legion-0.8.0.2: src/Network/Legion/Runtime.hs
{-# LANGUAGE DeriveGeneric #-}
{-# LANGUAGE LambdaCase #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE NamedFieldPuns #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE TemplateHaskell #-}
{- |
This module is responsible for the runtime operation of the legion
framework. This mostly means opening sockets and piping data around to the
various connected pieces.
-}
module Network.Legion.Runtime (
forkLegionary,
StartupMode(..),
Runtime,
makeRequest,
search,
) where
import Control.Concurrent (forkIO)
import Control.Concurrent.Chan (writeChan, newChan, Chan)
import Control.Concurrent.MVar (newEmptyMVar, takeMVar, putMVar)
import Control.Monad (void, forever, join)
import Control.Monad.Catch (catchAll, try, SomeException, throwM)
import Control.Monad.IO.Class (MonadIO, liftIO)
import Control.Monad.Logger (logWarn, logError, logInfo, LoggingT,
MonadLoggerIO, runLoggingT, askLoggerIO, logDebug)
import Control.Monad.Trans.Class (lift)
import Control.Monad.Trans.State (StateT, runStateT, get, put, modify)
import Data.Binary (encode, Binary)
import Data.Conduit (Source, ($$), (=$=), yield, await, awaitForever,
transPipe, ConduitM, runConduit, Sink)
import Data.Conduit.Network (sourceSocket)
import Data.Conduit.Serialization.Binary (conduitDecode)
import Data.Map (Map)
import Data.Set (Set)
import Data.Text (pack)
import GHC.Generics (Generic)
import Network.Legion.Admin (runAdmin, AdminMessage(GetState, GetPart,
Eject, GetIndex, GetDivergent, GetStates))
import Network.Legion.Application (LegionConstraints, Persistence, list)
import Network.Legion.BSockAddr (BSockAddr(BSockAddr))
import Network.Legion.ClusterState (ClusterPowerState)
import Network.Legion.Conduit (merge, chanToSink, chanToSource)
import Network.Legion.Distribution (Peer, newPeer)
import Network.Legion.Fork (forkC)
import Network.Legion.Index (IndexRecord(IndexRecord), irTag, irKey,
SearchTag(SearchTag))
import Network.Legion.LIO (LIO)
import Network.Legion.Lift (lift2, lift3)
import Network.Legion.PartitionKey (PartitionKey)
import Network.Legion.PartitionState (PartitionPowerState)
import Network.Legion.Runtime.ConnectionManager (newConnectionManager,
ConnectionManager, newPeers)
import Network.Legion.Runtime.PeerMessage (PeerMessage(PeerMessage),
PeerMessagePayload(ForwardRequest, ForwardResponse, ClusterMerge,
PartitionMerge, Search, SearchResponse, JoinNext, JoinNextResponse),
MessageId, newSequence, nextMessageId, JoinNextResponse(Joined,
JoinFinished))
import Network.Legion.Settings (RuntimeSettings(RuntimeSettings,
adminHost, adminPort, peerBindAddr, joinBindAddr))
import Network.Legion.StateMachine (partitionMerge, clusterMerge,
newNodeState, UserResponse(Forward, Respond), userRequest, eject,
minimumCompleteServiceSet, joinNext, joinNextResponse)
import Network.Legion.StateMachine.Monad (NodeState, runSM, ClusterAction,
SM, popActions)
import Network.Legion.UUID (getUUID)
import Network.Socket (Family(AF_INET, AF_INET6, AF_UNIX, AF_CAN),
SocketOption(ReuseAddr), SocketType(Stream), accept, bind,
defaultProtocol, listen, setSocketOption, socket, SockAddr(SockAddrInet,
SockAddrInet6, SockAddrUnix, SockAddrCan), connect, getPeerName, Socket)
import Network.Socket.ByteString.Lazy (sendAll)
import qualified Data.Conduit.List as CL
import qualified Data.Map as Map
import qualified Data.Set as Set
import qualified Network.Legion.ClusterState as C
import qualified Network.Legion.Runtime.ConnectionManager as CM
import qualified Network.Legion.StateMachine as SM
import qualified Network.Legion.StateMachine.Monad as SMM
{- |
Run the legion node framework program, with the given user definitions,
framework settings, and request source. This function never returns
(except maybe with an exception if something goes horribly wrong).
For the vast majority of service implementations, you are going to need
to implement some halfway complex concurrency in order to populate the
request source, and to handle the responses. Unless you know exactly
what you are doing, you probably want to use `forkLegionary` instead.
-}
runLegionary :: (LegionConstraints e o s)
=> Persistence e o s
{- ^ The persistence layer used to back the legion framework. -}
-> RuntimeSettings
{- ^ Settings and configuration of the legionframework. -}
-> StartupMode
-> Source IO (RequestMsg e o)
{- ^ A source of requests, together with a way to respond to the requets. -}
-> LoggingT IO ()
{-
Don't expose 'LIO' here because 'LIO' is a strictly internal
symbol. 'LoggingT IO' is what we expose to the world.
-}
runLegionary
persistence
settings@RuntimeSettings {adminHost, adminPort}
startupMode
requestSource
= do
{- Start the various messages sources. -}
peerS <- loggingC =<< startPeerListener settings
adminS <- loggingC =<< runAdmin adminPort adminHost
joinS <- loggingC (joinMsgSource settings)
(self, nodeState, peers) <- makeNodeState settings startupMode
rts <- newRuntimeState self peers
let
messageSource = transPipe lift (
(joinS =$= CL.map J) `merge`
(peerS =$= CL.map P) `merge`
(requestSource =$= CL.map R) `merge`
(adminS =$= CL.map A)
)
void . runRTS persistence nodeState rts . runConduit $
messageSource
=$= messageSink
where
newRuntimeState :: (Binary e, Binary o, Binary s)
=> Peer
-> Map Peer BSockAddr
-> LoggingT IO (RuntimeState e o s)
newRuntimeState self peers = do
cm <- newConnectionManager peers
firstMessageId <- newSequence
return RuntimeState {
forwarded = Map.empty,
nextId = firstMessageId,
cm,
self,
searches = Map.empty
}
{- |
Turn an LIO-based conduit into an IO-based conduit, so that it
will work with `merge`.
-}
loggingC :: ConduitM e o LIO r -> LIO (ConduitM e o IO r)
loggingC c = do
logging <- askLoggerIO
return (transPipe (`runLoggingT` logging) c)
{- |
This is how requests are packaged when they are sent to the legion framework
for handling. It includes the request information itself, a partition key to
which the request is directed, and a way for the framework to deliver the
response to some interested party.
-}
data RequestMsg e o
= Request PartitionKey e (o -> IO ())
| SearchDispatch SearchTag (Maybe IndexRecord -> IO ())
instance (Show e) => Show (RequestMsg e o) where
show (Request k e _) = "(Request " ++ show k ++ " " ++ show e ++ " _)"
show (SearchDispatch s _) = "(SearchDispatch " ++ show s ++ " _)"
messageSink :: (LegionConstraints e o s)
=> Sink (RuntimeMessage e o s) (RTS e o s) ()
messageSink = awaitForever (\msg -> do
$(logDebug) . pack $ "Receieved: " ++ show msg
lift $ do
handleMessage msg
updatePeers
clusterActions
)
{- | Make progress on outstanding cluster actions. -}
clusterActions :: RTS e o s ()
clusterActions =
mapM_ clusterAction =<< popActions
where
{- |
Actually perform a cluster action as directed by the state
machine.
-}
clusterAction
:: ClusterAction e o s
-> RTS e o s ()
clusterAction (SMM.ClusterMerge peer ps) =
void $ send peer (ClusterMerge ps)
clusterAction (SMM.PartitionMerge peer key ps) =
void $ send peer (PartitionMerge key ps)
clusterAction (SMM.PartitionJoin peer keys) =
void $ send peer (JoinNext keys)
{- |
Make sure the connection manager knows about any new peers that have
joined the cluster.
-}
updatePeers :: RTS e o s ()
updatePeers = do
peers <- SM.getPeers
RuntimeState {cm} <- lift get
lift2 $ newPeers cm peers
{- |
Handle an individual runtime message, accepting an initial runtime
state and an initial node state, and producing an updated runtime
state and node state.
-}
handleMessage :: (LegionConstraints e o s)
=> RuntimeMessage e o s
-> RTS e o s ()
handleMessage {- Join Next Response -}
(P (PeerMessage source _ (JoinNextResponse _messageId response)))
=
joinNextResponse source (toMaybe response)
where
toMaybe
:: JoinNextResponse e o s
-> Maybe (PartitionKey, PartitionPowerState e o s)
toMaybe (Joined key partition) = Just (key, partition)
toMaybe JoinFinished = Nothing
handleMessage {- Join Next -}
(P (PeerMessage source messageId (JoinNext askKeys)))
=
joinNext source askKeys >>= \case
Nothing -> void $
send source (JoinNextResponse messageId JoinFinished)
Just (gotKey, partition) -> void $
send source (JoinNextResponse messageId (Joined gotKey partition))
handleMessage {- Partition Merge -}
(P (PeerMessage _ _ (PartitionMerge key ps)))
=
partitionMerge key ps
handleMessage {- Cluster Merge -}
(P (PeerMessage _ _ (ClusterMerge cs)))
=
clusterMerge cs
handleMessage {- Forward Request -}
(P (msg@(PeerMessage source mid (ForwardRequest key request))))
= do
output <- userRequest key request
case output of
Respond response -> void $ send source (ForwardResponse mid response)
Forward peer -> forward peer msg
handleMessage {- Forward Response -}
(msg@(P (PeerMessage _ _ (ForwardResponse mid response))))
= do
rts <- lift get
case lookupDelete mid (forwarded rts) of
(Nothing, fwd) -> do
$(logWarn) . pack $ "Unsolicited ForwardResponse: " ++ show msg
(lift . put) rts {forwarded = fwd}
(Just respond, fwd) -> do
lift2 $ respond response
(lift . put) rts {forwarded = fwd}
handleMessage {- User Request -}
(R (Request key request respond))
= do
output <- userRequest key request
case output of
Respond response -> lift3 (respond response)
Forward peer -> do
messageId <- send peer (ForwardRequest key request)
(lift . modify) $ \rts@RuntimeState {forwarded} -> rts {
forwarded = Map.insert messageId (lift . respond) forwarded
}
handleMessage {- Search Dispatch -}
{-
This is where we send out search request to all the appropriate
nodes in the cluster.
-}
(R (SearchDispatch searchTag respond))
=
Map.lookup searchTag . searches <$> lift get >>= \case
Nothing -> do
{-
No identical search is currently being executed, kick off a
new one.
-}
mcss <- minimumCompleteServiceSet
mapM_ sendOne (Set.toList mcss)
rts@RuntimeState {searches} <- lift get
(lift . put) rts {
searches = Map.insert
searchTag
(mcss, Nothing, [lift . respond])
searches
}
Just (peers, best, responders) -> do
{-
A search for this tag is already in progress, just add the
responder to the responder list.
-}
rts@RuntimeState {searches} <- lift get
(lift . put) rts {
searches = Map.insert
searchTag
(peers, best, (lift . respond):responders)
searches
}
where
sendOne :: Peer -> RTS e o s ()
sendOne peer =
void $ send peer (Search searchTag)
handleMessage {- Search Execution -}
{- This is where we handle local search execution. -}
(P (PeerMessage source _ (Search searchTag)))
= do
output <- SM.search searchTag
void $ send source (SearchResponse searchTag output)
handleMessage {- Search Response -}
{-
This is where we gather all the responses from the various peers
to which we dispatched search requests.
-}
(msg@(P (PeerMessage source _ (SearchResponse searchTag response))))
=
{- TODO: see if this function can't be made more elegant. -}
Map.lookup searchTag . searches <$> lift get >>= \case
Nothing ->
{- There is no search happening. -}
$(logWarn) . pack $ "Unsolicited SearchResponse: " ++ show msg
Just (peers, best, responders) ->
if source `Set.member` peers
then
let peers2 = Set.delete source peers
in if null peers2
then do
{-
All peers have responded, go ahead and respond to
the client.
-}
lift2 $ mapM_ ($ bestOf best response) responders
rts@RuntimeState {searches} <- lift get
(lift . put) rts {searches = Map.delete searchTag searches}
else do
{- We are still waiting on some outstanding requests. -}
rts@RuntimeState {searches} <- lift get
(lift . put) rts {
searches = Map.insert
searchTag
(peers2, bestOf best response, responders)
searches
}
else
{-
There is a search happening, but the peer that responded
is not part of it.
-}
$(logWarn) . pack $ "Unsolicited SearchResponse: " ++ show msg
where
{- |
Figure out which index record returned to us by the various peers
is the most appropriate to return to the user. This is mostly like
'min' but we can't use 'min' (or fancy applicative formulations)
because we want to favor 'Just' instead of 'Nothing'.
-}
bestOf :: Maybe IndexRecord -> Maybe IndexRecord -> Maybe IndexRecord
bestOf (Just a) (Just b) = Just (min a b)
bestOf Nothing b = b
bestOf a Nothing = a
handleMessage {- Join Request -}
(J (JoinRequest addy, respond))
= do
(peer, cluster) <- SM.join addy
lift2 $ respond (JoinOk peer cluster)
handleMessage {- Admin Get State -}
(A (GetState respond))
=
lift2 . respond =<< SMM.getNodeState
handleMessage {- Admin Get Partition -}
(A (GetPart key respond))
=
lift2 . respond =<< SM.getPartition key
handleMessage {- Admin Eject Peer -}
(A (Eject peer respond))
= do
{-
TODO: we should attempt to notify the ejected peer that it has
been ejected instead of just cutting it off and washing our hands
of it. I have a vague notion that maybe ejected peers should be
permanently recorded in the cluster state so that if they ever
reconnect then we can notify them that they are no longer welcome
to participate.
On a related note, we need to think very hard about the split brain
problem. A random thought about that is that we should consider the
extreme case where the network just fails completely and every node
believes that every other node should be or has been ejected. This
would obviously be catastrophic in terms of data durability unless
we have some way to reintegrate an ejected node. So, either we
have to guarantee that such a situation can never happen, or else
implement a reintegration strategy. It might be acceptable for
the reintegration strategy to be very costly if it is characterized
as an extreme recovery scenario.
Question: would a reintegration strategy become less costly if the
"next state id" for a peer were global across all power states
instead of local to each power state?
-}
eject peer
lift2 $ respond ()
handleMessage {- Admin Get Index -}
(A (GetIndex respond))
=
lift2 . respond =<< SMM.nsIndex <$> SMM.getNodeState
handleMessage {- Admin Get Divergent -}
(A (GetDivergent respond))
=
lift2 . respond =<< SMM.partitions <$> SMM.getNodeState
handleMessage {- Admin Get States -}
(A (GetStates respond))
= do
persistence <- SMM.getPersistence
lift2 . respond . Map.fromList =<< runConduit (
transPipe liftIO (list persistence)
=$= CL.consume
)
{- | This defines the various ways a node can be spun up. -}
data StartupMode
= NewCluster
{- ^
Indicates that we should bootstrap a new cluster at startup. The
persistence layer may be safely pre-populated because the new node
will claim the entire keyspace.
-}
| JoinCluster SockAddr
{- ^
Indicates that the node should try to join an existing cluster,
either by starting fresh, or by recovering from a shutdown or crash.
-}
deriving (Show, Eq)
{- |
Construct a source of incoming peer messages. We have to start the
peer listener first before we spin up the cluster management, which
is why this is an @LIO (Source LIO PeerMessage)@ instead of a
@Source LIO PeerMessage@.
-}
startPeerListener :: (LegionConstraints e o s)
=> RuntimeSettings
-> LIO (Source LIO (PeerMessage e o s))
startPeerListener RuntimeSettings {peerBindAddr} =
catchAll (do
(inputChan, so) <- lift $ do
inputChan <- newChan
so <- socket (fam peerBindAddr) Stream defaultProtocol
setSocketOption so ReuseAddr 1
bind so peerBindAddr
listen so 5
return (inputChan, so)
forkC "peer socket acceptor" $ acceptLoop so inputChan
return (chanToSource inputChan)
) (\err -> do
$(logError) . pack
$ "Couldn't start incomming peer message service, because of: "
++ show (err :: SomeException)
throwM err
)
where
acceptLoop :: (LegionConstraints e o s)
=> Socket
-> Chan (PeerMessage e o s)
-> LIO ()
acceptLoop so inputChan =
catchAll (
forever $ do
(conn, _) <- lift $ accept so
remoteAddr <- lift $ getPeerName conn
logging <- askLoggerIO
let runSocket =
sourceSocket conn
=$= conduitDecode
$$ msgSink
void
. lift
. forkIO
. (`runLoggingT` logging)
. logErrors remoteAddr
$ runSocket
) (\err -> do
$(logError) . pack
$ "error in peer message accept loop: "
++ show (err :: SomeException)
throwM err
)
where
msgSink = chanToSink inputChan
logErrors :: SockAddr -> LIO () -> LIO ()
logErrors remoteAddr io = do
result <- try io
case result of
Left err ->
$(logWarn) . pack
$ "Incomming peer connection (" ++ show remoteAddr
++ ") crashed because of: " ++ show (err :: SomeException)
Right v -> return v
{- | Figure out how to construct the initial node state. -}
makeNodeState
:: RuntimeSettings
-> StartupMode
-> LIO (Peer, NodeState e o s, Map Peer BSockAddr)
makeNodeState RuntimeSettings {peerBindAddr} NewCluster = do
{- Build a brand new node state, for the first node in a cluster. -}
self <- newPeer
clusterId <- getUUID
let
cluster = C.new clusterId self peerBindAddr
nodeState = newNodeState self cluster
return (self, nodeState, C.getPeers cluster)
makeNodeState RuntimeSettings {peerBindAddr} (JoinCluster addr) = do
{-
Join a cluster by either starting fresh, or recovering from a
shutdown or crash.
-}
$(logInfo) "Trying to join an existing cluster."
(self, cluster) <- joinCluster (JoinRequest (BSockAddr peerBindAddr))
let
nodeState = newNodeState self cluster
return (self, nodeState, C.getPeers cluster)
where
joinCluster :: JoinRequest -> LIO (Peer, ClusterPowerState)
joinCluster joinMsg = liftIO $ do
so <- socket (fam addr) Stream defaultProtocol
connect so addr
sendAll so (encode joinMsg)
{-
using sourceSocket and conduitDecode is easier than building
a recive/decode state loop, even though we only read a single
response.
-}
sourceSocket so =$= conduitDecode $$ do
response <- await
case response of
Nothing -> fail
$ "Couldn't join a cluster because there was no response "
++ "to our join request!"
Just (JoinOk self cps) ->
return (self, cps)
Just (JoinRejected reason) -> fail
$ "The cluster would not allow us to re-join. "
++ "The reason given was: " ++ show reason
{- | A source of cluster join request messages. -}
joinMsgSource
:: RuntimeSettings
-> Source LIO (JoinRequest, JoinResponse -> LIO ())
joinMsgSource RuntimeSettings {joinBindAddr} = join . lift $
catchAll (do
(chan, so) <- lift $ do
chan <- newChan
so <- socket (fam joinBindAddr) Stream defaultProtocol
setSocketOption so ReuseAddr 1
bind so joinBindAddr
listen so 5
return (chan, so)
forkC "join socket acceptor" $ acceptLoop so chan
return (chanToSource chan)
) (\err -> do
$(logError) . pack
$ "Couldn't start join request service, because of: "
++ show (err :: SomeException)
throwM err
)
where
acceptLoop :: Socket -> Chan (JoinRequest, JoinResponse -> LIO ()) -> LIO ()
acceptLoop so chan =
catchAll (
forever $ do
(conn, _) <- lift $ accept so
logging <- askLoggerIO
(void . lift . forkIO . (`runLoggingT` logging) . logErrors) (
sourceSocket conn
=$= conduitDecode
=$= attachResponder conn
$$ chanToSink chan
)
) (\err -> do
$(logError) . pack
$ "error in join request accept loop: "
++ show (err :: SomeException)
throwM err
)
where
logErrors :: LIO () -> LIO ()
logErrors io = do
result <- try io
case result of
Left err ->
$(logWarn) . pack
$ "Incomming join connection crashed because of: "
++ show (err :: SomeException)
Right v -> return v
attachResponder
:: Socket
-> ConduitM JoinRequest (JoinRequest, JoinResponse -> LIO ()) LIO ()
attachResponder conn = awaitForever (\msg -> do
mvar <- liftIO newEmptyMVar
yield (msg, lift . putMVar mvar)
response <- liftIO $ takeMVar mvar
liftIO $ sendAll conn (encode response)
)
{- | Guess the family of a `SockAddr`. -}
fam :: SockAddr -> Family
fam SockAddrInet {} = AF_INET
fam SockAddrInet6 {} = AF_INET6
fam SockAddrUnix {} = AF_UNIX
fam SockAddrCan {} = AF_CAN
{- |
Forks the legion framework in a background thread, and returns a way to
send user requests to it and retrieve the responses to those requests.
- @__e__@ is the type of request your application will handle. @__e__@ stands
for __"event"__.
- @__o__@ is the type of response produced by your application. @__o__@ stands
for __"output"__
- @__s__@ is the type of state maintained by your application. More
precisely, it is the type of the individual partitions that make up
your global application state. @__s__@ stands for __"state"__.
-}
forkLegionary :: (LegionConstraints e o s, MonadLoggerIO io)
=> Persistence e o s
{- ^ The persistence layer used to back the legion framework. -}
-> RuntimeSettings
{- ^ Settings and configuration of the legion framework. -}
-> StartupMode
-> io (Runtime e o)
forkLegionary persistence settings startupMode = do
logging <- askLoggerIO
liftIO . (`runLoggingT` logging) $ do
chan <- liftIO newChan
forkC "main legion thread" $
runLegionary persistence settings startupMode (chanToSource chan)
return Runtime {
rtMakeRequest = \key request -> liftIO $ do
responseVar <- newEmptyMVar
writeChan chan (Request key request (putMVar responseVar))
takeMVar responseVar,
rtSearch =
let
findNext :: SearchTag -> IO (Maybe IndexRecord)
findNext searchTag = do
responseVar <- newEmptyMVar
writeChan chan (SearchDispatch searchTag (putMVar responseVar))
takeMVar responseVar
in findNext
}
{- |
This type represents a handle to the runtime environment of your
Legion application. This allows you to make requests and access the
partition index.
'Runtime' is an opaque structure. Use 'makeRequest' to access it.
-}
data Runtime e o = Runtime {
{- |
Send an application request to the legion runtime, and get back
a response.
-}
rtMakeRequest :: PartitionKey -> e -> IO o,
{- | Query the index to find a set of partition keys. -}
rtSearch :: SearchTag -> IO (Maybe IndexRecord)
}
{- | Send a user request to the legion runtime. -}
makeRequest :: (MonadIO io) => Runtime e o -> PartitionKey -> e -> io o
makeRequest rt key = liftIO . rtMakeRequest rt key
{- |
Send a search request to the legion runtime. Returns results that are
__strictly greater than__ the provided 'SearchTag'.
-}
search :: (MonadIO io) => Runtime e o -> SearchTag -> Source io IndexRecord
search rt tag =
liftIO (rtSearch rt tag) >>= \case
Nothing -> return ()
Just record@IndexRecord {irTag, irKey} -> do
yield record
search rt (SearchTag irTag (Just irKey))
{- | This is the type of message passed around in the runtime. -}
data RuntimeMessage e o s
= P (PeerMessage e o s)
| R (RequestMsg e o)
| J (JoinRequest, JoinResponse -> LIO ())
| A (AdminMessage e o s)
instance (Show e, Show o, Show s) => Show (RuntimeMessage e o s) where
show (P m) = "(P " ++ show m ++ ")"
show (R m) = "(R " ++ show m ++ ")"
show (J (jr, _)) = "(J (" ++ show jr ++ ", _))"
show (A a) = "(A (" ++ show a ++ "))"
{- |
The runtime state.
The 'searches' field is a little weird.
It turns out that searches are deterministic over the parameters of
'SearchTag' and cluster state. This should make sense, because everything in
Haskell is deterministic given __all__ the parameters. Since the cluster
state only changes over time, searches that happen "at the same time" and
for the same 'SearchTag' can be considered identical. I don't think it is too
much of a stretch to say that searches that have overlapping execution times
can be considered to be happening "at the same time", therefore the
search tag becomes determining factor in the result of the search.
This is a long-winded way of justifying the fact that, if we are currently
executing a search and an identical search requests arrives, then the second
identical search is just piggy-backed on the results of the currently
executing search. Whether this counts as a premature optimization hack or a
beautifully elegant expression of platonic reality is left as an exercise for
the reader. It does help simplify the code a little bit because we don't have
to specify some kind of UUID to differentiate otherwise identical searches.
-}
data RuntimeState e o s = RuntimeState {
self :: Peer,
forwarded :: Map MessageId (o -> LIO ()),
nextId :: MessageId,
cm :: ConnectionManager e o s,
searches :: Map
SearchTag
(Set Peer, Maybe IndexRecord, [Maybe IndexRecord -> LIO ()])
}
{- | This is the type of a join request message. -}
data JoinRequest = JoinRequest BSockAddr
deriving (Generic, Show)
instance Binary JoinRequest
{- | The response to a JoinRequst message -}
data JoinResponse
= JoinOk Peer ClusterPowerState
| JoinRejected String
deriving (Generic)
instance Binary JoinResponse
{- | Lookup a key from a map, and also delete the key if it exists. -}
lookupDelete :: (Ord k) => k -> Map k v -> (Maybe v, Map k v)
lookupDelete = Map.updateLookupWithKey (const (const Nothing))
{- | The runtime monad. -}
type RTS e o s =
SM e o s (
StateT (RuntimeState e o s)
LIO)
{- | Shorthand for running the RTS monad. -}
runRTS
:: Persistence e o s
-> NodeState e o s
-> RuntimeState e o s
-> RTS e o s a
-> LIO (a, NodeState e o s, [ClusterAction e o s], RuntimeState e o s)
runRTS persistence ns rts =
fmap flatten
. (`runStateT` rts)
. runSM persistence ns
where
flatten ((a, b, c), d) = (a, b, c, d)
{- |
Send a peer message in the RTS monad, automatically taking care of
necessary state updates.
-}
send :: Peer -> PeerMessagePayload e o s -> RTS e o s MessageId
send target payload = do
rts@RuntimeState {cm, self, nextId} <- lift get
(lift . put) rts {nextId = nextMessageId nextId}
lift2 $ CM.send cm target (PeerMessage self nextId payload)
return nextId
{- | Forward an existing message to another peer. -}
forward :: Peer -> PeerMessage e o s -> RTS e o s ()
forward target message = do
RuntimeState {cm} <- lift get
lift2 $ CM.send cm target message