[GitHub] [solr] patsonluk commented on pull request #909: SOLR-16257: `ZkStateReader` changes to avoid race condition between `collectionWatches` and `watchedCollectionStates`

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patsonluk commented on PR #909:
URL: https://github.com/apache/solr/pull/909#issuecomment-1171782061

   > Ok I think I'm on your side now. But I do think there is some confusion between having a `null` value in `collectionsWatches` and having a `null` `currentDoc` in the value. Can you explain that difference?
   
   For sure! There are 3 variations:
   1. `collectionWatches` does not have key for such collection - That means the collection is not being watched
   2. `collectionWatches.get("test-collection")` returns null, this should not happen, as all the entries insert into the map is non null
   3. `collectionWatches.get("test-collection")` does returns a `DocCollectionWatch` but has field `currentDoc` as `null`, that means the collection is actively watched, however either the `refreshAndWatch` is not called yet, or last fetched state indicates that the collection is not yet existed or deleted from ZK.
   
   
   > 
   > Also can we rename `currentDoc` to `currentState`? Also `DocCollectionWatch` would be better named `StatefulCollectionWatch`, because the important characteristic is that its saving the current state of the collection.
   > 
   > Thanks again for the work here!
   
   Agree thanks! Doing the renaming as suggested!


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