[GitHub] [pulsar] merlimat commented on a change in pull request #10862: [Issue 10860][pulsar-metadata] Ensure metadata cache consistency across brokers

[GitBox <gi...@apache.org>]

merlimat commented on a change in pull request #10862:
URL: https://github.com/apache/pulsar/pull/10862#discussion_r647101647



##########
File path: pulsar-metadata/src/main/java/org/apache/pulsar/metadata/cache/impl/MetadataCacheImpl.java
##########
@@ -229,7 +240,11 @@ public MetadataCacheImpl(MetadataStore store, MetadataSerde<T> serde) {
         return store.delete(path, Optional.empty())
                 .thenAccept(v -> {
                     // Mark in the cache that the object was removed
-                    objCache.put(path, FutureUtils.value(Optional.empty()));
+                    // objCache.put(path, FutureUtils.value(Optional.empty()));

Review comment:
       I think that we could either invalidate it from the cache here, do the read to set the watch, or again, since it's mostly related with the ZK, do it there

##########
File path: pulsar-metadata/src/main/java/org/apache/pulsar/metadata/cache/impl/MetadataCacheImpl.java
##########
@@ -209,8 +211,17 @@ public MetadataCacheImpl(MetadataStore store, MetadataSerde<T> serde) {
         store.put(path, content, Optional.of(-1L))
                 .thenAccept(stat -> {
                     // Make sure we have the value cached before the operation is completed
-                    objCache.put(path, FutureUtils.value(Optional.of(new CacheGetResult<>(value, stat))));
-                    future.complete(null);
+                    // In addition to caching the value, we need to add a watch on the path,
+                    // so when/if it changes on any other node, we are notified and we can
+                    // update the cache
+                    objCache.get(path).whenComplete( (stat2, ex) -> {

Review comment:
       I think this logic should belong more to the ZK implementation, where we can set the watch after the put




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