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https://issues.apache.org/jira/browse/CURATOR-447?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16361409#comment-16361409
]
ASF GitHub Bot commented on CURATOR-447:
----------------------------------------
Github user dragonsinth commented on a diff in the pull request:
https://github.com/apache/curator/pull/250#discussion_r167672355
--- Diff:
curator-recipes/src/main/java/org/apache/curator/framework/recipes/cache/TreeCache.java
---
@@ -397,14 +396,11 @@ public void processResult(CuratorFramework client,
CuratorEvent event) throws Ex
break;
}
- ConcurrentMap<String, TreeNode> childMap = children;
- if ( childMap == null )
+ ConcurrentMap<String, TreeNode> childMap;
+ while ( (childMap = children) == null )
{
childMap = Maps.newConcurrentMap();
- if ( !childrenUpdater.compareAndSet(this, null,
childMap) )
- {
- childMap = children;
- }
+ if ( childrenUpdater.compareAndSet(this, null,
childMap) ) break;
--- End diff --
I see why you turned this into a loop (nice catch), but I think it reads a
little clearly and more deliberateif you revert back to the original code and
just change the `if` -> `while`. Ideally if Curator moves wholesale to Java
1.8, funcs, like:
```
ConcurrentMap<String, TreeNode> childMap =
childrenUpdater.updateAndGet(this, (oldChildren) -> {
return oldChildren != null ? oldChildren :
Maps.newConcurrentMap();
});
```
> TreeCache: Improve memory usage and concurrent update logic
> -----------------------------------------------------------
>
> Key: CURATOR-447
> URL: https://issues.apache.org/jira/browse/CURATOR-447
> Project: Apache Curator
> Issue Type: Improvement
> Components: Recipes
> Affects Versions: 3.3.0, 2.12.0
> Reporter: Nick Hill
> Priority: Minor
> Labels: performance
>
> Jira https://issues.apache.org/jira/browse/CURATOR-374 reduced per-node
> memory usage in {{TreeCache}}. It can be improved further via removal of the
> {{nodeState}} field - its {{LIVE}} state corresponds exactly to the adjacent
> {{childData}} field being non-null, and a sentinel {{ChildData}} value can be
> used for the {{DEAD}} state. This simplification also reduces the room for
> bugs and state inconsistencies.
> Other improvements included:
> * A further simplification to have {{TreeNode}} extend {{AtomicReference}},
> which obviates the need for an explicit {{childData}} field
> * More robust cache update logic (in get-children and get-data event
> callbacks)
> * Avoid overhead of incrementing/decrementing the {{outstandingOps}} atomic
> integer post-initialization
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