wuyi created SPARK-23888:
----------------------------
Summary: speculative task should not run on a given host where
another attempt is already running on
Key: SPARK-23888
URL: https://issues.apache.org/jira/browse/SPARK-23888
Project: Spark
Issue Type: Bug
Components: Spark Core
Affects Versions: 2.3.0
Reporter: wuyi
Fix For: 2.3.0
There's a bug in:
{code:java}
/** Check whether a task is currently running an attempt on a given host */
private def hasAttemptOnHost(taskIndex: Int, host: String): Boolean = {
taskAttempts(taskIndex).exists(_.host == host)
}
{code}
This will ignore hosts which have finished attempts, so we should check whether
the attempt is currently running on the given host.
And it is possible for a speculative task to run on a host where another
attempt failed here before.
Assume we have only two machines: host1, host2. We first run task0.0 on host1.
Then, due to a long time waiting for task0.0, we launch a speculative task0.1
on host2. And, task0.1 finally failed on host1, but it can not re-run since
there's already a copy running on host2. After another long time, we launch a
new speculative task0.2. And, now, we can run task0.2 on host1 again, since
there's no more running attempt on host1.
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