narendly commented on a change in pull request #799: [MSDS] Add REST endpoint
to get mapping of all sharding keys by realm
URL: https://github.com/apache/helix/pull/799#discussion_r382970187
##########
File path:
helix-rest/src/main/java/org/apache/helix/rest/metadatastore/ZkMetadataStoreDirectory.java
##########
@@ -111,6 +111,16 @@ public ZkMetadataStoreDirectory(Map<String, String>
routingZkAddressMap)
return allShardingKeys;
}
+ @Override
+ public Map<String, List<String>> getShardingKeysByRealm(String namespace) {
+ Map<String, List<String>> shardingKeysByRealmMap =
_realmToShardingKeysMap.get(namespace);
+ if (shardingKeysByRealmMap == null) {
+ throw new NoSuchElementException("Namespace " + namespace + " does not
exist!");
+ }
+
+ return shardingKeysByRealmMap;
Review comment:
That's a very good point and I am glad that you've considered potential
cases like the one you described in your comments.
The potential race condition you raised would be valid if we allowed
`namespace`s to be removed, but thanks to the way we define namespaces, they
are never removed (only updated). So I don't think we need to be worried about
that particular race condition here - do you agree? If so, we could simplify
the code as originally suggested.
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