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Greedily advance safe commit on new global checkpoint #48559

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merged 2 commits into from
Oct 29, 2019
Merged

Greedily advance safe commit on new global checkpoint #48559

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98fa5f4
Greedy advance safe commit on new global checkpoint
dnhatn Oct 28, 2019
d66389a
track max_seq_no of the next safe commit
dnhatn Oct 28, 2019
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18 changes: 9 additions & 9 deletions server/src/main/java/org/elasticsearch/index/engine/CombinedDeletionPolicy.java
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Original file line number Diff line number Diff line change
Expand Up @@ -51,6 +51,7 @@ public class CombinedDeletionPolicy extends IndexDeletionPolicy {
private final LongSupplier globalCheckpointSupplier;
private final ObjectIntHashMap<IndexCommit> snapshottedCommits; // Number of snapshots held against each commit point.
private volatile IndexCommit safeCommit; // the most recent safe commit point - its max_seqno at most the persisted global checkpoint.
private volatile long maxSeqNoOfNextSafeCommit;
private volatile IndexCommit lastCommit; // the most recent commit point
private volatile SafeCommitInfo safeCommitInfo = SafeCommitInfo.EMPTY;

Expand Down Expand Up @@ -83,6 +84,11 @@ public void onCommit(List<? extends IndexCommit> commits) throws IOException {
this.safeCommitInfo = SafeCommitInfo.EMPTY;
this.lastCommit = commits.get(commits.size() - 1);
this.safeCommit = commits.get(keptPosition);
if (keptPosition == commits.size() - 1) {
this.maxSeqNoOfNextSafeCommit = Long.MAX_VALUE;
} else {
this.maxSeqNoOfNextSafeCommit = Long.parseLong(commits.get(keptPosition + 1).getUserData().get(SequenceNumbers.MAX_SEQ_NO));
}
for (int i = 0; i < keptPosition; i++) {
if (snapshottedCommits.containsKey(commits.get(i)) == false) {
deleteCommit(commits.get(i));
Expand Down Expand Up @@ -217,16 +223,10 @@ synchronized boolean hasSnapshottedCommits() {
}

/**
* Checks if the deletion policy can release some index commits with the latest global checkpoint.
* Checks if the deletion policy can delete some index commits with the latest global checkpoint.
*/
boolean hasUnreferencedCommits() throws IOException {
final IndexCommit lastCommit = this.lastCommit;
if (safeCommit != lastCommit) { // Race condition can happen but harmless
final long maxSeqNoFromLastCommit = Long.parseLong(lastCommit.getUserData().get(SequenceNumbers.MAX_SEQ_NO));
// We can clean up the current safe commit if the last commit is safe
return globalCheckpointSupplier.getAsLong() >= maxSeqNoFromLastCommit;
}
return false;
boolean hasUnreferencedCommits() {
return maxSeqNoOfNextSafeCommit <= globalCheckpointSupplier.getAsLong();
}

/**
Expand Down
22 changes: 14 additions & 8 deletions server/src/test/java/org/elasticsearch/index/engine/CombinedDeletionPolicyTests.java
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Expand Up @@ -229,22 +229,28 @@ public void testCheckUnreferencedCommits() throws Exception {
lastCheckpoint = randomLongBetween(lastCheckpoint, lastMaxSeqNo);
commitList.add(mockIndexCommit(lastCheckpoint, lastMaxSeqNo, translogUUID, lastTranslogGen));
}
IndexCommit safeCommit = randomFrom(commitList);
globalCheckpoint.set(Long.parseLong(safeCommit.getUserData().get(SequenceNumbers.MAX_SEQ_NO)));
int safeCommitIndex = randomIntBetween(0, commitList.size() - 1);
globalCheckpoint.set(Long.parseLong(commitList.get(safeCommitIndex).getUserData().get(SequenceNumbers.MAX_SEQ_NO)));
commitList.forEach(this::resetDeletion);
indexPolicy.onCommit(commitList);
if (safeCommit == commitList.get(commitList.size() - 1)) {

if (safeCommitIndex == commitList.size() - 1) {
// Safe commit is the last commit - no need to clean up
assertThat(translogPolicy.getMinTranslogGenerationForRecovery(), equalTo(lastTranslogGen));
assertThat(translogPolicy.getTranslogGenerationOfLastCommit(), equalTo(lastTranslogGen));
assertThat(indexPolicy.hasUnreferencedCommits(), equalTo(false));
} else {
// Advanced but not enough
globalCheckpoint.set(randomLongBetween(globalCheckpoint.get(), lastMaxSeqNo - 1));
assertThat(indexPolicy.hasUnreferencedCommits(), equalTo(false));
// Advanced enough
// Advanced but not enough for any commit after the safe commit becomes safe
IndexCommit nextSafeCommit = commitList.get(safeCommitIndex + 1);
globalCheckpoint.set(randomLongBetween(globalCheckpoint.get(),
Long.parseLong(nextSafeCommit.getUserData().get(SequenceNumbers.MAX_SEQ_NO)) - 1));
assertFalse(indexPolicy.hasUnreferencedCommits());
// Advanced enough for some index commit becomes safe
globalCheckpoint.set(randomLongBetween(
Long.parseLong(nextSafeCommit.getUserData().get(SequenceNumbers.MAX_SEQ_NO)), lastMaxSeqNo));
assertTrue(indexPolicy.hasUnreferencedCommits());
// Advanced enough for the last commit becomes safe
globalCheckpoint.set(randomLongBetween(lastMaxSeqNo, Long.MAX_VALUE));
assertThat(indexPolicy.hasUnreferencedCommits(), equalTo(true));
commitList.forEach(this::resetDeletion);
indexPolicy.onCommit(commitList);
// Safe commit is the last commit - no need to clean up
Expand Down