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Posted to dev@curator.apache.org by "Rohan Suri (JIRA)" <ji...@apache.org> on 2018/08/10 12:16:00 UTC
[jira] [Updated] (CURATOR-476) PathChildrenCache never get
initialized if a child dies before a data watch is registered for it
[ https://issues.apache.org/jira/browse/CURATOR-476?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Rohan Suri updated CURATOR-476:
-------------------------------
Description:
PathChildrenCache started with PathChildrenCache.StartMode.POST_INITIALIZED_EVENT there could be the following scenario:
1. PCC calls getChildren("../parent") and gets the list of it's children
2. PCC calls processChildren(...) where it puts them into it's \{initialSet} – set of children whose data it will fetch and cache
3. Later in the same method it calls getDataAndStat(..."/parent/somechild") where it calls getData(...) on this child and registers a dataWatcher for this child
Midst of step 2&3, child node could get deleted – but since step 3 hasn't completed yet, the dataWatcher isn't triggered (since it is not even registered)
and we miss the NodeDeleted event.
Since our \{initialSet} still contains the child path, the initialized event is never fired.
The fix:
As of now there's only one codepath to removing a path from the \{initialSet} (from the data watcher)
The remove should also be called in the callback of our getData(..."/parent/somechild") being done in Step 3 if the resultCode=-101(KeeperException.NoNode)
was:
PathChildrenCache started with PathChildrenCache.StartMode.POST_INITIALIZED_EVENT there could be the following scenario:
1. PCC calls getChildren("../parent") and gets the list of it's children
2. PCC calls processChildren(...) where it puts them into it's \{initialSet} -- set of children whose data it will fetch and cache
3. Later in the same method it calls getDataAndStat(..."/parent/somechild") where it calls getData(...) on this child and registers a dataWatcher for this child
Midst of step 2&3, child node could get deleted -- but since step 3 hasn't completed yet, the dataWatcher isn't triggered (since it is not even registered)
and we miss the NodeDeleted event.
Since our \{initialSet} still contains the child path, the initialized event is never fired.
The fix:
As of now there's only one codepath to removing a path from the \{initialSet} (from the data watcher)
The remove should also be called in the callback of our getData(..."/parent/somechild") being done in Step 3 if the resultCode=-101(KeeperException.NoNode)
> PathChildrenCache never get initialized if a child dies before a data watch is registered for it
> ------------------------------------------------------------------------------------------------
>
> Key: CURATOR-476
> URL: https://issues.apache.org/jira/browse/CURATOR-476
> Project: Apache Curator
> Issue Type: Bug
> Components: Recipes
> Reporter: Rohan Suri
> Priority: Major
>
> PathChildrenCache started with PathChildrenCache.StartMode.POST_INITIALIZED_EVENT there could be the following scenario:
> 1. PCC calls getChildren("../parent") and gets the list of it's children
> 2. PCC calls processChildren(...) where it puts them into it's \{initialSet} – set of children whose data it will fetch and cache
> 3. Later in the same method it calls getDataAndStat(..."/parent/somechild") where it calls getData(...) on this child and registers a dataWatcher for this child
> Midst of step 2&3, child node could get deleted – but since step 3 hasn't completed yet, the dataWatcher isn't triggered (since it is not even registered)
> and we miss the NodeDeleted event.
> Since our \{initialSet} still contains the child path, the initialized event is never fired.
> The fix:
> As of now there's only one codepath to removing a path from the \{initialSet} (from the data watcher)
> The remove should also be called in the callback of our getData(..."/parent/somechild") being done in Step 3 if the resultCode=-101(KeeperException.NoNode)
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