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[FLINK-29095][state] Improve logging in SharedStateRegistry #20722

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[FLINK-29095][state] Improve logging in SharedStateRegistry #20722

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119 changes: 68 additions & 51 deletions flink-runtime/src/main/java/org/apache/flink/runtime/state/SharedStateRegistryImpl.java
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Original file line number Diff line number Diff line change
Expand Up @@ -79,12 +79,12 @@ public SharedStateRegistryImpl(Executor asyncDisposalExecutor) {

@Override
public StreamStateHandle registerReference(
SharedStateRegistryKey registrationKey,
StreamStateHandle state,
long checkpointID,
boolean preventDiscardingCreatedCheckpoint) {
final SharedStateRegistryKey registrationKey,
final StreamStateHandle newHandle,
final long checkpointID,
final boolean preventDiscardingCreatedCheckpoint) {

checkNotNull(state);
checkNotNull(newHandle);

StreamStateHandle scheduledStateDeletion = null;
SharedStateEntry entry;
Expand All @@ -95,60 +95,77 @@ public StreamStateHandle registerReference(
entry = registeredStates.get(registrationKey);

if (entry == null) {
// Additional check that should never fail, because only state handles that are not
// placeholders should
// ever be inserted to the registry.
checkState(
!isPlaceholder(state),
!isPlaceholder(newHandle),
"Attempt to reference unknown state: " + registrationKey);

entry = new SharedStateEntry(state, checkpointID);
LOG.trace(
"Registered new shared state {} under key {}.", newHandle, registrationKey);
entry = new SharedStateEntry(newHandle, checkpointID);
registeredStates.put(registrationKey, entry);
LOG.trace("Registered new shared state {} under key {}.", entry, registrationKey);

} else {
// Delete if this is a real duplicate.
// Note that task (backend) is not required to re-upload state
// if the confirmation notification was missing.
// However, it's also not required to use exactly the same handle or placeholder
if (!Objects.equals(state, entry.stateHandle)) {
if (entry.confirmed || isPlaceholder(state)) {
scheduledStateDeletion = state;
} else {
// Old entry is not in a confirmed checkpoint yet, and the new one differs.
// This might result from (omitted KG range here for simplicity):
// 1. Flink recovers from a failure using a checkpoint 1
// 2. State Backend is initialized to UID xyz and a set of SST: { 01.sst }
// 3. JM triggers checkpoint 2
// 4. TM sends handle: "xyz-002.sst"; JM registers it under "xyz-002.sst"
// 5. TM crashes; everything is repeated from (2)
// 6. TM recovers from CP 1 again: backend UID "xyz", SST { 01.sst }
// 7. JM triggers checkpoint 3
// 8. TM sends NEW state "xyz-002.sst"
// 9. JM discards it as duplicate
// 10. checkpoint completes, but a wrong SST file is used
// So we use a new entry and discard the old one:
scheduledStateDeletion = entry.stateHandle;
entry.stateHandle = state;
}
LOG.trace(
"Identified duplicate state registration under key {}. New state {} was determined to "
+ "be an unnecessary copy of existing state {} and will be dropped.",
registrationKey,
state,
entry.stateHandle);
}
// no further handling
return entry.stateHandle;

} else if (entry.stateHandle == newHandle) {
// might be a bug but state backend is not required to use a place-holder
LOG.debug(
"Duplicated registration under key {} with the same object: {}",
registrationKey,
newHandle);
} else if (Objects.equals(entry.stateHandle, newHandle)) {
// might be a bug but state backend is not required to use a place-holder
LOG.debug(
"Duplicated registration under key {} with the new object: {}.",
registrationKey,
newHandle);
} else if (isPlaceholder(newHandle)) {
LOG.trace(
"Updating last checkpoint for {} from {} to {}",
"Duplicated registration under key {} with a placeholder (normal case)",
registrationKey);
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Maybe lack of scheduledStateDeletion = newHandle;?

} else if (entry.confirmed) {
LOG.info(
"Duplicated registration under key {} of a new state: {}. "
+ "This might happen if checkpoint confirmation was delayed and state backend re-uploaded the state. "
+ "Discarding the new state and keeping the old one which is included into a completed checkpoint",
registrationKey,
entry.lastUsedCheckpointID,
checkpointID);
entry.advanceLastUsingCheckpointID(checkpointID);
if (preventDiscardingCreatedCheckpoint) {
entry.preventDiscardingCreatedCheckpoint();
}
newHandle);
scheduledStateDeletion = newHandle;
} else {
// Old entry is not in a confirmed checkpoint yet, and the new one differs.
// This might result from (omitted KG range here for simplicity):
// 1. Flink recovers from a failure using a checkpoint 1
// 2. State Backend is initialized to UID xyz and a set of SST: { 01.sst }
// 3. JM triggers checkpoint 2
// 4. TM sends handle: "xyz-002.sst"; JM registers it under "xyz-002.sst"
// 5. TM crashes; everything is repeated from (2)
// 6. TM recovers from CP 1 again: backend UID "xyz", SST { 01.sst }
// 7. JM triggers checkpoint 3
// 8. TM sends NEW state "xyz-002.sst"
// 9. JM discards it as duplicate
// 10. checkpoint completes, but a wrong SST file is used
// So we use a new entry and discard the old one:
LOG.info(
"Duplicated registration under key {} of a new state: {}. "
+ "This might happen during the task failover if state backend creates different states with the same key before and after the failure. "
+ "Discarding the OLD state and keeping the NEW one which is included into a completed checkpoint",
registrationKey,
newHandle);
scheduledStateDeletion = entry.stateHandle;
entry.stateHandle = newHandle;
}
}

LOG.trace(
"Updating last checkpoint for {} from {} to {}",
registrationKey,
entry.lastUsedCheckpointID,
checkpointID);
entry.advanceLastUsingCheckpointID(checkpointID);

if (preventDiscardingCreatedCheckpoint) {
entry.preventDiscardingCreatedCheckpoint();
}
} // end of synchronized (registeredStates)

scheduleAsyncDelete(scheduledStateDeletion);
return entry.stateHandle;
Expand Down