Lambda Node.js function Can't Access Aurora MySQL

Question

I have a Node.js (ver 16) app in a Lambda Function and I run it on my local machine fine, however when I run the function on AWS I get the following error:

```
{
  "errorType": "Error",
  "errorMessage": "ER_ACCESS_DENIED_ERROR: Access denied for user 'mailQueue'@'172.31.40.76' (using password: YES)",
  "trace": [
    "Error: ER_ACCESS_DENIED_ERROR: Access denied for user 'mailQueue'@'172.31.40.76' (using password: YES)",
    "    at Handshake.Sequence._packetToError (/var/task/node_modules/mysql/lib/protocol/sequences/Sequence.js:47:14)",
    "    at Handshake.ErrorPacket (/var/task/node_modules/mysql/lib/protocol/sequences/Handshake.js:123:18)",
    "    at Protocol._parsePacket (/var/task/node_modules/mysql/lib/protocol/Protocol.js:291:23)",
    "    at Parser._parsePacket (/var/task/node_modules/mysql/lib/protocol/Parser.js:433:10)",
    "    at Parser.write (/var/task/node_modules/mysql/lib/protocol/Parser.js:43:10)",
    "    at Protocol.write (/var/task/node_modules/mysql/lib/protocol/Protocol.js:38:16)",
    "    at Socket. (/var/task/node_modules/mysql/lib/Connection.js:88:28)",
    "    at Socket. (/var/task/node_modules/mysql/lib/Connection.js:526:10)",
    "    at Socket.emit (node:events:527:28)",
    "    at Socket.emit (node:domain:475:12)",
    "    --------------------",
    "    at Protocol._enqueue (/var/task/node_modules/mysql/lib/protocol/Protocol.js:144:48)",
    "    at Protocol.handshake (/var/task/node_modules/mysql/lib/protocol/Protocol.js:51:23)",
    "    at PoolConnection.connect (/var/task/node_modules/mysql/lib/Connection.js:116:18)",
    "    at Pool.getConnection (/var/task/node_modules/mysql/lib/Pool.js:48:16)",
    "    at Runtime.exports.handler (/var/task/index.js:15:10)",
    "    at Runtime.handleOnceNonStreaming (file:///var/runtime/index.mjs:1028:29)"
  ]
}
```

The Aurora Security group allows connections from 172.31.0.0/16 and the reachability analyser gives it the ok.

So it appears to be mySQL having issues. The user appears to have correct permissions from any host.

```
SHOW GRANTS FOR 'mailQueue'

> GRANT USAGE ON *.* TO `mailQueue`@`%`
> GRANT ALL PRIVILEGES ON `emailTransactions`.* TO `mailQueue`@`%` WITH GRANT OPTION
```

Any suggestions from anyone?

Confirmed all settings with manuals and searched the net, I'm stumped.

Answer

The error suggests your lambda is able to reach Aurora but not authenticate. I know you have already verified everything, but do recheck the credentials Lambda is using to access Aurora

Answer

For Troubleshooting purposes , you could deploy an EC2 instance in same subnet that is allowed by Aurora MySQL Security Group, attempt to connect using the mysql client with the credentials you are using within your lambda or if using IAM authentication you can follow steps [here](https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/UsingWithRDS.IAMDBAuth.Connecting.AWSCLI.html#UsingWithRDS.IAMDBAuth.Connecting.AWSCLI.Connect)

Lambda Node.js function Can't Access Aurora MySQL

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