John Doe created MAPREDUCE-7507:
-----------------------------------
Summary: Interleaving of double execution getTask() can cause a
NullPointerException
Key: MAPREDUCE-7507
URL: https://issues.apache.org/jira/browse/MAPREDUCE-7507
Project: Hadoop Map/Reduce
Issue Type: Bug
Components: client
Affects Versions: 3.4.1
Reporter: John Doe
If the method `getTask()` in the class `TaskAttemptListenerImpl` is executed
twice, the interleaving can cause a concurrency bug (atomicity) and throw a
null pointer exception.
Suppose both executions reach the point before `
jvmIDToActiveAttemptMap.remove()`, the first executed one will behave normally,
but for the latter one, its `task` will be null and then get a null pointer
exception.
{code:java}
if (!jvmIDToActiveAttemptMap.containsKey(wJvmID)) {
LOG.info("JVM with ID: " + jvmId + " is invalid and will be killed.");
jvmTask = TASK_FOR_INVALID_JVM;
} else {
if (!launchedJVMs.contains(wJvmID)) {
jvmTask = null;
LOG.info("JVM with ID: " + jvmId
+ " asking for task before AM launch registered. Given null task");
} else {
// remove the task as it is no more needed and free up the memory.
// Also we have already told the JVM to process a task, so it is no
// longer pending, and further request should ask it to exit.
org.apache.hadoop.mapred.Task task =
jvmIDToActiveAttemptMap.remove(wJvmID);
launchedJVMs.remove(wJvmID);
LOG.info("JVM with ID: " + jvmId + " given task: " + task.getTaskID());
task.setEncryptedSpillKey(encryptedSpillKey);
jvmTask = new JvmTask(task, false);
}
}
{code}
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