[jira] [Created] (KAFKA-4950) ConcurrentModificationException when iterating over Kafka Metrics

[Dumitru Postoronca (JIRA)]

Dumitru Postoronca created KAFKA-4950:
-----------------------------------------

             Summary: ConcurrentModificationException when iterating over Kafka 
Metrics
                 Key: KAFKA-4950
                 URL: https://issues.apache.org/jira/browse/KAFKA-4950
             Project: Kafka
          Issue Type: Bug
    Affects Versions: 0.10.1.1
            Reporter: Dumitru Postoronca
            Priority: Minor


It looks like the when calling {{PartitionStates.partitionSet()}}, while the 
resulting Hashmap is being built, the internal state of the allocations can 
change, which leads to ConcurrentModificationException during the copy 
operation.

{code}
java.util.ConcurrentModificationException
        at 
java.util.LinkedHashMap$LinkedHashIterator.nextNode(LinkedHashMap.java:719)
        at 
java.util.LinkedHashMap$LinkedKeyIterator.next(LinkedHashMap.java:742)
        at java.util.AbstractCollection.addAll(AbstractCollection.java:343)
        at java.util.HashSet.<init>(HashSet.java:119)
        at 
org.apache.kafka.common.internals.PartitionStates.partitionSet(PartitionStates.java:66)
        at 
org.apache.kafka.clients.consumer.internals.SubscriptionState.assignedPartitions(SubscriptionState.java:291)
        at 
org.apache.kafka.clients.consumer.internals.ConsumerCoordinator$ConsumerCoordinatorMetrics$1.measure(ConsumerCoordinator.java:783)
        at 
org.apache.kafka.common.metrics.KafkaMetric.value(KafkaMetric.java:61)
        at 
org.apache.kafka.common.metrics.KafkaMetric.value(KafkaMetric.java:52)
{code}

{code}
// client code:
private final KafkaConsumer client;

        Map<MetricName, org.apache.kafka.common.Metric> m = client.metrics();
        for (Map.Entry<MetricName, org.apache.kafka.common.Metric> e : 
m.entrySet()) {
            gauges.put(name(e.getKey().group(), e.getKey().name(), "count"), 
new Gauge<Double>() {
                @Override
                public Double getValue() {
                    return e.getValue().value(); // exception thrown here
                }
            });
        }

{code}



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