Thinking that I wanted to clear out old logs, I made the mistake of deleting my Lambda's "Log Stream" on CloudWatch.
The result, as I should have expected if I was awake, is that now CloudWatch isn't getting the Lambda's console logs at all. Oops.
The log group still exists. I can see how to create a new log stream.
What I haven't been able to find on the web is clear instructions to get the existing Lambda to output to this new stream... ie, to repair what I did.
Can someone provide instructions or a pointer to them, please? I'm sure I'm not the only one who's made this mistake, so I think it's an answer worth having on tap.
UPDATE: Decided to try recovering by creating an entirely new Lambda, running the same code and configured the same way, expecting that it would Just Work; my understanding was that a new Lambda binds to a CloudWatch group automagically.
Then I ran my test, clicked the twist-arrow to see the end of the output, and hit "Click here to view the corresponding CloudWatch log group.". It opened Cloudwatch looking at the expected log group name -- with a big red warning that this group did not exist. Clicking "(Logs)" at the top of the test output gave the same behavior.
I tried creating the group manually, but now I'm back where I was -- lambda runs, I get local log output, but the logs are not reaching CloudWatch.
So it looks like there's something deeper wrong. CloudWatch is still getting logs from the critical lambda (the one driving my newly-released Alexa skill), and the less-critical one (scheduled update for the skill's database) is running OK so I don't absolutely need its logs right now -- but I need to figure this out so I can read them if that background task ever breaks.
Since this is now looking like real Unexpected Behavior rather than user error, I'll take it to the AWS forums and post here if they come up with an answer. On that system, the question is now at https://repost.aws/questions/QUDzF2c_m0TPCwl3Ufa527Wg/lambda-logging-to-cloud-watch-seems-to-be-broken
Programmer's mantra: "If it was easy, they wouldn't need us..."
CodePudding user response：
After a Lambda function is executed, you can go to the Monitoring tab and click View logs in CloudWatch -- it will take you to the location where the logs should be present.
If you know that the function has executed but no logs are appearing, then confirm that your Lambda function has the AWSLambdaBasicExecutionRole assigned to the IAM Role being used by the Lambda function. This grants permission for the Lambda function to write to CloudWatch Logs.