Failed use apigwManagementApi.postToConnection in $connect route - amazon-web-services

Question

I want to return connectionId to a client after the client connect to aws websocket.
I'm using apigwManagementApi.postToConnection to send a response to a client, but I always get an absurd error message.
I already try to debug & search in google, but I can't find a solution for this.
patch.js
require('aws-sdk/lib/node_loader');
var AWS = require('aws-sdk/lib/core');
var Service = AWS.Service;
var apiLoader = AWS.apiLoader;
apiLoader.services['apigatewaymanagementapi'] = {};
AWS.ApiGatewayManagementApi = Service.defineService('apigatewaymanagementapi', ['2018-11-29']);
Object.defineProperty(apiLoader.services['apigatewaymanagementapi'], '2018-11-29', {
get: function get() {
var model = {
"metadata": {
"apiVersion": "2018-11-29",
"endpointPrefix": "execute-api",
"signingName": "execute-api",
"serviceFullName": "AmazonApiGatewayManagementApi",
"serviceId": "ApiGatewayManagementApi",
"protocol": "rest-json",
"jsonVersion": "1.1",
"uid": "apigatewaymanagementapi-2018-11-29",
"signatureVersion": "v4"
},
"operations": {
"PostToConnection": {
"http": {
"requestUri": "/#connections/{connectionId}",
"responseCode": 200
},
"input": {
"type": "structure",
"members": {
"Data": {
"type": "blob"
},
"ConnectionId": {
"location": "uri",
"locationName": "connectionId"
}
},
"required": [
"ConnectionId",
"Data"
],
"payload": "Data"
}
}
},
"shapes": {}
}
model.paginators = {
"pagination": {}
}
return model;
},
enumerable: true,
configurable: true
});
module.exports = AWS.ApiGatewayManagementApi;
index.js
const AWS = require('aws-sdk');
require('./patch.js');
exports.handler = async(event) => {
const connectionId = event.requestContext.connectionId;
const apigwManagementApi = new AWS.ApiGatewayManagementApi({
apiVersion: '2018-11-29',
endpoint: event.requestContext.domainName + '/' + event.requestContext.stage
});
await apigwManagementApi.postToConnection({ ConnectionId: connectionId, Data: connectionId }).promise();
return {};
};
client.js
const WebSocket = require('ws');
const ws = new WebSocket('wss://****');
ws.on('open', () => {
console.log('connected ===================>')
ws.on('message', data => console.warn(`From server: ${data}`));
});
Error in cloudwatch
{
"errorMessage": "410",
"errorType": "UnknownError",
"stackTrace": [
"Object.extractError (/var/runtime/node_modules/aws-sdk/lib/protocol/json.js:48:27)",
"Request.extractError (/var/runtime/node_modules/aws-sdk/lib/protocol/rest_json.js:52:8)",
"Request.callListeners (/var/runtime/node_modules/aws-sdk/lib/sequential_executor.js:105:20)",
"Request.emit (/var/runtime/node_modules/aws-sdk/lib/sequential_executor.js:77:10)",
"Request.emit (/var/runtime/node_modules/aws-sdk/lib/request.js:683:14)",
"Request.transition (/var/runtime/node_modules/aws-sdk/lib/request.js:22:10)",
"AcceptorStateMachine.runTo (/var/runtime/node_modules/aws-sdk/lib/state_machine.js:14:12)",
"/var/runtime/node_modules/aws-sdk/lib/state_machine.js:26:10",
"Request.<anonymous> (/var/runtime/node_modules/aws-sdk/lib/request.js:38:9)",
"Request.<anonymous> (/var/runtime/node_modules/aws-sdk/lib/request.js:685:12)"
]
}
I don't know why, but if I'm trying in a custom route, this code can work.
Does anyone know how to solve this?

Answer 1

I'd suggest to look into this example from AWS, there is on connect response for subprotocol confirmation, but I think any payload can be provided.
The most important bit is the route integration settings in the template, basically, the following two lines in the route integration properties:
IntegrationMethod: POST
ConnectionType: INTERNET
then response will be sent to the connected client.

Answer 2

The only way I've found to make this work is to use a DynamoDB table to store connections, then set up a trigger from the table back to a Lambda function.
There are a few catches though. This Lambda function wont work like your index.js file above. You'll have to use NPM install --save aws-sdk on a folder with your index.js file, zip it and upload it to the lambda function, so that the SDK is localized.
You will also need to set up a user with proper access and put the credentials into a your Lambda function.
Note, if you see a 410 error, that means the connection is no longer there, so you're going in the right direction at that point.
const AWS = require('aws-sdk');
require('./patch.js');
var log = console.log;
AWS.config.update({
accessKeyId: "YOURDATAHERE",
secretAccessKey: "YOURDATAHERE"
});
let send = undefined;
function init() {
const apigwManagementApi = new AWS.ApiGatewayManagementApi({
apiVersion: '2018-11-29',
endpoint: "HARDCODEYOURENDPOINTHERE"
});
send = async (connectionId, data) => {
await apigwManagementApi.postToConnection({ ConnectionId: connectionId, Data: `${data}` }).promise();
}
}
exports.handler = async (event, context) => {
init();
console.log('Received event:', JSON.stringify(event, null, 2));
for (const record of event.Records) {
//console.log(record.eventID);
console.log(record.eventName);
console.log('DynamoDB Record: %j', record.dynamodb);
if(record.eventName == "INSERT"){
var connectionId = record.dynamodb.NewImage.connectionId.S;
try{
await send(connectionId, connectionId);
}catch(err){
log("Error", err);
}
log("sent");
}
}
return `Successfully processed ${event.Records.length} records.`;
};