Provide `IGNORE` option for `AWS_XRAY_CONTEXT_MISSING` configuration variable

[NathanielRN]

Description

In #52, it was noted that calls to unsupported APIs will result in exceptions that break a customer's app. We suggested a workaround where setting AWS_XRAY_CONTEXT_MISSING=LOG_ERROR logs instead of throwing an exception as explained in our X-Ray Java SDK Documentation.

However, there are so many logs that the log file is flooded.

We should update the code to support an option like IGNORE so that neither an exception is raised nor a log message is printed out. (Or we can log at a Debug log level with LOG_DEBUG).

Perhaps we can even make it only log once so that the customer can still notice the issue.

aws-xray-sdk-python/aws_xray_sdk/core/context.py

Lines 122 to 125 in f5f9c47

	if self.context_missing == 'RUNTIME_ERROR':
	raise SegmentNotFoundException(MISSING_SEGMENT_MSG)
	else:
	log.error(MISSING_SEGMENT_MSG)

[eercanayar]

Thanks @NathanielRN for your bias for action! 🚀 I would vote for the IGNORE option to silence all missing segment logs, even without logging once; because of following reasons:

• The setting AWS_XRAY_CONTEXT_MISSING = IGNORE is not default, so the user will take action to set it IGNORE, so it's an informed decision.
• If the traced resource is a short-lived function and uses a function with a missing context just once, it'll produce the same amount of logs since the first occurrence will be logged.

[willarmiros]

Thank you for raising this request! We will prioritize it as soon as we can, but would also be open to a PR to add support for this. It should be fairly straightforward to add (modifying where Nathan linked) - just be sure to document in README!

[stijndehaes]

I added a PR for this: #338