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From "Ming Ma (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HDFS-7725) Incorrect "nodes in service" metrics caused all writes to fail
Date Mon, 30 Mar 2015 23:55:53 GMT

     [ https://issues.apache.org/jira/browse/HDFS-7725?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Ming Ma updated HDFS-7725:
--------------------------
    Description: 
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. cc
/ [~zhz], [~andrew.wang], [~atm] 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

  was:
`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. cc
/ [~zhz], [~andrew.wang], [~atm] 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


> 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
>            Assignee: Ming Ma
>         Attachments: HDFS-7725.patch
>
>
> 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.
cc / [~zhz], [~andrew.wang], [~atm] 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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