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AWS Application Load Balancer Throwing 502

- 1 answer

I am currently learning about AWS and I have a single EC2 instance running with a nodejs server on port 3000, an Application load balancer with SSL setup that listen on port 80 and 443 (http & https). When I make requests to the http route it returns back the successful health check message. But when I try to access my api via the https method, I get a 502 Error. I googled around and read some articles and they pointed out that the nodejs server keepAliveTimeout and headersTimeout should be higher than the timeout option of the ALB. I tried that and it didn't work. I also tried to set the max-http-header-value to 16384, I also tried to check the access logs for the load balancer on my S3 bucket and the logs just showed that I am getting a 502 error and nothing more. What could be the issue? Because I have tried all solutions that presented but they don't seem to work.

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Answer

The first thing to check is that your server is responding to requests. Try connecting to port 3000 on the server, either from the server itself (eg curl localhost:3000) or from outside the server (which will require the Security Group to permit access to port 3000).

Once you have confirm that the server is responding, configure Security Groups as:

  • A Security Group on the Application Load Balancer (ALB-SG) that permits Inbound access on ports 80 and 443
  • A Security Group on the Amazon EC2 instance (App-SG) that permits inbound access on port 3000 from ALB-SG

That is, App-SG should specifically refer to ALB-SG in its Inbound rules.

Then, configure the Load Balancer to have a Target Group that points at port 3000 on the app server and provide it a URL for the Health Check (that could simply be /).

Then, connect to the Application Load Balancer and see whether you can access your app.

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source: stackoverflow.com
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