Stefan Podkowinski created CASSANDRA-12653:
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Summary: In-flight shadow round requests
Key: CASSANDRA-12653
URL: https://issues.apache.org/jira/browse/CASSANDRA-12653
Project: Cassandra
Issue Type: Bug
Components: Distributed Metadata
Reporter: Stefan Podkowinski
Priority: Minor
Bootstrapping or replacing a node in the cluster requires to gather and check
some host IDs or tokens by doing a gossip "shadow round" once before joining
the cluster. This is done by sending a gossip SYN to all seeds until we receive
a response with the cluster state, from where we can move on in the bootstrap
process. Receiving a response will call the shadow round done and calls
{{Gossiper.resetEndpointStateMap}} for cleaning up the received state again.
The issue here is that at this point there might be other in-flight requests
and it's very likely that shadow round responses from other seeds will be
received afterwards, while the current state of the bootstrap process doesn't
expect this to happen (e.g. gossiper may or may not be enabled).
One side effect will be that MigrationTasks are spawned for each shadow round
reply except the first. Tasks might or might not execute based on whether at
execution time {{Gossiper.resetEndpointStateMap}} had been called, which
effects the outcome of {{FailureDetector.instance.isAlive(endpoint))}} at start
of the task. You'll see error log messages such as follows when this happend:
{noformat}
INFO [SharedPool-Worker-1] 2016-09-08 08:36:39,255 Gossiper.java:993 -
InetAddress /xx.xx.xx.xx is now UP
ERROR [MigrationStage:1] 2016-09-08 08:36:39,255 FailureDetector.java:223 -
unknown endpoint /xx.xx.xx.xx
{noformat}
Although is isn't pretty, I currently don't see any serious harm from this, but
it would be good to get a second opinion (feel free to close as "wont fix").
/cc [~Stefania] [~thobbs]
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