Kevin W Monroe created BIGTOP-2836:
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Summary: charm metric collector race condition
Key: BIGTOP-2836
URL: https://issues.apache.org/jira/browse/BIGTOP-2836
Project: Bigtop
Issue Type: Bug
Components: deployment
Affects Versions: 1.2.0, 1.2.1
Reporter: Kevin W Monroe
Assignee: Kevin W Monroe
Priority: Minor
Fix For: 1.3.0
Initially thought fixed in BIGTOP-2801, it seems the charm metric collector can
still cause a failed deployment. As a refresher, metrics give users the
ability see stuff like how many datanodes or zookeeper peers are deployed in an
environment.
The first attempt at fixing this was to include a precondition before
collecting metrics, for example, ensure the namenode is "ready" before running
"hdfs getconf".
However, in this example, there can be a period of time where the charm tells
the NN to start (at which point the "ready" state is set), yet the NN takes a
while to format HDFS. If the metric collector runs during this time, 'hdfs
getconf' will fail, which means the metric hook fails, which means the
deployment fails.
There are a variety of ways to mitigate this:
1. Don't set "ready" until the NN is all the way up.
2. Don't let a metric hook fail the entire deployment.
3. Alter the collector so it handles a failed 'hdfs getconf' gracefully.
#1: added to our todo, but will take more time to implement.
#2: opened an issue against the metric layer to see if this is possible.
This JIRA will focus on fixing the problem with option #3.
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