Description
Expected Behavior
All keys appended by calling logger.appendKeys are cleared before the next invocation.
Current Behavior
If the Lambda function throws an error, then any keys appended will be present in the subsequent execution. At a minimum, they are present in the Lambda invocation event log if logEvents is enabled.
Code snippet
Here's a unit test that reproduces the issue. It uses sinon and chai but should be easily ported to other testing libraries. Imports are excluded for readability.
describe('injectLambdaContext', () => {
const logger = new Logger({ serviceName: 'example' });
let loggerStub: sinon.SinonStub;
let capturedLoggerStates: unknown[] = [];
beforeEach(() => {
loggerStub = sinon.stub(logger, 'info').callThrough();
loggerStub.withArgs('Lambda invocation event').callsFake(() => {
// Capture logger's internal state when middleware logs invocation
// @ts-ignore - accessing private field to capture logged attributes
capturedLoggerStates.push({ ...(logger as any).temporaryLogAttributes });
});
});
afterEach(() => {
loggerStub.restore();
capturedLoggerStates = [];
});
it('should clear log keys between invocations when an exception is thrown', async () => {
const handlerFunction = async (): Promise<never> => {
logger.appendKeys({ testKey: 'testValue' });
throw new Error('oh no');
};
const handler = middy(handlerFunction).use(
injectLambdaContext(logger, { logEvent: true, resetKeys: true }),
);
await expect(handler({}, lambdaContext)).to.be.rejected;
await expect(handler({}, lambdaContext)).to.be.rejected;
expect(capturedLoggerStates).to.have.length(
2,
'Expected two invocations to have been logged',
);
expect(capturedLoggerStates[1]).to.not.have.property('testKey'); // this assertion fails
});
});Steps to Reproduce
In addition to running the unit test, deploy a Lambda function that
- Appends keys to the logger
- Throws an exception
You'll see in the second Lambda invocation that the log line Lambda invocation event has those keys set.
Possible Solution
The issue is that we don't call resetKeys in the middleware's onError. We should either reset keys in the error handler, or move the logic to the before handler.
Powertools for AWS Lambda (TypeScript) version
latest
AWS Lambda function runtime
20.x
Packaging format used
npm
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