Waiting for provisioned concurrency on Lambdas

[NikolayMetchev]

If you have an AWS Lambda with provisioned concurrency on an alias and you update the alias. The effect isn't immediate. It takes time for the provisioned concurrency to be updated for the Lambda alias. Is there a code example of how to wait for the provisioned concurrency to be updated before proceeding.

[lauzadis]

Does updating the alias transition the Lambda function's LastUpdateStatus to "InProgress"? If so, you can use the waiter function LambdaClient.waitUntilFunctionUpdatedV2(...) to wait for the LastUpdateStatus to transition to "Successful".

Here is our developer guide entry on waiters: https://docs.aws.amazon.com/sdk-for-kotlin/latest/developer-guide/waiters.html

[NikolayMetchev]

As far as I can tell the waiter function only checks lastUpdateStatus which is "Successful" even if ProvisionedConcurrencyStatus is Pending.

[NikolayMetchev]

In fact that makes sense because the Provisioned Concurrency Status is not on a function itself but rather on a version/alias so it can't be part of the function update.

[ianbotsf]

I don't think a waiter exists for this. If it did, it would need to operate on the getProvisionedConcurrencyConfig API. Waiters are modeled directly by the service and since Lambda doesn't include one here we can't provide a method for it.

You'll likely need to write your own logic for polling getProvisionedConcurrencyConfig until the response contains "Status": "READY" (as opposed to "IN_PROGRESS" or "FAILED").

[ianbotsf]

Something like this I think:

suspend fun waitUntilConcurrencyUpdated(func: String, alias: String) {
    while (true) {
        val status = lambda.getProvisionedConcurrencyConfig {
            functionName = func
            qualifier = alias
        }

        when (status.status) {
            ProvisionedConcurrencyStatusEnum.Ready -> return
            ProvisionedConcurrencyStatusEnum.Failed -> error("Could not update provisioned concurrency")
            else -> { /* continue loop */ }
        }

        delay(3.seconds) // wait a sensible amount of time to avoid throttling
    }
}

[NikolayMetchev]

Thanks. I already implemented something very similar. What are the chances a waiter gets added in the future?

[NikolayMetchev]

Namely ProvisionedConcurrencyStatusEnum

[RanVaknin]

Hi @NikolayMetchev ,

I have created a request to add this waiter with the Lambda service team (ticket #P139856257).
We don't know if / when this will get added, but if you have access to AWS Support via the developer console, you can open a support ticket and reference the ticket ID I shared above to try and get an update on this.

Since it seems like you're unblocked for now, and this is not actionable by the SDK team I'm inclined to close this discussion.

Thanks again for bringing this to our attention.
All the best,
Ran~