jsancio commented on code in PR #22505:
URL: https://github.com/apache/kafka/pull/22505#discussion_r3375083375
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raft/src/main/java/org/apache/kafka/raft/internals/BlockingMessageQueue.java:
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@@ -17,60 +17,51 @@
package org.apache.kafka.raft.internals;
import org.apache.kafka.common.errors.InterruptException;
-import org.apache.kafka.common.protocol.ApiMessage;
-import org.apache.kafka.raft.RaftMessage;
import org.apache.kafka.raft.RaftMessageQueue;
+import java.util.Optional;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;
public class BlockingMessageQueue implements RaftMessageQueue {
- private static final RaftMessage WAKEUP_MESSAGE = new RaftMessage() {
- @Override
- public int correlationId() {
- return 0;
- }
-
- @Override
- public ApiMessage data() {
- return null;
- }
- };
-
- private final BlockingQueue<RaftMessage> queue = new
LinkedBlockingQueue<>();
- private final AtomicInteger size = new AtomicInteger(0);
+ private final BlockingQueue<QueueEntry> queue = new
LinkedBlockingQueue<>();
+ private final AtomicInteger messageCount = new AtomicInteger(0);
@Override
- public RaftMessage poll(long timeoutMs) {
+ public Optional<QueueEntry> poll(long timeoutMs) {
try {
- RaftMessage message = queue.poll(timeoutMs, TimeUnit.MILLISECONDS);
- if (message == null || message == WAKEUP_MESSAGE) {
- return null;
- } else {
- size.decrementAndGet();
- return message;
+ var entry = queue.poll(timeoutMs, TimeUnit.MILLISECONDS);
+ while (entry != null && entry.message() == null) {
+ // Drain the queue of all of the wakeup events
+ entry = queue.poll();
+ }
+ if (entry != null) {
+ messageCount.decrementAndGet();
}
+ return Optional.ofNullable(entry);
} catch (InterruptedException e) {
throw new InterruptException(e);
}
}
@Override
- public void add(RaftMessage message) {
- queue.add(message);
- size.incrementAndGet();
+ public void add(QueueEntry entry) {
+ queue.add(entry);
+ if (entry.message() != null) {
+ messageCount.incrementAndGet();
+ }
Review Comment:
Technically, the user can blockingMessageQueue.add(new QueueEntry(null)).
This would succeed and the current implementation would treat it as a wake up
message.
The other solution is to throw an illegal argument exception if message is
null in the BlockingMessageQueue::add method. I was originally going to add
that but maybe it is okay for BlockingMessageQueue to just treat those the same
as BlockingMessageQueue::wakeup. This is what the current code does.
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