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https://issues.apache.org/jira/browse/HDFS-3510?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Colin Patrick McCabe updated HDFS-3510:
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Attachment: HDFS-3510.010.patch
Earlier Suresh commented that we should support more than 1MB of preallocation
at a time. This patch makes that possible.
* EditLogOutputStream: rename PREALLOCATION_LENGTH to MIN_PREALLOCATION_LENGTH,
to reflect the fact that we can now pre-allocate more than 1MB at a time.
* FSEditLogOp#Reader#verifyTerminator: allow more than 1.5MB of padding at the
end of the edit log. In order to do this, the verifyTerminator function
disables the StreamLimiter, and uses the InputStream#mark interface.
* EditLogOutputStream: in contrast to the previous patch, move the
preallocation logic into EditLogOutputStream#preallocate, where it originally
was. Handle pre-allocating more than 1MB at a time. Keep the LOG.debug
message on every preallocation.
* There are many new unit tests
> Improve FSEditLog pre-allocation
> --------------------------------
>
> Key: HDFS-3510
> URL: https://issues.apache.org/jira/browse/HDFS-3510
> Project: Hadoop HDFS
> Issue Type: Bug
> Affects Versions: 1.0.0, 2.0.0-alpha
> Reporter: Colin Patrick McCabe
> Assignee: Colin Patrick McCabe
> Fix For: 1.0.0, 2.0.1-alpha
>
> Attachments: HDFS-3510-b1.001.patch, HDFS-3510-b1.002.patch,
> HDFS-3510.001.patch, HDFS-3510.003.patch, HDFS-3510.004.patch,
> HDFS-3510.004.patch, HDFS-3510.006.patch, HDFS-3510.007.patch,
> HDFS-3510.008.patch, HDFS-3510.009.patch, HDFS-3510.010.patch
>
>
> It is good to avoid running out of space in the middle of writing a batch of
> edits, because when it happens, we often get partial edits at the end of the
> log.
> Edit log preallocation can solve this problem (see HADOOP-2330 for a full
> description of edit log preallocation).
> The current pre-allocation code was introduced for performance reasons, not
> for preventing partial edits. As a consequence, we sometimes do a write
> without using pre-allocation. We should change the pre-allocation code so
> that it always preallocates at least enough space before writing out the
> edits.
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