Always report healthy when instance has caught up with outstanding tasks Once the instance has caught up with outstanding pull-replication tasks on startup, we consider the node healthy and ready to receive write traffic. As such, any subsequent invocations of the check should return a healthy status, regardless of pending or inflight tasks being present. Bug: Issue 312895374 Change-Id: I831dbb723a8a3af15eb12331e6073396534cdde8

diff --git a/src/main/java/com/googlesource/gerrit/plugins/replication/pull/health/PullReplicationTasksHealthCheck.java b/src/main/java/com/googlesource/gerrit/plugins/replication/pull/health/PullReplicationTasksHealthCheck.java
index a621778..778a6cc 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/replication/pull/health/PullReplicationTasksHealthCheck.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/replication/pull/health/PullReplicationTasksHealthCheck.java

@@ -46,6 +46,7 @@
   private final SourcesCollection sourcesCollection;
   private final Ticker ticker;
   private Optional<Long> successfulSince = Optional.empty();
+  private boolean isCaughtUp;
 
   @Inject
   public PullReplicationTasksHealthCheck(
@@ -86,6 +87,9 @@
 
   @Override
   protected Result doCheck() throws Exception {
+    if (isCaughtUp) {
+      return Result.PASSED;
+    }
     long checkTime = ticker.read();
     List<Source> sources = sourcesCollection.getAll();
     boolean hasNoOutstandingTasks =
@@ -108,9 +112,9 @@
   }
 
   private HealthCheck.Result reportResult(long checkTime) {
-    return successfulSince
-        .filter(ss -> checkTime >= ss + periodOfTimeNanos)
-        .map(ss -> Result.PASSED)
-        .orElse(Result.FAILED);
+    Optional<Result> maybePassed =
+        successfulSince.filter(ss -> checkTime >= ss + periodOfTimeNanos).map(ss -> Result.PASSED);
+    isCaughtUp = maybePassed.isPresent();
+    return maybePassed.orElse(Result.FAILED);
   }
 }

diff --git a/src/main/resources/Documentation/healthcheck.md b/src/main/resources/Documentation/healthcheck.md
index 3b84642..afe773b 100644
--- a/src/main/resources/Documentation/healthcheck.md
+++ b/src/main/resources/Documentation/healthcheck.md

@@ -2,8 +2,8 @@
 ==============
 
 The @PLUGIN@ plugin registers the `pull-replication-outstanding-tasks`
-healthcheck. This check will mark a gerrit instance as healthy
-only when the node has caught up with all the outstanding
+healthcheck. This check will mark a gerrit instance as healthy upon
+startup only when the node has caught up with all the outstanding
 pull-replication tasks. The goal is to mark the node as healthy when it
 is ready to receive write traffic. "Caught up" means:
 
@@ -14,6 +14,10 @@
 
 See [Healthcheck based on replication tasks](https://issues.gerritcodereview.com/issues/312895374) for more details.
 
+**It is worth noting that once the healthcheck eventually succeeds and
+the instance is marked healthy, the check is then skipped (ie any
+subsequent invocations will always mark the instance as healthy
+irrespective of any pending or inflight tasks being present).**
 
 Health check configuration
 --------------------------

diff --git a/src/test/java/com/googlesource/gerrit/plugins/replication/pull/health/PullReplicationTasksHealthCheckTest.java b/src/test/java/com/googlesource/gerrit/plugins/replication/pull/health/PullReplicationTasksHealthCheckTest.java
index 6dfbc03..06fa996 100644
--- a/src/test/java/com/googlesource/gerrit/plugins/replication/pull/health/PullReplicationTasksHealthCheckTest.java
+++ b/src/test/java/com/googlesource/gerrit/plugins/replication/pull/health/PullReplicationTasksHealthCheckTest.java

@@ -179,6 +179,26 @@
     assertThat(check.run().result).isEqualTo(HealthCheck.Result.PASSED);
   }
 
+  @Test
+  public void shouldAlwaysReportHealthyAfterItHasCaughtUpWithOutstandingTasks() {
+    int numCheckIterations = 2;
+    when(source.pendingTasksCount()).thenReturn(0L, 0L, 1L);
+    when(source.inflightTasksCount()).thenReturn(0L);
+
+    Injector injector = testInjector(new TestModule(List.of(), periodOfTimeMillisStr));
+    PullReplicationTasksHealthCheck check =
+        injector.getInstance(PullReplicationTasksHealthCheck.class);
+
+    assertThat(
+            runNTimes(
+                numCheckIterations,
+                check,
+                () -> fakeTicker.advance(Duration.ofMillis(periodOfTimeMillis))))
+        .containsExactly(HealthCheck.Result.FAILED, HealthCheck.Result.PASSED);
+
+    assertThat(check.run().result).isEqualTo(HealthCheck.Result.PASSED);
+  }
+
   private Injector testInjector(AbstractModule testModule) {
     return Guice.createInjector(new HealthCheckExtensionApiModule(), testModule);
   }