Caddy v2 lb based on $arg_NAME (Nginx)

Help
1

1. The problem I’m having:

Hello!
Help me please migrate from Nginx to Caddy v2. I have nginx config with few upstreams and Hash load balace policy based on $arg_NAME. How I can do this in Caddy v2? I did’t find example in Docs.

upstream backends {
  hash $arg_NAME consistent;
  server 1.1.1.1:80;
  server 1.1.1.2:80;
}

server {
  listen 80;
  server_name test.example.com;

    location / {
        proxy_pass http://backends ;
        proxy_set_header Connection "upgrade";
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Host $http_host;
        proxy_set_header X-Forwarded-Host $http_host;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Proto $scheme;
    }
}

2. Error messages and/or full log output:

PASTE OVER THIS, BETWEEN THE ``` LINES.
Please use the preview pane to ensure it looks nice.

3. Caddy version:

v2.6.4

4. How I installed and ran Caddy:

a. System environment:

Debian

b. Command:

docker run -ti caddy:2.6.4-alpine sh

c. Service/unit/compose file:

PASTE OVER THIS, BETWEEN THE ``` LINES.
Please use the preview pane to ensure it looks nice.

d. My complete Caddy config:

http://test.example.com {
  reverse_proxy {arg.NAME} 1.1.1.1:80 1.1.1.2:80 {
    lb_policy uri_hash
    header_up Connection Upgrade
    header_up Upgrade websocket
  }
}

5. Links to relevant resources:

2

Please completely fill out the help topic template. We can’t help you otherwise.

3

First post updated

4

I don’t know what $arg_NAME is supposed to be. Where is it getting this value?

I don’t think we have support for arbitrary value’d hashing for load balancing. You can see the policies we have here reverse_proxy (Caddyfile directive) — Caddy Documentation

That placeholder doesn’t make sense there, since it’s not an upstream address.

5

$arg_NAME, NAME - it’s argument name from uri. Caddy can’t map upstreams based on args?

6

I still don’t understand what you mean by “args”. That’s vague. How is the URI parsed? Show an example request (i.e. a URI you would receive on your server) and what the “arg” would be in that case.

But yes, the uri_hash policy doesn’t take arguments. It hashes the entire URI and the same URI will reach the same upstream, consistently.

7

What I need. Web server can accept requests with different path or fragment but with same argument like ?hello=world in uri. All this requests must be forwarded to one backend. In nginx configuration I can set lb policy hash and set var $arg_NAME where NAME is argument name. How I can do set same policy in Caddy?

8

Ah okay, so you mean by query, not by “args”.

Currently there’s no LB policy by query, but it would be trivial to add one. You’re the first to ask for that.

9

Second question please. How I can map same query with different arguments like
/qwerty?arg1=asd
/qwerty?arg4=hjjj#frag
to same backend in pool?

10

I’m not sure that’s possible to predict. Load balancing uses a hashing algorithm given a value. If you provide a different value, there’s no way to predict it’ll end up at the same backend.

Also btw, the URI fragment (i.e. the #frag part) never gets sent to the server. That’s client-side only. It’s impossible to route based on the fragment.

If you want to route specific query params to a specific upstream, you probably want to use the map directive instead:

11

This topic was automatically closed 30 days after the last reply. New replies are no longer allowed.