AWS Lambda and Redis client. Why can't I call callback?

问题:

I'm trying to write an AWS Lambda function which uses Redis. When I run the code below:

'use strict'  function handler (data, context, callback) {   const redis = require("redis")   const _ = require("lodash")   console.log('before client')   const client = redis.createClient({     url: 'redis://cache-url.euw1.cache.amazonaws.com:6379',   })   console.log('after client')   callback(null, {status: 'result'})   console.log('after callback') }  exports.handler = handler 

I have an answer like this:

{   "errorMessage": "2016-09-20T15:22:27.301Z 07d24e0b-7f46-11e6-85e9-e5f48906c0da Task timed out after 3.00 seconds" } 

and logs look like:

which, IMHO, means that callback was called but nothing happened.

When I remove client's initialization I see proper response.

Any Ideas?

回答1:

From the official documentation:

When the callback is called, the Lambda function exits only after the Node.js event loop is empty.

Since you are calling the callback, but your Lambda function invocation is not ending, it appears you still have something on the event loop. Your function isn't really doing anything except creating a Redis connection. I'm guessing you need to close the Redis connection when you are done with it, in order to clear the event loop and allow the Lambda invocation to complete.

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