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https://issues.apache.org/jira/browse/HDFS-14314?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16780153#comment-16780153
]
star commented on HDFS-14314:
-----------------------------
checkstyle seems not consistent.
Same code ".thenAnswer" at line 1000, 1002, 1003 has
indentation 6, which passes checking, While code at 1010 and 1024 throws error.
How to fix such error?
> fullBlockReportLeaseId should be reset after registering to NN
> --------------------------------------------------------------
>
> Key: HDFS-14314
> URL: https://issues.apache.org/jira/browse/HDFS-14314
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: datanode
> Affects Versions: 2.8.4
> Environment:
>
>
> Reporter: star
> Priority: Critical
> Fix For: 2.8.4
>
> Attachments: HDFS-14314-trunk.001.patch, HDFS-14314-trunk.001.patch,
> HDFS-14314-trunk.002.patch, HDFS-14314-trunk.003.patch,
> HDFS-14314-trunk.004.patch, HDFS-14314.0.patch, HDFS-14314.2.patch,
> HDFS-14314.patch
>
>
> since HDFS-7923 ,to rate-limit DN block report, DN will ask for a full
> block lease id from active NN before sending full block to NN. Then DN will
> send full block report together with lease id. If the lease id is invalid, NN
> will reject the full block report and log "not in the pending set".
> In a case when DN is doing full block reporting while NN is restarted.
> It happens that DN will later send a full block report with lease id
> ,acquired from previous NN instance, which is invalid to the new NN instance.
> Though DN recognized the new NN instance by heartbeat and reregister itself,
> it did not reset the lease id from previous instance.
> The issuse may cause DNs to temporarily go dead, making it unsafe to
> restart NN especially in hadoop cluster which has large amount of DNs.
> HDFS-12914 reported the issue without any clues why it occurred and remain
> unsolved.
> To make it clear, look at code below. We take it from method
> offerService of class BPServiceActor. We eliminate some code to focus on
> current issue. fullBlockReportLeaseId is a local variable to hold lease id
> from NN. Exceptions will occur at blockReport call when NN restarting, which
> will be caught by catch block in while loop. Thus fullBlockReportLeaseId will
> not be set to 0. After NN restarted, DN will send full block report which
> will be rejected by the new NN instance. DN will never send full block report
> until the next full block report schedule, about an hour later.
> Solution is simple, just reset fullBlockReportLeaseId to 0 after any
> exception or after registering to NN. Thus it will ask for a valid
> fullBlockReportLeaseId from new NN instance.
> {code:java}
> private void offerService() throws Exception {
> long fullBlockReportLeaseId = 0;
> //
> // Now loop for a long time....
> //
> while (shouldRun()) {
> try {
> final long startTime = scheduler.monotonicNow();
> //
> // Every so often, send heartbeat or block-report
> //
> final boolean sendHeartbeat = scheduler.isHeartbeatDue(startTime);
> HeartbeatResponse resp = null;
> if (sendHeartbeat) {
>
> boolean requestBlockReportLease = (fullBlockReportLeaseId == 0) &&
> scheduler.isBlockReportDue(startTime);
> scheduler.scheduleNextHeartbeat();
> if (!dn.areHeartbeatsDisabledForTests()) {
> resp = sendHeartBeat(requestBlockReportLease);
> assert resp != null;
> if (resp.getFullBlockReportLeaseId() != 0) {
> if (fullBlockReportLeaseId != 0) {
> LOG.warn(nnAddr + " sent back a full block report lease " +
> "ID of 0x" +
> Long.toHexString(resp.getFullBlockReportLeaseId()) +
> ", but we already have a lease ID of 0x" +
> Long.toHexString(fullBlockReportLeaseId) + ". " +
> "Overwriting old lease ID.");
> }
> fullBlockReportLeaseId = resp.getFullBlockReportLeaseId();
> }
>
> }
> }
>
>
> if ((fullBlockReportLeaseId != 0) || forceFullBr) {
> //Exception occurred here when NN restarting
> cmds = blockReport(fullBlockReportLeaseId);
> fullBlockReportLeaseId = 0;
> }
>
> } catch(RemoteException re) {
>
> } // while (shouldRun())
> } // offerService{code}
>
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