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https://issues.apache.org/jira/browse/HDFS-3120?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Eli Collins updated HDFS-3120:
------------------------------
Description:
The work on branch-20-append was to support *sync*, for durable HBase WALs, not
*append*. The branch-20-append implementation is known to be buggy. There's
been confusion about this, we often answer queries on the list [like
this|http://search-hadoop.com/m/wfed01VOIJ5]. Unfortunately, the way to enable
correct sync on branch-1 for HBase is to set dfs.support.append to true in your
config, which has the side effect of enabling append (which we don't want to
do).
For v1.x let's:
# Always enable the sync path (currently only enabled if dfs.support.append is
set)
# Remove the dfs.support.append configuration option. Let's keep the code paths
though in case we ever fix append on branch-1, in which case we can add the
config option back
For 2.x let's
# Always enable the hsync/hflush path
# The dfs.support.appends only enables the append specific paths (since the
hsync/hflush paths are now always on). Append will still default to being
enabled so there is no net effect by default.
was:
The work on branch-20-append was to support *sync*, for durable HBase WALs, not
*append*. The branch-20-append implementation is known to be buggy. There's
been confusion about this, we often answer queries on the list [like
this|http://search-hadoop.com/m/wfed01VOIJ5]. Unfortunately, the way to enable
correct sync on branch-1 for HBase is to set dfs.support.append to true in your
config, which has the side effect of enabling append (which we don't want to
do).
Let's add a new *dfs.support.sync* option that enables working sync (which is
basically the current dfs.support.append flag modulo one place where it's not
referring to sync). For compatibility, if dfs.support.append is set,
dfs.support.sync will be set as well. This way someone can enable sync for
HBase and still keep the current behavior that if dfs.support.append is not set
then an append operation will result in an IOE indicating append is not
supported. We should do this on trunk as well, as there's no reason to conflate
hsync and append with a single config even if append works.
> Enable hsync and hflush by default
> ----------------------------------
>
> Key: HDFS-3120
> URL: https://issues.apache.org/jira/browse/HDFS-3120
> Project: Hadoop HDFS
> Issue Type: Improvement
> Reporter: Eli Collins
> Assignee: Eli Collins
> Fix For: 2.0.0
>
> Attachments: hdfs-3120.txt, hdfs-3120.txt
>
>
> The work on branch-20-append was to support *sync*, for durable HBase WALs,
> not *append*. The branch-20-append implementation is known to be buggy.
> There's been confusion about this, we often answer queries on the list [like
> this|http://search-hadoop.com/m/wfed01VOIJ5]. Unfortunately, the way to
> enable correct sync on branch-1 for HBase is to set dfs.support.append to
> true in your config, which has the side effect of enabling append (which we
> don't want to do).
> For v1.x let's:
> # Always enable the sync path (currently only enabled if dfs.support.append
> is set)
> # Remove the dfs.support.append configuration option. Let's keep the code
> paths though in case we ever fix append on branch-1, in which case we can add
> the config option back
> For 2.x let's
> # Always enable the hsync/hflush path
> # The dfs.support.appends only enables the append specific paths (since the
> hsync/hflush paths are now always on). Append will still default to being
> enabled so there is no net effect by default.
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