Richard Low created CASSANDRA-6571:
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Summary: 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
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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