Stefan Egli created SLING-5027:
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Summary: vote loop until vote is promoted
Key: SLING-5027
URL: https://issues.apache.org/jira/browse/SLING-5027
Project: Sling
Issue Type: Bug
Components: Extensions
Affects Versions: Discovery Impl 1.1.0
Reporter: Stefan Egli
Assignee: Stefan Egli
Fix For: Discovery Impl 1.1.8
{{VotingHandler.analyzeVotings}} has the risk of running into a busy vote loop
during the duration of an {{/ongoingVotings}}:
* {{analyzeVotings}} is invoked either when something changes in
{{/var/discovery/impl/ongoingVotings}} or as part of a heartbeat
* as part of this, it figures out the ongoingVotings, decides on which it has
to vote (should there be more than 1, and it doesn't vote if it was the
initiator) then potentially does a {{vote(,true)}} on it
* in {{vote()}} it not only sets the {{vote}} property accordingly (true or
false) - it additionally, since
[SLING-3434|https://issues.apache.org/jira/browse/SLING-3434?focusedCommentId=14297078&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-14297078],
also sets the {{votedAt}} property (timestamp)
* since the above is a change in {{/ongoingVotings}}, this will trigger an
observation event - which again triggers the {{analyzeVotings}} to be called,
which will again find an ongoing vote, vote upon, trigger an observation event
etc. Resulting in an endless loop that involves repository and an observation
handler
* now the above loop only occurs since the introduction of the {{votedAt}}
property - as that is changing on each iteration. Without that, voting again
with the same boolean would not result in an observation event and the loop
would not happen at all.
* in any case, the loop lasts at maximum until the initiator finally got all
the votes and can promote the vote to an {{/establishedView}}. This should
typically be a fast operation - but if the cluster is under heavy load and
experiences delays for some reason, this busy loop can last a little while.
So this loop is a regression introduced with SLING-3434.
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