NealSun96 commented on a change in pull request #955: Fix MSD routing data
refreshing for update methods
URL: https://github.com/apache/helix/pull/955#discussion_r409085250
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File path:
helix-rest/src/main/java/org/apache/helix/rest/metadatastore/ZkMetadataStoreDirectory.java
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@@ -304,42 +314,35 @@ public boolean deleteShardingKey(String namespace,
String realm, String sharding
*/
@Override
public void refreshRoutingData(String namespace) {
- // Safe to ignore the callback if any of the maps are null.
- // If routingDataMap is null, then it will be populated by the constructor
anyway
- // If routingDataMap is not null, then it's safe for the callback function
to update it
- if (_routingZkAddressMap == null || _realmToShardingKeysMap == null
- || _routingDataReaderMap == null || _routingDataWriterMap == null) {
- LOG.warn(
- "refreshRoutingData callback called before ZKMetadataStoreDirectory
was fully initialized. Skipping refresh!");
Review comment:
When the `ZkMetadataStoreDirectory` is initialized, it initializes
`ZkRoutingDataReader` which subscribe to ZNode changes and calls
`refreshRoutingData()` when an event happens. It's possible that an event comes
in before `ZkMetadataStoreDirectory` finishes initialization, which we don't
want to handle.
This is my understanding to it. This was introduced to me first by @narendly
, and he was also the first to write this statement so he could provide further
comments if necessary.
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