No, it will be called per bolt instance. That's why init code needs to be
guarded behind a double-check lock to guarantee it only executes once per
JVM.
e.g.
private static volatile boolean initialized = false;
...
if (!initialized) {
synchronized(MyInitCode.class) {
if (!initialized) {
// do stuff
initialized = true;
}
}
}
Until there's a set of lifecycle hooks, that's about as good as I've cared
to make it.
Michael Rose (@Xorlev <https://twitter.com/xorlev>)
Senior Platform Engineer, FullContact <http://www.fullcontact.com/>
[email protected]
On Mon, Jun 2, 2014 at 8:27 PM, Chris Bedford <[email protected]> wrote:
> This looks promising. thanks.
>
> hope you don't mind one more question -- if i create my own
> implementation of ITaskHook and add it do the config as you illustrated in
> prev. msg.. will the prepare() method of my implementation be called
> exactly once shortly after StormTopology is deserialized by the worker
> node process ?
>
> - chris
>
>
>
>
> On Mon, Jun 2, 2014 at 7:09 PM, Michael Rose <[email protected]>
> wrote:
>
>> You don't have to include a specific bolt for init code. It's not
>> difficult to push your init code into a separate class and call it from
>> your bolts, lock on that class, run init, and then allow other instances to
>> skip over it.
>>
>> Without changing bolt/spout code, I've taken to including a task hook for
>> init code (e.g. properties / Guice). Check out BaseTaskHook, it's easily
>> extendible and can be included pretty easily too:
>>
>> stormConfig.put(Config.TOPOLOGY_AUTO_TASK_HOOKS,
>> Lists.newArrayList(MyTaskHook.class.getName()));
>>
>> Michael Rose (@Xorlev <https://twitter.com/xorlev>)
>> Senior Platform Engineer, FullContact <http://www.fullcontact.com/>
>> [email protected]
>>
>>
>> On Mon, Jun 2, 2014 at 7:25 PM, Chris Bedford <[email protected]>
>> wrote:
>>
>>> Yes.. if i used prepare or open on spouts or bolts it would work, but
>>> unfortunately it would be a bit brittle. I'd have to include a spout or
>>> bolt just for initializing my invariant code... i'd rather do that when the
>>> topology is activated on the worker.. so this seems like a good use of an
>>> activated() method on the StormTopology class (where activated()
>>> would be called after the StormTopology is deserialized by the worker node
>>> process).
>>>
>>> But, if there is no such method, I will make do with what is there.
>>>
>>> thanks for your response.
>>>
>>> chris
>>>
>>>
>>>
>>> On Mon, Jun 2, 2014 at 6:28 AM, Marc Vaillant <[email protected]>
>>> wrote:
>>>
>>>> The bolt base classes have a prepare method:
>>>>
>>>>
>>>> https://storm.incubator.apache.org/apidocs/backtype/storm/topology/base/BaseBasicBolt.html
>>>>
>>>> and the spout base classes have a similar activate method:
>>>>
>>>>
>>>> https://storm.incubator.apache.org/apidocs/backtype/storm/topology/base/BaseRichSpout.html
>>>>
>>>> Is that sufficient for your needs or were you thinking of something
>>>> different?
>>>>
>>>> Marc
>>>>
>>>> On Sun, Jun 01, 2014 at 04:47:03PM -0700, Chris Bedford wrote:
>>>> > Hi there -
>>>> >
>>>> > I would like to set up some state that spouts and bolts share, and
>>>> I'd like to
>>>> > prepare this state when the StormTopology gets 'activated' on a
>>>> worker.
>>>> >
>>>> > it would be great if the StormTopology had something like a prepare
>>>> or open
>>>> > method to indicate when it is starting. I looked but i could find no
>>>> such API.
>>>> > Maybe I should submit an enhancement request ?
>>>> >
>>>> > Thanks in advance for your responses,
>>>> > - Chris
>>>> >
>>>> >
>>>> >
>>>> > [ if anyone is curious, the shared state is for all my application
>>>> code to
>>>> > check or not check invariants. the invariant checking takes
>>>> additional time,
>>>> > so we don't want to do it in production.. but during
>>>> testing/development it
>>>> > helps catch bugs].
>>>> >
>>>> > --
>>>> > Chris Bedford
>>>> >
>>>> > Founder & Lead Lackey
>>>> > Build Lackey Labs: http://buildlackey.com
>>>> > Go Grails!: http://blog.buildlackey.com
>>>> >
>>>> >
>>>>
>>>
>>>
>>>
>>> --
>>> Chris Bedford
>>>
>>> Founder & Lead Lackey
>>> Build Lackey Labs: http://buildlackey.com
>>> Go Grails!: http://blog.buildlackey.com
>>>
>>>
>>>
>>
>
>
> --
> Chris Bedford
>
> Founder & Lead Lackey
> Build Lackey Labs: http://buildlackey.com
> Go Grails!: http://blog.buildlackey.com
>
>
>
