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https://issues.apache.org/jira/browse/HDFS-7980?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14696376#comment-14696376
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Zhihua Deng commented on HDFS-7980:
-----------------------------------
Recently, we encountered the same problem in our cluster of version 2.4.1
and created a
patch(https://github.com/dengzhhu653/hdfs-2.4.1/blob/master/hadoop-241.patch)
according to the patch attached. let the restarted NN process the first full
report by the faster processFirstBlockReport method, and add an condition
AddBlockResult.ADDED==result in addStoredBlockImmediate method when
FSNameSystem tries to invoke incrementSafeBlockCount method.
The problem is I am not so sure if there exists any potential issues of the
patch when I apply it to our cluster , any advises and opinions will be greatly
appreciated and taken seriously, thanks!
> Incremental BlockReport will dramatically slow down the startup of a namenode
> ------------------------------------------------------------------------------
>
> Key: HDFS-7980
> URL: https://issues.apache.org/jira/browse/HDFS-7980
> Project: Hadoop HDFS
> Issue Type: Bug
> Reporter: Hui Zheng
> Assignee: Walter Su
> Labels: 2.6.1-candidate
> Fix For: 2.7.1
>
> Attachments: HDFS-7980.001.patch, HDFS-7980.002.patch,
> HDFS-7980.003.patch, HDFS-7980.004.patch, HDFS-7980.004.repost.patch
>
>
> In the current implementation the datanode will call the
> reportReceivedDeletedBlocks() method that is a IncrementalBlockReport before
> calling the bpNamenode.blockReport() method. So in a large(several thousands
> of datanodes) and busy cluster it will slow down(more than one hour) the
> startup of namenode.
> {code}
> List<DatanodeCommand> blockReport() throws IOException {
> // send block report if timer has expired.
> final long startTime = now();
> if (startTime - lastBlockReport <= dnConf.blockReportInterval) {
> return null;
> }
> final ArrayList<DatanodeCommand> cmds = new ArrayList<DatanodeCommand>();
> // Flush any block information that precedes the block report. Otherwise
> // we have a chance that we will miss the delHint information
> // or we will report an RBW replica after the BlockReport already reports
> // a FINALIZED one.
> reportReceivedDeletedBlocks();
> lastDeletedReport = startTime;
> .........
> // Send the reports to the NN.
> int numReportsSent = 0;
> int numRPCs = 0;
> boolean success = false;
> long brSendStartTime = now();
> try {
> if (totalBlockCount < dnConf.blockReportSplitThreshold) {
> // Below split threshold, send all reports in a single message.
> DatanodeCommand cmd = bpNamenode.blockReport(
> bpRegistration, bpos.getBlockPoolId(), reports);
> {code}
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