[
https://issues.apache.org/jira/browse/HDFS-7980?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14377689#comment-14377689
]
Hui Zheng commented on HDFS-7980:
---------------------------------
In our environment there are over 3000 datanodes, 100 million file and 150
million blocks.
When all the datanodes are working, it will take more than one hour to restart
the namenode(the time is almost used for block report).
But if we
first stop all the datanodes,
then restart the namenode,
last start all the datanodes after the namenode finishes loading editlog,
it will only take around 20 minutes.
> 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
>
> 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}
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
