Abhishek Rawat created IMPALA-12382:
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Summary: Coordinator could schedule fragments on gracefully
shutdown executors
Key: IMPALA-12382
URL: https://issues.apache.org/jira/browse/IMPALA-12382
Project: IMPALA
Issue Type: Improvement
Reporter: Abhishek Rawat
Statestore does failure detection based on consecutive heartbeat failures. This
is by default configured to be 10 (statestore_max_missed_heartbeats) at 1
second intervals (statestore_heartbeat_frequency_ms). This could however take
much longer than 10 seconds overall, especially if statestore is busy and due
to rpc timeout duration.
In the following example it took 50 seconds for failure detection:
{code:java}
I0817 12:32:06.824721 86 statestore.cc:1157] Unable to send heartbeat
message to subscriber
impa...@impala-executor-001-5.impala-executor.impala-1692115218-htqx.svc.cluster.local:27010,
received error: RPC Error: Client for 10.80.199.159:23000 hit an unexpected
exception: No more data to read., type:
N6apache6thrift9transport19TTransportExceptionE, rpc:
N6impala18THeartbeatResponseE, send: done
I0817 12:32:06.824741 86 failure-detector.cc:91] 1 consecutive heartbeats
failed for
'impa...@impala-executor-001-5.impala-executor.impala-1692115218-htqx.svc.cluster.local:27010'.
State is OK
.....
.....
.....
I0817 12:32:56.800251 83 statestore.cc:1157] Unable to send heartbeat
message to subscriber
impa...@impala-executor-001-5.impala-executor.impala-1692115218-htqx.svc.cluster.local:27010,
received error: RPC Error: Client for 10.80.199.159:23000 hit an unexpected
exception: No more data to read., type:
N6apache6thrift9transport19TTransportExceptionE, rpc:
N6impala18THeartbeatResponseE, send: done
I0817 12:32:56.800267 83 failure-detector.cc:91] 10 consecutive heartbeats
failed for
'impa...@impala-executor-001-5.impala-executor.impala-1692115218-htqx.svc.cluster.local:27010'.
State is FAILED
I0817 12:32:56.800276 83 statestore.cc:1168] Subscriber
'impa...@impala-executor-001-5.impala-executor.impala-1692115218-htqx.svc.cluster.local:27010'
has failed, disconnected or re-registered (last known registration ID:
c84bf70f03acda2b:b34a812c5e96e687){code}
As a result there is a window when statestore is determining node failure and
coordinator might schedule fragments on that particular executor(s). The exec
RPC will fail and if transparent query retries is enabled, coordinator will
immediately retry the query and it will fail again.
Ideally in such situations coordinator should be notified sooner about a failed
executor. Statestore could send priority topic update to coordinator when it
enters failure detection logic. This should reduce the chances of coordinator
scheduling query fragment on a failed executor.
The other argument could be to tune the heartbeat frequency and interval
parameters. But, it's hard to find configuration which works for all cases.
And, so while the default values are reasonable, under certain conditions they
could be unreasonable as seen in the above example.
It might make sense to especially handle the case where executors are shutdown
gracefully and in such case statestore shouldn't do failure detection and
instead fail these executor immediately.
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