在RDS中访问MySQL或MS SQL时的AWS Lambda node.js ETIMEDOUT

Question

I am trying to a connect a AWS Lambda function to a database in RDS, I followed a few posts that have suggested they both need to be inside the same VPC, but have been told by Amazon support that this is not the case. Although I have tried a multi subnet VPC with nat gateway and security groups allowing access to each, with no prevail.

I am able to talk to the Database instances in SQL management studio or MySQL workbench without a problem.

10:13:00 2017-05-16T10:13:00.509Z Callback connection.connect() 10:13:00 2017-05-16T10:13:00.547Z Error ETIMEDOUT

I have tried a few different methods of connection now, I used an example as seen in the post, the only difference is this databases wasn't in RDS.

Querying a MySQL database from a NodeJS AWS Lambda Function

I have tried a MSSQL and MSSQL databases instances, both experiences a timeout on connection. I have attached all relevant policy's to the lambda function.

I have included below one of my simple tests, just to try and get a connection.

Test Code added below, not this at the bottom of a alexa call.

function mysqltest2() {
    var mysql      = require('mysql');
    var connection = mysql.createConnection({
      host     : 'endpoint.rds.amazonaws.com',
      user     : 'user',
      password : 'pass',
      database : 'db'
      });
                  var test;
                  console.log(`Intent Request`);
                  console.log('Then run MySQL code:');
                  connection.connect(function(err) {
                      console.log('Inside connection.connect() callback');
                      if (!err) {
                          console.log("Database is connected ... ");
                          connection.query("SELECT 1 + 1 AS solution",
                              function(err, result) {
                                  console.log("Inside connection.query() callback")
                                  if (!err) {
                                      console.log(result);
                                      console.log("Query Successful! Ending Connection.");
                                      test = result;
                                      connection.end();
                            } else {
                                      console.log("Query error!");
                                  }
                              });
                      } else {
                          console.log("Error connecting database ..." +             err.message);
                      }
                  });
                  return test;
  }

Answer 1

There were two problems.

1 VPC Setup

VPC setup, reading @ Michael - sqlbot post about VPCs helped a lot.

When using lambda within a VPC the following needs to be taken into consideration.

• The Lambda execution role needs to be able to create, describe and delete network interfaces.
• The Lambda function and the RDS instances need to be in the same VPC.
• The Lambda function and the RDS instances need to be in the same subnets.
• The Lambda function and the RDS instances need to share a security group.
• That security group needs to have a rule allowing traffic from other entities in the same security group.

• The subnet needs to have spare address space to allow lambda to create Elastic Network Interfaces.

  Source Amazon Web Services Support

2. Node.js Callbacks

The second was basically callback hell in node.js

As the function was being called from Alexa intent it was executing the the content.success before the callback had fired. This was then causing a timeout the next time the code executed due to it still being busy executing the previous command. I solved this by making all the callbacks nested and generating the SpeechletResponse in the callback.