错误：在 Lambda 和 node.js 中使用 AWS X-ray 时，“无法从上下文中获取当前子/段”

Question

I am trying to use implement the AWS X-ray into my current project (using Node.js and Serverless framework). I am trying to wire the X-ray to one of my lambda function, I got the problem of

Error: Failed to get the current sub/segment from the context.
    at Object.contextMissingRuntimeError [as contextMissing] (/.../node_modules/aws-xray-sdk-core/lib/context_utils.js:21:15)
    at Object.getSegment (/.../node_modules/aws-xray-sdk-core/lib/context_utils.js:92:45)
    at Object.resolveSegment (/.../node_modules/aws-xray-sdk-core/lib/context_utils.js:73:19).....

code below:

import { DynamoDB } from "aws-sdk";
import AWSXRay from 'aws-xray-sdk';

export const handler = async (event, context, callback) => {

    const dynamo = new DynamoDB.DocumentClient({
        service: new DynamoDB({ region })
    });

    AWSXRay.captureAWSClient(dynamo.service);

    try {
        // call dynamoDB function 
    } catch(err) {
        //...
    }
}

for this problem, I use the solution from https://forums.aws.amazon.com/thread.jspa?messageID=821510&#821510

the other solution I tried is from https://forums.aws.amazon.com/thread.jspa?messageID=829923&#829923

code is like

import AWSXRay from 'aws-xray-sdk';
const AWS = AWSXRay.captureAWS(require('aws-sdk'));

export const handler = async (event, context, callback) => {

    const dynamo = new AWS.DynamoDB.DocumentClient({region});

    //....
}

Still not working...

Appreciated to the help of any kind.

Answer 1

As you mention, that happened because you're running locally (using serverless-offline plugin) and the serverless-offline plugin doesn't provide a valid XRAY context.

One possible way to pass this error and still be able to call your function locally is setting AWS_XRAY_CONTEXT_MISSING environment variable to LOG_ERROR instead of RUNTIME_ERROR (default).

Something like :

serverless invoke local -f functionName -e AWS_XRAY_CONTEXT_MISSING=LOG_ERROR

I didn't test this using serverless framework but it worked when the same error occurred calling an amplify function locally :

amplify function invoke <function-name>

Answer 2

I encountered this error also. To fix it, I disabled XRay when running locally. XRay isn't needed when running locally because I can just set up debug log statements at that time.

This is what the code would look like

let AWS = require('aws-sdk');
if (!process.env.IS_OFFLINE) {
    const AWSXRay = require('aws-xray-sdk');
    AWS = AWSXRay.captureAWS(require('aws-sdk'));
}

If you don't like this approach, you can set up a contextStrategy to not error out when the context is missing.

Link here

AWSXRay.setContextMissingStrategy("LOG_ERROR");

Answer 3

If you don't want the error clogging up your output you can add a helper that ignores only that error.

// Removes noisy Error: Failed to get the current sub/segment from the context due to Xray
export async function disableXrayError() {
  console.error = jest.fn((err) => {
    if (err.message.includes("Failed to get the current sub/segment from the context")) {
      return;
    } else {
      console.error(err);
    }
  });
}