[
https://issues.apache.org/jira/browse/HADOOP-3628?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12623026#action_12623026
]
Konstantin Shvachko commented on HADOOP-3628:
---------------------------------------------
I do not see any difference in behavior of ping in case (UNDEFINED: CREATED:
INITIALIZED: STARTED) and LIVE:
In both cases ping will return nothing and the caller will not be able to know
whether the service is live or not.
Do I understand the purpose of ping() correctly?
In case of FAILED: TERMINATED: ping() throws ServiceStateException, and this is
only way to know that the service is not live.
But is this the right way to pass information outside? Exceptions are for
errors right?
I think ping() is somewhat redundant because Service already has
getServiceState(). This is as close to ping as it could be, imo.
> 1. is a datanode considered live only once registered?
May be it needs to be clarified. Data-node indeed is not alive until it
registers for the first time. It later can be asked to re-register
when name-node restarts, but it still should be considered alive when the
name-node is down and therefore formally the data-node
is not registered with anything out there.
> 2. similarly, should the ping() require dnRegistration to be non null?
After registration dnRegistration is not null, so ping can suppose that. If
ping() is really necessary, see above.
> Add a lifecycle interface for Hadoop components: namenodes, job clients, etc.
> -----------------------------------------------------------------------------
>
> Key: HADOOP-3628
> URL: https://issues.apache.org/jira/browse/HADOOP-3628
> Project: Hadoop Core
> Issue Type: Improvement
> Components: dfs, mapred
> Affects Versions: 0.19.0
> Reporter: Steve Loughran
> Assignee: Steve Loughran
> Attachments: AbstractHadoopComponent.java, hadoop-3628.patch,
> hadoop-3628.patch, hadoop-3628.patch, hadoop-3628.patch, hadoop-3628.patch,
> hadoop-3628.patch, hadoop-3628.patch, hadoop-3628.patch
>
>
> I'd like to propose we have a standard interface for hadoop components, the
> things that get started or stopped when you bring up a namenode. currently,
> some of these classes have a stop() or shutdown() method, with no standard
> name/interface, but no way of seeing if they are live, checking their health
> of shutting them down reliably. Indeed, there is a tendency for the spawned
> threads to not want to die; to require the entire process to be killed to
> stop the workers.
> Having a standard interface would make it easier for
> * management tools to manage the different things
> * monitoring the state of things
> * subclassing
> The latter is interesting as right now TaskTracker and JobTracker start up
> threads in their constructor; that's very dangerous as subclasses may have
> their methods called before they are full initialised. Adding this interface
> would be the right time to clean up the startup process so that subclassing
> is less risky.
--
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.
