Improve logging in LeaderChecker #78883
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DaveCTurner
added
>enhancement
:Distributed/Cluster Coordination
Today if the `LeaderChecker` decides it's time to restart discovery then
we log a verbose and confusing message that looks something like this:
[instance-0000000006] master node [...] failed, restarting discovery
org.elasticsearch.ElasticsearchException: node [...] failed [3] consecutive checks
at org.elasticsearch.cluster.coordination.LeaderChecker$CheckScheduler$1.handleException(LeaderChecker.java:275) ~[elasticsearch-7.14.1.jar:7.14.1]
...
at java.lang.Thread.run(Thread.java:831) [?:?]
Caused by: org.elasticsearch.transport.RemoteTransportException: [...][internal:coordination/fault_detection/leader_check]
Caused by: org.elasticsearch.cluster.coordination.CoordinationStateRejectedException: rejecting leader check since [...] has been removed from the cluster
at org.elasticsearch.cluster.coordination.LeaderChecker.handleLeaderCheck(LeaderChecker.java:181) ~[elasticsearch-7.14.1.jar:7.14.1]
...
at java.lang.Thread.run(Thread.java:831) ~[?:?]
There's quite a few problems with this:
- We use `DiscoveryNode#toString` which is far too chatty.
- There's basically nothing useful in these stack traces.
- It's easy to miss the `RemoteTransportException` in the middle.
- It's also easy to miss the root cause below it.
- We say the master node failed which sounds very bad but, well, you
know, that's just like, uh, our opinion. The master node is often
fine, it just rejected our checks for some reason.
- Reports of unstable clusters include these messages because they're
noisy and look important, but don't include the more informative ones
from the master because the master logs look quieter.
This commit reworks the logging in this area to avoid these problems:
- We use `DiscoveryNode#descriptionWithoutAttributes` throughout.
- We suppress the full stack traces unless `DEBUG` logging is on.
- The `LeaderChecker` now provides the message to be logged, rather than
putting all the details into an exception that wraps around the root
cause.
- The message describes the root cause rather than just saying that the
"master node failed"
- We distinguish timeouts from rejections and report the count of each.
- The message guides towards checking the master node logs too.
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Pinging @elastic/es-distributed (Team:Distributed) |
DaveCTurner
commented
Oct 11, 2021
| private class CheckScheduler implements Releasable { | ||
|
|
||
| private final AtomicBoolean isClosed = new AtomicBoolean(); | ||
| private final AtomicLong failureCountSinceLastSuccess = new AtomicLong(); |
There was a problem hiding this comment.
We don't actually need an AtomicLong here, there's only ever one request in flight so everything is properly synchronised already.
DaveCTurner
added a commit
that referenced
this pull request
Oct 15, 2021
Today if the `LeaderChecker` decides it's time to restart discovery then
we log a verbose and confusing message that looks something like this:
[instance-0000000006] master node [...] failed, restarting discovery
org.elasticsearch.ElasticsearchException: node [...] failed [3] consecutive checks
at org.elasticsearch.cluster.coordination.LeaderChecker$CheckScheduler$1.handleException(LeaderChecker.java:275) ~[elasticsearch-7.14.1.jar:7.14.1]
...
at java.lang.Thread.run(Thread.java:831) [?:?]
Caused by: org.elasticsearch.transport.RemoteTransportException: [...][internal:coordination/fault_detection/leader_check]
Caused by: org.elasticsearch.cluster.coordination.CoordinationStateRejectedException: rejecting leader check since [...] has been removed from the cluster
at org.elasticsearch.cluster.coordination.LeaderChecker.handleLeaderCheck(LeaderChecker.java:181) ~[elasticsearch-7.14.1.jar:7.14.1]
...
at java.lang.Thread.run(Thread.java:831) ~[?:?]
There's quite a few problems with this:
- We use `DiscoveryNode#toString` which is far too chatty.
- There's basically nothing useful in these stack traces.
- It's easy to miss the `RemoteTransportException` in the middle.
- It's also easy to miss the root cause below it.
- We say the master node failed which sounds very bad but, well, you
know, that's just like, uh, our opinion. The master node is often
fine, it just rejected our checks for some reason.
- Reports of unstable clusters include these messages because they're
noisy and look important, but don't include the more informative ones
from the master because the master logs look quieter.
This commit reworks the logging in this area to avoid these problems:
- We use `DiscoveryNode#descriptionWithoutAttributes` throughout.
- We suppress the full stack traces unless `DEBUG` logging is on.
- The `LeaderChecker` now provides the message to be logged, rather than
putting all the details into an exception that wraps around the root
cause.
- The message describes the root cause rather than just saying that the
"master node failed"
- We distinguish timeouts from rejections and report the count of each.
- The message guides towards checking the master node logs too.
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Today if the
LeaderCheckerdecides it's time to restart discovery thenwe log a verbose and confusing message that looks something like this:
There's quite a few problems with this:
DiscoveryNode#toStringwhich is far too chatty.RemoteTransportExceptionin the middle.know, that's just like, uh, our opinion. The master node is often
fine, it just rejected our checks for some reason.
noisy and look important, but don't include the more informative ones
from the master because the master logs look quieter.
This commit reworks the logging in this area to avoid these problems:
DiscoveryNode#descriptionWithoutAttributesthroughout.DEBUGlogging is on.LeaderCheckernow provides the message to be logged, rather thanputting all the details into an exception that wraps around the root
cause.
"master node failed"