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https://issues.apache.org/jira/browse/HDFS-8965?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14716004#comment-14716004
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Andrew Wang commented on HDFS-8965:
-----------------------------------
Hi Colin, thanks for working on this. Seems like the idea is to, for
length-prefixed edit logs, to check the checksum before reading the fields.
Sensible and good change, overall looks good. Mostly nit comments:
* A comment mentions a 1-byte txid, I think you meant opid. Having the expected
format in the comment is super helpful too, thanks. Mind replicating it for the
other two readers too?
* Why move the temp array into a member? It'll probably be stack allocated and
thus no GC pressure, 4KB should fit too.
* Great opportunity to fix the LayoutVersion.EDITS_CHESKUM typo
* LengthPrefixedReader#scanOp, shouldn't this be basically readOp but without
the second pass to readFields? Not sure why it doesn't validate the max edit
size or the checksum. The TODO is relevant.
* Can we get a unit test for this situation?
* Is some code sharing is possible among the three readOp's for getting the
FSEditLogOp, this bit?
{noformat}
byte opCodeByte;
try {
opCodeByte = in.readByte();
} catch (EOFException eof) {
// EOF at an opcode boundary is expected.
return null;
}
FSEditLogOpCodes opCode = FSEditLogOpCodes.fromByte(opCodeByte);
if (opCode == OP_INVALID) {
verifyTerminator();
return null;
}
FSEditLogOp op = cache.get(opCode);
if (op == null) {
throw new IOException("Read invalid opcode " + opCode);
}
{noformat}
> Harden edit log reading code against out of memory errors
> ---------------------------------------------------------
>
> Key: HDFS-8965
> URL: https://issues.apache.org/jira/browse/HDFS-8965
> Project: Hadoop HDFS
> Issue Type: Improvement
> Affects Versions: 2.0.0-alpha
> Reporter: Colin Patrick McCabe
> Assignee: Colin Patrick McCabe
> Attachments: HDFS-8965.001.patch, HDFS-8965.002.patch,
> HDFS-8965.003.patch
>
>
> We should harden the edit log reading code against out of memory errors. Now
> that each op has a length prefix and a checksum, we can validate the checksum
> before trying to load the Op data. This should avoid out of memory errors
> when trying to load garbage data as Op data.
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