[SLING-10489] Ignore partially started, newly joining instances to avoid disturbing discovery (for a while)

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: Discovery Commons 1.0.24, Discovery Base 2.0.10, Discovery Oak 1.2.34
• Fix Version/s: Discovery Base 2.0.12, Discovery Commons 1.0.26, Discovery Oak 1.2.36
• Component/s: Discovery
• Assignee: Stefan Egli
• Reporter: Stefan Egli
• Created: 15/Jun/21 15:08
• Updated: 14/Mar/22 15:27
• Resolved: 10/Mar/22 17:47

Description

Discovery.oak requires that both Oak and Sling are operating normally in order to declare victory and announce a new topology.

The startup phase is especially tricky in this regard, since there are multiple elements that need to get updated (some are in the Oak layer, some in Sling) :

• lease & clusterNodeId : this is maintained by Oak
• idMap : this is maintained by IdMapService (Sling)
• leaderElectionId : this is maintained by OakViewChecker (Sling)
• syncToken : this is maintained by SyncTokenService (Sling)

Situations have been seen where Oak starts up fine, but higher level (eg Sling) bundles were not activated within a reasonable amount of time. This lead to discovery staying in TOPOLOGY_CHANGING state for longer than expected.

There should be a mechanism that ignores (suppresses) newly joining instances if they start up only partially. However, after a certain timeout this mechanism should give up.