Transient.Move

transient-universe extends the seamless composability of concurrent multi-threaded programs provided by transient to a multi-node cloud. Distributed concurrent programs are created and composed seamlessly and effortlessly as if they were written for a single node. transient-universe has diverse applications from simple distributed applications to massively parallel and distributed map-reduce problems. If you are considering Apache Spark or Cloud Haskell then transient might be a simpler yet better solution for you.

Transient makes it easy to write composable, distributed event driven reactive UI applications with client side and server side code composed freely in the same application. For example, Axiom is a transient based unified client and server side web application framework that provides a better programming model and composability compared to frameworks like ReactJS.

Overview

The Cloud monad adds the following facilities to complement the TransIO monad:

• Create a distributed compute cluster of nodes
• Move computations across nodes at any point during computation
• Run computations on multiple nodes in parallel

Further Reading

• Tutorial
• Examples
• Blog post

Running the Monad

newtype Cloud a

Constructors

Cloud

Fields

• runCloud' :: TransIO a

Instances

Monad Cloud

Methods

(>>=) :: Cloud a -> (a -> Cloud b) -> Cloud b

(>>) :: Cloud a -> Cloud b -> Cloud b

return :: a -> Cloud a

fail :: String -> Cloud a

Functor Cloud

Methods

fmap :: (a -> b) -> Cloud a -> Cloud b

(<$) :: a -> Cloud b -> Cloud a

Applicative Cloud

Methods

pure :: a -> Cloud a

(<*>) :: Cloud (a -> b) -> Cloud a -> Cloud b

liftA2 :: (a -> b -> c) -> Cloud a -> Cloud b -> Cloud c

(*>) :: Cloud a -> Cloud b -> Cloud b

(<*) :: Cloud a -> Cloud b -> Cloud a

Alternative Cloud

Methods

empty :: Cloud a

(<|>) :: Cloud a -> Cloud a -> Cloud a

some :: Cloud a -> Cloud [a]

many :: Cloud a -> Cloud [a]

MonadState EventF Cloud

Methods

get :: Cloud EventF

put :: EventF -> Cloud ()

state :: (EventF -> (a, EventF)) -> Cloud a

(Fractional a, Eq a) => Fractional (Cloud a)

Methods

(/) :: Cloud a -> Cloud a -> Cloud a

recip :: Cloud a -> Cloud a

fromRational :: Rational -> Cloud a

(Eq a, Num a) => Num (Cloud a)

Methods

(+) :: Cloud a -> Cloud a -> Cloud a

(-) :: Cloud a -> Cloud a -> Cloud a

(*) :: Cloud a -> Cloud a -> Cloud a

negate :: Cloud a -> Cloud a

abs :: Cloud a -> Cloud a

signum :: Cloud a -> Cloud a

fromInteger :: Integer -> Cloud a

Monoid a => Monoid (Cloud a)

Methods

mempty :: Cloud a

mappend :: Cloud a -> Cloud a -> Cloud a

mconcat :: [Cloud a] -> Cloud a

runCloud :: Cloud a -> TransIO a

Execute a distributed computation inside a TransIO computation. All the computations in the TransIO monad that enclose the cloud computation must be logged

runCloudIO :: Typeable a => Cloud a -> IO (Maybe a)

Run a distributed computation inside the IO monad. Enables asynchronous console input (see keep).

runCloudIO' :: Typeable a => Cloud a -> IO (Maybe a)

Run a distributed computation inside the IO monad with no console input.

Node & Cluster Management

To join the cluster a node connects to a well known node already part of the cluster.

import Transient.Move (runCloudIO, lliftIO, createNode, connect, getNodes, onAll)

main = runCloudIO $ do
    this   <- lliftIO (createNode "192.168.1.2" 8000)
    master <- lliftIO (createNode "192.168.1.1" 8000)
    connect this master
    onAll getNodes >>= lliftIO . putStrLn . show

data Node

Constructors

Node

Fields

• nodeHost :: HostName
• nodePort :: Int
• connection :: Maybe (MVar Pool)
• nodeServices :: Service

Instances

Eq Node

Methods

(==) :: Node -> Node -> Bool

(/=) :: Node -> Node -> Bool

Ord Node

Methods

compare :: Node -> Node -> Ordering

(<) :: Node -> Node -> Bool

(<=) :: Node -> Node -> Bool

(>) :: Node -> Node -> Bool

(>=) :: Node -> Node -> Bool

max :: Node -> Node -> Node

min :: Node -> Node -> Node

Read Node

Methods

readsPrec :: Int -> ReadS Node

readList :: ReadS [Node]

readPrec :: ReadPrec Node

readListPrec :: ReadPrec [Node]

Show Node

Methods

showsPrec :: Int -> Node -> ShowS

show :: Node -> String

showList :: [Node] -> ShowS

Creating nodes

type Service = [(Package, Program)]

createNodeServ :: HostName -> Int -> Service -> IO Node

Create a node from a hostname (or IP address), port number and a list of services.

createNode :: HostName -> Int -> IO Node

createWebNode :: IO Node

Joining the cluster

connect :: Node -> Node -> Cloud ()

Add a node (first parameter) to the cluster using a node that is already part of the cluster (second parameter). The added node starts listening for incoming connections and the rest of the computation is executed on this newly added node.

connect' :: Node -> Cloud ()

Reconcile the list of nodes in the cluster using a remote node already part of the cluster. Reconciliation end up in each node in the cluster having the same list of nodes.

listen :: Node -> Cloud ()

Setup the node to start listening for incoming connections.

addNodes :: [Node] -> TransIO ()

Add a list of nodes to the list of existing cluster nodes.

shuffleNodes :: MonadIO m => m [Node]

Shuffle the list of cluster nodes and return the shuffled list.

Querying nodes

getMyNode :: TransIO Node

Return the local node i.e. the node where this computation is running.

getWebServerNode :: TransIO Node

getNodes :: MonadIO m => m [Node]

Return the list of nodes in the cluster.

nodeList :: TVar [Node]

isBrowserInstance :: Bool

Returns True if we are running in the browser.

Running Local Computations

local :: Loggable a => TransIO a -> Cloud a

Means that this computation will be executed in the current node. the result will be logged so the closure will be recovered if the computation is translated to other node by means of primitives like beamTo, forkTo, runAt, teleport, clustered, mclustered etc

onAll :: TransIO a -> Cloud a

alternative to local It means that if the computation is translated to other node this will be executed again if this has not been executed inside a local computation.

onAll foo
local foo'
local $ do
      bar
      runCloud $ do
              onAll baz
              runAt node ....
callTo node' .....

Here foo will be executed in node' but foo' bar and baz don't.

However foo bar and baz will e executed in node.

lazy :: TransIO a -> Cloud a

only executes if the result is demanded. It is useful when the conputation result is only used in the remote node, but it is not serializable.

fixRemote :: TransIO b -> Cloud b

executes a non-serilizable action in the remote node, whose result can be used by subsequent remote invocations

loggedc :: Loggable a => Cloud a -> Cloud a

lliftIO :: Loggable a => IO a -> Cloud a

the Cloud monad has no MonadIO instance. `lliftIO= local . liftIO`

localIO :: Loggable a => IO a -> Cloud a

`localIO = lliftIO`

fullStop :: TransIO stop

stop the current computation and does not execute any alternative computation

Moving Computations

wormhole :: Loggable a => Node -> Cloud a -> Cloud a

A wormhole opens a connection with another node anywhere in a computation. teleport uses this connection to translate the computation back and forth between the two nodes connected

teleport :: Cloud ()

copyData :: (Typeable * b, Read b, Show b) => b -> Cloud b

copy a session data variable from the local to the remote node. If there is none set in the local node, The parameter is the default value. In this case, the default value is also set in the local node.

fixClosure :: Cloud ()

experimental: subsequent remote invocatioms will send logs to this closure. Therefore logs will be shorter.

Also, non serializable statements before it will not be re-executed

Running at a Remote Node

beamTo :: Node -> Cloud ()

continue the execution in a new node

forkTo :: Node -> Cloud ()

execute in the remote node a process with the same execution state

callTo :: Loggable a => Node -> Cloud a -> Cloud a

open a wormhole to another node and executes an action on it. currently by default it keep open the connection to receive additional requests and responses (streaming)

runAt :: Loggable a => Node -> Cloud a -> Cloud a

Execute a computation in the node that initiated the connection.

if the sequence of connections is n1 -> n2 -> n3 then `atCallingNode $ atCallingNode foo` in n3 would execute foo in n1, -- while `atRemote $ atRemote foo` would execute it in n3 atCallingNode :: Loggable a => Cloud a -> Cloud a atCallingNode proc= connectCaller $ atRemote proc

synonymous of callTo

atRemote :: Loggable a => Cloud a -> Cloud a

Within a connection to a node opened by wormhole, it run the computation in the remote node and return the result back to the original node.

If atRemote is executed in the remote node, then the computation is executed in the original node

wormhole node2 $ do
    t <- atRemote $ do
          r <- foo              -- executed in node2
          s <- atRemote bar r   -- executed in the original node
          baz s                 -- in node2
    bat t                      -- in the original node

Running at Multiple Nodes

clustered :: Loggable a => Cloud a -> Cloud a

execute a Transient action in each of the nodes connected.

The response of each node is received by the invoking node and processed by the rest of the procedure. By default, each response is processed in a new thread. To restrict the number of threads use the thread control primitives.

this snippet receive a message from each of the simulated nodes:

main = keep $ do
   let nodes= map createLocalNode [2000..2005]
   addNodes nodes
   (foldl (<|>) empty $ map listen nodes) <|> return ()

   r <- clustered $ do
              Connection (Just(PortNumber port, _, _, _)) _ <- getSData
              return $ "hi from " ++ show port++ "\n"
   liftIO $ putStrLn r
   where
   createLocalNode n= createNode "localhost" (PortNumber n)

mclustered :: (Monoid a, Loggable a) => Cloud a -> Cloud a

callNodes :: (Show a2, Show a1, Read a2, Read a1, Typeable * a2, Typeable * a1) => (Cloud a2 -> Cloud a1 -> Cloud a1) -> Cloud a1 -> Cloud a2 -> Cloud a1

Messaging

putMailbox :: Typeable val => val -> TransIO ()

write to the mailbox Mailboxes are node-wide, for all processes that share the same connection data, that is, are under the same listen or connect while EVars are only visible by the process that initialized it and his children. Internally, the mailbox is in a well known EVar stored by listen in the Connection state.

putMailbox' :: (Typeable key, Ord key, Typeable val) => key -> val -> TransIO ()

write to a mailbox identified by an identifier besides the type

getMailbox :: Typeable val => TransIO val

get messages from the mailbox that matches with the type expected. The order of reading is defined by readTChan This is reactive. it means that each new message trigger the execution of the continuation each message wake up all the getMailbox computations waiting for it.

getMailbox' :: (Typeable key, Ord key, Typeable val) => key -> TransIO val

read from a mailbox identified by an identifier besides the type

cleanMailbox :: Typeable a => a -> TransIO ()

delete all subscriptions for that mailbox expecting this kind of data

cleanMailbox' :: Typeable a => Int -> a -> TransIO ()

clean a mailbox identified by an Int and the type

Thread Control

single :: TransIO a -> TransIO a

run a single thread with that action for each connection created. When the same action is re-executed within that connection, all the threads generated by the previous execution are killed

  box <-  foo
  r <- runAt node . local . single $ getMailbox box
  localIO $ print r

if foo return differnt mainbox indentifiers, the above code would print the messages of the last one. Without single, it would print the messages of all of them.

unique :: a -> TransIO ()

run an unique continuation for each connection. The first thread that execute unique is executed for that connection. The rest are ignored.

Buffering Control

setBuffSize :: Int -> TransIO ()

getBuffSize :: TransIO BuffSize

REST API

api :: TransIO ByteString -> Cloud ()

data HTTPMethod

Constructors

GET

POST

Instances

Read HTTPMethod

Methods

readsPrec :: Int -> ReadS HTTPMethod

readList :: ReadS [HTTPMethod]

readPrec :: ReadPrec HTTPMethod

readListPrec :: ReadPrec [HTTPMethod]

Show HTTPMethod

Methods

showsPrec :: Int -> HTTPMethod -> ShowS

show :: HTTPMethod -> String

showList :: [HTTPMethod] -> ShowS

type PostParams = [(ByteString, String)]