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Lambda Invoke

An important aspect when working with Lambdas is the ability to invoke one like a remote function. The Boto3 Lambda.Client.invoke function is one way to run your Lambda code. Smyth recognizes the need to simulate that as well.

Example

my_project/src/my_app/handlers.py
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import boto3

lambda_client = boto3.client(
    "lambda", 
    endpoint_url="http://localhost:8080"  # (1)!
)  

def order_handler(event, context):
    lambda_client.invoke(
        FunctionName="email_handler",  # (3)!
        InvocationType="Event",  # or RequestResponse
        Payload=b'{"to": "hello@mirumee.com", "subject": "Order made"}',
    )
    return {"statusCode": 200, "body": f"Orders requests: {COUNT}"}

def email_handler(event, context):
    print(event)  # (2)!
    return {"statusCode": 200, "body": f"Products requests: {COUNT}"}
  1. Set the endpoint URL to your Smyth host and port.
  2. The payload being sent to the handler: {"to": "hello@mirumee.com", "subject": "Order made"}.
  3. Corresponds to the TOML config [tool.smyth.handlers.email_handler].

How It Works

No matter what url_path your handler is registered under in your config, every handler is also available via Smyth's "/2015-03-31/functions/{function:str}/invocations" URL. The difference from the url_path invocation is that when using the "direct invocation," the event generator is hardcoded to the smyth.event.generate_lambda_invocation_event_data function.

In the example above, the config might look like this:

myproject/pyproject.toml
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[tool.smyth]
host = "0.0.0.0"
port = 8080

[tool.smyth.handlers.order_handler]
handler_path = "my_app.handlers.order_handler"
url_path = "/orders/{path:path}"

[tool.smyth.handlers.email_handler]
handler_path = "my_app.handlers.email_handler"
url_path = "/emails/{path:path}"

Line 9, which names the handler, is the important one here. Line 11 is required, but you don't have to use the HTTP request method to reach that handler.