Under-replicated blocks are not calculated if the name-node is forced out of
safe-mode.
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Key: HADOOP-4597
URL: https://issues.apache.org/jira/browse/HADOOP-4597
Project: Hadoop Core
Issue Type: Bug
Components: dfs
Affects Versions: 0.18.0
Reporter: Konstantin Shvachko
Assignee: Konstantin Shvachko
Priority: Blocker
Fix For: 0.18.3
Currently during name-node startup under-replicated blocks are not added to the
neededReplications queue until the name-node leaves safe mode. This is an
optimization since otherwise all blocks will first go into the under-replicated
queue and then most of them will be removed from it.
When the name-node leaves safe-mode automatically it checks all blocks to have
a correct number of replicas ({{processMisReplicatedBlocks()}}).
When the name-node leaves safe-mode manually it does not perform the checkup.
In the latter case all under-replicated blocks remain not replicated forever
because there is no alternative mechanism to trigger replications.
The proposal is to call {{processMisReplicatedBlocks()}} any time the name-node
leaves safe mode - automatically or manually.
In addition to solving that problem this could be an alternative mechanism for
refreshing {{neededReplications}} and {{excessReplicateMap}} sets.
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