Can't get AWS Lambda function to log (text output) to CloudWatch

amazon-web-services aws-lambda amazon-cloudwatch
ffxsam picture ffxsam · May 23, 2016 · Viewed 47.7k times · Source

I'm trying to set up a Lambda function that will process a file when it's uploaded to an S3 bucket. I need a way to see the output of console.log when I upload a file, but I can't figure out how to link my Lambda function to CloudWatch.

I figured about by looking at the context object that my log group is /aws/lambda/wavToMp3 and the log stream is 2016/05/23/[$LATEST]hex_code_redacted. So I created that group and stream in CloudWatch, yet nothing is being logged to it.

Answer

hoonoh picture hoonoh · Jan 26, 2017

After you update your policy, it seems that you have to update your function's settings to refresh all job instances to read new policies.

So if you just click 'test' button from Lambda console after you update your role policy in IAM, the cached Lambda instances will still have old role permissions, so you will still see no logs being written to Cloudwatch logs.

Just change your timeout by a second and click on 'save and test' button, and you will start to see logs in Cloudwatch.

Related questions

Specify log group for an AWS lambda?

Is there a way to specify the CloudWatch log group that an AWS lambda logs to? It seems to be generated directly from the lambda name; however, it would be especially convenient to, for example, aggregate multiple lambdas to a …

Read More
how to connect a cloudwatch alarm to a lambda function

How do you connect an aws cloud watch alarm to a lambda function invocation? I am programmatically adding a cloud watch alarm to the ELBs that we create as part of a cloud formation stack via AWS CloudFormation Templates. I …

Read More
How to pass values to a Lambda function in CloudWatch?

What's the best way to wrap functions in a way that handles a ping from a CloudWatch timer? For example, take the lambda function below: export const fn = (event, context, callback) => { const { year, make, model, } = event.queryStringParameters return otherFn({ …

Read More