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https://issues.apache.org/jira/browse/HDFS-7097?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14225424#comment-14225424
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Hudson commented on HDFS-7097:
------------------------------
FAILURE: Integrated in Hadoop-trunk-Commit #6605 (See
[https://builds.apache.org/job/Hadoop-trunk-Commit/6605/])
HDFS-7097. Allow block reports to be processed during checkpointing on standby
name node. (kihwal via wang) (wang: rev
f43a20c529ac3f104add95b222de6580757b3763)
*
hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/ha/StandbyCheckpointer.java
*
hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSImageFormat.java
* hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
*
hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/ha/EditLogTailer.java
*
hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSNamesystem.java
*
hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/ha/TestStandbyCheckpoints.java
> Allow block reports to be processed during checkpointing on standby name node
> -----------------------------------------------------------------------------
>
> Key: HDFS-7097
> URL: https://issues.apache.org/jira/browse/HDFS-7097
> Project: Hadoop HDFS
> Issue Type: Bug
> Reporter: Kihwal Lee
> Assignee: Kihwal Lee
> Priority: Critical
> Attachments: HDFS-7097.patch, HDFS-7097.patch, HDFS-7097.patch,
> HDFS-7097.patch, HDFS-7097.ultimate.trunk.patch
>
>
> On a reasonably busy HDFS cluster, there are stream of creates, causing data
> nodes to generate incremental block reports. When a standby name node is
> checkpointing, RPC handler threads trying to process a full or incremental
> block report is blocked on the name system's {{fsLock}}, because the
> checkpointer acquires the read lock on it. This can create a serious problem
> if the size of name space is big and checkpointing takes a long time.
> All available RPC handlers can be tied up very quickly. If you have 100
> handlers, it only takes 34 file creates. If a separate service RPC port is
> not used, HA transition will have to wait in the call queue for minutes. Even
> if a separate service RPC port is configured, hearbeats from datanodes will
> be blocked. A standby NN with a big name space can lose all data nodes after
> checkpointing. The rpc calls will also be retransmitted by data nodes many
> times, filling up the call queue and potentially causing listen queue
> overflow.
> Since block reports are not modifying any state that is being saved to
> fsimage, I propose letting them through during checkpointing.
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