packages feed

Parry (empty) → 0.1.0.0

raw patch · 8 files changed

+2037/−0 lines, 8 filesdep +RSAdep +SafeSemaphoredep +basesetup-changed

Dependencies added: RSA, SafeSemaphore, base, binary, bytestring, containers, directory, ghc-prim, network, old-locale, process, random, time, unix

Files

+ LICENSE view
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Of course, your program's commands+might be different; for a GUI interface, you would use an "about box".++  You should also get your employer (if you work as a programmer) or school,+if any, to sign a "copyright disclaimer" for the program, if necessary.+For more information on this, and how to apply and follow the GNU GPL, see+<http://www.gnu.org/licenses/>.++  The GNU General Public License does not permit incorporating your program+into proprietary programs.  If your program is a subroutine library, you+may consider it more useful to permit linking proprietary applications with+the library.  If this is what you want to do, use the GNU Lesser General+Public License instead of this License.  But first, please read+<http://www.gnu.org/philosophy/why-not-lgpl.html>.+
+ Parry.cabal view
@@ -0,0 +1,33 @@+name:                Parry+version:             0.1.0.0+synopsis:            A proven synchronization server for high performance computing.++category:            Parry+description:         Parry is a scheduler for the exhaustive exploration of tree-like spaces. It is designed to be robust to client crashes and cluster walltimes, and is guaranteed to never \"forget about\" a job until it is done.+++homepage:            http://parry.lif.univ-mrs.fr+license:             GPL-3+license-file:        LICENSE+author:              Pierre-Etienne Meunier+maintainer:          pierre-etienne.meunier@lif.univ-mrs.fr++build-type:          Simple++cabal-version:       >=1.10++library+  exposed-modules:     Parry.Server, Parry.Client, Parry.Protocol,Parry.WebUI+  other-modules:       Parry.Util+  -- other-extensions:+  if !os(windows)+    build-depends:       base>=4.6 && <5,random,binary,time,bytestring>=0.10,RSA,network,directory,process,containers,SafeSemaphore,old-locale,ghc-prim,unix+  else+    build-depends:       base>=4.6 && <5,random,binary,time,bytestring>=0.10,RSA,network,directory,process,containers,SafeSemaphore,old-locale,ghc-prim+  -- hs-source-dirs:+  default-language:    Haskell2010++  if !os(windows)+    cpp-options: "-DUNIX"+  else+    cpp-options: ""
+ Parry/Client.lhs view
@@ -0,0 +1,372 @@+\ignore{+\begin{code}+{-#OPTIONS -cpp #-}+{-|+Module      :  Parry.Client+Copyright   :  (c) Pierre-Étienne Meunier 2014+License     :  GPL-3+Maintainer  :  pierre-etienne.meunier@lif.univ-mrs.fr+Stability   :  experimental+Portability :  All++Tool to build clients for Parry.+-}+\end{code}+}++We now prove the client functions. More precisely, we prove that the clients+that can be built using the functions in this module are valid and fluent,+provided that their ``worker'' function explores the space correctly. We include+the whole source code of this module for the sake of completeness.++\hfill++\begin{code}+module Parry.Client(+  -- * Jobs on the client side+  Client(..),+  -- * Writing clients+  client,Config(..),defaultConfig+  ) where+import Network+import System.IO+import System.Exit+#ifdef UNIX+import System.Posix.Signals+#endif+import Control.Concurrent+import Control.Exception as E+import Data.List+import Codec.Crypto.RSA.Pure+import qualified Data.ByteString.Lazy.Char8 as B8+import qualified Data.ByteString.Char8 as S+import Data.Binary+import Parry.Util+import Parry.Protocol+++-- | For a job to be usable by Parry's clients, it must be a member of this class.+class Client j where+  -- | This function is used by the client to distinguish results from regular jobs.+  isResult::j->Bool+\end{code}+\ignore{+\begin{code}+-- | Client configuration+data Config=Config {+  -- | The server's host name (either a DNS name or an IP address).+  server::String,+  -- | The port number (for instance @'Network.PortNumber' 5129@).+  port::PortID,+  -- | The private key to sign messages.+  privateKey::PrivateKey,+  -- | The public key, that the server must know of before the clients connect.+  publicKey::PublicKey+  }++-- | A default configuration, matching the server's+-- 'Parry.Server.defaultConfig'.  Note that, like in the server, you+-- must provide your own private key for signing the protocol+-- messages. See 'Parry.Server.defaultConfig' for an example method to+-- generate these keys.+defaultConfig::PrivateKey->PublicKey->Config+defaultConfig pr pu=Config {+  server="127.0.0.1",+  port=PortNumber 5129,+  privateKey=pr,+  publicKey=pu+  }+\end{code}+}+\begin{lemma}+\label{lem:signAndSend}+The {\tt signAndSend\_} and {\tt signAndSend} functions send only one kind of+messages on the network, with two lines: the first line is an encoding+via {\tt encode16l} of $m$, the encoding via {\tt encode} of a constructor+of the {\tt ClientMessage} type.+The second line is the RSA signature of $m$ using the private key in the+{\tt conf} argument.+\begin{proof}++The results follows from the fact that this function uses only two lines to send+messages on the network, and these two lines have the claimed form.++\hfill++\begin{code}+-- | A wrapper around signAndSend, to force the type of @j@, which is+-- needed for the protocol's @Alive@ messages.+signAndSend_::(Binary j)=>Config->j->ClientMessage j->IO (ServerMessage j)+signAndSend_ conf _ a=signAndSend conf a++-- | Sign a message and send it.+signAndSend::(Binary j)=>Config->ClientMessage j->IO (ServerMessage j)+signAndSend conf m=do {+  let { msg=encode m };+  case sign (privateKey conf) msg of {+    Right b->E.catch (do {+                         l<-bracket (connectTo (server conf) (port conf)) (hClose)+                            (\h->do {+                                B8.hPutStrLn h $ encode16l msg;+                                B8.hPutStrLn h $ encode16l b;+                                hFlush h;+                                S.hGetLine h;+                                });+                         case decodeOrFail $ decode16l $ B8.fromStrict l of {+                           Right (_,_,a)->return a;+                           Left _->do {+                             threadDelay 1000000;+                             signAndSend conf m+                             }+                           }})+             (\e->do {+                 let { _=e::IOError };+                 print e;+                 threadDelay 1000000;signAndSend conf m+                 });+    er->do {+      print er;hFlush stdout;threadDelay 100000;signAndSend conf m+      }+    }}+\end{code}++\end{proof}+\end{lemma}++To prove the remaining functions, we need to introduce the following invariant+on their arguments:+\begin{invariant}+\label{h}+When the {\tt cur} variable is not {\tt Nothing},+the {\tt jobs} and {\tt results} variables contain,+respectively, the list of all jobs of the contents of {\tt cur} that have not+been completely explored, and the list of results found during the exploration+of all other subjobs of the job in {\tt cur}.+\end{invariant}+++\begin{lemma}+\label{lem:dowork}+If there is a function {\tt doWork} such that, at the same time:+\begin{enumerate}+\item For all values of {\tt b}, {\tt save} and {\tt j}, {\tt doWork b save j}+only calls {\tt save} with arguments {\tt l} and {\tt r}, where {\tt r} is the+list of all results that have been found when the subjobs of {\tt j} that have+not been completely explored are all in list {\tt l}.++\item For all values of {\tt b}, {\tt save} and {\tt j}, {\tt doWork b save+j} returns the list of all subjobs of {\tt j} that have not been explored, and+all results that have been found in {\tt j}, in the remaining subjobs of {\tt j}.++\end{enumerate}+Then {\tt client conf doWork} is a valid and fluent client.+\begin{proof}++We first prove fluency: in the two functions below ({\tt work} and {\tt+client}), the only messages sent to the network are either sent using {\tt+signAndSend}, or else consist of a single line containing exactly {\tt Hello},+which is the definition of fluency (by Lemma \ref{lem:signAndSend}).++We now prove that {\tt client conf doWork} is valid. Indeed, condition+\ref{valid:newjobs} of validity ({\tt NewJobs} messages contain all subjobs of+the current job) is clearly respected by the {\tt work} function: indeed, by the+definition of a result, the {\tt todo} variable in {\tt work} is the list of all+subjobs that have not been explored. Condition \ref{valid:jobdone} is also+respected, because it is not applicable to the {\tt work} function.++Moreover, the {\tt work} function returns either {\tt Nothing}, or {\tt Just+(j,r)} where {\tt j} is a job, and {\tt r} is the list of all results found+during the exploration of {\tt j}. We prove this recursively on its code:++\hfill+\begin{code}+work::(Client j,Binary j)=>Config->MVar [j]->MVar[j]->MVar (Maybe j)->+      (Bool->([j]->[j]->IO ())->j->IO [j])->Bool->Integer->j->IO (Maybe (j,[j]))+work conf jobs results cur doWork shared num j=do+  let save jobs_ results_ jobs results=do+        modifyMVar_ jobs_ $ \_->return jobs+        modifyMVar_ results_ $ \_->return results+  someWork<-doWork shared (save jobs results) j+  let (result,todo)=partition isResult someWork+  case todo of+\end{code}+\hfill++Either {\tt doWork} has returned no new jobs, in which case the induction+hypothesis clearly holds, because the exploration of the current job is over.++\hfill+\begin{code}+    []->return (Just (j,result))+\end{code}+\hfill++Or {\tt doWork} returns some new jobs. In this case, {\tt work} is called on+{\tt u} only after reply {\tt Ack} has been received from the server,+acknowledging that the current job registered for this client has been updated.+Therefore, {\tt work} is called recursively on the current job of this client,+and hence, the claim also holds, by recursion.++\hfill+\begin{code}+    u:v->do+      x<-signAndSend conf (NewJobs {clientId=num,jobResults=result,+                                    currentJob=j,nextJob=u,newJobs=v })+      modifyMVar_ cur (\_->do {+                          modifyMVar_ results (\_->return []);+                          modifyMVar_ jobs (\_->return [u]);+                          return (Just u)+                          })+      case x of+        Ack->work conf jobs results cur doWork (shared && (null v)) num u;+        _->return Nothing+\end{code}+\hfill++We will now prove validity for the code of the {\tt client} function.+We have assumed that the {\tt save} function above is only called on+a list {\tt l} of subjobs, and a list {\tt r} of results, such that+{\tt l} contains all subjobs of the initial job {\tt j} that have+not been completely explored when results {\tt r} are found.++Therefore, in the {\tt work} function above, Invariant \ref{h} on+the {\tt jobs\_} and {\tt results\_} variables is clearly maintained:++\hfill+\ignore{+\begin{code}+-- | @'client' config work@ calls its argument function @work@ on a+-- boolean @s@ (if the server asked to share jobs) and the actual job+-- @j@ that must be done. @work@ must return a list of resulting jobs,+-- that may include results (see 'Parry.Protocol.Client').+--+-- Workers asked to share their input job should share it as early as+-- possible: this usually means that the job already got killed in a+-- previous attempt, probably because of its length.+\end{code}+}+\begin{code}+client::(Binary j,Client j)=>+        Config->(Bool->([j]->[j]->IO())->j->IO [j])->IO ()+client conf doWork=+  let startConnection=do+        hPutStrLn stderr "Connecting..."+        hFlush stderr+        l<-E.catch (bracket (connectTo (server conf) (port conf)) hClose+                    (\h->do {+                        B8.hPutStrLn h (B8.pack "Hello");+                        hFlush h;+                        l<-S.hGetLine h;+                        case decodeOrFail (decode16l (B8.fromStrict l)) of {+                          Right x->return (Right x);+                          Left _->return (Left ())+                          }}))+           (\e->let _=e::IOError in do { hPutStrLn stderr $ show e; return (Left ()) })+        case l of+          Right (_,_,num)->do+            jobs<-newMVar []+            results<-newMVar []+            cur<-newMVar Nothing+\end{code}+\hfill++At this point, {\tt cur} contains {\tt Nothing}: Invariant \ref{h} is clearly+maintained.++Now remark that, when the {\tt saveAll} function below is called, and the {\tt+cur} variable contains {\tt Nothing}, no message is sent. Therefore, if+Invariant \ref{h} holds when {\tt saveAll} is called, the corresponding {\tt NewJobs}+message respects the validity condition.++\hfill+\begin{code}+            let saveAll=withMVar jobs $ \j->+                  withMVar cur $ \curj->+                  case (j,curj) of {+                    (h:s,Just cu)->+                       withMVar results $ \res->do {+                         _<-signAndSend conf (+                            NewJobs { clientId=num,+                                      jobResults=res,+                                      currentJob=cu,+                                      nextJob=h,+                                      newJobs=s+                                    });+                         return ()};+                       _->return ()+                    }+            myth<-myThreadId+            threads<-newMVar myth+#ifdef UNIX+            installHandler sigTERM+              (Catch (modifyMVar_ threads (\a->do {if a==myth then return () else+                                                     killThread a;return myth}))) Nothing+#endif+            let getAJob=do+                  job_<-signAndSend conf (GetJob num (publicKey conf));+                  case job_ of+                    Job share j->do+                      modifyMVar_ cur (\_->do {+                                          modifyMVar_ jobs (\_->return [j]);+                                          modifyMVar_ results (\_->return []);+                                          return (Just j)+                                          });+                      workerMVar<-newEmptyMVar;+\end{code}+\hfill++At this point, Invariant \ref{h} still holds: the only subjob of the current job+is itself, and no results have been found.++\hfill+\begin{code}+                      workerThread<-+                        forkFinally+                        (do {+                            x<-work conf jobs results cur doWork share num j;+                            case x of {+                              Just (j',r)->do {+                                 _<-signAndSend conf+                                    (JobDone {clientId=num,+                                              currentJob=j',+                                              jobResults=r });+                                 return () };+                              Nothing->return ()+                              }})+                        (\_->putMVar workerMVar ())+\end{code}+\hfill++Here, the validity condition holds for the {\tt JobDone} message: indeed, the+current job has been completely explored, and found exactly the results in {\tt+r}.++\hfill+\begin{code}+                      let heartbeat=do+                            answer<-signAndSend_ conf j (Alive num)+                            case answer of+                              Ack->do { threadDelay 300000000; heartbeat }+                              _->do { saveAll; killThread workerThread }+                      heartbeatMVar<-newEmptyMVar+                      hbThread<-forkIO+                                (heartbeat`finally`(putMVar heartbeatMVar ()))+                      modifyMVar_ threads (\_->return workerThread)+                      takeMVar workerMVar+                      killThread hbThread+                      takeMVar heartbeatMVar+                      stop<-withMVar threads (\t->return (t==myth))+                      if stop then do { saveAll; exitSuccess } else getAJob+                    Finished->return ();+                    _->do+                      threadDelay 10000000+                      getAJob+            getAJob+          Left _->do+            threadDelay 5000000+            startConnection+  in+   startConnection+\end{code}+\end{proof}+\end{lemma}
+ Parry/Protocol.lhs view
@@ -0,0 +1,54 @@+\ignore{+\begin{code}+{-|+Module      :  Parry.Protocol+Copyright   :  (c) Pierre-Étienne Meunier 2014+License     :  GPL-3+Maintainer  :  pierre-etienne.meunier@lif.univ-mrs.fr+Stability   :  experimental+Portability :  All++This module contains all data types exchanged between the client+and the server, except for the initial \"@Hello@\" message, and is+mostly exposed for full disclosure of the protocol's proof.+-}+{-# LANGUAGE DeriveGeneric #-}+\end{code}+}++The first module we need is {\tt Parry.Protocol}, that defines the type of+messages exchanged between the client and server. We assume, in the rest of the+proof, that the {\tt encode} and {\tt decode} functions generated by the {\tt+Binary} instances of these datatypes verify {\tt decode.encode} is the identity.++\hfill++\begin{code}+module Parry.Protocol where+import Data.Binary+import GHC.Generics (Generic)+import Codec.Crypto.RSA.Pure++-- | The type of messages sent by the client, exposed here for full+-- disclosure of the protocol's proof.+data ClientMessage j=+  GetJob Integer PublicKey+  | JobDone { clientId::Integer, jobResults::[j], currentJob::j }+  | NewJobs { clientId::Integer, jobResults::[j], currentJob::j,+              nextJob::j, newJobs::[j] }+  | Alive Integer+  deriving (Generic, Show)++-- | The type of messages sent by the server, exposed here for full+-- disclosure of the protocol's proof.+data ServerMessage j=+  Job Bool j+  | Finished+  | Ack+  | Die+  deriving (Generic,Show)++instance (Binary j)=>Binary (ClientMessage j)+instance (Binary j)=>Binary (ServerMessage j)+\end{code}+\vspace{1em}
+ Parry/Server.lhs view
@@ -0,0 +1,595 @@+\ignore{+\begin{code}+{-#OPTIONS -cpp #-}+{-#LANGUAGE OverloadedStrings,MultiParamTypeClasses,DeriveGeneric,BangPatterns #-}+{-|+Module      :  Parry.Server+Copyright   :  (c) Pierre-Étienne Meunier 2014+License     :  GPL-3+Maintainer  :  pierre-etienne.meunier@lif.univ-mrs.fr+Stability   :  experimental+Portability :  All++Tools to build synchronization servers. For instance, to write a simple+server with just a web interface on port 8000, you would use:++> import Control.Concurrent+> import Parry.Server+> import Parry.WebUI+>+> main::IO ()+> main=do+>   state<-initState initial+>   _<-forkIO $ webUI 8000 state+>   server (defaultConfig public) state+-}+\end{code}+}++We now proceed to the proof of the server. The file is included for the sake of+completeness. In particular, remark that the whole state of the server is defined as+a single data type called {\tt State}. We will use this fact to prove+invariants on the whole server state.+\vspace{1em}++\begin{code}+module Parry.Server (+  -- * Jobs on the server side+  Exhaustive(..),+  Result(..),+  -- * Server's internal state+  initState,+  stateFromFile,+  saveThread,+  State(..),+  -- * Server configuration and functions+  Config(..),defaultConfig,server+  ) where+import Control.Concurrent+import Control.Exception as E+import Control.Monad+import Control.Concurrent.MSem as Sem+import Network+import System.IO+import System.Directory+import Data.List+import Data.Time.Format()+import Data.Time.Clock.POSIX+#ifdef UNIX+import System.Posix.Signals+#endif++import qualified Data.ByteString.Char8 as B+import qualified Data.ByteString.Lazy.Char8 as LB+import qualified Data.Map as M+import qualified Data.Set as S+import GHC.Generics+import Data.Binary++import Codec.Crypto.RSA.Pure++import Parry.Protocol+import Parry.Util++-- | The class of jobs and job results that Parry can deal with. For+-- efficiency and to keep types simple, jobs and results are stored in+-- a single type.+class Exhaustive j where+  -- | Indication of the depth of a job in the explored tree. The server sends+  -- the least deep jobs first, as an optimization of network use.+  depth :: j->Int+  -- | Number of times a job has been killed. When a job is killed,+  -- either because it must be reshared, or because the client itself+  -- was killed, it is scheduled to be re-executed by the server.+  killed::j->Int+  -- | Called each time a job needs to be killed. For better resharing,+  -- this function must verify @killed (kill j) >= killed j@.+  kill::j->j++-- | The class of results, and how to combine them in the server state.+class Result j r where+  -- | A function to tell how to combine job results. That function will be+  -- called on the hostname of the reporting client, with the finished job it+  -- sent, and the current result from the server state.+  addResult::HostName->r->j->r++-- | This type is exposed mostly for writing alternative user interfaces.+-- Other operations must be done using the functions in this module, or+-- the correction of the protocol can be lost.+data State j r=State {+  -- | Available jobs+  jobs::S.Set (Int,j),+  -- | Map from the machine id to its hostname, its current job, its+  -- starting time, the last time we heard from it.+  ongoing::M.Map Integer (HostName,PublicKey,j,Double,Double),+  -- | Set of unemployed machines+  unemployed::S.Set Integer,+  -- | The results.+  results::r,+  -- | The smallest available machine id. In a run of the server, it+  -- is guaranteed that are never assigned the same.+  newId::Integer,+  -- | Total number of jobs killed from the beginning (for benchmarking purposes).+  killings::Int,+  -- | Number of jobs finished (for benchmarking purposes).+  solved::Integer,+  -- | The list of authorized RSA public keys.+  authorizedKeys::[PublicKey]+  } deriving (Show,Read,Generic)++instance (Binary j,Binary r)=>Binary (State j r)+\end{code}+++\hfill++\begin{definition}+In a server state {\tt st}, the \emph{current job} of a client is the job+registered in the {\tt ongoing} field of {\tt st}.+\end{definition}++\begin{definition}+\label{def:valid}+We call a client \emph{valid} if, at the same time:+\begin{enumerate}++\item \label{valid:newjobs}+Its {\tt NewJobs} messages contain all the results in subjobs of its+current job that have been completely explored, and the subjobs of its current+job that have not been completely explored, divided into three fields: the+results it has found, its next current job, and other subjobs.++\item \label{valid:jobdone}+It does not send a {\tt JobDone} message before the task representing its+current job is completely explored.++\end{enumerate}+\end{definition}++++The main function, {\tt answer}, keeps track of the clients. We now prove the+following Lemma:++\begin{lemma}+\label{lem:answer}+If {\tt st} is a state of the server containing (in the union of {\tt job st}+and {\tt ongoing st}) jobs representing all the tasks that have not yet been explored,+and for any job {\tt j}, {\tt j} and {\tt kill j} represent the same task,+then for any message {\tt m} sent by a valid client, all values of {\tt host}+and {\tt time}, {\tt answer host time st m} (the Haskell syntax for ``the value+of function {\tt answer}, called with arguments {\tt t}, {\tt host}, {\tt st} and+{\tt m}'')+is a couple+ $(\mathtt{st'},\mathtt{m'})$, where {\tt st'} is a state of the server+containing the roots of all subtrees that have not yet been explored ({\tt m'}+is the message to be sent to the client).++Moreover, all results sent by the clients are added to the server state using+the {\tt addResult} function.++\begin{proof}++We prove it for all the cases.++\begin{code}+answer::(Exhaustive j,Result j r,Eq j,Ord j,Binary j)=>+        Double->String->State j r->ClientMessage j+        ->(State j r,ServerMessage j)+answer t host st (GetJob num key)=+  case M.lookup num (ongoing st) of+    Just (ho,key0,j0,t0,_)->+\end{code}++If the client is registered as an ``ongoing'' job, we can simply send it the job+it is supposed to be working on. In this case, the invariant is still+maintained, as we do not change its recorded current job (here, we only update the+time at which we last saw this client).++\begin{code}+      if ho==host && key0==key then+        (st { ongoing=M.insert num (ho,key,j0,t0,t) (ongoing st) },+         Job (not $ S.null $ unemployed st) j0)+      else+        (st,Die)+    Nothing->+\end{code}+Else, client {\tt num} is not in the map of ongoing jobs.+If there are no more jobs to be done:++\begin{itemize}++\item if there are no more jobs being worked on, we do not modify the state, and+we tell the client to stop (with a {\tt Finished} message).++\item else, we simply record that job as ``unemployed''. The next time a client+reports its state, it will be asked to share its current job. This does not+change the jobs registered in the server's state anyway.+\end{itemize}++\begin{code}+      if S.null (jobs st) then+        if M.null (ongoing st) then+          (st,Finished)+        else+          (st { unemployed=S.insert num (unemployed st) },Die)+\end{code}++Else, if there are still jobs to be done, we pick any such job (using {\tt+S.deleteFindMin}). According to the documentation of Haskell's {\tt Data.Map}+module, $\mathtt{jobs\ st}$ is equal to+$\{\mathtt{h}\}\cup\mathtt{nextJobs}$. Therefore, since {\tt num} is not a+member of {\tt ongoing st}, the returned state contains, in the union of its+{\tt ongoing} and {\tt jobs} fields, exactly the same jobs as in {\tt st}.++\begin{code}+      else+        let ((_,h),nextJobs)=S.deleteFindMin (jobs st)+            shareIt=killed h>0+        in+         (st { jobs=nextJobs,+               unemployed=S.delete num (unemployed st),+               ongoing=M.insert num (host,key,h,t,t) (ongoing st) },+          Job shareIt h)+\end{code}+\hfill++Another message the server can receive is the {\tt NewJobs} message, when+clients reshare their work:+In this case, the client sends its number {\tt num}, the initial+job {\tt initialJob} it was given, the new job {\tt job} that it will now work+on, a list {\tt js} of jobs that need to be shared, and a list of results.+We can think of this message as equivalent to \emph{``I, valid client {\tt num},+hereby RSA-certify that job {\tt currentJob j} you gave me has subjobs+{\tt newJobs j}, and results {\tt results j}''}.++\hfill+\begin{code}+answer t host st j@(NewJobs {})=+  case M.lookup (clientId j) (ongoing st) of+    Nothing->(st,Die)+    Just (ho,key,j0,t0,_)->+      if host==ho && j0==currentJob j then+        (st { jobs=foldl' (\s x->S.insert (depth x,x) s) (jobs st) (newJobs j),+              ongoing=M.insert (clientId j)+                      (host,key,nextJob j,t0,t)+                      (ongoing st),+              results=foldl' (addResult host) (results st) (jobResults j) }, Ack)+      else+        (st, Die)+\end{code}+\hfill+++If the client is not registered as an ``ongoing job'', this message is ignored,+the state is not modified, and the client is sent the {\tt Die} message.++Else, we assumed that this {\tt NewJobs} message can only be sent by a valid+client.  Therefore, it contains all subjobs of its current job that have not+been explored, along with the job it will start working on, and the list of all+results that have been found during the exploration of the other subjobs of its+current job. Since all these subjobs are stored in the {\tt jobs} field of the+state, and the {\tt ongoing} field is updated with the client's new current job,+our claim still holds.++\hfill++\begin{code}+answer _ _ st j@(JobDone {})=+  case M.lookup (clientId j) (ongoing st) of+    Nothing->(st,Die);+    Just (host,_,j0,_,_)->+      if j0==currentJob j then+        (st { ongoing=M.delete (clientId j) (ongoing st),+              results=foldl' (addResult host) (results st) (jobResults j),+              solved=solved st+1 }, Ack)+      else+        (st,Die)+\end{code}++\hfill++In this case, if the client is not registered as an ongoing job, we do not+modify the state. Else, we can safely delete the corresponding job from the+state, and add its results to the state's results field: indeed, since we+assumed that this message is sent by a valid client, that job has been explored+completely. The intuitive version of this message is \emph{``I, valid client+{\tt num}, hereby RSA-certify that I have explored job {\tt currentJob j}+completely, and that it contains exactly results {\tt results j}''}.++\hfill++The last case of {\tt answer} is when the client sends an ``Alive'' message:+\begin{code}+answer t host st (Alive num)=+  case M.lookup num (ongoing st) of+    Nothing->(st,Die);+    Just (ho,key,j,t0,_)->+      if ho==host && (S.null (unemployed st) || (not $ S.null $ jobs st)) then+        (st { ongoing=M.insert num (ho,key,j,t0,t) (ongoing st) },Ack)+      else+        (st,Die)+\end{code}++\hfill++In this case, the set of jobs is not modified, and hence our claim holds.+\end{proof}+\end{lemma}++Our next task is to prove {\tt reply}, the network interface to the {\tt answer}+function. We first need hypotheses on how this interface works, and especially+how the messages are written and read at the ends of the connection.++\begin{definition}++A client is \emph{fluent} if the messages it sends on the network are of exactly+two kinds:++\begin{itemize}++\item Messages with a single line containing exactly {\tt Hello}.++\item Messages with two lines:+\begin{itemize}++\item the first line is the encoding via {\tt encode16l} of $m$, where $m$ is+the encoding via {\tt encode} of a constructor of the {\tt ClientMessage} type.++\item the second line is the RSA signature, using the client's private key,+of $m$.+\end{itemize}++\end{itemize}++\end{definition}++\begin{lemma} \label{lem:reply} If all the clients that have their public key in+{\tt authorizedKeys st}, where {\tt st} is the state of the server, are valid+and fluent, and {\tt st} contains all the jobs that have not been completely+explored (in the {\tt ongoing} and {\tt jobs} fields), then so does it after one+run of {\tt reply}, assuming that $\mathtt{decode}\circ\mathtt{encode}$ (from+Haskell's {\tt Data.Binary} module) is the identity, and+$\mathtt{decode16}\circ\mathtt{encode16l}$ (from module {\tt Parry.Util}) is the+identity.++\begin{proof}+We prove this invariant on the code of the {\tt reply} function, which handles+every connection to our server.\vspace{1em}++\begin{code}+reply::(Binary j,Exhaustive j,Result j r,Ord j)=>+       MVar (State j r) -> Handle -> HostName -> IO ()+reply state rhandle host=(do+  l<-B.hGetLine rhandle+  if l==B.pack "Hello" then+    modifyMVar_ state $ \st->do+      LB.hPutStrLn rhandle $ encode16l $ encode $ newId st+      return $ st { newId=newId st+1 }+\end{code}++\hfill++When the first line is the initial {\tt Hello} message, the claim holds: indeed,+the only field of the server state that is modified is the {\tt newId} one,+which represents the first unused client number.++In all other cases, we do the following:++\hfill+\begin{code}+    else do+    st<-withMVar state return+    sig<-B.hGetLine rhandle+    let dec=LB.fromStrict $ decode16 l+        msg=decode dec+        num=case msg of+          GetJob x _->x+          JobDone x _ _->x+          NewJobs x _ _ _ _->x+          Alive x->x+        key=case msg of+          GetJob _ pub->+            if any (==pub) (authorizedKeys st) then+              Just pub+            else+              Nothing+          _->(case M.lookup num $ ongoing st of+                 Just (_,pub,_,_,_)->Just pub+                 Nothing->Nothing)+\end{code}++\hfill++We will now verify the message signature, using either the public key registered+for this client in the {\tt ongoing} field of the server's state, or the public+key sent by the client itself, in the case of the {\tt GetJob} message (if that+key is registered in the {\tt authorizedKeys} field of the server state):++\hfill++\begin{code}+    message<-case key of+      Nothing->return Die+      Just pub->+        case verify pub dec (LB.fromStrict $ decode16 sig) of+          Right True->do+            t<-getPOSIXTime+            modifyMVar state $ \st0->+              let (!a,!b)=answer (realToFrac t) host st0 msg in+              return (a,b)+          _->return Die+    LB.hPutStrLn rhandle (encode16l $ encode message)+  )+\end{code}++\hfill++Since we assumed that $\mathtt{decode}\circ\mathtt{encode}$ and+ $\mathtt{decode16}\circ\mathtt{encode16l}$ are both the identity function,+variable {\tt msg} contains the message sent by the client. Because the client+is valid (because its public key is in the {\tt authorizedKeys} field of the+server state), we can conclude using Lemma \ref{lem:answer} that the invariant+is maintained by the {\tt reply} function, because the only call modifying the+state is a call to {\tt answer}.++\end{proof}+\end{lemma}++The last piece of server code that we need to prove is the {\tt cleanupThread}+function, whose aim is to collect all dead machines. We do need this function,+especially on standard clusters with small walltimes compared to the task.++\begin{lemma}+\label{lem:cleanupThread}+If the {\tt kill} function, defined on jobs, does not change the task+represented by the job, and {\tt state} is a server state containing (in the+{\tt ongoing} and {\tt jobs} fields) all the jobs that have not been explored,+then so is it after one run of {\tt cleanupThread state}.++\begin{proof}++In the following function: the state is only modified by partitionning the {\tt+ongoing st} map into two maps {\tt a} and {\tt b}, and adding all the jobs of+{\tt a} to the {\tt jobs st} set, possibly calling {\tt kill} on some of+them. Therefore, the tasks represented by jobs in the union of {\tt jobs st} and+{\tt ongoing st} is not modified.++\hfill+\begin{code}+cleanupThread::(Ord j,Exhaustive j)=>MVar (State j r)->IO ()+cleanupThread state=do {+  t_<-getPOSIXTime;+  let { t=realToFrac t_ };+  modifyMVar_ state $ \st0->do {+    -- Find machines that have not given news for more than 10 minutes.+    let { (a,b)=M.partition (\(_,_,_,_,t1)->(t-t1) > 600) (ongoing st0);+          st=st0 { jobs=+                      M.foldl' (\set (_,_,job,t0,_)->+                                 S.insert (depth job,+                                           if t-t0 > 3600 then+                                             kill job+                                           else job) set)+                      (jobs st0)+                      a,+                   ongoing=b }+        };+    return st+    };+  -- Sleep 30 seconds, and clean again.+  threadDelay 30000000;+  cleanupThread state+  }+\end{code}+\end{proof}+\end{lemma}++Finally, the entry point to our server library is the {\tt server} function:++\begin{lemma}+\label{lem:server}+If:+\begin{itemize}++\item all tasks that have not been completely explored have job representants+in the {\tt ongoing} and {\tt jobs} fields of the {\tt state} argument to {\tt server},++\item all clients that sign their messages with a private RSA key whose corresponding+public key is in the {\tt state} variable are valid and fluent,++\item $\mathtt{decode}\circ\mathtt{encode}$ and+ $\mathtt{decode16}\circ\mathtt{encode16l}$ are both the identity function,+\end{itemize}++then after any number of messages received by the server, variable {\tt state}+also contains jobs representing tasks that have not been completely explored,+in the union of its {\tt ongoing} and {\tt jobs} fields.++\begin{proof}++Clearly, everything {\tt server} does is calling functions that maintain this+invariant, by Lemmas \ref{lem:reply} for {\tt reply} and \ref{lem:cleanupThread}+for {\tt cleanupThread}.++\begin{code}+-- | Starts the synchronization server.+server::(Ord j, Binary j, Exhaustive j, Result j r)=>+        Config->MVar (State j r)->IO ()+server config state=withSocketsDo $ do {+#ifdef UNIX+  installHandler sigPIPE Ignore Nothing;+#endif+  threads<-Sem.new $ maxThreads config;+  _<-forkIO $ cleanupThread state;+  forever $ do {+    E.catch (bracket (listenOn (port config)) sClose $+             \sock->forever $ do {+               bracket (do { (s,a,_)<-accept sock; wait threads; return (s,a) })+               (\(s,_)->do { signal threads; hClose s})+               (\(s,a)->reply state s a)+               })+    (\e->let _=e::SomeException in appendFile (logFile config) (show e++"\n"));+    threadDelay 100000;+    };+  }+\end{code}+\end{proof}+\end{lemma}+\ignore{+\begin{code}+-- | Server configuration+data Config=Config {+  -- | The network port the synchronization server will listen on.+  port::PortID,+  -- | The maximal number of simultaneous threads that can be launched.+  maxThreads::Int,+  -- | Log file+  logFile::FilePath+  }++-- | Default server configuration, matching the client. Note that you+-- must provide your own public key for signing the messages.++defaultConfig::Config+defaultConfig=Config { port=PortNumber 5129, maxThreads=20, logFile="parry.err" }++-- | Creates a valid server state from an initial job.+initState::(Exhaustive j,Ord j,Result j r)=>[j]->r->IO (MVar (State j r))+initState initial r0=+  newMVar $ State { jobs=foldl (\s j->S.insert (depth j,j) s) S.empty initial,+                    ongoing=M.empty,+                    results=r0,+                    unemployed=S.empty,+                    newId=0,+                    killings=0,solved=0,+                    authorizedKeys=[] };+\end{code}++\begin{code}+-- | Reads initial state from a file, or calls 'initState' if the file does+-- not exist.+stateFromFile::(Binary r,Binary j,Exhaustive j, Result j r,Ord j)=>FilePath->[j]->r->IO (MVar (State j r))+stateFromFile f initial r0=do {+  e<-doesFileExist f;+  state<-if e then do {+    st<-decodeFile f;+    newMVar st+    } else initState initial r0;+  return state+  }++-- | Saves state to the given file with the given periodicity, in+-- microseconds. This function does not return, so calling it inside a+-- 'Control.Concurrent.forkIO' is probably the best thing to do.+saveThread::(Binary r,Binary j)=>FilePath->Int->MVar (State j r)->IO ()+saveThread f del state=+  let { save=do {+           e<-doesFileExist f;+           if e then renameFile f (f++".last") else return ();+           withMVar state $ \st->LB.writeFile f $ encode st;+           threadDelay del;+           save+           }}+  in save+\end{code}+}
+ Parry/Util.hs view
@@ -0,0 +1,65 @@+-- | Common utility functions, used both in the client and the server.+module Parry.Util(+  -- * Hexadecimal encoders and decoders.+  encode16,decode16,encode16l,decode16l+  ) where++import qualified Data.ByteString.Lazy.Internal as ILB+import qualified Data.ByteString.Internal as IB+import qualified Data.ByteString as B+import qualified Data.ByteString.Unsafe as UB+import qualified Data.ByteString.Char8 as B8+import Foreign.Ptr+import Foreign.Storable+import Data.Bits+import Data.Word++-- | Encodes a strict bytestring to its hexadecimal representation. See 'decode16'.+encode16 :: B.ByteString -> B.ByteString+encode16 bytes=+  let { len=B.length bytes } in+  IB.unsafeCreate (len*2) $ \pp->+  let { fill p0 i+        | i>=len=return ()+        | otherwise=do {+          let { c=UB.unsafeIndex bytes i;+                c0=c`shiftR`4;+                c1=c.&.0xf };+          poke p0 $ if c0<=9 then 48+c0 else 97+c0-10;+          poke (p0`plusPtr`1) $ if c1<=9 then 48+c1 else 97+c1-10;+          fill (p0`plusPtr`2) $ i+1+          }}+  in+   fill pp 0++atomHex::Word8->Word8+atomHex c=+  if c<=(fromIntegral $ fromEnum '9') then+    c-(fromIntegral $ fromEnum '0')+  else+    c-(fromIntegral $ fromEnum 'a')+10++-- | Decodes a strict bytestring from its hexadecimal representation. See 'encode16'.+decode16::B8.ByteString->B8.ByteString+decode16 bytes=+  let { len=B.length bytes } in+  IB.unsafeCreate (len`quot`2) $ \pp->+  let { fill p0 i+        | i>=len=return ()+        | otherwise=do {+          let { c0=atomHex $ UB.unsafeIndex bytes i; c1=atomHex $ UB.unsafeIndex bytes (i+1) };+          poke p0 $ (c0`shiftL`4) .|. c1;+          fill (p0`plusPtr`1) $ i+2+          }}+  in+   fill pp 0++-- | Encodes a lazy bytestring to its hexadecimal representation.+encode16l::ILB.ByteString->ILB.ByteString+encode16l ILB.Empty=ILB.Empty+encode16l (ILB.Chunk x xs)=ILB.Chunk (encode16 x) (encode16l xs)++-- | Decodes a lazy bytestring from its hexadecimal representation.+decode16l::ILB.ByteString->ILB.ByteString+decode16l ILB.Empty=ILB.Empty+decode16l (ILB.Chunk x xs)=ILB.Chunk (decode16 x) (decode16l xs)
+ Parry/WebUI.hs view
@@ -0,0 +1,241 @@+{-#LANGUAGE OverloadedStrings,MultiParamTypeClasses #-}+{-|+Module      :  Parry.DefaultUI+Copyright   :  (c) Pierre-Étienne Meunier 2014+License     :  GPL-3+Maintainer  :  pierre-etienne.meunier@lif.univ-mrs.fr+Stability   :  experimental+Portability :  All+-}+module Parry.WebUI (+  webUI,Html(..)+  ) where+import Control.Concurrent+import Network+import qualified Data.Map as M+import qualified Data.Set as S+import System.IO+import Data.Time.Clock+import Data.Time.Clock.POSIX+import Data.Time.Format+import System.Locale+import System.Directory+import System.Process+import qualified Data.ByteString.Char8 as B+import qualified Data.ByteString.Lazy.Char8 as L+import Data.ByteString.Lazy.Builder+import Data.ByteString.Lazy.Builder.ASCII+import Control.Exception+import Numeric+import Parry.Server+import Data.Monoid++type Graphs=MVar (L.ByteString,L.ByteString,L.ByteString,L.ByteString)++makeSvg::(Exhaustive j)=>Graphs->MVar (State j r)->IO ()+makeSvg graphs state=onException (+  do {+    st<-withMVar state $ return;+    if M.size (ongoing st)==0 && (S.size (jobs st)==0) then return () else do {+      t<-getPOSIXTime;+      let { show_t=intDec $ round $ realToFrac t };++      L.appendFile "parry.log" $+      toLazyByteString $+      show_t `mappend` (byteString " ") `mappend` (intDec $ M.size $ ongoing st)+      `mappend` (byteString " ") `mappend` (intDec $ S.size $ jobs st)+      `mappend` (byteString "\n");++      let { jobs_=jobs st;+            ongoing_=ongoing st;+            (adepth0,njobs0)=M.foldl' (\(d,n) (_,_,j,_,_)->(d+depth j,n+1)) (0,0) $ ongoing_ :: (Int,Int);+            (adepth1,njobs1)=S.foldl' (\(d,n) (_,j)->(d+depth j,n+1)) (0,0) $ jobs_ :: (Int,Int);+            depth0=if njobs0>0 then (fromIntegral adepth0)/(fromIntegral njobs0) else 0 :: Double;+            depth1=if njobs1>0 then (fromIntegral adepth1)/(fromIntegral njobs1) else 0 :: Double;+            depth2=M.foldl' (\d (_,_,j,_,_)->min d $ depth j) maxBound $ ongoing_ :: Int;+            depth3=S.foldl' (\d (_,j)->min d $ depth j) maxBound $ jobs_ :: Int+          };++      L.appendFile "solved.log" $+      toLazyByteString $+      show_t `mappend` (byteString " ") `mappend` (integerDec $ solved st) `mappend` (byteString "\n");++      if njobs0>0 then+         L.appendFile "depth.log" $+         toLazyByteString $+         show_t `mappend` (byteString " ") `mappend` (doubleDec depth0)`mappend` (byteString "\n")+      else L.appendFile "depth.log" "\n";++      if njobs1>0 then+         L.appendFile "depth_av.log" $+         toLazyByteString $+         show_t `mappend` (byteString " ") `mappend` (doubleDec depth1)`mappend` (byteString "\n")+      else L.appendFile "depth_av.log" "\n";+++      if depth2<maxBound then+         L.appendFile "depth_min.log" $+         toLazyByteString $+         show_t `mappend` (byteString " ")`mappend` (intDec depth2) `mappend` (byteString "\n")+      else L.appendFile "depth_min.log" "\n";++      if depth3<maxBound then+         L.appendFile "depth_min_av.log" $+         toLazyByteString $+         show_t `mappend` (byteString " ")`mappend` (intDec depth3) `mappend` (byteString "\n")+      else L.appendFile "depth_min_av.log" "\n";++      _<-readProcessWithExitCode "gnuplot" [] $+         concat [+           "set term svg\nset output \"solved.svg\"\nset title \"Number of finished jobs\"\nset xtics rotate by -90\nset style data fsteps\nset xlabel \"Date\"\nset timefmt \"%s\"\nset format x \"%m/%d/%Y %H:%M\"\nset xdata time\nset ylabel \"Jobs\"\nset grid\nset key left\nplot \"solved.log\" using 1:2 with lines title \"Finished jobs\"\n",+           "set output \"machines.svg\"\nset title \"Number of jobs\"\nset xtics rotate by -90\nset style data fsteps\nset xlabel \"Date\"\nset timefmt \"%s\"\nset format x \"%m/%d/%Y %H:%M\"\nset xdata time\nset ylabel \"Machines\"\nset grid\nset key left\nplot \"parry.log\" using 1:2 with lines title \"Ongoing jobs\", \"parry.log\" using 1:3 with lines title\"Available jobs\"\n",+           "set output \"depth_av.svg\"\nset title \"Average depth of jobs\"\nset ylabel \"Depth\"\nset timefmt \"%s\"\nset format x \"%m/%d/%Y %H:%M\"\nset xdata time\nplot \"depth.log\" using 1:2 with lines title \"Ongoing jobs\",\"depth_av.log\" using 1:2 with lines title \"Available jobs\"\n\n",+           "set output \"depth_min.svg\"\nset title \"Minimal depth of jobs\"\nset ylabel \"Depth\"\nset timefmt \"%s\"\nset format x \"%m/%d/%Y %H:%M\"\nset xdata time\nplot \"depth_min.log\" using 1:2 with lines title \"Ongoing jobs\",\"depth_min_av.log\" using 1:2 with lines title \"Available jobs\""];+      let { readOr x=do { e<-doesFileExist x; if e then L.readFile x else return blankSvg }};+      a<-readOr "machines.svg";+      b<-readOr "depth_av.svg";+      c<-readOr "depth_min.svg";+      e<-readOr "solved.svg";+      modifyMVar_ graphs $ \_->return (a,b,c,e);+      return ()+      }})+        (return ())++class Html a where+  toHtml::a->Builder+++webserver::(Html j,Html r)=>+           Graphs+           ->MVar (State j r)+           ->Handle->IO()+webserver graphs state dsth=do {+  req<-B.hGetLine dsth;+  let { getHeaders hdr=do {+           h<-B.hGetLine dsth;+           if B.length h<=1 then return $ reverse hdr else+             let { (a,b)=B.span (/=':') h } in+             getHeaders $ (B.takeWhile (/=' ') a,B.dropWhile (/=' ') $ B.drop 1 b):hdr+           };+      };+  hdr<-getHeaders [];+  _<-case lookup "Content-Length" hdr of {+    Just x->case reads (B.unpack x) of {+       [(a,_)]->B.hGet dsth a;+       _->return B.empty+       };+    _->return B.empty+    };+  let { repl code typ dat=do {+           B.hPutStr dsth "HTTP/1.1 ";+           B.hPutStr dsth code;+           B.hPutStr dsth " \r\n";+           B.hPutStr dsth typ;+           if L.length dat>0 then do {+             B.hPutStr dsth "Content-Length: ";+             L.hPutStr dsth (toLazyByteString $ int64Dec $ L.length dat);+             B.hPutStr dsth "\r\n\r\n";+             L.hPutStr dsth dat+             } else B.hPutStr dsth "\r\n"+           };+        ok dat=repl "200 OK" "Content-Type: text/html; charset=utf-8\r\n" dat;+        img dat=repl "200 OK" "Content-Type: image/svg+xml; charset=utf-8\r\n" dat;+        notFound dat=repl "404 Not found" "Content-Type: text/html; charset=utf-8\r\n" dat;+      };+  case B.split ' ' req of {+    "GET":addr:_->+       case addr of {+         "/machines.svg"-> do {+            (a,_,_,_)<-withMVar graphs return;+            img a+            };+         "/depth_min.svg" -> do {+            (_,a,_,_)<-withMVar graphs return;+            img a+            };+         "/depth_av.svg" -> do {+            (_,_,a,_)<-withMVar graphs return;+            img a+            };+         "/solved.svg" -> do {+           (_,_,_,a)<-withMVar graphs return;+           img a+           };+         "/"->do {+           st<-withMVar state $ return;+           let {page=+                   toLazyByteString $+                   (mconcat [+                       byteString $ "<!DOCTYPE HTML><html><head><meta http-equiv=\"Content-type\" content=\"text/html;charset=UTF-8\"/><title>Parry Web UI</title></head><body><h1 style=\"font-family:sans-serif;\">Results</h1>",+                       toHtml $ results st,+                       byteString "<img src=\"machines.svg\"/><br/><img src=\"solved.svg\"/><br/><img src=\"depth_min.svg\"/><br/><img src=\"depth_av.svg\"/><br/>",+                       byteString "<h1 style=\"font-family:sans-serif\">Available jobs</h1><p>"+                       ])+                   `mappend`+                   {-+                   (mconcat $ map (\(_,x)->+                                    mconcat [byteString "<p>",toHtml x,byteString "</p>"]+                                  ) $ S.toList $ jobs st)+-}+                   (intDec $ S.size $ jobs st)+                   `mappend`+                   (byteString "</p><h1 style=\"font-family:sans-serif\">Ongoing jobs</h1><div style=\"font-family:monospace\">")+                   `mappend`+                   (mconcat $ map (\(x,(h,_,j,t,t'))->+                                    (byteString "<p>")+                                    `mappend`+                                    integerDec x+                                    `mappend`+                                    (byteString " ")+                                    `mappend`+                                    (byteString $ B.pack h)+                                    `mappend`+                                    (byteString "<br/>Started: ")+                                    `mappend`+                                    (string8 $+                                     formatTime defaultTimeLocale "%c" $+                                     posixSecondsToUTCTime $ realToFrac t)+                                    `mappend`+                                    (byteString "<br/>")+                                    `mappend`+                                    toHtml j+                                    `mappend`+                                    (byteString "</p>")+                                  ) $ M.toList $ ongoing st)+                   `mappend`+                   (byteString "</div></body></html>")+               };+           ok $ page+           };+         _->notFound ""+         };+       _->ok ""+    };+  hClose dsth;+  }+++blankSvg::L.ByteString+blankSvg=+  "<!DOCTYPE svg PUBLIC \"-//W3C//DTD SVG 1.1//EN\" \"http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd\"><svg xmlns=\"http://www.w3.org/2000/svg\" xmlns:xlink=\"http://www.w3.org/1999/xlink\"></svg>"+++-- | Starts the default web server.+webUI::(Exhaustive j,Html j,Html r)=>PortNumber->MVar (State j r)->IO ()+webUI wport state=do {+  sock <- listenOn (PortNumber wport);+  graphs<-newMVar $ (blankSvg,blankSvg,blankSvg,blankSvg);+  makeSvg graphs state;+  let {list=do {+          (s,_,_)<-accept sock;+          _<-forkIO $ webserver graphs state s;+          list+          };+       svg=do {+         threadDelay $ 30000000;+         makeSvg graphs state;+         svg+         }};+  _<-forkIO svg;+  list+  }
+ Setup.hs view
@@ -0,0 +1,2 @@+import Distribution.Simple+main = defaultMain