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https://issues.apache.org/jira/browse/HDFS-15794?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17272999#comment-17272999
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Kihwal Lee commented on HDFS-15794:
-----------------------------------
{quote}The problem here is that when the NameNode is blocked in processing the
IBR, the FBR requested by the DN from the NameNode will be affected. Similarly,
when the NameNode processing FBR is blocked.
{quote}
The serial processing of IBR and FBR is not a side-effect of way a data
structure is used (single queue). In current namespace and block manager
design, each report is processed with the fsn write lock held. The queue made
it possible to process multiple IBRs under one lock, thus increasing
throughput. Having multiple queues for IBRs and FBRs won't help with
concurrency. In fact, it will complicate things, as it needs to maintain
certain processing order across multiple queues.
In order to make a meaningful performance improvement, we have to make NN
perform concurrent block report processing.
> IBR and FBR use different queues to load data.
> ----------------------------------------------
>
> Key: HDFS-15794
> URL: https://issues.apache.org/jira/browse/HDFS-15794
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: namenode
> Reporter: JiangHua Zhu
> Assignee: JiangHua Zhu
> Priority: Major
>
> When DataNode reports data to NameNode, IBR and FBR are included here.
> After the NameNode receives the DataNode request, it temporarily stores the
> data in a queue, here it refers to
> BlockManager#BlockReportProcessingThread#queue.
> NameNodeRpcServer#blockReport()
> for (int r = 0; r <reports.length; r++) {
> final BlockListAsLongs blocks = reports[r].getBlocks();
> final int index = r;
> noStaleStorages = bm.runBlockOp(() ->
> bm.processReport(nodeReg, reports[index].getStorage(),
> blocks, context));
> }
> NameNodeRpcServer#blockReport()
> for (final StorageReceivedDeletedBlocks r: receivedAndDeletedBlocks) {
> bm.enqueueBlockOp(new Runnable() {
> @Override
> public void run() {
> try {
> namesystem.processIncrementalBlockReport(nodeReg, r);
> } catch (Exception ex) {
> // usually because the node is unregistered/dead. next heartbeat
> // will correct the problem
> blockStateChangeLog.error(
> "*BLOCK* NameNode.blockReceivedAndDeleted: "
> + "failed from "+ nodeReg + ":" + ex.getMessage());
> }
> }
> });
> }
> The problem here is that when the NameNode is blocked in processing the IBR,
> the FBR requested by the DN from the NameNode will be affected. Similarly,
> when the NameNode processing FBR is blocked.
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