Nginx – GET to NGINX reverse proxy works but POST gives me a 502 Bad Gateway Response

curlnginxreverse-proxy

I am using NGINX as a reverse proxy and just put up a new service written in Go.

The service has two endpoints

GET /tracking/ping

POST /tracking/customer

In NGINX, I am using the following to proxy the request

location /v1/location/ {
    proxy_pass http://path-to-tracking-service:8181/;
}

When curl the two endpoints such as the following, I get different results.

The GET /tracking/ping endpoint

curl -X GET https://example.com/v1/location/tracking/ping
"Pong!"

The 'POST /tracking/customer` endpoint

curl -H "Content-Type: application/json" -d '{"userId":"1234"}'  https://example.com/v1/location/tracking/customer
<html>
<head><title>502 Bad Gateway</title></head>
<body bgcolor="white">
<center><h1>502 Bad Gateway</h1></center>
<hr><center>nginx/1.9.12</center>
</body>

Not sure why this would happen. I am proxying other services I have and POST requests work perfectly fine.

Here is the nginx.conf

user nginx;
worker_processes 1;

error_log  /var/log/nginx/error.log warn;
pid        /var/run/nginx.pid;


events {
    worker_connections  1024;
}

http {
    include       /etc/nginx/mime.types;
    default_type  application/octet-stream;

    log_format  main  '$remote_addr - $remote_user [$time_local] "$request" '
                    '$status $body_bytes_sent "$http_referer" '
                    '"$http_user_agent" "$http_x_forwarded_for"';

    access_log  /var/log/nginx/access.log  main;

    sendfile        on;
    #tcp_nopush     on;

    keepalive_timeout  65;

    proxy_connect_timeout       600;
proxy_send_timeout          600;
proxy_read_timeout          600;
send_timeout                600;

    #gzip  on;

    #include /etc/nginx/conf.d/*.conf;

    #server {
        #include /etc/nginx/sites-enabled/*;
    #}

    server {
        listen 80;
        server_name *.example.com;
        #return 301 https://$host$request_uri;
        include /etc/nginx/sites-enabled/*;
    }

    server {


    #listen 80;
    listen 443 ssl;
    server_name *.example.com;

    ssl_certificate           /etc/ssl/example.crt;
    ssl_certificate_key       /etc/ssl/example.key;

    #ssl on;
    ssl_session_cache  builtin:1000  shared:SSL:10m;
    ssl_protocols  TLSv1 TLSv1.1 TLSv1.2;
    ssl_ciphers HIGH:!aNULL:!eNULL:!EXPORT:!CAMELLIA:!DES:!MD5:!PSK:!RC4;
    ssl_prefer_server_ciphers on;

    include /etc/nginx/sites-enabled/*;
    }
}

I have separate files that are being linked to /sites-enabled that include my proxy_params declarations.

Two of them are the following

location /v1/location/ {
    proxy_pass http://example.com:8181/;
}

location /v1/ {
    proxy_pass http://example.com:8282/;
}

I could see their maybe being an issue with it getting confused by the /v1 on both the proxies, but it works for the GET endpoint.

EDIT

Some people have brought up the point that it may be panicking so I checked the docker logs for the go container and got the following

location-tracking-staging-1 | 2016-03-14T02:35:33.580963673Z 2016/03/14 02:35:33 http: panic serving 10.7.1.5:35613: no reachable servers
location-tracking-staging-1 | 2016-03-14T02:35:33.581005488Z goroutine 97 [running]:
location-tracking-staging-1 | 2016-03-14T02:35:33.581012905Z net/http.(*conn).serve.func1(0xc820057b00)
location-tracking-staging-1 | 2016-03-14T02:35:33.581017348Z    /usr/local/go/src/net/http/server.go:1389 +0xc1
location-tracking-staging-1 | 2016-03-14T02:35:33.581030498Z panic(0x81e620, 0xc82013c5e0)
location-tracking-staging-1 | 2016-03-14T02:35:33.581034545Z    /usr/local/go/src/runtime/panic.go:426 +0x4e9
location-tracking-staging-1 | 2016-03-14T02:35:33.581038792Z main.RepoCreateVendorLocation(0xc82011ecb8, 0x4, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, ...)
location-tracking-staging-1 | 2016-03-14T02:35:33.581042502Z    /go/src/location-tracking/repo.go:19 +0x178
location-tracking-staging-1 | 2016-03-14T02:35:33.581047145Z main.VendorLocationCreate(0x7f8a4366d978, 0xc8200c2ea0, 0xc820119260)
location-tracking-staging-1 | 2016-03-14T02:35:33.581050747Z    /go/src/location-tracking/handlers.go:63 +0x47b
location-tracking-staging-1 | 2016-03-14T02:35:33.581054911Z net/http.HandlerFunc.ServeHTTP(0x9965b0, 0x7f8a4366d978, 0xc8200c2ea0, 0xc820119260)
location-tracking-staging-1 | 2016-03-14T02:35:33.581058786Z    /usr/local/go/src/net/http/server.go:1618 +0x3a
location-tracking-staging-1 | 2016-03-14T02:35:33.581062770Z github.com/gorilla/mux.(*Router).ServeHTTP(0xc820010640, 0x7f8a4366d978, 0xc8200c2ea0, 0xc820119260)
location-tracking-staging-1 | 2016-03-14T02:35:33.581066604Z    /go/src/github.com/gorilla/mux/mux.go:103 +0x270
location-tracking-staging-1 | 2016-03-14T02:35:33.581070176Z net/http.serverHandler.ServeHTTP(0xc820056300, 0x7f8a4366d978, 0xc8200c2ea0, 0xc820119260)
location-tracking-staging-1 | 2016-03-14T02:35:33.581073992Z    /usr/local/go/src/net/http/server.go:2081 +0x19e
location-tracking-staging-1 | 2016-03-14T02:35:33.581077629Z net/http.(*conn).serve(0xc820057b00)
location-tracking-staging-1 | 2016-03-14T02:35:33.581081221Z    /usr/local/go/src/net/http/server.go:1472 +0xf2e
location-tracking-staging-1 | 2016-03-14T02:35:33.581084811Z created by net/http.(*Server).Serve
location-tracking-staging-1 | 2016-03-14T02:35:33.581088336Z    /usr/local/go/src/net/http/server.go:2137 +0x44e

Best Answer

Plan

Problem with "502 Bad Gateway" giving config

  • cat /etc/nginx/sites-enabled/example.local
server {
        location /random {
                proxy_pass http://127.0.0.1:5000;
        }
}

root@sf:/var/www# curl -d "foo=bar&bin=baz" http://localhost:5000

<html><body><h1>hi!</h1></body></html>

root@sf:/var/www# curl -d "foo=bar&bin=baz" https://example.local/random

<html>
<head><title>502 Bad Gateway</title></head>
....

Solution

nginx config after changes:

server {
...
        error_page 502 =200 @502;

        location /random {
                proxy_pass http://127.0.0.1:5000;
        }


        location @502 {
                root /var/www/sf_random;
                proxy_method GET;
                proxy_pass http://127.0.0.1:5000;
        }
}

  • config syntax validation

    nginx -t

  • after successful validation

    service nginx restart

And I got it working :)

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