szetszwo commented on code in PR #1311:
URL: https://github.com/apache/ratis/pull/1311#discussion_r2518897416
##########
ratis-server/src/main/java/org/apache/ratis/server/impl/ReadRequests.java:
##########
@@ -79,35 +90,36 @@ private void handleTimeout(long readIndex) {
/** Complete all the entries less than or equal to the given applied
index. */
- synchronized void complete(Long appliedIndex) {
+ synchronized void complete(long appliedIndex) {
+ if (appliedIndex > lastAppliedIndex) {
+ lastAppliedIndex = appliedIndex;
+ } else {
+ // appliedIndex <= lastAppliedIndex: nothing to do
+ if (!sorted.isEmpty()) {
+ // Assert: all keys > lastAppliedIndex.
+ final long first = sorted.firstKey();
+ Preconditions.assertTrue(first > lastAppliedIndex,
+ () -> "first = " + first + " <= lastAppliedIndex = " +
lastAppliedIndex);
+ }
+ return;
+ }
final NavigableMap<Long, CompletableFuture<Long>> headMap =
sorted.headMap(appliedIndex, true);
headMap.values().forEach(f -> f.complete(appliedIndex));
headMap.clear();
}
}
private final ReadIndexQueue readIndexQueue;
- private final StateMachine stateMachine;
- ReadRequests(RaftProperties properties, StateMachine stateMachine) {
- this.readIndexQueue = new
ReadIndexQueue(RaftServerConfigKeys.Read.timeout(properties));
- this.stateMachine = stateMachine;
+ ReadRequests(long appliedIndex, RaftProperties properties) {
+ this.readIndexQueue = new ReadIndexQueue(appliedIndex,
RaftServerConfigKeys.Read.timeout(properties));
}
- Consumer<Long> getAppliedIndexConsumer() {
+ LongConsumer getAppliedIndexConsumer() {
return readIndexQueue::complete;
}
CompletableFuture<Long> waitToAdvance(long readIndex) {
- final long lastApplied = stateMachine.getLastAppliedTermIndex().getIndex();
- if (lastApplied >= readIndex) {
- return CompletableFuture.completedFuture(lastApplied);
- }
- final CompletableFuture<Long> f = readIndexQueue.add(readIndex);
- final long current = stateMachine.getLastAppliedTermIndex().getIndex();
- if (current > lastApplied) {
- readIndexQueue.complete(current);
- }
Review Comment:
@SzyWilliam , thanks for reminding me about RATIS-1927!
In this pr, the check is moved to a synchronized block in
ReadIndexQueue.add(..) and `lastAppliedIndex` is also updated synchronously.
So, it won't have a race condition anymore.
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