[GitHub] [ratis] szetszwo commented on a change in pull request #611: RATIS-1534. SegmentedRaftLogWorker support async flush

[GitBox <gi...@apache.org>]

szetszwo commented on a change in pull request #611:
URL: https://github.com/apache/ratis/pull/611#discussion_r814852687



##########
File path: ratis-server/src/main/java/org/apache/ratis/server/raftlog/segmented/SegmentedRaftLogWorker.java
##########
@@ -321,6 +326,10 @@ private void run() {
           }
           task.done();
         }
+        if (shouldFlush()) {
+          raftLogMetrics.onRaftLogFlush();
+          flushWrites();
+        }

Review comment:
       Good catch.  We should check flush in the loop.  Let's refactor the code a little be as below:
   ```
   @@ -321,6 +326,7 @@ class SegmentedRaftLogWorker {
              }
              task.done();
            }
   +        flushIfNecessary();
          } catch (InterruptedException e) {
            Thread.currentThread().interrupt();
            if (running) {
   @@ -344,13 +350,17 @@ class SegmentedRaftLogWorker {
      }
    
      private boolean shouldFlush() {
   -    return pendingFlushNum >= forceSyncNum ||
   -        (pendingFlushNum > 0 && queue.isEmpty());
   +    if (out == null) {
   +      return false;
   +    } else if (pendingFlushNum >= forceSyncNum) {
   +      return true;
   +    }
   +    return pendingFlushNum > 0 && queue.isEmpty() && lastFlush.elapsedTime().compareTo(flushIntervalMin) > 0;
      }
    
      @SuppressFBWarnings("NP_NULL_PARAM_DEREF")
   -  private void flushWrites() throws IOException {
   -    if (out != null) {
   +  private void flushIfNecessary() throws IOException {
   +    if (shouldFlush()) {
          LOG.debug("{}: flush {}", name, out);
          final Timer.Context timerContext = logFlushTimer.time();
          try {
   @@ -369,6 +379,7 @@ class SegmentedRaftLogWorker {
            }
          } finally {
            timerContext.stop();
   +        lastFlush = Timestamp.currentTime();
          }
          updateFlushedIndexIncreasingly();
        }
   @@ -513,10 +524,7 @@ class SegmentedRaftLogWorker {
          out.write(entry);
          lastWrittenIndex = entry.getIndex();
          pendingFlushNum++;
   -      if (shouldFlush()) {
   -        raftLogMetrics.onRaftLogFlush();
   -        flushWrites();
   -      }
   +      flushIfNecessary();
        }
   ```
   




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