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https://issues.apache.org/jira/browse/HDFS-10301?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15335100#comment-15335100
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Colin Patrick McCabe commented on HDFS-10301:
---------------------------------------------
{code}
+ if (context.getTotalRpcs() == context.getCurRpc() + 1) {
+ long leaseId = this.getBlockReportLeaseManager().removeLease(node);
+ BlockManagerFaultInjector.getInstance().
+ removeBlockReportLease(node, leaseId);
}
+ LOG.debug("Processing RPC with index " + context.getCurRpc()
+ + " out of total " + context.getTotalRpcs() + " RPCs in "
+ + "processReport 0x" +
+ Long.toHexString(context.getReportId()));
}
{code}
This won't work in the presence of reordered RPCs. If the RPCs are reordered
so that curRpc 1 arrives before curRpc 0, the lease will be removed and RPC 0
will be rejected.
{code}
for (int r = 0; r < reports.length; r++) {
final BlockListAsLongs blocks = reports[r].getBlocks();
if (blocks != BlockListAsLongs.STORAGE_REPORT_ONLY) {
{code}
Using object equality to compare two {{BlockListAsLongs}} objects is very
surprising to anyone reading the code. In general, I find the idea of
overloading the block list to sometimes not be a block list to be very weird
and surprising. If we are going to do it, it certainly needs a lot of comments
in the code to explain what's going on. I think it would be clearer and less
error-prone just to add an optional list of storage ID strings in the
{{.proto}} file.
{code}
if (nn.getFSImage().isUpgradeFinalized()) {
Set<String> storageIDsInBlockReport = new HashSet<>();
if (context.getTotalRpcs() == context.getCurRpc() + 1) {
for (StorageBlockReport report : reports) {
storageIDsInBlockReport.add(report.getStorage().getStorageID());
}
bm.removeZombieStorages(nodeReg, context, storageIDsInBlockReport);
}
}
{code}
This isn't going to work in the presence of reordered RPCs, is it? If curRpc 1
appears before curRpc 0, we'll never get into this clause at all and so zombies
won't be removed. Considering you are so concerned that my patch didn't solve
the interleaved and/or reordered RPC case, this seems like something you should
solve. I also don't understand what the rationale for ignoring zombies during
an upgrade is. Keep in mind zombie storages can lead to data loss under some
conditions (see HDFS-7960 for details).
> BlockReport retransmissions may lead to storages falsely being declared
> zombie if storage report processing happens out of order
> --------------------------------------------------------------------------------------------------------------------------------
>
> Key: HDFS-10301
> URL: https://issues.apache.org/jira/browse/HDFS-10301
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: namenode
> Affects Versions: 2.6.1
> Reporter: Konstantin Shvachko
> Assignee: Vinitha Reddy Gankidi
> Priority: Critical
> Attachments: HDFS-10301.002.patch, HDFS-10301.003.patch,
> HDFS-10301.004.patch, HDFS-10301.005.patch, HDFS-10301.006.patch,
> HDFS-10301.01.patch, HDFS-10301.sample.patch, zombieStorageLogs.rtf
>
>
> When NameNode is busy a DataNode can timeout sending a block report. Then it
> sends the block report again. Then NameNode while process these two reports
> at the same time can interleave processing storages from different reports.
> This screws up the blockReportId field, which makes NameNode think that some
> storages are zombie. Replicas from zombie storages are immediately removed,
> causing missing blocks.
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