AHeise commented on a change in pull request #16971:
URL: https://github.com/apache/flink/pull/16971#discussion_r695551636
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File path:
flink-runtime/src/test/java/org/apache/flink/runtime/testutils/InMemoryReporter.java
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@@ -159,17 +168,51 @@ void applyRemovals() {
@Override
public void notifyOfAddedMetric(Metric metric, String metricName,
MetricGroup group) {
- MetricGroup metricGroup = unwrap(group);
- LOG.debug("Registered {} @ {}", metricName, metricGroup);
- synchronized (this) {
- metrics.computeIfAbsent(metricGroup, dummy -> new
HashMap<>()).put(metricName, metric);
+ if (captureMode != CaptureMode.NONE) {
+ MetricGroup metricGroup = unwrap(group);
+ LOG.debug("Registered {} @ {}", metricName, metricGroup);
+ synchronized (this) {
+ metrics.computeIfAbsent(metricGroup, dummy -> new HashMap<>())
Review comment:
I'm always having a hard time to reason about nested data structures and
their synchronization behavior. For example, could a metric be lost because we
eagerly deregister the last metric at the same time a new metric is added? Then
`notifyOfRemovedMetric` might fetch the group first and determines it is empty.
At the same time, `notifyOfAddedMetric` has fetched the still-registered but
empty group and added the new metric. But this is now lost since
`notifyOfRemovedMetric` eventually removes the group.
So before trying to optimize it, I first would go with the simplest
approach. If we see it becomes a bottle-neck (which I doubt) we can still
optimize it later. Then I might have the mental capacity for thinking all cases
through (or we find someone else).
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