# How do I serve a single static file from HAProxy?

**URL:** <https://discourse.haproxy.org/t/how-do-i-serve-a-single-static-file-from-haproxy/32>\
**Category:** Help!\
**Created:** [December 9, 2015, 10:02pm UTC](https://discourse.haproxy.org/t/how-do-i-serve-a-single-static-file-from-haproxy/32 "2015-12-09T22:02:57Z")\
**Posts on this page:** 16\
**Page:** 1

<div class="post-metadata">

**Author:** ![sam](https://sea2.discourse-cdn.com/flex016/user_avatar/discourse.haproxy.org/sam/32/83_2.png) [@sam](https://discourse.haproxy.org/u/sam)\
**Post date:** [December 9, 2015, 10:02pm UTC](https://discourse.haproxy.org/t/how-do-i-serve-a-single-static-file-from-haproxy/32/1 "2015-12-09T22:02:57Z")

</div>

We have a custom backend we use to serve a single static file:

```nohighlight
acl is_robots_txt path /robots.txt
use_backend robotstxt if is_robots_txt is_cdn

backend robotstxt
  mode http
  errorfile 503 /etc/haproxy/errors/200robots.http

```

The file contains:

```auto
HTTP/1.0 200 Found
Cache-Control: no-cache
Connection: close
Content-Type: text/plain

# Discourse CDN, all crawling is allowed (cdn contains images and text files)
User-Agent: *
Allow: /

```

This means that when people hit: `https://cdn.discourse.org/robots.txt` well they get the robots file.

This hack works OK, except that now we are logging a bunch of `503` statuses in the logs which in reality are `200`s, this in turn makes log analysis a bit annoying.

Is there another hack we can use that allows us to serve a single static file from a backend and retain status 200 in the logs?

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**Author:** ![willy](https://avatars.discourse-cdn.com/v4/letter/w/c2a13f/32.png) [@willy](https://discourse.haproxy.org/u/willy)\
**Post date:** [December 10, 2015, 11:22am UTC](https://discourse.haproxy.org/t/how-do-i-serve-a-single-static-file-from-haproxy/32/2 "2015-12-10T11:22:13Z")

</div>

You may disable logging in this backend, which is probably the best thing to do anyway since you don’t care about who retrieves this file :

`http-request set-log-level silent`

I wanted to have the “return-raw” and “return-html” actions merged into 1.6 but we didn’t have time to do them.

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**Author:** ![sam](https://sea2.discourse-cdn.com/flex016/user_avatar/discourse.haproxy.org/sam/32/83_2.png) [@sam](https://discourse.haproxy.org/u/sam)\
**Post date:** [December 10, 2015, 9:37pm UTC](https://discourse.haproxy.org/t/how-do-i-serve-a-single-static-file-from-haproxy/32/3 "2015-12-10T21:37:24Z")

</div>

I see, ideally I want to keep the logging, can I achieve my desired result with a LUA script running in the backend serving the request?

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**Author:** ![Baptiste](https://avatars.discourse-cdn.com/v4/letter/b/cab0a1/32.png) [@Baptiste](https://discourse.haproxy.org/u/Baptiste)\
**Post date:** [December 10, 2015, 11:02pm UTC](https://discourse.haproxy.org/t/how-do-i-serve-a-single-static-file-from-haproxy/32/4 "2015-12-10T23:02:52Z")

</div>

Hi Sam,

Yes, you may be able to create a lua service which delivers the content of you robots.txt.  
Then you may have a 200 in th logs.

Baptiste

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<div class="post-metadata">

**Author:** ![darix](https://sea2.discourse-cdn.com/flex016/user_avatar/discourse.haproxy.org/darix/32/37_2.png) [@darix](https://discourse.haproxy.org/u/darix)\
**Post date:** [February 18, 2016, 1:36pm UTC](https://discourse.haproxy.org/t/how-do-i-serve-a-single-static-file-from-haproxy/32/5 "2016-02-18T13:36:08Z")

</div>

could it be done for 1.6.4 maybe or does it require bigger changes?

also yay my favorite forum software for my favorite proxy!

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<div class="post-metadata">

**Author:** ![darix](https://sea2.discourse-cdn.com/flex016/user_avatar/discourse.haproxy.org/darix/32/37_2.png) [@darix](https://discourse.haproxy.org/u/darix)\
**Post date:** [February 18, 2016, 1:46pm UTC](https://discourse.haproxy.org/t/how-do-i-serve-a-single-static-file-from-haproxy/32/6 "2016-02-18T13:46:47Z")

</div>

time to find out how stable 1.7 is 😛

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<div class="post-metadata">

**Author:** ![mattpark](https://sea2.discourse-cdn.com/flex016/user_avatar/discourse.haproxy.org/mattpark/32/88_2.png) [@mattpark](https://discourse.haproxy.org/u/mattpark)\
**Post date:** [June 15, 2016, 1:52pm UTC](https://discourse.haproxy.org/t/how-do-i-serve-a-single-static-file-from-haproxy/32/7 "2016-06-15T13:52:32Z")

</div>

Anyone have a good example of how to serve a single static file using lua?  
Looks a bit less hacky than above, would like to create a landing page for an ssl verify required scenario, vs. just present a request for cert.

There is a hello world example here, but it doesn’t have much:

> **[What's New in HAProxy 1.6 - HAProxy Technologies](https://www.haproxy.com/blog/whats-new-in-haproxy-1-6/)**
>
> \[ANNOUNCE\] HAProxy 1.6.0 released Yesterday, 13th of October, Willy has announced the release of HAProxy 1.6.0, after 16 months of development! First good news is that release cycle goes a bit faster and we aim to carry on making it as fast. A total...

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<div class="post-metadata">

**Author:** ![mattpark](https://sea2.discourse-cdn.com/flex016/user_avatar/discourse.haproxy.org/mattpark/32/88_2.png) [@mattpark](https://discourse.haproxy.org/u/mattpark)\
**Post date:** [June 15, 2016, 2:02pm UTC](https://discourse.haproxy.org/t/how-do-i-serve-a-single-static-file-from-haproxy/32/8 "2016-06-15T14:02:21Z")

</div>

Also I saw someone just do:

```
listen http-webservices
    bind :8080 
    monitor-uri /c 
    errorfile 200 /etc/haproxy/errorfiles/200.http
```

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<div class="post-metadata">

**Author:** ![MrTechGadget](https://avatars.discourse-cdn.com/v4/letter/m/45deac/32.png) [@MrTechGadget](https://discourse.haproxy.org/u/MrTechGadget)\
**Post date:** [July 9, 2017, 7:16pm UTC](https://discourse.haproxy.org/t/how-do-i-serve-a-single-static-file-from-haproxy/32/9 "2017-07-09T19:16:28Z")

</div>

I got a LUA response working based on the rabbit trail @mattpark started me down. I am using this with HAproxy running on pfSense.

I have several responses in a single lua file and just call them by function name (service at the bottom)

Here is an example from my lua file, just replace the response data with the contents of your robots.txt, indicating new lines by a `\n` . If you want this to be HTML (or any other file type) just change the Content-Type header as needed.

```
http_resp = function(applet) 
local response = "Your Content goes here.\n use backslash+n to generate a new line"
applet:add_header("Content-Length", string.len(response)) 
applet:add_header("Content-Type", "text/plain") 
applet:set_status(200) 
applet:start_response() 
applet:send(response) 
end 

core.register_service("http_resp", "http", http_resp)
```

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<div class="post-metadata">

**Author:** ![MrTechGadget](https://avatars.discourse-cdn.com/v4/letter/m/45deac/32.png) [@MrTechGadget](https://discourse.haproxy.org/u/MrTechGadget)\
**Post date:** [July 9, 2017, 7:20pm UTC](https://discourse.haproxy.org/t/how-do-i-serve-a-single-static-file-from-haproxy/32/10 "2017-07-09T19:20:27Z")

</div>

@sam, I’m sure you found an acceptable solution a long time ago, but I found this thread today and am not using this solution to disallow robots indexing on all of my backends at once with this frontend LUA config.

My specific robots.txt response uses this as the ACL to match to call the function.  
Name Expression Value Actions  
robots Path ends with: robots.txt

frontend config:

```
	acl robots	path_end -i robots.txt
	http-request use-service lua.robots if robots aclcrt_SharedFront

```

LUA file:

```
robots = function(applet) 
local response = "User-agent: *\nDisallow: /"
applet:add_header("Content-Length", string.len(response)) 
applet:add_header("Content-Type", "text/plain") 
applet:set_status(200) 
applet:start_response() 
applet:send(response) 
end 

core.register_service("robots", "http", robots)
```

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<div class="post-metadata">

**Author:** ![gladiac](https://avatars.discourse-cdn.com/v4/letter/g/96bed5/32.png) [@gladiac](https://discourse.haproxy.org/u/gladiac)\
**Post date:** [December 23, 2018, 1:34pm UTC](https://discourse.haproxy.org/t/how-do-i-serve-a-single-static-file-from-haproxy/32/11 "2018-12-23T13:34:23Z")

</div>

Hey there,  
I came up with the following solution for serving files just **like a web-server** would do with the help of LUA. The following _frontend-config_ sets the HTTP-header **X-LUA-LOADFILE-DOCROOT** with a local directory path which serves as the document-root. Furthermore, it defines a lua-service called load-file. See:

```
lua-load /etc/haproxy/lua/load-file.lua

...

backend lua-load-file
  http-request set-header X-LUA-LOADFILE-DOCROOT /etc/haproxy/docroot
  http-request use-service lua.load-file

```

As you can see I load a lua-file called _load-file.lua_. The contents of that file are as follows:

```
core.register_service("load-file", "http", function(applet)
  local docroot
  local location
  local file
  local retval
  local response
  local extension

  if(applet.path == nil or applet.headers["x-lua-loadfile-docroot"] == nil or applet.headers["x-lua-loadfile-docroot"][0] == "") then
    retval = 500
    response = "Internal Server Error"
  else
    docroot = applet.headers["x-lua-loadfile-docroot"][0]
    location = applet.path
    if(location == "" or location == "/") then
      location = "/index.html"
    end
    file = io.open(docroot .. location, "r")
    if(file == nil) then
      retval = 404
      response = "File Not Found"
    else
      retval = 200
      response = file:read("*all")
      file:close()
    end
  end

  extension = string.match(location, ".(%w+)$")
  if extension == "css" then applet:add_header("content-type", "text/css")
    elseif extension == "gif" then applet:add_header("content-type", "image/gif")
    elseif extension == "htm" then applet:add_header("content-type", "text/html")
    elseif extension == "html" then applet:add_header("content-type", "text/html")
    elseif extension == "ico" then applet:add_header("content-type", "image/x-icon")
    elseif extension == "jpg" then applet:add_header("content-type", "image/jpeg")
    elseif extension == "jpeg" then applet:add_header("content-type", "image/jpeg")
    elseif extension == "js" then applet:add_header("content-type", "application/javascript; charset=UTF-8")
    elseif extension == "json" then applet:add_header("content-type", "application/json")
    elseif extension == "mpeg" then applet:add_header("content-type", "video/mpeg")
    elseif extension == "png" then applet:add_header("content-type", "image/png")
    elseif extension == "txt" then applet:add_header("content-type", "text/plain")
    elseif extension == "xml" then applet:add_header("content-type", "application/xml")
    elseif extension == "zip" then applet:add_header("content-type", "application/zip")
  end

  applet:set_status(retval)
  if(response ~= nil and response ~= "") then
    applet:add_header("content-length", string.len(response))
  end
  applet:start_response()
  applet:send(response)
end)

```

Basically, this code reads files from a specified document-root location in the filesystem based on the query string and generates appropriate HTTP-responses just as a normal webserver would do. That is why the script needs a document-root do be configured via the HTTP-header **X-LUA-LOADFILE-DOCROOT**. Furthermore, the code also does some very basic mimetype handling - extend the list according your needs. I hope someone finds this useful.

cheers!

---

<div class="post-metadata">

**Author:** ![supermathie](https://sea2.discourse-cdn.com/flex016/user_avatar/discourse.haproxy.org/supermathie/32/373_2.png) [@supermathie](https://discourse.haproxy.org/u/supermathie)\
**Post date:** [November 10, 2020, 11:36pm UTC](https://discourse.haproxy.org/t/how-do-i-serve-a-single-static-file-from-haproxy/32/12 "2020-11-10T23:36:25Z")

</div>

We’ve _finally_ decided to solve this problem properly by implementing in LUA.

EDIT: link removed due to [doing IO in LUA being a terrible idea](https://discourse.haproxy.org/t/how-do-i-serve-a-single-static-file-from-haproxy/32/13).

---

<div class="post-metadata">

**Author:** ![lukastribus](https://avatars.discourse-cdn.com/v4/letter/l/7ea924/32.png) [@lukastribus](https://discourse.haproxy.org/u/lukastribus)\
**Post date:** [November 10, 2020, 11:56pm UTC](https://discourse.haproxy.org/t/how-do-i-serve-a-single-static-file-from-haproxy/32/13 "2020-11-10T23:56:54Z")

</div>

You should never access the file system from LUA. Especially not based on user-triggered requests:

> <https://github.com/haproxy/haproxy/blob/8f04e1849d40243ba7c103b06bd2c061840ceabc/doc/lua.txt#L144>

> The list of prohibited standard Lua functions during the runtime contains all those that do filesystem access:
> 
> - os.remove()
> - os.rename()
> - os.tmpname()
> - package.\*()
> - io.\*()
> - file.\*()

You `CANNOT` emulate a webserver with LUA, those are blocking syscalls, they don’t belong in an event driven software like haproxy.

In haproxy 2.2, you can use [http-request return](https://cbonte.github.io/haproxy-dconv/2.2/configuration.html#4.2-http-request%20return) if the errorfile workaround disgusts you.

---

<div class="post-metadata">

**Author:** ![supermathie](https://sea2.discourse-cdn.com/flex016/user_avatar/discourse.haproxy.org/supermathie/32/373_2.png) [@supermathie](https://discourse.haproxy.org/u/supermathie)\
**Post date:** [November 11, 2020, 8:27pm UTC](https://discourse.haproxy.org/t/how-do-i-serve-a-single-static-file-from-haproxy/32/14 "2020-11-11T20:27:20Z")

</div>

Thanks for the advice - I was feeling a _little_ bit bad about doing IO like that and was thinking that I should be reading it in at start and caching it, but since `http-request return` _does exactly that_ we’re now trying out HAProxy 2.3.

EDIT: this site now being served by HAProxy 2.3 ❤

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<div class="post-metadata">

**Author:** ![avillost](https://avatars.discourse-cdn.com/v4/letter/a/65b543/32.png) [@avillost](https://discourse.haproxy.org/u/avillost)\
**Post date:** [January 5, 2021, 4:52pm UTC](https://discourse.haproxy.org/t/how-do-i-serve-a-single-static-file-from-haproxy/32/15 "2021-01-05T16:52:22Z")

</div>

can you please provide an example of how you accomplished this with http-request return?  
Thanks,  
Steve

---

<div class="post-metadata">

**Author:** ![supermathie](https://sea2.discourse-cdn.com/flex016/user_avatar/discourse.haproxy.org/supermathie/32/373_2.png) [@supermathie](https://discourse.haproxy.org/u/supermathie)\
**Post date:** [January 5, 2021, 6:28pm UTC](https://discourse.haproxy.org/t/how-do-i-serve-a-single-static-file-from-haproxy/32/16 "2021-01-05T18:28:10Z")

</div>

For example:

```nohighlight
http-request return status 200 content-type "text/plain" file "/static/200robots.txt" hdr "cache-control" "no-cache"

```