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https://issues.apache.org/jira/browse/SOLR-8323?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15264743#comment-15264743
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ASF GitHub Bot commented on SOLR-8323:
--------------------------------------
Github user dragonsinth commented on a diff in the pull request:
https://github.com/apache/lucene-solr/pull/32#discussion_r61644721
--- Diff:
solr/solrj/src/java/org/apache/solr/common/cloud/ZkStateReader.java ---
@@ -491,19 +493,28 @@ private void refreshLegacyClusterState(Watcher
watcher)
final Stat stat = new Stat();
final byte[] data = zkClient.getData(CLUSTER_STATE, watcher, stat,
true);
final ClusterState loadedData = ClusterState.load(stat.getVersion(),
data, emptySet(), CLUSTER_STATE);
+ final Set<String> liveNodes = new HashSet<>(this.liveNodes);
synchronized (getUpdateLock()) {
if (this.legacyClusterStateVersion >= stat.getVersion()) {
// Nothing to do, someone else updated same or newer.
return;
}
- this.legacyCollectionStates = loadedData.getCollectionStates();
- this.legacyClusterStateVersion = stat.getVersion();
- for (Map.Entry<String, ClusterState.CollectionRef> entry :
this.legacyCollectionStates.entrySet()) {
- if (entry.getValue().isLazilyLoaded() == false) {
- // a watched collection - trigger notifications
- notifyStateWatchers(entry.getKey(), entry.getValue().get());
+ LOG.info("Updating legacy cluster state - {} entries in
legacyCollectionStates", legacyCollectionStates.size());
+ for (Map.Entry<String, CollectionWatch> watchEntry :
this.collectionWatches.entrySet()) {
+ String coll = watchEntry.getKey();
+ CollectionWatch collWatch = watchEntry.getValue();
+ ClusterState.CollectionRef ref =
this.legacyCollectionStates.get(coll);
+ if (ref == null)
+ continue;
+ // watched collection, so this will always be local
+ DocCollection newState = ref.get();
+ if (!collWatch.stateWatchers.isEmpty()
+ &&
!Objects.equals(loadedData.getCollectionStates().get(coll).get(), newState)) {
+ notifyStateWatchers(liveNodes, coll, newState);
--- End diff --
I just realized you don't want to call user code while holding the update
lock. I think you're going to need to move this out of the synchronized block.
In fact.... this is really nasty now that I think about it. In general,
you're going to want to defer calling any user code until the current
constuctState() operation finishes. Otherwise, the user code is potentially
going to see a stale copy of the state that you haven't finished updating yet.
I think we're going to have to build a queue of outstanding state watchers
to notify and always call them later, probably in an executor. I know that
sounds like a bit of work, but I'm not sure I can see how it would be safe
otherwise.
@markrmiller any thoughts?
> Add CollectionWatcher API to ZkStateReader
> ------------------------------------------
>
> Key: SOLR-8323
> URL: https://issues.apache.org/jira/browse/SOLR-8323
> Project: Solr
> Issue Type: Improvement
> Affects Versions: master
> Reporter: Alan Woodward
> Assignee: Alan Woodward
> Attachments: SOLR-8323.patch, SOLR-8323.patch, SOLR-8323.patch,
> SOLR-8323.patch
>
>
> An API to watch for changes to collection state would be a generally useful
> thing, both internally and for client use.
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