szetszwo commented on code in PR #688:
URL: https://github.com/apache/ratis/pull/688#discussion_r926948970
##########
ratis-server-api/src/main/java/org/apache/ratis/server/RaftServerConfigKeys.java:
##########
@@ -285,6 +285,15 @@ static void setPurgeUptoSnapshotIndex(RaftProperties
properties, boolean shouldP
setBoolean(properties::setBoolean, PURGE_UPTO_SNAPSHOT_INDEX_KEY,
shouldPurgeUptoSnapshotIndex);
}
+ String PURGE_PRESERVE_LOG_NUM_KEY = PREFIX + "purge.preserve.log.num";
Review Comment:
"preserve" is a good word choice. Let's call it ".purge. preservation" so
that it is similar to ".purge.gap".
BTW, it needs a "." in the beginning.
##########
ratis-server/src/main/java/org/apache/ratis/server/impl/StateMachineUpdater.java:
##########
@@ -297,7 +299,8 @@ private void takeSnapshot() {
CommitInfoProto::getCommitIndex);
purgeIndex = LongStream.concat(LongStream.of(i),
commitIndexStream).min().orElse(i);
}
- raftLog.purge(purgeIndex);
+ final long purgeIndexWithPreserve = Math.max(0L, purgeIndex -
purgePreserveLogNum);
+ raftLog.purge(purgeIndexWithPreserve);
Review Comment:
Let's change it in RaftLogBase.purge(..) so that the new code will be next
to the purgeGap code. We may add a `purgePreservation` field and use it as
below
```
+++
b/ratis-server/src/main/java/org/apache/ratis/server/raftlog/RaftLogBase.java
@@ -301,6 +301,10 @@ public abstract class RaftLogBase implements RaftLog {
@Override
public final CompletableFuture<Long> purge(long suggestedIndex) {
+ if (purgePreservation > 0) {
+ final long currentIndex = getNextIndex() - 1;
+ suggestedIndex = Math.min(suggestedIndex, currentIndex -
purgePreservation);
+ }
final long lastPurge = purgeIndex.get();
if (suggestedIndex - lastPurge < purgeGap) {
return CompletableFuture.completedFuture(lastPurge);
```
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