Detect exceptions raised outside of the handler

[TalUsvyatsky]

What does this PR do?

This PR adds telemetry for exceptions that occur outside of the handler function.

When an exception occurs outside of the handler function:

1. aws.lambda.enhanced.errors is emitted
2. A trace with an error span is created

Motivation

• https://datadoghq.atlassian.net/browse/SVLS-4666
• Users should have visibility into this category of errors.
• When a line of code raises outside of the handler function, then datadog is not able to detect the error. #210

Testing Guidelines

1. Created a handler file like this:

  import json
 
  0/0 # Purposely raise an exception

  def hello(event, context):
      body = {
          "message": "some message",
          "input": event,
      }
      return {"statusCode": 200, "body": json.dumps(body)}

2. Deployed my function and invoked it via function URL
3. Saw traces with an error span from the call (example trace)
4. Saw aws.lambda.enhanced.errors emitted (graph)
5. Traces appear in serverless detail page invocation table (link to search for function)
6. Issues appear in error tracking and are informative

Additional Notes

Types of Changes

• Bug fix
• New feature
• Breaking change
• Misc (docs, refactoring, dependency upgrade, etc.)

Check all that apply

• This PR's description is comprehensive
• This PR contains breaking changes that are documented in the description
• This PR introduces new APIs or parameters that are documented and unlikely to change in the foreseeable future
• This PR impacts documentation, and it has been updated (or a ticket has been logged)
• This PR's changes are covered by the automated tests
• This PR collects user input/sensitive content into Datadog
• This PR passes the integration tests (ask a Datadog member to run the tests)

https://datadoghq.atlassian.net/browse/SVLS-4666

[purple4reina]

FYI, pulling from main should fix the check layer size test failure.

[duncanista]

Amazing work – LGTM.

There's one nit:

datadog-lambda-python/datadog_lambda/tracing.py

Lines 1236 to 1255 in 21012cb

	tags = None
	if context:
	function_arn = (context.invoked_function_arn or "").lower()
	tk = function_arn.split(":")
	function_arn = ":".join(tk[0:7]) if len(tk) > 7 else function_arn
	function_version = tk[7] if len(tk) > 7 else "$LATEST"
	tags = {
	"cold_start": str(is_cold_start).lower(),
	"function_arn": function_arn,
	"function_version": function_version,
	"request_id": context.aws_request_id,
	"resource_names": context.function_name,
	"functionname": context.function_name.lower()
	if context.function_name
	else None,
	"datadog_lambda": datadog_lambda_version,
	"dd_trace": ddtrace_version,
	"span.name": "aws.lambda",
	}
	tags = tags or {}

Should we care about some of the tags that can be added from this? i.e. functionname, cold_start (which should always be true if we are loading), datadog_lambda_version, ddtrace_version

[duncanista]

LGTM – left a nit.

[joeyzhao2018]

LGTM 👍