TcpFailureDetector a node could disapear while replicated map try to use it.
But ReplicatedMap use always Channel.SEND_OPTIONS_DEFAULT where the value is Channel.SEND_OPTIONS_USE_ACK. So a message sent to a missing node will fail with an exception.

Personnaly I override TcpFailureDetector.heartbeat() to avoid performBasicCheck() if I use a static configuration (TcpPingInterceptor call performForcedCheck()).
But this doesn't fix ReplicatedMap issue.

Better fix could avoid adding missing member to membership list:
* Add a method like memberAlive(MemberImpl) to Membership without side effect (add the member)
* in TcpFailureDetector.performBasicCheck(): check this new method before adding the node

This doesn't fix the AbstractReplicatedMap issue which work always with acknoledge from other nodes.

Same code for Tomcat 6.

best regards
Comment 1 Keiichi Fujino 2012-10-25 12:00:47 UTC
Thanks for the report.
Fixed in trunk and 7.0.x and will be included in 7.0.33 onwards.
Proposed for 6.0.x.
Comment 2 Mark Thomas 2013-02-15 20:27:16 UTC
Fixed in 6.0.x and will be included in 6.0.37 onwards.