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https://issues.apache.org/jira/browse/HDFS-5461?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13821648#comment-13821648
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Colin Patrick McCabe commented on HDFS-5461:
--------------------------------------------
We need to have a try/catch around both the creation of {{BlockReaderLocal}}
and {{BlockReaderFactory.getLegacyBlockReaderLocal}} that catches
{{OutOfMemoryException}}, since if one fails, the other definitely will do.
One thing that I don't like about this is that we're not actually testing the
failure case in the unit test. How about adding a configurable upper limit for
the size of the {{DirectBufferPool}}? Then a unit test could set this and
trigger the failure case. You're already tracking the used bytes, so it should
be simple to implement via {{compareAndSet}}. This will also be good for users
who don't want to use all their native memory for these buffers.
{code}
+ /**
+ * Return the currently using memory sum size in MB.
+ */
+ public long getUsingMemoryMB() {
+ return usingMemoryBytes.get()/(1024 * 1024);
+ }
{code}
Let's just return this in bytes. Using megabytes just opens up a can of worms
(some people think it's base-10, others think it's base-2, etc). And obviously
it's less precise.
> fallback to non-ssr(local short circuit reads) while oom detected
> -----------------------------------------------------------------
>
> Key: HDFS-5461
> URL: https://issues.apache.org/jira/browse/HDFS-5461
> Project: Hadoop HDFS
> Issue Type: Improvement
> Affects Versions: 3.0.0, 2.2.0
> Reporter: Liang Xie
> Assignee: Liang Xie
> Attachments: HDFS-5461.txt
>
>
> Currently, the DirectBufferPool used by ssr feature seems doesn't have a
> upper-bound limit except DirectMemory VM option. So there's a risk to
> encounter direct memory oom. see HBASE-8143 for example.
> IMHO, maybe we could improve it a bit:
> 1) detect OOM or reach a setting up-limit from caller, then fallback to
> non-ssr
> 2) add a new metric about current raw consumed direct memory size.
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