MFlow

Non monadic low level support stuff for the MFlow application server. (See MFlow.Form for the higher level interfaces) it implements an scheduler of queued Processable messages that are served according with the source identification and the verb invoked. The scheduler executed the appropriate workflow (using the workflow package). The workflow may send additional messages to the source, identified by a Token . The computation state is optionally logged and recovered.

The message communication is trough polimorphic, monoidal queues. There is no asumption about message codification, so instantiations of this scheduler for different infrastructures is possible, including non-Web based ones as long as they support or emulate cookies.

MFlow.Hack is an instantiation for the Hack interface in a Web context.

MFlow.Wai is a instantiation for the WAI interface.

MFlow.Forms implements a monadic type safe interface with composabe widgets and a higher comunication interface.

MFlow.Forms.XHtml is an instantiation for the Text.XHtml format

MFlow.Forms.HSP is an instantiation for the Haskell Server Pages format

In order to manage resources, there are primitives that kill the process and its state after a timeout.

All these details are hidden in the monad of MFlow.Forms that provides an higher level interface.

Fragment based streaming sendFragment sendEndFragment are provided only at this level.

stateless and transient server processeses are also possible. stateless are request-response with no intermediate messaging dialog. transient processes have no persistent state, so they restart anew after a timeout or a crash.

Documentation

type Params = [(String, String)]

type Workflow m = WF Stat m

data HttpData

Constructors

HttpData Params [Cookie] ByteString

Error WFErrors ByteString

Instances

Show HttpData

Typeable HttpData

Monoid HttpData

ToHttpData HttpData

ToResponse HttpData

class Processable a where

Methods

pwfname :: a -> String

puser :: a -> String

pind :: a -> String

getParams :: a -> Params

Instances

Processable Request

Processable Req

class ToHttpData a where

Methods

toHttpData :: a -> HttpData

Instances

ToHttpData String

ToByteString a => ToHttpData a

ToHttpData ByteString

ToHttpData HttpData

data Token

a Token identifies a flow that handle messages. The scheduler compose a Token with every Processable message that arrives and send the mesage to the appropriate flow.

Constructors

Token

Fields

twfname :: String

tuser :: String

tind :: String

q :: MVar Req

qr :: MVar Resp

Instances

Read Token

Show Token

Typeable Token

Indexable Token

Serializable Token

type ProcList = WorkflowList IO Token ()

List of (wfname, workflow) pairs, to be scheduled depending on the message's pwfname

low level comunication primitives. Use ask instead

flushRec :: Token -> IO ()

receive :: Typeable a => Token -> IO a

receiveReq :: Token -> IO Req

receiveReqTimeout :: Int -> Integer -> Token -> IO Req

send :: ToHttpData a => Token -> a -> IO ()

send a complete response

sendFlush :: ToHttpData a => Token -> a -> IO ()

sendFragment :: ToHttpData a => Token -> a -> IO ()

send a response fragment. Useful for streaming. the last packet must sent trough send

sendEndFragment :: ToHttpData a => Token -> a -> IO ()

Flow configuration

addMessageFlows :: [([Char], Token -> Workflow IO ())] -> IO ()

add a list of flows to be scheduled. Each entry in the list is a pair (path, flow)

getMessageFlows :: IO (Map String (Token -> Workflow IO ()))

return the list of the scheduler

transient :: (Token -> IO ()) -> Token -> Workflow IO ()

Executes a monadic computation that send and receive messages, but does not store its state in permanent storage. The process once stopped, will restart anew

stateless :: ToHttpData b => (Params -> IO b) -> Token -> Workflow IO ()

executes a simple monadic computation that receive the params and return a response

It is used with addMessageFlows hackMessageFlow or waiMessageFlow

anonymous :: [Char]

The anonymous user

noScript :: [Char]

It is the path of the root flow

hlog :: Handle

The handler of the error log

setNotFoundResponse :: MonadIO m => (ByteString -> ByteString) -> m ()

set the 404 not found response

getNotFoundResponse :: ByteString -> ByteString

ByteString tags

very basic but efficient tag formatting

btag :: String -> Attribs -> ByteString -> ByteString

Writes a XML tag in a ByteString. It is the most basic form of formatting. For more sophisticated formatting , use MFlow.Forms.XHtml or MFlow.Forms.HSP.

bhtml :: Attribs -> ByteString -> ByteString

 bhtml ats v= btag "html" ats v

bbody :: Attribs -> ByteString -> ByteString

 bbody ats v= btag "body" ats v

type Attribs = [(String, String)]

internal use

addTokenToList :: Token -> IO ()

deleteTokenInList :: Token -> IO ()

msgScheduler :: (Typeable a, Processable a) => a -> IO (HttpData, ThreadId)

The scheduler creates a Token with every Processable message that arrives and send the mesage to the appropriate flow, get the response and return it.