[SOLR-12213] Consider removing the collectionPropsNotifications thread from ZkStateReader

• Type: Improvement
• Status: Open
• Priority: Minor
• Resolution: Unresolved
• Affects Version/s: 7.4, 8.0
• Assignee: Unassigned
• Reporter: Tomas Eduardo Fernandez Lobbe
• Created: 11/Apr/18 20:57
• Updated: 08/Jun/19 15:16

Description

From SOLR-12172:
shalinmangar

Tomás Fernández Löbbe – I don't think we should introduce another thread(pool) just for this feature. We can use a method similar to updateWatchedCollection which checks if the new znode version is greater than the old one. This ensures that we replace the old collection props only if the new one is actually newer.

tomasflobbe

Thanks for the review Shalin Shekhar Mangar. I thought about doing something like that, but decided not to since it requires to keep something like a map with collection -> version and handling it made the code more complex. I'll put up a patch, maybe it's still better to go that route anyway

tomasflobbe

Shalin Shekhar Mangar, just by keeping the synchronization I added to refreshAndWatch in the previous commit we can guarantee that we won't be setting the collection property map to an older value, however, I don't think we can guarantee that the notifications to watchers won't be out of order without using the single thread executor. Are you suggesting that we go that way anyway?