fastMergeServer.C

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/// \file
/// \ingroup tutorial_net
/// This script shows how to make a simple iterative server that
/// can receive TMemFile from multiple clients and merge them into
/// a single file without block.
///
/// Note: This server assumes that the client will reset the histogram
/// after each upload to simplify the merging.
///
/// This server can accept connections while handling currently open connections.
/// Compare this script to hserv.C that blocks on accept.
/// In this script a server socket is created and added to a monitor.
/// A monitor object is used to monitor connection requests on
/// the server socket. After accepting the connection
/// the new socket is added to the monitor and immediately ready
/// for use. Once two connections are accepted the server socket
/// is removed from the monitor and closed. The monitor continues
/// monitoring the sockets.
///
/// To run this demo do the following:
///   - Open three windows
///   - Start ROOT in all three windows
///   - Execute in the first window: .x fastMergerServer.C
///   - Execute in the second and third windows: .x treeClient.C
///
/// \macro_code
///
/// \author Fons Rademakers
 
#include "TMessage.h"
#include "TBenchmark.h"
#include "TSocket.h"
#include "TH2.h"
#include "TTree.h"
#include "TMemFile.h"
#include "TRandom.h"
#include "TError.h"
#include "TFileMerger.h"
 
#include "TServerSocket.h"
#include "TPad.h"
#include "TCanvas.h"
#include "TMonitor.h"
 
#include "TFileCacheWrite.h"
 
void fastMergeServer(bool cache = false) {
   // Open a server socket looking for connections on a named service or
   // on a specified port.
   //TServerSocket *ss = new TServerSocket("rootserv", kTRUE);
   TServerSocket *ss = new TServerSocket(9090, kTRUE);
   if (!ss->IsValid()) {
      return;
   }
 
   TMonitor *mon = new TMonitor;
 
   mon->Add(ss);
 
   UInt_t clientCount = 0;
   TMemFile *transient = nullptr;
 
   TFileMerger merger(kFALSE,kFALSE);
   merger.SetPrintLevel(0);
 
   enum StatusKind {
      kStartConnection = 0,
      kProtocol = 1,
 
      kProtocolVersion = 1
   };
   if (cache) new TFileCacheWrite(merger.GetOutputFile(),32*1024*1024);
   while (true) {
      TMessage *mess;
      TSocket  *s;
 
      s = mon->Select();
 
      if (s->IsA() == TServerSocket::Class()) {
         if (clientCount > 100) {
            printf("only accept 100 clients connections\n");
            mon->Remove(ss);
            ss->Close();
         } else {
            TSocket *client = ((TServerSocket *)s)->Accept();
            client->Send(clientCount, kStartConnection);
            client->Send(kProtocolVersion, kProtocol);
            ++clientCount;
            mon->Add(client);
            printf("Accept %d connections\n",clientCount);
         }
         continue;
      }
 
      s->Recv(mess);
 
      if (mess==nullptr) {
         Error("fastMergeServer","The client did not send a message\n");
      } else if (mess->What() == kMESS_STRING) {
         char str[64];
         mess->ReadString(str, 64);
         printf("Client %d: %s\n", clientCount, str);
         mon->Remove(s);
         printf("Client %d: bytes recv = %d, bytes sent = %d\n", clientCount, s->GetBytesRecv(),
                s->GetBytesSent());
         s->Close();
         --clientCount;
         if (mon->GetActive() == 0 || clientCount == 0) {
            printf("No more active clients... stopping\n");
            break;
         }
      } else if (mess->What() == kMESS_ANY) {
 
         Long64_t length;
         TString filename;
         Int_t clientId;
         mess->ReadInt(clientId);
         mess->ReadTString(filename);
         mess->ReadLong64(length); // '*mess >> length;' is broken in CINT for Long64_t.
 
         Info("fastMergeServer","Receive input from client %d for %s",clientId,filename.Data());
 
         delete transient;
         transient = new TMemFile(filename,mess->Buffer() + mess->Length(),length);
         mess->SetBufferOffset(mess->Length()+length);
         merger.OutputFile(filename,"UPDATE");
         merger.AddAdoptFile(transient);
 
         merger.PartialMerge(TFileMerger::kAllIncremental);
         transient = nullptr;
      } else if (mess->What() == kMESS_OBJECT) {
         printf("got object of class: %s\n", mess->GetClass()->GetName());
      } else {
         printf("*** Unexpected message ***\n");
      }
 
      delete mess;
   }
}