Ming Ma created HDFS-7725:
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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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