HTTP status code 0 in Caddy logs for a reverse proxy (with template)

Help
1

1. Caddy version:

v2.4.3 h1:Y1FaV2N4WO3rBqxSYA8UZsZTQdN+PwcoOcAiZTM8C0I=

2. How I installed, and run Caddy:

docker

a. System environment:

Docker on Ubuntu 20.20

c. Service/unit/compose file:

#
# Production frontend and backend and docs
#
# PYramid backend API server is localhost:3456
# SvelteKit Node.js frontend SSR server is localhost:3000
#
http://example.com {

    # Backend API request
    handle /api* {
        # This is the upstream Waitress server
        reverse_proxy 127.0.0.1:3456 {
            # Backend API must respond to an individual API call under 20s seconds
            transport http {
                response_header_timeout 20s
            }
        }
    }

    # Special URL endpoint for Google and other bots
    # that are robots.txt blocked from API
    handle_path /sitemap/* {
        # Same as /api, just a path rewrite using Caddy handle_path
        # https://webinstall.dev/caddy/
        rewrite * /api{path}
        reverse_proxy 127.0.0.1:3456
    }

    # Serve docs as files rsync'ed to the server
    # See trading-strategy/.github/workflows/rsync-docs.yml for more details
    # https://caddy.community/t/caddy-file-server-browse-not-working-when-root-a-specific-directory/15342/3
    redir /docs /docs/
    handle_path /docs* {
        # See docker-compose
        # mapped to /home/docs/html
        root * /docs
        file_server
    }


    # SvelteKit production server from frontend repository
    handle {
        reverse_proxy 127.0.0.1:3000 {
        header_up X-Forwarded-Host {host}
            # Frontend must render the page under 20 seconds
            transport http {
                response_header_timeout 20s
            }
        }
    }

    # Set the default 404 page
    # https://caddyserver.com/docs/caddyfile/directives/handle_errors
    handle_errors {
        respond "{http.error.status_code} {http.error.status_text}"
    }

    # Create a log file log {
        format json
        output file /var/log/caddy/access.log
        #output stdout
        # Caddy cannot have two log outputs at the same time
    }

}

3. The problem I’m having:

I am grepping through Caddy JSON access logs and sometimes I see HTTP status code (status field) set to zero. What does this mean?

4. Error messages and/or full log output:

Caddy log JSON object:

{"level":"info","ts":1674820082.9167147,"logger":"http.log.access.log0","msg":"handled request","request":{"remote_addr":"zzzzz,"proto":"HTTP/1.1","method":"GET","host":"tradingstrategy.ai","uri":"zzzzzzz","headers":{"Cdn-Loop":["cloudflare"],"Accept-Encoding":["gzip"],"Cf-Visitor":["{\"scheme\":\"https\"}"],"Cf-Ipcountry":["SG"],"Cf-Connecting-Ip":["zzzzz"],"Connection":["Keep-Alive"],"X-Forwarded-For":["139.180.132.162"],"Cf-Ray":["790141cc89a86c06-SIN"],"X-Forwarded-Proto":["https"]}},"common_log":"zzzzz - - [27/Jan/2023:11:48:02 +0000] \"GET /api/zzzzz HTTP/1.1\" 0 0","duration":0.00009558,"size":0,"status":0,"resp_headers":{"Server":["Caddy"]}}```

5. What I already tried:

Google.

2

That’s a very old version. Please upgrade to v2.6.2.

Status code 0 is the same as an HTTP 200 status response. It usually happens when the request goes unhandled by Caddy (as in no configured routes wrote a response).

Is that request for a different hostname? It looks like your server is only listening for HTTP requests for example.com. If a different hostname is used, then Caddy won’t handle it because it doesn’t match example.com, so it writes an empty response.

1 Like
3

Thank you Francis. Your reply gave me a hint. I believe status code 0 responses are just random bot traffic to the IP address that has nothing to do with my server.

4

That’s typically the case, yeah. There’s lots of bots crawling the web, making requests to try to find exploitable vulnerabilities. Most of that traffic is harmless and can be ignored.

5

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