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From "Ming Ma (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HDFS-7725) Incorrect "nodes in service" metrics caused all writes to fail
Date Mon, 02 Feb 2015 18:43:36 GMT
Ming Ma created HDFS-7725:
-----------------------------

             Summary: Incorrect "nodes in service" metrics caused all writes to fail
                 Key: HDFS-7725
                 URL: https://issues.apache.org/jira/browse/HDFS-7725
             Project: Hadoop HDFS
          Issue Type: Bug
            Reporter: Ming Ma


One of our clusters sometimes couldn't allocate blocks from any DNs. BlockPlacementPolicyDefault
complains with the following messages for all DNs.

{noformat}
the node is too busy (load:x > y)
{noformat}


It turns out the {{HeartbeatManager}}'s {{nodesInService}} was computed incorrectly when admins
decomm or recomm dead nodes. Here are two scenarios.

* Decomm dead nodes. It turns out HDFS-7374 has fixed it; not sure if it is intentional. Here
is the sequence of event without HDFS-7374.
** Cluster has one live node. nodesInService == 1
** The node becomes dead. nodesInService == 0
** Decomm the node. nodesInService == -1

* However, HDFS-7374 introduces another inconsistency when recomm is involved.
** Cluster has one live node. nodesInService == 1
** The node becomes dead. nodesInService == 0
** Decomm the node. nodesInService == 0
** Recomm the node. nodesInService == 1



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