[jira] [Created] (SOLR-11730) Test NodeLost / NodeAdded dynamics

["Andrzej Bialecki (JIRA)" <ji...@apache.org>]

Andrzej Bialecki  created SOLR-11730:
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             Summary: Test NodeLost / NodeAdded dynamics
                 Key: SOLR-11730
                 URL: https://issues.apache.org/jira/browse/SOLR-11730
             Project: Solr
          Issue Type: Sub-task
      Security Level: Public (Default Security Level. Issues are Public)
            Reporter: Andrzej Bialecki 


Let's consider a "flaky node" scenario.

A node is going up and down at short intervals (eg. due to a flaky network cable). If the frequency of these events coincides with {{waitFor}} interval in {{nodeLost}} trigger configuration, the node may never be reported to the autoscaling framework as lost. Similarly it may never be reported as added back if it's lost again within the {{waitFor}} period of {{nodeAdded}} trigger.

Other scenarios are possible here too, depending on timing:
* node being constantly reported as lost
* node being constantly reported as added

One possible solution for the autoscaling triggers is that the framework should keep a short-term ({{waitFor * 2}} long?) memory of a node state that the trigger is tracking in order to eliminate flaky nodes (ie. those that transitioned between states more than once within the period).

Situation like this is detrimental to SolrCloud behavior regardless of autoscaling actions, so it should probably be addressed at a node level by eg. shutting down Solr node after the number of disconnects in a time window reaches a certain threshold.



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