[jira] [Created] (IGNITE-19955) Fix create zone on restart rewrites existing data nodes

[Mirza Aliev (Jira)]

Mirza Aliev created IGNITE-19955:
------------------------------------

             Summary: Fix create zone on restart rewrites existing data nodes
                 Key: IGNITE-19955
                 URL: https://issues.apache.org/jira/browse/IGNITE-19955
             Project: Ignite
          Issue Type: Bug
            Reporter: Mirza Aliev


Currently we have the logic for initialisation of newly created zone that it 
writes keys

{noformat}
zoneDataNodesKey(zoneId), zoneScaleUpChangeTriggerKey(zoneId), 
zoneScaleDownChangeTriggerKey(zoneId), zonesChangeTriggerKey(zoneId)
{noformat}
to metastorage, and condition is 

{noformat}
    static CompoundCondition triggerKeyConditionForZonesChanges(long revision, 
int zoneId) {
        return or(
                notExists(zonesChangeTriggerKey(zoneId)),
                
value(zonesChangeTriggerKey(zoneId)).lt(ByteUtils.longToBytes(revision))
        );
{noformat}

Recovery process implies that the create zone event will be processed again, 
but with the higher revision, so data nodes will be rewritten.

We need to handle this situation, so data nodes will be consistent after 
restart.

Possible solution is to change condition to 


{noformat}
    static SimpleCondition triggerKeyConditionForZonesCreation(long revision, 
int zoneId) {
        return notExists(zonesChangeTriggerKey(zoneId));
    }

    static SimpleCondition triggerKeyConditionForZonesDelete(int zoneId) {
        return exists(zonesChangeTriggerKey(zoneId));
    }
{noformat}
 
so we could not rely on revision and check only existence of the key, when we 
create or remove zone. The problem in this solution is that reordering of the 
create and remove on some node could lead to not consistent state for zones key 
in metastorage
   



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