Great. that is exactly what I needed.
> On Sep 28, 2015, at 2:42 PM, Mark Payne <marka...@hotmail.com> wrote:
>
> Sumo,
>
> Generally, the approach that we take is to perform that type of operation in
> a method that has the @OnScheduled annotation.
>
> Then you do it only once when the Processor is scheduled.
>
> If you want to ensure that it happens only one time for the lifecycle of the
> JVM, you could use a boolean to keep track of whether or
> not the action has been performed. For example:
>
> private volatile boolean expensiveActionPerformed = false;
>
> @OnScheduled
> public void doExpensiveSetup(final ProcessContext context) {
> if (!expensiveActionPerformed) {
>
> // do expensive action
>
> expensiveActionPerformed = true;
> }
> }
>
>
> Thanks
> -Mark
>
>
>> On Sep 28, 2015, at 5:38 PM, Sumanth Chinthagunta <xmlk...@gmail.com> wrote:
>>
>> Thanks Mark for pointing me to GetTwitter example. I will try to follow this
>> pattern.
>> PropertyDescriptor is only available in onTrigger method via ProcessContext.
>> I needed to get hold of Service from initialize method using
>> ProcessorInitializationContexts as documented in the Developer guide. this
>> helps me to do expensive Service calls once not doing every time onTrigger
>> method is invoked.
>>
>> Thanks
>> Sumo
>>
>>
>>> On Sep 28, 2015, at 5:32 AM, Mark Payne <marka...@hotmail.com> wrote:
>>>
>>> Sumo,
>>>
>>> The preferred mechanism for obtaining a Controller Service is to do so via
>>> a PropertyDescriptor. You would
>>> specify that the property represents a Controller Service by using the
>>> identifiesControllerService(Class) method.
>>> This is discussed in the "Interacting with a Controller Service" section of
>>> the Developer's Guide [1].
>>>
>>> In terms of communicating with some asynchronous process, generally the
>>> best solution is to use a queue and
>>> then read from that queue in the onTrigger method. You will not be able to
>>> call the onTrigger method properly
>>> yourself, as it is designed to be called by the framework at the
>>> appropriate time. I would recommend using
>>> a BlockingQueue with a small capacity, as you do not want your Java Heap to
>>> fill up with objects from this
>>> Processor if the Processor is stopped for a while. You can look at how this
>>> is done in the GetTwitter processor,
>>> if you would like to have an example to look at.
>>>
>>> Let us know if you have any more questions, or if anything is still not
>>> clear!
>>>
>>> Thanks
>>> -Mark
>>>
>>>
>>> [1]
>>> http://nifi.apache.org/docs/nifi-docs/html/developer-guide.html#interacting-with-controller-service
>>>
>>>
>>>
>>>> On Sep 27, 2015, at 3:53 PM, Sumanth Chinthagunta <xmlk...@gmail.com>
>>>> wrote:
>>>>
>>>>
>>>> Hi All,
>>>> I am new to NiFi and I'm stuck with couple issues:
>>>>
>>>> 1. Unable to get hold of ControllerService from Processor’s init method.
>>>> I wanted to pre-set some dependencies in my Processor during init phase
>>>> instead of querying them repeatedly in onTrigger method.
>>>> I am getting null for service and not sure what I have to pass for
>>>> 'serviceIdentifier’ . I couldn't find documentation or examples on how to
>>>> give Identifier to a service.
>>>>
>>>>
>>>> final VertxServiceInterface vertxService = (VertxServiceInterface)
>>>> context.getControllerServiceLookup().getControllerService("VertxService”)
>>>>
>>>>
>>>> https://github.com/xmlking/nifi-websocket/blob/master/src/main/java/com/crossbusiness/nifi/processors/PutEventBus.java#L55
>>>>
>>>> <https://github.com/xmlking/nifi-websocket/blob/master/src/main/java/com/crossbusiness/nifi/processors/PutEventBus.java#L55>
>>>>
>>>> 2. for my usecase I get data published to a topic from EventBus with
>>>> following code.
>>>>
>>>> EventBus eb = vertx.eventBus();
>>>>
>>>> eb.consumer("news.uk.sport", message -> {
>>>> System.out.println("I have received a message: " +
>>>> message.body());
>>>> });
>>>>
>>>> I am working on a date ingest processor (push based) that needs to
>>>> listen for new messages on a topic and send them to flow as FlowFile.
>>>> In my case data source is EvenBus that expose emit messages via
>>>> callback API.
>>>> I am looking for ideas on how to call Processor’s onTrigger method when
>>>> the above callback is evoked.
>>>> Should I have to use my own intermediate queue and poll it in onTrigger
>>>> method?
>>>> is there a better way to trigger the onTrigger method programmatically
>>>> ?
>>>>
>>>> Thanks
>>>> Sumo
>>>
>>
>
