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Flume >> mail # dev >> EventDrivenSource and dead threads

Juhani Connolly 2013-01-17, 03:45
Brock Noland 2013-01-17, 04:20
Juhani Connolly 2013-01-17, 05:08
Connor Woodson 2013-01-17, 06:01
Juhani Connolly 2013-01-17, 06:21
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Re: EventDrivenSource and dead threads
What I was trying to say is that the ScribeSource should not be responsible
for restarting itself (just from my understanding of your idea; it breaks
the existing paradigm as components should not have to control their own
lifecycle). Going from Brock's link, I feel the most dynamic solution would
be possible to just add in a lifecyle state RESTART and place it in that
switch statement; when that state is reached, it tries to stop then restart
the component and then sets the desired state to START (or STOP if it
couldn't start it again, or set error=true if it couldn't stop it).

And in a way to prevent overriding getLifecycleState to return RESTART,
there could either be an inherited function from AbstractSource to call for
a restart, there could maybe be an option to set it to RESTART on crash, or
something else.

I'll admit though that I know little about the lifecycle system, so I have
no idea if this idea is any better.

- Connor
On Wed, Jan 16, 2013 at 10:21 PM, Juhani Connolly <

> Sink, Source and Channel all extend LifecycleAware, so the function is
> available to all components already.
> I was more questioning whether it was reasonable to start including logic
> to determine the state. That being said, I think the precedent of just
> returning the state set by start/stop is more one of habit, so on further
> thought I don't see it as being unreasonable. I'm going to give fixing
> ScribeSource with it a poke.
> As to new lifecycle states, I took a pass at reworking the lifecycle model
> with guavas service implementation in the past, but it took some very
> significant changes and didn't get the momentum/interest necessary to keep
> working on it. That ticket is here https://issues.apache.org/**
> jira/browse/FLUME-966 <https://issues.apache.org/jira/browse/FLUME-966> .
> Brock might be working on it now though the issue doesn't appear to have
> had attention since october.
> On 01/17/2013 03:01 PM, Connor Woodson wrote:
>> Why limit it to the sources? If there is going to be a change to one
>> component's lifecycle, then I see no reason not to change every
>> component's
>> lifecycle.
>> Sinks and Channels could very well have this problem; so what about giving
>> each LifecycleAware component a takePulse method (or something); or to
>> avoid creating a new method, add a new lifecycle state 'crashed' or such
>> which, when detected, causes a restart of the component. Then components
>> would just need to override getLifecycleState (if this method is polled
>> regularly; I don't know. maybe use a listener for when there's a state
>> change) to detect if it has crashed/needs to be restarted.
>> Just my thoughts,
>> - Connor
>> On Wed, Jan 16, 2013 at 9:08 PM, Juhani Connolly <
>> wrote:
>>  Hmm, overriding the implementation of getLifecycleState provided by
>>> AbstractSource could work. It would be going against the convention that
>>> has been maintained in all other components(that I can think of)
>>> On 01/17/2013 01:20 PM, Brock Noland wrote:
>>>  Hi,
>>>> Yes I can definitely see the issue. It sucks that we'd have to add yet
>>>> another thread. An alternative which wouldn't require another thread
>>>> would be to check the optional interface in the supervisor,
>>>> approximately here:
>>>> https://github.com/apache/****flume/blob/trunk/flume-ng-**<https://github.com/apache/**flume/blob/trunk/flume-ng-**>
>>>> core/src/main/java/org/apache/****flume/lifecycle/**
>>>> LifecycleSupervisor.java#L240<**https://github.com/apache/**
>>>> flume/blob/trunk/flume-ng-**core/src/main/java/org/apache/**
>>>> flume/lifecycle/**LifecycleSupervisor.java#L240<https://github.com/apache/flume/blob/trunk/flume-ng-core/src/main/java/org/apache/flume/lifecycle/LifecycleSupervisor.java#L240>
>>>> >
>>>> However, I am not sold on the supervisor being the best place to fix
Brock Noland 2013-01-17, 07:37
Juhani Connolly 2013-01-17, 08:27
Connor Woodson 2013-01-17, 08:54