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From "sankalp kohli (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-6571) Quickly restarted nodes can list others as down indefinitely
Date Sun, 12 Jan 2014 06:18:51 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-6571?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13868955#comment-13868955
] 

sankalp kohli commented on CASSANDRA-6571:
------------------------------------------

"I tried to fix this by defaulting isAlive=false in the constructor of EndpointState."
This won't fix the problem as endpoint can be alive. 
I tried my fix and it seems to work but someone else should also test it. 

> Quickly restarted nodes can list others as down indefinitely
> ------------------------------------------------------------
>
>                 Key: CASSANDRA-6571
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-6571
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Core
>            Reporter: Richard Low
>            Assignee: sankalp kohli
>              Labels: gossip
>             Fix For: 2.0.5
>
>         Attachments: 6571.txt
>
>
> In a healthy cluster, if a node is restarted quickly, it may list other nodes as down
when it comes back up and never list them as up.  I reproduced it on a small cluster running
in Docker containers.
> 1. Have a healthy 5 node cluster:
> {quote}
> $ nodetool status
> Datacenter: datacenter1
> =======================
> Status=Up/Down
> |/ State=Normal/Leaving/Joining/Moving
> --  Address          Load       Tokens  Owns (effective)  Host ID                   
           Rack
> UN  192.168.100.1    40.88 KB   256     38.3%             92930ef6-1b29-49f0-a8cd-f962b55dca1b
 rack1
> UN  192.168.100.254  80.63 KB   256     39.6%             ef15a717-9d60-48fb-80a9-e0973abdd55e
 rack1
> UN  192.168.100.3    87.78 KB   256     40.8%             4e6765db-97ed-4429-a9f4-8e29de247f18
 rack1
> UN  192.168.100.2    75.22 KB   256     40.6%             e89bc581-5345-4abd-88ba-7018371940fc
 rack1
> UN  192.168.100.4    80.83 KB   256     40.8%             466a9798-d484-44f0-aae8-bb2b78d80331
 rack1
> {quote}
> 2. Kill a node and restart it quickly:
> bq. kill -9 <pid> && start-cassandra
> 3. Wait for the node to come back and more often than not, it lists one or more other
nodes as down indefinitely:
> {quote}
> $ nodetool status
> Datacenter: datacenter1
> =======================
> Status=Up/Down
> |/ State=Normal/Leaving/Joining/Moving
> --  Address          Load       Tokens  Owns (effective)  Host ID                   
           Rack
> UN  192.168.100.1    40.88 KB   256     38.3%             92930ef6-1b29-49f0-a8cd-f962b55dca1b
 rack1
> UN  192.168.100.254  80.63 KB   256     39.6%             ef15a717-9d60-48fb-80a9-e0973abdd55e
 rack1
> DN  192.168.100.3    87.78 KB   256     40.8%             4e6765db-97ed-4429-a9f4-8e29de247f18
 rack1
> DN  192.168.100.2    75.22 KB   256     40.6%             e89bc581-5345-4abd-88ba-7018371940fc
 rack1
> DN  192.168.100.4    80.83 KB   256     40.8%             466a9798-d484-44f0-aae8-bb2b78d80331
 rack1
> {quote}
> From trace logging, here's what I think is going on:
> 1. The nodes are all happy gossiping
> 2. Restart node X. When it comes back up it starts gossiping with the other nodes.
> 3. Before node X marks node Y as alive, X sends an echo message (introduced in CASSANDRA-3533)
> 4. The echo message is received by Y. To reply, Y attempts to reuse a connection to X.
The connection is dead, but the message is attempted anyway but fails.
> 5. X never receives the echo back, so Y isn't marked as alive.
> 6. X gossips to Y again, but because the endpoint isAlive() returns true, it never calls
markAlive() to properly set Y as alive.
> I tried to fix this by defaulting isAlive=false in the constructor of EndpointState.
This made it less likely to mark a node as down but it still happens.
> The workaround is to leave a node down for a while so the connections die on the remaining
nodes.



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