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https://issues.apache.org/jira/browse/HDFS-7435?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14357666#comment-14357666
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Jing Zhao commented on HDFS-7435:
---------------------------------
Thanks for updating the patch, Daryn. The latest patch looks good to me, and I
think the new capabilities field in NamespaceInfo is a good idea. Some minors:
# Need to fix javadoc for {{decodeBuffer}}, {{encode}}, and {{getBlocksBuffer}}
in BlockListAsLongs.
# Here "older" I guess you mean the current version compared with a future
version. Maybe we should make it more clear in the comment.
{code}
// reserve upper bits for future use. decoding masks off these bits to
// allow compatibility for older namenodes
private static long NUM_BYTES_MASK = (-1L) >>> (64 - 48);
private static long REPLICA_STATE_MASK = (-1L) >>> (64 - 4);
{code}
# Looks like the following code can be simplified and we actually do not need
"isSupported"?
{code}
+ Capability(boolean isSupported) {
+ int bits = ordinal() - 1;
+ mask = (bits < 0) ? 0 : (1L << bits);
+ if (isSupported) {
+ CAPABILITIES_SUPPORTED |= mask;
+ }
+ }
{code}
> PB encoding of block reports is very inefficient
> ------------------------------------------------
>
> Key: HDFS-7435
> URL: https://issues.apache.org/jira/browse/HDFS-7435
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: datanode, namenode
> Affects Versions: 2.0.0-alpha, 3.0.0
> Reporter: Daryn Sharp
> Assignee: Daryn Sharp
> Priority: Critical
> Attachments: HDFS-7435.000.patch, HDFS-7435.001.patch,
> HDFS-7435.002.patch, HDFS-7435.patch, HDFS-7435.patch, HDFS-7435.patch,
> HDFS-7435.patch, HDFS-7435.patch, HDFS-7435.patch, HDFS-7435.patch
>
>
> Block reports are encoded as a PB repeating long. Repeating fields use an
> {{ArrayList}} with default capacity of 10. A block report containing tens or
> hundreds of thousand of longs (3 for each replica) is extremely expensive
> since the {{ArrayList}} must realloc many times. Also, decoding repeating
> fields will box the primitive longs which must then be unboxed.
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