Add an assert to detect double decrementing of ingest metrics (#81450)

elastic · Dec 7, 2021 · 9d793e0 · 9d793e0
1 parent 8ba6f55
commit 9d793e0
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Showing 2 changed files with 16 additions and 1 deletion.
diff --git a/server/src/main/java/org/elasticsearch/ingest/IngestMetric.java b/server/src/main/java/org/elasticsearch/ingest/IngestMetric.java
@@ -52,7 +52,8 @@ void preIngest() {
      * @param ingestTimeInNanos The time it took to perform the action.
      */
     void postIngest(long ingestTimeInNanos) {
-        ingestCurrent.decrementAndGet();
+        long current = ingestCurrent.decrementAndGet();
+        assert current >= 0 : "ingest metric current count double-decremented";
         this.ingestTimeInNanos.inc(ingestTimeInNanos);
         ingestCount.inc();
     }

diff --git a/server/src/test/java/org/elasticsearch/ingest/IngestMetricTests.java b/server/src/test/java/org/elasticsearch/ingest/IngestMetricTests.java
@@ -31,4 +31,18 @@ public void testIngestTimeInNanos() {
         assertThat(1L, equalTo(metric.createStats().getIngestTimeInMillis()));
     }
 
+    public void testPostIngestDoubleDecrement() {
+        IngestMetric metric = new IngestMetric();
+
+        metric.preIngest();
+        assertThat(1L, equalTo(metric.createStats().getIngestCurrent()));
+
+        metric.postIngest(500000L);
+        assertThat(0L, equalTo(metric.createStats().getIngestCurrent()));
+
+        // the second postIngest triggers an assertion error
+        expectThrows(AssertionError.class, () -> metric.postIngest(500000L));
+        assertThat(-1L, equalTo(metric.createStats().getIngestCurrent()));
+    }
+
 }