[HDFS-dev] [jira] [Created] (HDFS-2081) trying to read configuration in hdfs write path might result in deadlock

trying to read configuration in hdfs write path might result in deadlock
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Key: HDFS-2081
URL: https://issues.apache.org/jira/browse/HDFS-2081
Project: Hadoop HDFS
Issue Type: Bug
Affects Versions: 0.23.0
Environment: MR-279 branch. This is specific to yarn since yarn tries to write the configuration file to hdfs while holding the lock of the configuration file.
Reporter: John George
Assignee: John George
Fix For: 0.23.0

Attachments: HDFS-2081.patch


While trying to run yarn with 1024 block size, it looks as though the dfsclients are hung waiting to write to DN. The reason is because yarn holds the configuration file lock and tries to write to hdfs which in turn tries to read from the configuration which requires the same lock.
The temporary fix is to make sure that dfsclient threads dont read the config in its write path. There might be better long term solutions like read/write locks and this needs to be investigated in another JIRA.