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https://issues.apache.org/jira/browse/KAFKA-6345?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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radai rosenblatt resolved KAFKA-6345.
-------------------------------------
Resolution: Fixed
> NetworkClient.inFlightRequestCount() is not thread safe, causing
> ConcurrentModificationExceptions when sensors are read
> -----------------------------------------------------------------------------------------------------------------------
>
> Key: KAFKA-6345
> URL: https://issues.apache.org/jira/browse/KAFKA-6345
> Project: Kafka
> Issue Type: Bug
> Components: clients
> Affects Versions: 1.0.0
> Reporter: radai rosenblatt
> Assignee: Sean McCauliff
> Priority: Major
> Fix For: 1.1.0
>
>
> example stack trace (code is ~0.10.2.*)
> {code}
> java.util.ConcurrentModificationException:
> java.util.ConcurrentModificationException
> at java.util.HashMap$HashIterator.nextNode(HashMap.java:1429)
> at java.util.HashMap$ValueIterator.next(HashMap.java:1458)
> at
> org.apache.kafka.clients.InFlightRequests.inFlightRequestCount(InFlightRequests.java:109)
> at
> org.apache.kafka.clients.NetworkClient.inFlightRequestCount(NetworkClient.java:382)
> at
> org.apache.kafka.clients.producer.internals.Sender$SenderMetrics$1.measure(Sender.java:480)
> at
> org.apache.kafka.common.metrics.KafkaMetric.value(KafkaMetric.java:61)
> at
> org.apache.kafka.common.metrics.KafkaMetric.value(KafkaMetric.java:52)
> at
> org.apache.kafka.common.metrics.JmxReporter$KafkaMbean.getAttribute(JmxReporter.java:183)
> at
> org.apache.kafka.common.metrics.JmxReporter$KafkaMbean.getAttributes(JmxReporter.java:193)
> at
> com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.getAttributes(DefaultMBeanServerInterceptor.java:709)
> at
> com.sun.jmx.mbeanserver.JmxMBeanServer.getAttributes(JmxMBeanServer.java:705)
> {code}
> looking at latest trunk, the code is still vulnerable:
> # NetworkClient.inFlightRequestCount() eventually iterates over
> InFlightRequests.requests.values(), which is backed by a (non-thread-safe)
> HashMap
> # this will be called from the "requests-in-flight" sensor's measure() method
> (Sender.java line ~765 in SenderMetrics ctr), which would be driven by some
> thread reading JMX values
> # HashMap in question would also be updated by some client io thread calling
> NetworkClient.doSend() - which calls into InFlightRequests.add())
> i guess the only upside is that this exception will always happen on the
> thread reading the JMX values and never on the actual client io thread ...
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