HDFS-2312. FSNamesystem javadoc incorrectly says its for DNs. (harsh)
git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1337761 13f79535-47bb-0310-9956-ffa450edef68
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@ -141,6 +141,8 @@ Trunk (unreleased changes)
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HDFS-3243. TestParallelRead timing out on jenkins. (Henry Robinson via todd)
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HDFS-3265. PowerPc Build error. (Kumar Ravi via mattf)
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HDFS-2312. FSNamesystem javadoc incorrectly says its for DNs. (harsh)
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Release 2.0.0 - UNRELEASED
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@ -197,18 +197,33 @@
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import com.google.common.base.Preconditions;
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import com.google.common.collect.Lists;
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/***************************************************
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* FSNamesystem does the actual bookkeeping work for the
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* DataNode.
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/**
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* FSNamesystem is a container of both transient
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* and persisted name-space state, and does all the book-keeping
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* work on a NameNode.
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*
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* It tracks several important tables.
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* Its roles are briefly described below:
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*
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* 1) valid fsname --> blocklist (kept on disk, logged)
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* 1) Is the container for BlockManager, DatanodeManager,
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* DelegationTokens, LeaseManager, etc. services.
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* 2) RPC calls that modify or inspect the name-space
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* should get delegated here.
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* 3) Anything that touches only blocks (eg. block reports),
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* it delegates to BlockManager.
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* 4) Anything that touches only file information (eg. permissions, mkdirs),
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* it delegates to FSDirectory.
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* 5) Anything that crosses two of the above components should be
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* coordinated here.
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* 6) Logs mutations to FSEditLog.
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*
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* This class and its contents keep:
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*
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* 1) Valid fsname --> blocklist (kept on disk, logged)
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* 2) Set of all valid blocks (inverted #1)
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* 3) block --> machinelist (kept in memory, rebuilt dynamically from reports)
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* 4) machine --> blocklist (inverted #2)
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* 5) LRU cache of updated-heartbeat machines
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***************************************************/
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*/
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@InterfaceAudience.Private
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@Metrics(context="dfs")
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public class FSNamesystem implements Namesystem, FSClusterStats,
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