Pavel Kovalenko created IGNITE-10485:
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Summary: Ability to get know more about cluster state before
NODE_JOINED event is fired cluster-wide
Key: IGNITE-10485
URL: https://issues.apache.org/jira/browse/IGNITE-10485
Project: Ignite
Issue Type: Improvement
Components: cache
Reporter: Pavel Kovalenko
Fix For: 2.8
Currently there are no good possibilities to get more knowledge about cluster
before PME on node join start.
It might be usefult to do some pre-work (activate components if cluster is
active, calculate baseline affinity, cleanup pds if baseline changed, etc.)
before actual NODE_JOIN event is triggered cluster-wide and PME is started.
Such pre-work will significantly speed-up PME in case of node join.
Currently the only place where it can be done is during processing NodeAdded
message on local joining node.
But it's not a good idea, because it will freeze processing new discovery
messages cluster-wide.
I see 2 ways how to implement it:
1) Introduce new intermediate state of node when it's discovered, but discovery
event on node join is not triggered yet. This is right, but complicated change,
because it requires revisiting joining process both in Tcp and Zk discovery
protocols with extra failover scenarios.
2) Try to get this information and do pre-work before discovery manager start,
using e.g. GridRestProcessor. This looks much simplier, but we can have some
races there, when during pre-work cluster state has been changed (deactivation,
baseline change). In this case we should rollback it or just stop/restart the
node to avoid cluster instability. However these are rare scenarios in real
world (e.g. start baseline node and start deactivation process right after node
recovery is finished).
For starters we can expose baseline and cluster state in our rest endpoint and
try to move out mentioned above pre-work things from PME.
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