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https://issues.apache.org/jira/browse/KAFKA-14119?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Eric Wu resolved KAFKA-14119.
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Resolution: Not A Bug
> Sensor in metrics has potential thread safety issues
> ----------------------------------------------------
>
> Key: KAFKA-14119
> URL: https://issues.apache.org/jira/browse/KAFKA-14119
> Project: Kafka
> Issue Type: Bug
> Components: metrics
> Reporter: Eric Wu
> Priority: Major
>
> There are potential issues of a `Sensor` not being protected from race
> conditions when it
> [records|https://github.com/apache/kafka/blob/6ac58ac6fcd53a512ea0bc0b3dc66f49870ff0cb/clients/src/main/java/org/apache/kafka/common/metrics/Sensor.java#L230]
> a value.
> It can be reproduced with a unit test, e.g., in `SensorTest`:
> {code:java}
> @Test
> public void testSensorRecordThreadSafety() {
> Time time = new MockTime(0, System.currentTimeMillis(), 0);
> Metrics metrics = new Metrics(time);
> Sensor sensor = metrics.sensor("sensor");
> MetricName metric = new MetricName("test", "test", "test",
> Collections.emptyMap());
> sensor.add(metric, new Value());
> int totalRequests = 10;
> AtomicInteger count = new AtomicInteger();
> Executor threadPool = Executors.newFixedThreadPool(totalRequests);
> CompletableFuture[] futures = new CompletableFuture[totalRequests];
> for (int i = 0; i < totalRequests; i++) {
> futures[i] = CompletableFuture.runAsync(() -> {
> try {
> Thread.sleep(10); // to make it easier to repro
> } catch (InterruptedException e) {
> throw new RuntimeException(e);
> }
> sensor.record(count.addAndGet(1));
> }, threadPool);
> }
> CompletableFuture.allOf(futures).join();
>
> assertEquals(1, sensor.metrics().size());
> double value = (double) sensor.metrics().get(0).metricValue();
> assertEquals(totalRequests, value);
> }{code}
> It needs some tweaks to make the fields visible in the test. Given a few
> runs, the test should fail which demonstrates the thread safety issue.
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