Lucu is an HTTP daemonic library. It can be embedded in any Haskell program and runs in an independent thread.

Features:

Full support of HTTP\1.1/

Lucu supports request pipelining, chunked I/O, ETag comparison and "100 Continue".

Performance

Lucu doesn't fork/exec to handle requests like CGI. It just spawns a new thread. Inter-process communication is done with STM.

Lucu is not a replacement for Apache. It is intended to be used to create an efficient web-based application without messing around FastCGI. It is also intended to be run behind a reverse-proxy so it doesn't have the following (otherwise essential) facilities:

Logging

Lucu doesn't log any requests from any clients.

Client Filtering

Lucu always accepts any clients. No IP filter is implemented.

SSL Support

Lucu can handle only HTTP.

Bandwidth Limitting

Lucu doesn't limit bandwidth it consumes.

Protection Against Wicked Clients

Lucu is fragile against wicked clients. No attacker should be able to cause a buffer-overflow but can possibly DoS it.

This is the entry point of Lucu httpd. It listens to a socket and waits for clients. Computation of runHttpd never stops by itself so the only way to stop it is to raise an exception in the thread computing it.

Note that runHttpd automatically makes SIGPIPE be ignored by computing installHandler sigPIPE Ignore Nothing. This can hardly cause a problem but it may do.

Example:

 module Main where
 import Network.HTTP.Lucu
 
 main :: IO ()
 main = let config    = defaultConfig
            resources = mkResTree [ ([], helloWorld) ]
        in
          runHttpd config resourcees []

 helloWorld :: ResourceDef
 helloWorld = ResourceDef {
                resUsesNativeThread = False
              , resIsGreedy         = False
              , resGet
                  = Just $ do setContentType $ read "text/plain"
                              output "Hello, world!"
              , resHead   = Nothing
              , resPost   = Nothing
              , resPut    = Nothing
              , resDelete = Nothing
              }

mkResTree converts a list of (path, def) to a ResTree e.g.

   mkResTree [ ([]        , Network.HTTP.Lucu.StaticFile.staticFile "/usr/include/stdio.h" ) -- /
             , (["unistd"], Network.HTTP.Lucu.StaticFile.staticFile "/usr/include/unistd.h") -- /unistd
             ]

Computation of abort status headers msg aborts the Network.HTTP.Lucu.Resource.Resource monad with given status, additional response headers, and optional message string.

What this really does is to just throw a special DynException. The exception will be caught by the Lucu.

1. If the Network.HTTP.Lucu.Resource.Resource is in the /Deciding Header/ or any precedent states, it is possible to use the status and such like as a HTTP response to be sent to the client.

2. Otherwise the HTTP response can't be modified anymore so the only possible thing the system can do is to dump it to the stderr. See cnfDumpTooLateAbortionToStderr.

Note that the status code doesn't have to be an error code so you can use this action for redirection as well as error reporting e.g.

 abort MovedPermanently
       [("Location", "http://example.net/")]
       (Just "It has been moved to example.net")