kaisun2000 commented on a change in pull request #365: Fix RoutingTableProvider
statePropagationLatency metric reporting bug
URL: https://github.com/apache/helix/pull/365#discussion_r309460908
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File path:
helix-core/src/main/java/org/apache/helix/common/caches/AbstractDataCache.java
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@@ -48,15 +50,17 @@ public AbstractDataCache(ControlContextProvider
controlContextProvider) {
* Selectively fetch Helix Properties from ZK by comparing the version of
local cached one with the one on ZK.
* If version on ZK is newer, fetch it from zk and update local cache.
* @param accessor the HelixDataAccessor
- * @param reloadKeys keys needs to be reload
+ * @param reloadKeysIn keys needs to be reload
* @param cachedKeys keys already exists in the cache
* @param cachedPropertyMap cached map of propertykey -> property object
+ * @param reloadKeysOut keys actually reloaded; may include more keys than
reloadKeysIn
* @return updated properties map
*/
protected Map<PropertyKey, T> refreshProperties(
- HelixDataAccessor accessor, List<PropertyKey> reloadKeys,
List<PropertyKey> cachedKeys,
- Map<PropertyKey, T> cachedPropertyMap) {
+ HelixDataAccessor accessor, Set<PropertyKey> reloadKeysIn,
List<PropertyKey> cachedKeys,
+ Map<PropertyKey, T> cachedPropertyMap, Set<PropertyKey> reloadKeysOut) {
Review comment:
Jiajun suggested this approach. This method already return other values. So
we can't put the modified reloaded keys as a return value. Changing the current
input is definitely confusing. That is the why there is bugs for now. So Jiajun
suggestion of using a "out" parameter seems to make sense.
In fact, some language by design has "OUT" parameters. Java can use
modifiable collections to simulate this behavior. C also commonly use similar
tricks.
https://www.codeproject.com/Questions/167362/how-i-can-use-out-parameter-in-java
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