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https://issues.apache.org/jira/browse/YARN-366?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13626930#comment-13626930
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Sandy Ryza commented on YARN-366:
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bq. Let's make it a class-name
Sounds good.
bq. I don't like how we are passing configuration around in the
ContainerManagerImpl constructor, we have Service.init(Configuration) exactly
for this purpose.
This is what I tried first, but I came across the following problem, stemming
from the fact that both WebServer and ContainerManager have a a
ContainersMonitor:
* ContainerManager needs to pass its dispatcher to its ContainersMonitor when
it instantiates it.
* To address this, we can instantiate ContainersMonitor in ContainerManager's
init instead of its constructor.
* The way that composite services work, parent service inits tend to happen
before child service inits.
* In NodeManager's init method, it instantiates a WebServer, which takes a
ContainersMonitor as an argument.
* Because of the above, the NodeManager's ContainerManager's ContainersMonitor
will not be instantiated yet.
To work around this, we'd need to do something like move the hierarchy around a
little or set the WebServer's ContainersMonitor separately from the WebServer's
instantiation. What do you think?
> Add a tracing async dispatcher to simplify debugging
> ----------------------------------------------------
>
> Key: YARN-366
> URL: https://issues.apache.org/jira/browse/YARN-366
> Project: Hadoop YARN
> Issue Type: New Feature
> Components: nodemanager, resourcemanager
> Affects Versions: 2.0.2-alpha
> Reporter: Sandy Ryza
> Assignee: Sandy Ryza
> Attachments: YARN-366-1.patch, YARN-366-2.patch, YARN-366.patch
>
>
> Exceptions thrown in YARN/MR code with asynchronous event handling do not
> contain informative stack traces, as all handle() methods sit directly under
> the dispatcher thread's loop.
> This makes errors very difficult to debug for those who are not intimately
> familiar with the code, as it is difficult to see which chain of events
> caused a particular outcome.
> I propose adding an AsyncDispatcher that instruments events with tracing
> information. Whenever an event is dispatched during the handling of another
> event, the dispatcher would annotate that event with a pointer to its parent.
> When the dispatcher catches an exception, it could reconstruct a "stack"
> trace of the chain of events that led to it, and be able to log something
> informative.
> This would be an experimental feature, off by default, unless extensive
> testing showed that it did not have a significant performance impact.
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