Solved: Pub/Sub takes so much time in Cloud Functions, Jav...

hiking93 · 06-23-2022 03:12 AM

I'm publishing a Pub/Sub message in a HttpFunction , here's how I measure the execution time:

val builder: Publisher.Builder
measureTimeMillis {
    builder = Publisher.newBuilder(
        ProjectTopicName.of(projectId, topicName),
    )
}.also {
    LOGGER.info("Pub/Sub publisher newBuilder() took ${it}ms.")
}
val publisher: Publisher
measureTimeMillis {
    publisher = builder.build()
}.also {
    LOGGER.info("Pub/Sub publisher build() took ${it}ms.")
}
measureTimeMillis {
    publisher.publish(pubsubMessage)
}.also {
    LOGGER.info("Pub/Sub publish() took ${it}ms.")
}
measureTimeMillis {
    publisher.shutdown()
}.also {
    LOGGER.info("Pub/Sub shutdown() took ${it}ms.")
}

And the result is:

Pub/Sub publisher newBuilder() took 302ms.
Pub/Sub publisher build() took 3103ms.
Pub/Sub publish() took 93ms.
Pub/Sub shutdown() took 2006ms.

The deployment is configured as Java 11, 512MB. As the Slack Tutorial recommends to publish a topic to prevent the 3 second timeout, the publishing itself takes more than that. Is there anything that I'm doing it wrong?

osvaldolopez

Make sure you’re not loading dependencies that your function doesn’t use.

As described in the Performance section [1] of the document Tips & Tricks that I shared with you in the last post, it states that:

Because functions are stateless, the execution environment is often initialized from scratch (during what is known as a cold start).

If your functions import modules, the load time for those modules can add to the invocation latency during a cold start.

If your application is latency-sensitive, as is stated here [2]:

You can avoid cold starts for your application and reduce application latency by setting a minimum number of instances.

Cloud Functions scales by creating new instances of your function. Each of these instances can handle only one request at a time, so large spikes in request volume often cause longer wait times as new instances are created to handle the demand.

Take a look at this Stackoverflow post [3] to get extra support about reducing times related to cold starts.

[1]: https://cloud.google.com/functions/docs/bestpractices/tips#performance

[2]:https://cloud.google.com/functions/docs/configuring/min-instances

[3]:https://stackoverflow.com/a/51790072/17544309

View solution in original post

osvaldolopez

It depends on the commands you're using. What are you trying to achieve? Are you expecting your function to respond within 3 seconds of receiving a webhook request? These Cloud Function’s tips & tricks may be helpful [1].

[1]:https://cloud.google.com/functions/docs/bestpractices/tips#ensure_http_functions_send_an_http_respon...

hiking93

I‘m implementing a Slack Slash Command, which needs to respond within 3 seconds.

I have 2 functions, A and B.

Function A receives HTTP request, publish a Pub/Sub event, then response immediately.

Function B receives Pub/Sub event from A, then calls 3rd party APIs. After that, it makes a POST request to the Slack response URL.

I'm following the Pub/Sub tutorial. It works, but takes so much time (can be 15 secs. or more) on Function A, especially on a cold start.

osvaldolopez