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Nginx: Everything about proxy_pass

Daniel Albuschat on August 20, 2019

With the advent of Microservices™, ingress routing and routing between services has been an every-increasing demand. I currently default to nginx f...

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Peters Chikezie • Mar 6 '21 • Edited

hello, Daniel thanks for this post.

However, I am having trouble passing all paths from a request to the server.

example:

servername = 127.0.0.1;

location / {
proxy_pass 192.168.4.22:3000/;
}

I want all requests with dynamic paths coming from e.g 127.0.0.1/ be matched to the above location and passed to the proxy.

I get a 404 from the server when my URL looks like 127.0.0.1/foo/bar but when its just 127.0.0.1, it works fine.

is there something i am not doing right?

Daniel Albuschat • Mar 7 '21 • Edited

Hey Peters,

was it just a formatting issue in the comment, or are you missing the // in http://127.0.0.1 in the proxy_pass statement?

Peters Chikezie • Mar 7 '21

Hi Daniel,

It's a formating issue.

Daniel Albuschat • Mar 7 '21

Hm... looks correct, though. Maybe the error lies elsewhere?

Peters Chikezie • Mar 7 '21

Any idea where to look?

I have two sites enabled. The default nginx site running on port 80 and my API site running on a different port.

Daniel Albuschat • Mar 7 '21

Oh, then you forgot to provide the correct port in the URL. What you posted uses the default port 80, so it uses the default nginx site. Use http://127.0.0.1:<you-port>/foo/bar

Peters Chikezie • Mar 7 '21

I actually have the correct port in the file. The one I posted here is just an example. The IP is different

Peters Chikezie • Mar 8 '21 • Edited

Hi Daniel,

Here is how the site looks

upstream backend {
 server 192.168.34.23:3000;
}
server {
        listen 5000 default_server;
        listen [::]:5000 default_server;

        root /var/www/html;
        index index.html index.htm index.nginx-debian.html;

        server_name http://example.com;

         location / {
                proxy_pass http://backend/;
                try_files $uri $uri/ =404;
        }
}

Peters Chikezie • Mar 8 '21

i am thinking, could the root there be the problem?

Peters Chikezie • Mar 8 '21

I have removed it and it's still the same thing.

Peters Chikezie • Mar 8 '21 • Edited

Hi again Daniel,

I have been able to solve it.

I had to comment this line in the location

location / {
                proxy_pass http://backend/;
                #try_files $uri $uri/ =404;
        }

Thanks for your time. It's really appreciated

Aditya Todkar • Oct 20 '22 • Edited

In my case I have react + node app + nginx setup and I want to run webflow website only on /blog/* routes. I have added location blog like this:

location /blog {
      proxy_pass https://myblog-blog.webflow.io;
}

But in that case react + node routes and /blog/* routes work fine. Only issue is /blog route gives 404. Any suggestions on what can be done to fix it?

Daniel Albuschat • Oct 20 '22

Heya Aditya!

Could you have a closer look at which server gives you the 404? i.e. does the server logs of myblog-blog.webflow.io show an incoming request that is answered with 404, or is nginx already giving the 404? Maybe you can tell from how the 404 page looks like.

Aditya Todkar • Oct 20 '22

404 page of webflow is displayed. Do you think this university.webflow.com/lesson/href... can help in my case? I am currently not using paid plan so cannot use href-prefix. So I wanted to know if there is something which I can do in nginx config file.

Carlos Trapet • Aug 21 '19

"with no plausible reason or experience to back this decision, just because it seems to be the most used tool currently" - we all do, mate. Props for being honest though!

Really useful article, I wish I'd had this when I started my first job.
Back then I just assumed nginx was magic.

sansnom • Nov 12 '19

I was completely clueless why the proxy_pass wasn't working with the "set directive". Thanks for sharing. :)

In fact, the "set directive" is also the only way to force nginx to resolve the domain name again (using the parameters defined in the resolver). Otherwise, it will be cached forever...

Wojciech Sielski • Aug 22 '19

"is that nginx is very picky about hostname resolution. For some unexplainable reason, nginx will try to resolve all hosts defined in proxy_pass directives on startup"

In some particular use-cases - especially when using static configuration - this is THE main reason why nginx is not production ready. One temporarily unresolved backend host can cause nginx farm not restartable. This is exact opposite behavior from very disliked nowadays: Apache httpd.

From the other hand for dynamic generated configuration this is a good tool, but has many good successors too: traefik, istio, linkerd, fabio...

There is another piece: missing a global configuration ProxyPreserveHost Off - you cannot do that globally in nginx. You need to specify it per each proxy_paas

using proxy_set_header Host foo.bar. That makes config very unreadable.

coxse • Sep 2 '21

Hi Daniel,

With regard to the actual URI that is forwarded, is it not $host that you need?

In the attached picture the yellow highlight is $host and the blue is the upstream $upstream.

Anyway, thanks for the post it really helped setting up our nginx proxy with decent logging.

Adrian

Mike Green • Mar 7

Hi - found this very useful, and have a question around the $upstream variable in the log format. Using nginx 1.24.0.
I couldn't get $server_name to: "$upstream_addr": to work - it barked with nginx: [emerg] unknown "upstream" variable

Based on the variables here - nginx.org/en/docs/stream/ngx_strea..., I changed it to $upstream_addr and it worked.

Entire log:

log_format upstream_logging '[$time_local] $remote_addr - $remote_user - '
      '$server_name to: "$upstream_addr": "$request" upstream_response_time '
      '$upstream_response_time msec $msec request_time $request_time';

Anyone know if this is a variable change or I misunderstood what $upstream in the log format was?

Grant Parks • Apr 24 '23

Thank you for this article. I couldn't get a location regex to work with proxy_pass that would work with my upstream's routing; you explained why. (I ended up sticking the file name in an X- header and using via proxy_pass_request_headers.) Now I'm trying to figure out how to get the numeric filename that nginx assigned to my upload in my upstream JS.

Xavier • Feb 14

Hi Daniel,

First of all, thanks for the post.

I am facing the same issue with nginx does not start when not all upstream hosts are available.
I was trying to reverse proxy the

public.domain.com/mydomain/dev06/api ===>

aws-mydomain-dev06.aws.org/api/

so I changed it to following,

location ~ ^/mydomain/dev06/(.*)$ {
    resolver 10.43.83.2;

    set $upstream https://aws-mydomain-dev06.aws.org/; 

    access_log  /var/log/nginx/access.dev06.log upstream_logging;
    error_log  /var/log/nginx/error.dev06.log debug;

    proxy_pass $upstream/$1$is_args$args;
 }

it returns 404, not found

using string proxy_pass aws-mydomain-dev06.aws.org/; works fine

Is there something I am not doing right? Or where can I have a look to fine out more?

Regards

Gustavo Pinsard • Dec 12 '22

Daniel,
I ended up here by chance. However, I was so impressed by the good work you've done in organizing this article that I decided to join dev.io - so I could post this and hopefully contribute back to the community.
This article is both useful and inspiring. Thanks!

posedge • Apr 29 '20

Thanks for sharing <3 I agree, that unintuitive config can drive someone crazy. Especially the relevance of the slashes.

Ion Mudreac • Aug 22 '19

Thank you, Daniel, for sharing your experience with proxy_pass issues, very useful

Dave • May 11 '22

This was incredibly detailed and clear. Thank you so much for sharing what you found. You're helping people more than a year down the road :)

M. Alexandre J-S William ELISÉ • Oct 22 '22

Hi Daniel,
This is a very enlighting article for me. Now I understand better how proxy_pass directive works. Thanks a lot for this article.