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Prevent parallel file lock clear #3714

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Prevent parallel file lock clear #3714

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b1198bc
Prevent parallel file lock clear
jjezra Oct 31, 2025
267a744
Use recursion guard
jjezra Nov 1, 2025
e81f7d2
Avoid spotbug issue
jjezra Nov 1, 2025
4d5d581
(WIP) clear clearingLockNow in a whenComplete future stage
jjezra Nov 14, 2025
903d058
Remove clearingLockNowLock
jjezra Nov 17, 2025
9460bfe
Test - do not merge
jjezra Nov 17, 2025
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13 changes: 13 additions & 0 deletions ...src/main/java/com/apple/foundationdb/record/lucene/directory/FDBDirectoryLockFactory.java
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Original file line number Diff line number Diff line change
Expand Up @@ -92,6 +92,8 @@ protected static class FDBDirectoryLock extends Lock {
*/
private FDBRecordContext closingContext = null;
private final Object fileLockSetLock = new Object();
private boolean clearingLockNow = false;
private final Object clearingLockNowLock = new Object();

private FDBDirectoryLock(final AgilityContext agilityContext, final String lockName, byte[] fileLockKey, int timeWindowMilliseconds) {
this.agilityContext = agilityContext;
Expand Down Expand Up @@ -210,6 +212,13 @@ private void fileLockCheckNewLock(byte[] val, long nowMillis) {
}

private void fileLockClearFlushAndClose(boolean isRecovery) {
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@ScottDugas ScottDugas Nov 14, 2025

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It sounds like there are some concurrency challenges with FDBDirectoryLock, it would probably be good to add some tests that try to clear this lock concurrently.

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@jjezra jjezra Nov 17, 2025

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I don't think that there are concurrent calls for this (within the same session) but recursive calls.

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@ScottDugas ScottDugas Nov 17, 2025

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ok, in that case, it would be good to have tests that cause this to happen recursively. that might be very hard at the higher levels, but should be doable at this level, right?

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@jjezra jjezra Nov 17, 2025

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I cannot recreate it and wondering if one the two rebases eliminated the scenario. Switching to draft for a full unit testing ...

synchronized (clearingLockNowLock) {
// Here: this function is being called from too many paths. Until cleanup, this guard is here to avoid recursions
if (clearingLockNow) {
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@ScottDugas ScottDugas Nov 14, 2025

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I've only seen it for lazy instantiation, but would it be worth to duplicate this before the synchronized lock to avoid entering the Synchronized lock if already clearing?

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@jjezra jjezra Nov 14, 2025

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I can either do that or remove the synchronized lock altogether (since our concern is recursion, the synchronized lock might be an overkill...)

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@jjezra jjezra Nov 17, 2025

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Removed clearingLockNowLock - this will now only protect from recursion, but not from concurrency (which - AFAIK - does not happen).

return;
}
clearingLockNow = true;
}
Function<FDBRecordContext, CompletableFuture<Void>> fileLockFunc = aContext ->
aContext.ensureActive().get(fileLockKey)
.thenAccept(val -> {
Expand Down Expand Up @@ -244,6 +253,10 @@ private void fileLockClearFlushAndClose(boolean isRecovery) {
} finally {
closed = flushed; // allow close retry
closingContext = null;
synchronized (clearingLockNowLock) {
// clearing under lock to avoid spotbugsMain's "Inconsistent synchronization" issue.
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@ScottDugas ScottDugas Nov 14, 2025

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Should this be in a finally around all the code above?
i.e. what happens if the asyncToSync calls above fail?

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@jjezra jjezra Nov 14, 2025

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Good point!
I've moved it to a fileLockFunc's whenComplete step.

clearingLockNow = false;
}
}
}

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