philipnee commented on code in PR #14752:
URL: https://github.com/apache/kafka/pull/14752#discussion_r1392962733
##########
clients/src/main/java/org/apache/kafka/clients/consumer/internals/WakeupTrigger.java:
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@@ -24,85 +25,133 @@
import java.util.concurrent.atomic.AtomicReference;
/**
- * Ensures blocking APIs can be woken up by the consumer.wakeup().
+ * Ensures blocking APIs can be woken up by {@link Consumer#wakeup()}.
*/
-public class WakeupTrigger {
- private final AtomicReference<Wakeupable> pendingTask = new
AtomicReference<>(null);
+class WakeupTrigger {
+
+ private final static Object FAIL_NEXT_MARKER = new Object();
+ private final AtomicReference<Object> activeTask = new
AtomicReference<>(null);
/**
- * Wakeup a pending task. If there isn't any pending task, return a
WakeupFuture, so that the subsequent call
- * would know wakeup was previously called.
- * <p>
- * If there are active tasks, complete it with WakeupException, then unset
pending task (return null here.
- * If the current task has already been woken-up, do nothing.
+ * Wakeup a pending task.
+ *
+ * <p/>
+ *
+ * There are three cases that can happen when this method is invoked:
+ *
+ * <ul>
+ * <li>
+ * If there is no <em>active</em> task from a previous call to
{@code setActiveTask}, we set an
+ * internal indicator that the <em>next</em> attempt to start a
long-running task (via a call to
+ * {@link #setActiveTask(CompletableFuture)}) will fail with a
{@link WakeupException}.
+ * </li>
+ * <li>
+ * If there is an <em>active</em> task (i.e. there was a previous
call to
+ * {@link #setActiveTask(CompletableFuture)} for a long-running
task), fail it via
+ * {@link CompletableFuture#completeExceptionally(Throwable)} and
then clear the <em>active</em> task.
+ * </li>
+ * <li>
+ * If there is already an pending wakeup from a previous call to
{@link Consumer#wakeup()}, do nothing.
Review Comment:
"a pending"
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