Snap.Http.Server.Types

Types used by the Snap HTTP Server.

Documentation

data ServerConfig hookState

Data and services that all HTTP response handlers share.

data PerSessionData

All of the things a session needs to service a single HTTP request.

ServerConfig

emptyServerConfig :: ServerConfig a

getters/setters

getDefaultTimeout :: ServerConfig hookState -> Int

getIsSecure :: ServerConfig hookState -> Bool

getLocalHostname :: ServerConfig hookState -> ByteString

getLogAccess :: ServerConfig hookState -> Request -> Response -> Word64 -> IO ()

getLogError :: ServerConfig hookState -> Builder -> IO ()

getNumAcceptLoops :: ServerConfig hookState -> Int

getOnDataFinished :: ServerConfig hookState -> DataFinishedHook hookState

getOnEscape :: ServerConfig hookState -> EscapeSnapHook hookState

getOnException :: ServerConfig hookState -> ExceptionHook hookState

getOnNewRequest :: ServerConfig hookState -> NewRequestHook hookState

getOnParse :: ServerConfig hookState -> ParseHook hookState

getOnUserHandlerFinished :: ServerConfig hookState -> UserHandlerFinishedHook hookState

setDefaultTimeout :: Int -> ServerConfig hookState -> ServerConfig hookState

setIsSecure :: Bool -> ServerConfig hookState -> ServerConfig hookState

setLocalHostname :: ByteString -> ServerConfig hookState -> ServerConfig hookState

setLogAccess :: (Request -> Response -> Word64 -> IO ()) -> ServerConfig hookState -> ServerConfig hookState

setLogError :: (Builder -> IO ()) -> ServerConfig hookState -> ServerConfig hookState

setNumAcceptLoops :: Int -> ServerConfig hookState -> ServerConfig hookState

setOnDataFinished :: DataFinishedHook hookState -> ServerConfig hookState -> ServerConfig hookState

setOnEscape :: EscapeSnapHook hookState -> ServerConfig hookState -> ServerConfig hookState

setOnException :: ExceptionHook hookState -> ServerConfig hookState -> ServerConfig hookState

setOnNewRequest :: NewRequestHook hookState -> ServerConfig hookState -> ServerConfig hookState

setOnParse :: ParseHook hookState -> ServerConfig hookState -> ServerConfig hookState

setOnUserHandlerFinished :: UserHandlerFinishedHook hookState -> ServerConfig hookState -> ServerConfig hookState

PerSessionData

getters

getTwiddleTimeout :: PerSessionData -> (Int -> Int) -> IO ()

isNewConnection :: PerSessionData -> IO Bool

getLocalAddress :: PerSessionData -> ByteString

getLocalPort :: PerSessionData -> Int

getRemoteAddress :: PerSessionData -> ByteString

getRemotePort :: PerSessionData -> Int

HTTP lifecycle

Request / Response lifecycle for "normal" requests (i.e. without errors):

1. accept a new connection, set it up (e.g. with SSL)
2. create a PerSessionData object
3. Enter the SessionHandler, which:
4. calls the NewRequestHook, making a new hookState object.
5. parses the HTTP request. If the session is over, we stop here.
6. calls the ParseHook
7. enters the ServerHandler, which is provided by another part of the framework
8. the server handler passes control to the user handler
9. a Response is produced, and the UserHandlerFinishedHook is called.
10. the Response is written to the client
11. the DataFinishedHook is called.
12. we go to #3.

Hooks

At various critical points in the HTTP lifecycle, the Snap server will call user-defined "hooks" that can be used for instrumentation or tracing of the process of building the HTTP response. The first hook called, the NewRequestHook, will generate a "hookState" object (having some user-defined abstract type), and this object will be passed to the rest of the hooks as the server handles the process of responding to the HTTP request.

For example, you could pass a set of hooks to the Snap server that measured timings for each URI handled by the server to produce online statistics and metrics using something like statsd (https://github.com/etsy/statsd).

type DataFinishedHook hookState = IORef hookState -> Request -> Response -> IO ()

The DataFinishedHook is called once the server has finished sending the HTTP response to the client.

type EscapeSnapHook hookState = IORef hookState -> IO ()

The EscapeSnapHook is called if the user handler escapes the HTTP session, e.g. for websockets.

type ExceptionHook hookState = IORef hookState -> SomeException -> IO ()

The ExceptionHook is called if an exception reaches the toplevel of the server, i.e. if an exception leaks out of the user handler or if an exception is raised during the sending of the HTTP response data.

type ParseHook hookState = IORef hookState -> Request -> IO ()

The ParseHook is called after the HTTP Request has been parsed by the server, but before the user handler starts running.

type NewRequestHook hookState = PerSessionData -> IO hookState

The NewRequestHook is called once processing for an HTTP request begins, i.e. after the connection has been accepted and we know that there's data available to read from the socket. The IORef passed to the hook initially contains a bottom value that will throw an exception if evaluated.

type UserHandlerFinishedHook hookState = IORef hookState -> Request -> Response -> IO ()

The UserHandlerFinishedHook is called once the user handler has finished running, but before the data for the HTTP response starts being sent to the client.

Handlers

type SendFileHandler

Arguments

 = Buffer

builder buffer

-> Builder

status line and headers

-> FilePath

file to send

-> Word64

start offset

-> Word64

number of bytes

-> IO ()

A SendFileHandler is called if the user handler requests that a file be sent using sendfile() on systems that support it (Linux, Mac OSX, and FreeBSD).

type ServerHandler hookState

Arguments

 = ServerConfig hookState

global server config

-> PerSessionData

per-connection data

-> Request

HTTP request object

-> IO (Request, Response)

This function, provided to the web server internals from the outside, is responsible for producing a Response once the server has parsed the Request.

data AcceptFunc

Socket types

data SocketConfig

Either the server should start listening on the given interface / port combination, or the server should start up with a Socket that has already had bind() and listen() called on it.

Constructors

StartListening ByteString Int

PreBound Socket