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https://issues.apache.org/jira/browse/HDFS-17868?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18048717#comment-18048717
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ASF GitHub Bot commented on HDFS-17868:
---------------------------------------
eubnara commented on code in PR #8159:
URL: https://github.com/apache/hadoop/pull/8159#discussion_r2657073710
##########
hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/NameNode.java:
##########
@@ -2363,8 +2375,15 @@ protected String reconfigurePropertyImpl(String
property, String newVal)
DFS_NAMENODE_REPLICATION_WORK_MULTIPLIER_PER_ITERATION)
||
property.equals(DFS_NAMENODE_RECONSTRUCTION_PENDING_TIMEOUT_SEC_KEY)) {
return reconfReplicationParameters(newVal, property);
- } else if (property.equals(DFS_BLOCK_REPLICATOR_CLASSNAME_KEY) || property
- .equals(DFS_BLOCK_PLACEMENT_EC_CLASSNAME_KEY)) {
+ } else if (property.equals(DFS_BLOCK_REPLICATOR_CLASSNAME_KEY)
+ || property.equals(DFS_BLOCK_PLACEMENT_EC_CLASSNAME_KEY)
+ || property.equals(DFS_BLOCK_REPLICATOR_CROSS_DC_ASYNC_ENABLED_KEY)
+ ||
property.equals(DFS_BLOCK_REPLICATOR_CROSS_DC_PREFERRED_DATACENTER_KEY)
+ ||
property.equals(DFS_BLOCK_REPLICATOR_CROSS_DC_BANDWIDTH_LIMIT_MB_KEY)
+ ||
property.equals(DFS_BLOCK_REPLICATOR_CROSS_DC_BANDWIDTH_REFILL_PERIOD_SEC_KEY)
+ || property.equals(DFS_BLOCK_REPLICATOR_CROSS_DC_SYNC_PATHS_KEY)
+ ||
property.equals(DFS_BLOCK_REPLICATOR_CROSS_DC_LIMITED_SYNC_PATHS_KEY)
Review Comment:
In order to change configurations without restarting NameNode, I added
`BlockPlacementStatusWithCrossDC` related configurations here.
However, if you change multiple configurations simultaneously and
reconfigure it, `reconfBlockPlacementPolicy()` called multiple times.
> introduce BlockPlacementPolicyCrossDC for multi datacenter stretched hdfs
> cluster
> ---------------------------------------------------------------------------------
>
> Key: HDFS-17868
> URL: https://issues.apache.org/jira/browse/HDFS-17868
> Project: Hadoop HDFS
> Issue Type: New Feature
> Components: block placement
> Reporter: YUBI LEE
> Priority: Major
> Labels: pull-request-available
>
> I was inspired by the ideas presented in
> https://dan.naver.com/25/sessions/692 and
> https://www.youtube.com/watch?v=1h4k_Dbt0t8 and implemented a new block
> placement policy called BlockPlacementPolicyCrossDC.
> Thanks to [~acedia28] for the original ideas. It would be great if
> [~acedia28] could share an improved or more mature version of this block
> placement policy.
> This implementation introduces the following configuration options
> (default values are shown in parentheses):
> {code}
> dfs.block.replicator.cross.dc.async.enabled (false)
> dfs.block.replicator.cross.dc.preferred.datacenter
> dfs.block.replicator.cross.dc.bandwidth.limit.mb (5120)
> dfs.block.replicator.cross.dc.bandwidth.refill.period.sec (1)
> dfs.block.replicator.cross.dc.sync.paths
> dfs.block.replicator.cross.dc.limited.sync.paths
> {code}
> Based on the ideas from the session mentioned above, this policy supports
> three different HDFS block write modes:
> 1. Synchronous write
> The standard HDFS behavior, where block replicas are synchronously written to
> all target DataNodes.
> 2. Limited synchronous write
> Uses bucket4j to control cross-datacenter traffic.
> Writes below the configured threshold are performed synchronously, while
> writes exceeding the threshold fall back to asynchronous replication.
> 3. Asynchronous write
> The client is initially given only DataNode candidates located in the same
> datacenter.
> Any under-replicas are created later through background HDFS replication to
> other datacenters.
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