Hi Robert,
Thanks for the reply. 'get_responses' method return a list of dictionaries and
'send_to_output' method takes each element of the list and simultaneously posts
it to an API end point.
My question is I just need to send a signal(write a message 'process completed'
) to pubsub topic2 only after completion of send_to_output step (i.e. after
processing entire list from before step).
If I add it after last step like below, I suspect it would write message for
every element of the list. Is there any way that I can do it only once at the
end?
beam.Map(lambda output: send_to_output(output)) | 'process completed' >>
beam.io.WriteStringsToPubSub(topic=known_args.output_topic)
Regards,
Anjana
________________________________________
From: Robert Bradshaw [rober...@google.com]
Sent: Thursday, September 19, 2019 2:31 PM
To: user
Cc: Richard Amrith Lourdu
Subject: Re: Publish message to pubsub topic after processing current input in
beam streaming pipeline
On Thu, Sep 19, 2019 at 11:05 AM Anjana Pydi
<anjan...@bahwancybertek.com> wrote:
>
> Hi ,
>
> I have a beam streaming pipeline which reads data from pubsub topic, use it
> to call an API and get responses, apply some transformations on the obtained
> responses and writes to output sinks.
>
> Now, I need to add logic to write a 'process completed' message to another
> pubsub topic once after the process gets finished. Can some one please
> provide your thoughts on how can I add it.
>
> I actually want to achieve this:
>
> topic1 (data)-> triggers pipeline and writes complete message at end-> topic2
> (complete msg)
Your code below looks fine so far. I'm assuming your send_to_output
function produces the message that you want to send to topic2, right?
(BTW, you can write beam.Map(send_to_topic) rather than having to
write beam.Map(lambda output: send_to_output(output)).)
In that case, you just need to add
data | beam.io.WriteStringsToPubSub(topic2)
> When topic1 sees message on topic2, it again posts new data to topic1
>
> Below is the code sample:
>
> pubsub_message = p | 'Read From Pubsub' >>
> beam.io.ReadStringsFromPubSub(topic=known_args.input_topic) | 'split and add'
> >> beam.ParDo(split_item)
>
> data = pubsub_message | 'API call' >> beam.FlatMap(lambda x:
> get_responses(x[0],
> datetime.strptime(x[1], "%Y-%m-%d %H:%M:%S"),
> datetime.strptime(x[2], "%Y-%m-%d %H:%M:%S"))) |
> 'WriteOutput' >> beam.Map(lambda output: send_to_output(output))
>
> Thanks,
> Anjana
>
>
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