Lim Yang Wei created CURATOR-636:
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Summary: Make PersistentTtlNode initialDelay more configurable
Key: CURATOR-636
URL: https://issues.apache.org/jira/browse/CURATOR-636
Project: Apache Curator
Issue Type: New Feature
Components: Recipes
Reporter: Lim Yang Wei
Currently when PersistentTtlNode starts, it will
# create a CONTAINER node
# create a CHILD node `_touch`
But there is a initialDelay between 1 and 2. If the initialDelay is long enough
and the client is disconnected, 1 will not be deleted forever (because
CONTAINER node only delete its parent when all its child is gone, but in this
case, it never has any of them).
The initialDelay could be configured, but not so flexible. The initialDelay is
calculated by the formula `ttl/touchScheduleFactor`, but this formula is also
used to how frequent we want to ping Zookeeper to keep our znodes alive, aka
period.
As you can see here (2nd parameter is initialDelay and 3rd parameter is for
period)
|// PersistentTtlNode.java
Future<?> future = executorService.scheduleAtFixedRate(touchTask, ttlMs /
touchScheduleFactor, ttlMs / touchScheduleFactor, TimeUnit.MILLISECONDS);
// Interface ScheduledExecutorService
[ScheduledFuture|https://docs.oracle.com/javase/jp/8/docs/api/java/util/concurrent/ScheduledFuture.html]<?>
scheduleAtFixedRate([Runnable|https://docs.oracle.com/javase/jp/8/docs/api/java/lang/Runnable.html]
command, long initialDelay, long period,
[TimeUnit|https://docs.oracle.com/javase/jp/8/docs/api/java/util/concurrent/TimeUnit.html]
unit)|
||
Let's say we have ttl of 5 minutes. We want to have 0 initialDelay so we will
set the touchScheduleFactor to 5 minutes too. This will give us 1ms (5
minutes/5 minutes) of initialDelay (which solves our problem) but spamming
Zookeeper every second.
So it would be nice if we can set `initialDelay`
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