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https://issues.apache.org/jira/browse/HDFS-7980?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14482513#comment-14482513
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Walter Su commented on HDFS-7980:
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I don't think we need to add a test case. It's too obvious
{{processFirstBlockReport}} will be called once.
> 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
> Attachments: HDFS-7980.001.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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