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194 lines
5.9 KiB
Markdown
194 lines
5.9 KiB
Markdown
# Tiny_httpd [](https://github.com/c-cube/tiny_httpd/actions)
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Minimal HTTP server using good old threads, with stream abstractions,
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simple routing, URL encoding/decoding, static asset serving,
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and optional compression with camlzip.
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It also supports [server-sent events](https://developer.mozilla.org/en-US/docs/Web/API/Server-sent_events/Using_server-sent_events)
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([w3c](https://html.spec.whatwg.org/multipage/server-sent-events.html#event-stream-interpretation))
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Free from all forms of `ppx`, async monads, etc. 🙃
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**Note**: it can be useful to add the `jemalloc` opam package for long running
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server, as it does a good job at controlling memory usage.
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The basic echo server from `src/examples/echo.ml`:
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```ocaml
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module S = Tiny_httpd
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let () =
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let server = S.create () in
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(* say hello *)
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S.add_route_handler ~meth:`GET server
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S.Route.(exact "hello" @/ string @/ return)
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(fun name _req -> S.Response.make_string (Ok ("hello " ^name ^"!\n")));
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(* echo request *)
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S.add_route_handler server
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S.Route.(exact "echo" @/ return)
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(fun req -> S.Response.make_string (Ok (Format.asprintf "echo:@ %a@." S.Request.pp req)));
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Printf.printf "listening on http://%s:%d\n%!" (S.addr server) (S.port server);
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match S.run server with
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| Ok () -> ()
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| Error e -> raise e
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```
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```sh
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$ dune exec src/examples/echo.exe &
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listening on http://127.0.0.1:8080
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# the path "hello/name" greets you.
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$ curl -X GET http://localhost:8080/hello/quadrarotaphile
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hello quadrarotaphile!
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# the path "echo" just prints the request.
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$ curl -X GET http://localhost:8080/echo --data "howdy y'all"
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echo:
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{meth=GET;
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headers=Host: localhost:8080
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User-Agent: curl/7.66.0
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Accept: */*
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Content-Length: 10
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Content-Type: application/x-www-form-urlencoded;
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path="/echo"; body="howdy y'all"}
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```
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## `http_of_dir`
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Similar to `python -m http.server`, a simple program `http_of_dir` is provided.
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It serves files from the current directory.
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```sh
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$ http_of_dir . -p 8080 &
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$ curl -X GET http://localhost:8080
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...
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<html list of current dir>
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...
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```
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## Static assets and files
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The program `http_of_dir` relies on the module `Tiny_httpd_dir`, which
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can serve directories, as well as _virtual file systems_.
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In 'examples/dune', we produce an OCaml module `vfs.ml` using
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the program `tiny-httpd-vfs-pack`. This module contains a VFS (virtual file
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system) which can be served as if it were an actual directory.
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The dune rule:
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```lisp
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(rule
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(targets vfs.ml)
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(deps (source_tree files) (:out test_output.txt.expected))
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(enabled_if (= %{system} "linux"))
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(action (run ../src/bin/vfs_pack.exe -o %{targets}
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--mirror=files/
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--file=test_out.txt,%{out}
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--url=example_dot_com,http://example.com)))
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```
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The code to serve the VFS from `vfs.ml` is as follows:
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```ocaml
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…
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Tiny_httpd_dir.add_vfs server
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~config:(Tiny_httpd_dir.config ~download:true
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~dir_behavior:Tiny_httpd_dir.Index_or_lists ())
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~vfs:Vfs.vfs ~prefix:"vfs";
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…
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```
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it allows downloading the files, and listing directories.
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If a directory contains `index.html` then this will be served
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instead of listing the content.
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## Steaming response body
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Tiny_httpd provides multiple ways of returning a body in a response.
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The response body type is:
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```ocaml
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type body =
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[ `String of string
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| `Stream of byte_stream
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| `Writer of Tiny_httpd_io.Writer.t
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| `Void ]
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```
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The simplest way is to return, say, `` `String "hello" ``. The response
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will have a set content-length header and its body is just the string.
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Some responses don't have a body at all, which is where `` `Void `` is useful.
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The `` `Stream _ `` case is more advanced and really only intended for experts.
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The `` `Writer w `` is new, and is intended as an easy way to write the
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body in a streaming fashion. See 'examples/writer.ml' to see a full example.
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Typically the idea is to create the body with `Tiny_httpd_io.Writer.make ~write ()`
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where `write` will be called with an output channel (the connection to the client),
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and can write whatever it wants to this channel. Once the `write` function returns
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the body has been fully sent and the next request can be processed.
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## Socket activation
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Since version 0.10, socket activation is supported indirectly, by allowing a
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socket to be explicitly passed in to the `create` function:
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```ocaml
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module S = Tiny_httpd
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let not_found _ _ = S.Response.fail ~code:404 "Not Found\n"
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let () =
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(* Module [Daemon] is from the [ocaml-systemd] package *)
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let server = match Daemon.listen_fds () with
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(* If no socket passed in, assume server was started explicitly i.e. without
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socket activation *)
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| [] -> S.create ()
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(* If a socket passed in e.g. by systemd, listen on that *)
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| sock :: _ -> S.create ~sock ()
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in
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S.add_route_handler server S.Route.rest_of_path not_found;
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Printf.printf "Listening on http://%s:%d\n%!" (S.addr server) (S.port server);
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match S.run server with
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| Ok () -> ()
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| Error e -> raise e
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```
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On Linux, this requires the
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[ocaml-systemd](https://github.com/juergenhoetzel/ocaml-systemd) package:
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```
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opam install ocaml-systemd
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```
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Tip: in the `dune` file, the package name should be `systemd`.
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In case you're not familiar with socket activation, Lennart Poettering's
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[blog post](http://0pointer.de/blog/projects/socket-activation.html) explains it
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well.
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## Why?
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Why not? If you just want a super basic local server (perhaps for exposing
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data from a local demon, like Cups or Syncthing do), no need for a ton of
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dependencies or high scalability libraries.
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Use cases might include:
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- serve content directly from a static blog generator;
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- provide a web UI to some tool (like CUPS and syncthing do);
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- implement a basic monitoring page for a service;
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- provide a simple json API for a service, on top of http;
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- use `http_of_dir` to serve odoc-generated docs or some assets directory.
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## Documentation
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See https://c-cube.github.io/tiny_httpd
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## License
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MIT.
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