Github user dragonsinth commented on a diff in the pull request:
https://github.com/apache/lucene-solr/pull/32#discussion_r61508998
--- Diff:
solr/solrj/src/java/org/apache/solr/common/cloud/ZkStateReader.java ---
@@ -1066,32 +1079,201 @@ public static String getCollectionPath(String
coll) {
return COLLECTIONS_ZKNODE+"/"+coll + "/state.json";
}
- public void addCollectionWatch(String coll) {
- if (interestingCollections.add(coll)) {
- LOG.info("addZkWatch [{}]", coll);
- new StateWatcher(coll).refreshAndWatch(false);
+ /**
+ * Notify this reader that a local Core is a member of a collection, and
so that collection
+ * state should be watched.
+ *
+ * Not a public API. This method should only be called from
ZkController.
+ *
+ * The number of cores per-collection is tracked, and adding multiple
cores from the same
+ * collection does not increase the number of watches.
+ *
+ * @param collection the collection that the core is a member of
+ *
+ * @see ZkStateReader#unregisterCore(String)
+ */
+ public void registerCore(String collection) {
+ AtomicBoolean reconstructState = new AtomicBoolean(false);
+ collectionWatches.compute(collection, (k, v) -> {
+ if (v == null) {
+ reconstructState.set(true);
+ v = new CollectionWatch();
+ }
+ v.coreRefCount++;
+ return v;
+ });
+ if (reconstructState.get()) {
+ new StateWatcher(collection).refreshAndWatch();
+ synchronized (getUpdateLock()) {
+ constructState();
+ }
+ }
+ }
+
+ /**
+ * Notify this reader that a local core that is a member of a collection
has been closed.
+ *
+ * Not a public API. This method should only be called from
ZkController.
+ *
+ * If no cores are registered for a collection, and there are no {@link
CollectionStateWatcher}s
+ * for that collection either, the collection watch will be removed.
+ *
+ * @param collection the collection that the core belongs to
+ */
+ public void unregisterCore(String collection) {
+ AtomicBoolean reconstructState = new AtomicBoolean(false);
+ collectionWatches.compute(collection, (k, v) -> {
+ if (v == null)
+ return null;
+ if (v.coreRefCount > 0)
+ v.coreRefCount--;
+ if (v.canBeRemoved()) {
+ watchedCollectionStates.remove(collection);
+ lazyCollectionStates.put(collection, new
LazyCollectionRef(collection));
+ reconstructState.set(true);
+ return null;
+ }
+ return v;
+ });
+ if (reconstructState.get()) {
+ synchronized (getUpdateLock()) {
+ constructState();
+ }
+ }
+ }
+
+ /**
+ * Register a CollectionStateWatcher to be called when the state of a
collection changes
+ *
+ * A given CollectionStateWatcher will be only called once. If you want
to have a persistent watcher,
+ * it should register itself again in its {@link
CollectionStateWatcher#onStateChanged(Set, DocCollection)}
+ * method.
+ */
+ public void registerCollectionStateWatcher(String collection,
CollectionStateWatcher stateWatcher) {
+ AtomicBoolean watchSet = new AtomicBoolean(false);
+ collectionWatches.compute(collection, (k, v) -> {
+ if (v == null) {
+ v = new CollectionWatch();
+ watchSet.set(true);
+ }
+ v.stateWatchers.add(stateWatcher);
+ return v;
+ });
+ if (watchSet.get()) {
+ new StateWatcher(collection).refreshAndWatch();
synchronized (getUpdateLock()) {
constructState();
}
}
}
+ /**
+ * Block until a CollectionStatePredicate returns true, or the wait
times out
+ *
+ * Note that the predicate may be called again even after it has
returned true, so
+ * implementors should avoid changing state within the predicate call
itself.
+ *
+ * @param collection the collection to watch
+ * @param wait how long to wait
+ * @param unit the units of the wait parameter
+ * @param predicate the predicate to call on state changes
+ * @throws InterruptedException on interrupt
+ * @throws TimeoutException on timeout
+ */
+ public void waitForState(final String collection, long wait, TimeUnit
unit, CollectionStatePredicate predicate)
--- End diff --
@shalinmangar this is what I was referring to, I know you're working on
getting Overseer to not peg ZK polling for state changes on unwatched
collections, this PR provides an easy mechanism to temporarily watch
collections of interest.
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