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From "Tim Owen (JIRA)" <>
Subject [jira] [Updated] (SOLR-9503) NPE in Replica Placement Rules when using Overseer Role with other rules
Date Mon, 12 Sep 2016 13:12:20 GMT


Tim Owen updated SOLR-9503:
    Attachment: SOLR-9503.patch

> NPE in Replica Placement Rules when using Overseer Role with other rules
> ------------------------------------------------------------------------
>                 Key: SOLR-9503
>                 URL:
>             Project: Solr
>          Issue Type: Bug
>      Security Level: Public(Default Security Level. Issues are Public) 
>          Components: Rules, SolrCloud
>    Affects Versions: 6.2, master (7.0)
>            Reporter: Tim Owen
>         Attachments: SOLR-9503.patch
> The overseer role introduced in SOLR-9251 works well if there's only a single Rule for
replica placement e.g. {code}rule=role:!overseer{code} but when combined with another rule,
e.g. {code}rule=role:!overseer&rule=host:*,shard:*,replica:<2{code} it can result in
a NullPointerException (in Rule.tryAssignNodeToShard)
> This happens because the code builds up a nodeVsTags map, but it only has entries for
nodes that have values for *all* tags used among the rules. This means not enough information
is available to other rules when they are being checked during replica assignment. In the
example rules above, if we have a cluster of 12 nodes and only 3 are given the Overseer role,
the others do not have any entry in the nodeVsTags map because they only have the host tag
value and not the role tag value.
> Looking at the code in ReplicaAssigner.getTagsForNodes, it is explicitly only keeping
entries that fulfil the constraint of having values for all tags used in the rules. Possibly
this constraint was suitable when rules were originally introduced, but the Role tag (used
for Overseers) is unlikely to be present for all nodes in the cluster, and similarly for sysprop
tags which may or not be set for a node.
> My patch removes this constraint, so the nodeVsTags map contains everything known about
all nodes, even if they have no value for a given tag. This allows the rule combination above
to work, and doesn't appear to cause any problems with the code paths that use the nodeVsTags
map. They handle null values quite well, and the tests pass.

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