Todd Lipcon created MAPREDUCE-7128:
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Summary: LocalJobRunner may fail due to metrics name collision
Key: MAPREDUCE-7128
URL: https://issues.apache.org/jira/browse/MAPREDUCE-7128
Project: Hadoop Map/Reduce
Issue Type: Bug
Reporter: Todd Lipcon
Running Hive in local mode, I got the following failure:
{code}
Caused by: org.apache.hadoop.metrics2.MetricsException: Metrics source
LocalJobRunnerMetrics-1090927800 already exists!
at
org.apache.hadoop.metrics2.lib.DefaultMetricsSystem.newSourceName(DefaultMetricsSystem.java:152)
at
org.apache.hadoop.metrics2.lib.DefaultMetricsSystem.sourceName(DefaultMetricsSystem.java:125)
at
org.apache.hadoop.metrics2.impl.MetricsSystemImpl.register(MetricsSystemImpl.java:229)
at
org.apache.hadoop.mapred.LocalJobRunnerMetrics.create(LocalJobRunnerMetrics.java:46)
...
{code}
It seems that it tries to generate a unique metrics source name using a random
32-bit integer. When running some longer-lived program that runs many separate
jobs (such as HS2) this can easily collide.
https://en.wikipedia.org/wiki/Birthday_attack has some tables for the
probabilities.
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