AWS ALB event source and provisioned concurrency don't work when enabled together

[ReddytoRumble]

Bug Report

Description

1. What did you do?
   I am deploying a lambda function with an alb event source and a provisioned concurrency.

2. What happened?
   The target group is created with the lambda as a target and uses the $Latest version. The lambda function is created with a provisioned concurrency of 4 which is pinned to a specific version of the lambda function (i.e not Latest) and also creates an alias called Provisioned.
   None of my requests to the lambda function are making use of the provisioned concurrency because of this misconfiguration

3. What should've happened?
   I was expecting the lambda that was registered to the target group to be registered with the version that the Provisioned alias was pinned to.

4. What's the content of your serverless.yml file?

server: #Function Name
    handler: src/lambda.handler
    environment:
      ...
    memorySize: 512
    timeout: 30
    reservedConcurrency: 100
    provisionedConcurrency: 4
    vpc:
      securityGroupIds: ${self:custom.${self:provider.stage}.appSecurityGroupIds}
      subnetIds: ${self:custom.${self:provider.stage}.appSubnetIds}
    events:
      - alb:
          listenerArn: 
            Ref: Listener
          priority: 70
          conditions:
            path: /*
            host: ${self:custom.${self:provider.stage}.dnsRecordName}

1. What's the output you get when you use the SLS_DEBUG=* environment variable (e.g. SLS_DEBUG=* serverless deploy)
   No errors reported with serverless deploy command

Similar or dependent issues:

[medikoo]

Thanks @ReddytoRumble for report. It indeed needs fixing. I believe that same as with API Gateway handling, we need to point ALB to generated alias. PR welcome

[cbm-egoubely]

Hello, I'm working on this, a PR will come in the next few days.