Filter console.error and console.log on CloudWatch

Question

I have a lambda function that have console.error and console.log which node.js print stderr and stdout respectively.

But when I go to CloudWatch, I get something like this:

2017-12-29 11:08:16.889 (+00:00) I can log with console.log
2017-12-29 11:08:16.889 (+00:00) I can log with console.error

It doesn't seem like they make any differentiation.

Am I missing something? Is there any way to check their difference, which wouldn't involve manually adding prefixes?

Answer 1

As this question was somehow popular I'll answer myself with the solution I applied.

AWS Lambda just doesn't differentiate between console.log and console.error in CloudWatch.

The only way is really to interject the functions inside the lambda with this for example:

const originalConsoleError = console.error;
const originalConsoleLog = console.log;

console.error = function (message) {
  originalConsoleError(`ERROR: ${message}`);
};

console.log = function (message) {
  originalConsoleLog(`INFO: ${message}`);
};

// Example usage
console.log('This is an informational message');
console.error('This is an error message');

2017-12-29 11:08:16.889 (+00:00) INFO: This is an informational message
2017-12-29 11:08:16.889 (+00:00) ERROR: This is an error message

And then if we want to filter we can use CloudWatch Insights:

fields @timestamp, @message
| filter @message like /INFO:/ or @message like /ERROR:/
| sort @timestamp desc