README.md

Tuning Lambda Performance

REMEMBER - Lambda's containers are reused.

1. Lazily load variables in the global scope
2. Don't load it if you don't need it - cold starts are affected.

The boto3 client init have cost. It is around 200ms.

Please MUST watch AWS re:Invent 2017: Become a Serverless Black Belt: Optimizing Your Serverless Appli (SRV401)

Step 1: Init boto3 session object every time.

The source code is here. If you run the following code, every time get_secret() function will init boto client.

@xray_recorder.capture('get_secret')
def get_secret():

    secret_name = "starAlliances/dev/seatMap/provider"
    region_name = "us-east-1"

    try:
        xray_recorder.begin_subsegment('init_client')
        # Create a Secrets Manager client
        session = boto3.session.Session()
        client = session.client(
            service_name='secretsmanager',
            region_name=region_name
        )
        xray_recorder.current_subsegment().put_annotation('init_client', 'done')
    finally:
        xray_recorder.end_subsegment()

You can see the result of time spent in the X-Ray. You will see the init spent 620ms.

Second and third calls. It is not from the cold start. You can see the init still spend a lot time time: ~ 300ms:

Step 2: Use global variable to improve the performance

The source code is here. You can see the following change with global variable and lazy load:

client = None

@xray_recorder.capture('get_secret')
def get_secret():

    secret_name = "starAlliances/dev/seatMap/provider"
    region_name = "us-east-1"

    try:
        xray_recorder.begin_subsegment('init_client')
        # Create a Secrets Manager client
        global client
        if not client:
            client = boto3.client(
                service_name='secretsmanager',
                region_name=region_name
            )
        xray_recorder.current_subsegment().put_annotation('init_client', 'done')
    finally:
        xray_recorder.end_subsegment()

When you run the lambda after 2nd time, you will big save time on the init: