Lucas Bradstreet created KAFKA-12791:
----------------------------------------
Summary: ConcurrentModificationException in KafkaProducer
constructor
Key: KAFKA-12791
URL: https://issues.apache.org/jira/browse/KAFKA-12791
Project: Kafka
Issue Type: Bug
Reporter: Lucas Bradstreet
Recently we have noticed multiple instances where KafkaProducers have failed to
constructe due to the following exception:
{noformat}
org.apache.kafka.common.KafkaException: Failed to construct kafka producer at
org.apache.kafka.clients.producer.KafkaProducer.<init>(KafkaProducer.java:440)
at
org.apache.kafka.clients.producer.KafkaProducer.<init>(KafkaProducer.java:291)
at
org.apache.kafka.clients.producer.KafkaProducer.<init>(KafkaProducer.java:318)
java.base/java.lang.Thread.run(Thread.java:832) Caused by:
java.util.ConcurrentModificationException at
java.base/java.util.HashMap$HashIterator.nextNode(HashMap.java:1584) at
java.base/java.util.HashMap$KeyIterator.next(HashMap.java:1607) at
java.base/java.util.AbstractSet.removeAll(AbstractSet.java:171) at
org.apache.kafka.common.config.AbstractConfig.unused(AbstractConfig.java:221)
at
org.apache.kafka.common.config.AbstractConfig.logUnused(AbstractConfig.java:379)
at
org.apache.kafka.clients.producer.KafkaProducer.<init>(KafkaProducer.java:433)
... 9 more exception.class:org.apache.kafka.common.KafkaException
exception.message:Failed to construct kafka producer
{noformat}
It appears that this is due to the fact that `used` below is a synchronized set:
{code:java}
public Set<String> unused() {
Set<String> keys = new HashSet<>(originals.keySet());
keys.removeAll(used);
return keys;
}{code}
It appears that `used` is being modified while removeAll is being called. This
may be due to the way that keys are added to it when used:
{code:java}
protected Object get(String key) {
if (!values.containsKey(key))
throw new ConfigException(String.format("Unknown configuration '%s'", key));
used.add(key);
return values.get(key);
}{code}
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