source: Evidence/Evidence.cc@ 254

/********************************************************************\

  General code to start a server of the Evidence Control System
  
  - The server is started with the given name.
  - DIM exit and error handlers are implemented.
  - A Message service is published with severity encoding. It can be updated
    with the Message() method. The text will also be logged.
  - If the severity of a Message() call is FATAL, exit() will be called (with
    this severity, the call to Message() is guranteed not to return).
  - Configuration data can be requested by GetConfig() and non-blocking by GetConfigNB().
  - If the configuration file changes a signal can be emitted which is caught by the standard
    signal handler. The handler invokes ConfigChanged() which can be redefined by the user application.
        The signal is delivered only to the main thread (where the constructor is executed) and thus
        blocking rpc can be made from it. The signal is set using ActivateSignal().
  - Signal handlers to ignore common signals are installed.
    These signals will then cause pause() to return which can be used
        by the application to terminate gracefully.
  - The static method ToString() converts the contents of a DIM service into text
  - A terminate-handler is installed for catching unhandled C++ exceptions.

  Oliver Grimm, June 2010
 
\********************************************************************/

#include "Evidence.h"
using namespace std;

//
// Internal configuration class of EvidenceServer
//

// Constructor
EvidenceServer::Config::Config(string Name): DimRpcInfo("ConfigRequest", NO_LINK), Name(Name) {

  // Initialise
  CurrentItem = string();
  ConfigTimeStamp = 0;
  ThreadID = pthread_self();

  // Subscribe to be informed on configuration file change
  Service = new DimInfo("Config/ModifyTime", NO_LINK, this);
}

// Destructor
EvidenceServer::Config::~Config() {
  
  delete Service;
}

// Track last modification time of configuration file
void EvidenceServer::Config::infoHandler() {

  This->Lock();
  ConfigTimeStamp = getInfo()->getInt();
  This->Unlock();

  if (pthread_kill(ThreadID, This->ConfigSignal) != 0) {
        This->Message(WARN, "Could not send signal to main thread");
  }
}

// Receive answer to remote procedure call
void EvidenceServer::Config::rpcInfoHandler(){

  This->Lock();
  // Update map
  List[CurrentItem].Value = string(getString(), getSize()-1);
  List[CurrentItem].Time = ConfigTimeStamp;
  // Clear to allow new rpc call
  CurrentItem.clear(); 
  This->Unlock();
}

// Return configuration data if still up to date or empty string otherwise
string EvidenceServer::Config::GetConfig(string Item, string Default) {

  string Result;

  // If up-to-date data in configuration list available, return this
  This->Lock();
  if ((List.count(Item) > 0) && (List[Item].Time >= ConfigTimeStamp)) Result = List[Item].Value;
  This->Unlock();
  if (!Result.empty()) return Result;

  // Blocking configuration request if in main thread
  if (pthread_self() == ThreadID) {
        DimRpcInfo Config((char *) "ConfigRequest", NO_LINK);
        Config.setData((char *) (Name + " " + Item).c_str());

        // Check if successful
        if (!EvidenceServer::ServiceOK(&Config)) {
      if (Default.empty()) {
                This->Message(FATAL, "Configuration server unreachable, can't retrieve '%s'", Item.c_str());
          }
          else Result = Default;
        }
        else {
          if (Config.getSize() <= 1) Result = Default;
          else Result = string(Config.getString(), Config.getSize()-1); // Retrieve string safely
    }

        // Update configuration map     
        if (!Result.empty()) {
          This->Lock();
          List[Item].Value = Result;
          List[Item].Time = ConfigTimeStamp;
          This->Unlock();
        }       
  }

  // Non-blocking configuration request from other threads
  if (pthread_self() != ThreadID) {
        This->Lock();
        if (List.count(Item) > 0) {
          // New request possible only when answer to previous request received
          if (CurrentItem.empty()) {
                CurrentItem = Item;
                setData(((char *) (Name + " " + Item).c_str()));
          }

          // Return current value
          Result = List[Item].Value;
          This->Unlock();
        }
  }

  return Result;
}


//////////////////////////
// EvidenceServer Class //
//////////////////////////

// Initialise
int EvidenceServer::ConfigSignal = 0;
EvidenceServer *EvidenceServer::This = NULL;

// Constructor
EvidenceServer::EvidenceServer(string ServerName): Name(ServerName) {

  // Initialize
  MessageService = NULL;
  MessageData = NULL;
  ExitRequest = false;
  This = this;

  // Initialise mutex
  int Ret;
  pthread_mutexattr_t Attr;

  if ((Ret = pthread_mutexattr_settype(&Attr, PTHREAD_MUTEX_ERRORCHECK)) != 0) {
    Message(FATAL, "pthread_mutex_settype() failed (%s)", strerror(Ret));
  }
  if ((Ret = pthread_mutex_init(&Mutex, &Attr)) != 0) {
    Message(FATAL, "pthread_mutex_init() failed (%s)", strerror(Ret));
  }

  // Catch some signals
  signal(SIGQUIT, &SignalHandler);  // CTRL-Backspace
  signal(SIGTERM, &SignalHandler);  // Termination signal
  signal(SIGINT, &SignalHandler);   // CTRL-C
  signal(SIGHUP, &SignalHandler);   // Terminal closed
  
  // Catch C++ unhandled exceptions
  set_terminate(Terminate);

  // Configuration class (must be instantiate after signal handling installed)
  ConfClass = new class Config(Name);

  // Message service and initial message
  MessageService = new DimService((Name+"/Message").c_str(), (char *) "I:1;C", NULL, 0);

  string Rev(EVIDENCE_REVISION); 
  Message(INFO, "Server started (%s, compiled %s %s)", (Rev.substr(1, Rev.size()-3)).c_str(),__DATE__, __TIME__);

  // Start server
  start(ServerName.c_str());
  addExitHandler(this);
}

// Destructor: Free memory
EvidenceServer::~EvidenceServer() {

  Message(INFO, "Server stopped");

  delete ConfClass;

  int Ret;
  if ((Ret = pthread_mutex_destroy(&Mutex)) != 0) {
        Message(ERROR, "pthread_mutex_destroy() failed (%s)", strerror(Ret));
  }
  
  delete MessageService;
  delete[] MessageData;  
}

// DIM exit handler
void EvidenceServer::exitHandler(int Code) {

  Message(INFO, "Exit handler called (DIM exit code %d)", Code);
  exit(EXIT_SUCCESS);
}

// DIM error handler
void EvidenceServer::errorHandler(int Severity, int Code, char *Text) {

  Message(ERROR, "%s (DIM error code %d, DIM severity %d)\n", Text, Code, Severity);
}

// Set server message (if Severity is FATAL, exit() will be invoked)
void EvidenceServer::Message(MessageType Severity, const char *Format, ...) {

  static const char* StateString[] = {"Info", "Warn", "Error", "Fatal"};
  static char ErrorString[] = "vasprintf() failed in Message()";
  char *Text;
  
  // Assemble message from application
  va_list ArgumentPointer;
  va_start(ArgumentPointer, Format);
  if (vasprintf(&Text, Format, ArgumentPointer) == -1) {
        Text = ErrorString;
        Severity = ERROR;
  }
  va_end(ArgumentPointer);

  // Generate new Message structure and free text
  struct Message *NewMsg = (struct Message *) new char [sizeof(struct Message)+strlen(Text)+1];
  NewMsg->Severity = Severity;
  strcpy(NewMsg->Text, Text);
  if (Text != ErrorString) free(Text);
  
  // Send message to console and log file
  printf("%s (%s): %s\n", MessageService->getName(), StateString[Severity], NewMsg->Text);
  SendToLog("%s (%s): %s", MessageService->getName(), StateString[Severity], NewMsg->Text);

  // Update DIM message service
  if (MessageService != NULL) {
        MessageService->updateService(NewMsg, sizeof(struct Message)+strlen(NewMsg->Text)+1);
  }

  // Terminate if severity if FATAL  
  if (Severity == FATAL) exit(EXIT_FAILURE);

  // Delete old message
  // Note that Lock()/Unlock() might fail with a FATAL message. To avoid an infinite loop,
  // check for FATAL severity is done before here.
  Lock();
  delete[] MessageData;
  MessageData = NewMsg;
  Unlock();  
}


// Set to central logging server with non-blocking command (may be used in DIM handler)
void EvidenceServer::SendToLog(const char *Format, ...) {

  char *Buffer;
  int Ret;

  // Evaluate variable argument list
  va_list ArgumentPointer;
  va_start(ArgumentPointer, Format);
  Ret = vasprintf(&Buffer, Format, ArgumentPointer);
  va_end(ArgumentPointer);

  // Send to logger
  if (Ret != -1) {
        DimClient::sendCommandNB("DColl/Log", Buffer);
        free (Buffer);
  }
  else Message(ERROR, "Could not create logging text in SendToLog(), vasprintf() failed");
}


// Get configuration data
//
// Program terminates if data is missing and no default given. Actual configuration
// request will be made only if config file has modification since last request.
// If called from infoHandler(), a non-blocking request will be made
string EvidenceServer::GetConfig(string Item, string Default) {

  string Result = ConfClass->GetConfig(Item, Default);
  if (Result.empty()) Message(FATAL, "Missing configuration data '%s'", Item.c_str());
  return Result;
}


// Set signal emitted when configuraton file changes, signal handler calls ConfigChanged()
void EvidenceServer::ActivateSignal(int Signal) {

  struct sigaction S;

  ConfigSignal = Signal;
  S.sa_handler = &SignalHandler;
  S.sa_flags = SA_RESTART;
  sigaction(Signal, &S, NULL);
}


// Locking and unlocking for list access
// Signal blocked before locking to avoid dead-lock by calling GetConfig() from ConfigChanged().
void EvidenceServer::Lock() {

  int Ret;
  sigset_t Set;

  if (ConfigSignal != 0) {
        Ret = abs(sigemptyset(&Set));
        Ret += abs(sigaddset(&Set, ConfigSignal));
        Ret += abs(pthread_sigmask(SIG_BLOCK, &Set, NULL));

        if (Ret != 0) Message(FATAL, "Signal masking failed in Lock()");
  }

  if ((Ret = pthread_mutex_lock(&Mutex)) != 0) {
        Message(FATAL, "pthread_mutex_lock() failed in Lock() (%s)", strerror(Ret));
  }
}

void EvidenceServer::Unlock() {

  int Ret;
  sigset_t Set;

  if ((Ret = pthread_mutex_unlock(&Mutex)) != 0) {
        Message(FATAL, "pthread_mutex_unlock() failed in Unlock() (%s)", strerror(Ret));
  }
  
  if (ConfigSignal != 0) {
        Ret = abs(sigemptyset(&Set));
        Ret += abs(sigaddset(&Set, ConfigSignal));
        Ret += abs(pthread_sigmask(SIG_UNBLOCK, &Set, NULL));

        if (Ret != 0) Message(FATAL, "Signal unmasking failed in Unlock()");
  }
}


// ====== Static methods ======

// Signal handler (causes pause() and other syscalls to return)
void EvidenceServer::SignalHandler(int Signal) {

  static bool Called = false;

  // If signal indicates configuration change, invoke call-back
  if (Signal == EvidenceServer::ConfigSignal) {
    This->ConfigChanged();
        return;
  }

  // At first invocation just request exit
  if (!Called) {
        Called = true;
        This->ExitRequest = true;
        return;
  }

  // If invoked twice, call exit()
  This->Message(WARN, "Signal handler called again, invoking exit() (signal %d)", Signal);
  exit(EXIT_FAILURE);
}

// C++ exception handler (derived from gcc __verbose_terminate_handler())
void EvidenceServer::Terminate() {

  ostringstream Msg;
  static bool Terminating = false;

  if (Terminating) {
        Msg << This->Name << ": Terminate() called recursively, calling abort()";
        printf("%s\n", Msg.str().c_str());
        This->SendToLog(Msg.str().c_str());
        abort();
  }

  Terminating = true;

  // Make sure there was an exception; terminate is also called for an
  // attempt to rethrow when there is no suitable exception.
  type_info *Type = abi::__cxa_current_exception_type();
  if (Type != NULL) {
        int Status = -1;
        char *Demangled = NULL;

        Demangled = abi::__cxa_demangle(Type->name(), 0, 0, &Status);
        Msg << "Terminate() called after throwing an instance of '" << (Status==0 ? Demangled : Type->name()) << "'";
        free(Demangled);

        // If exception derived from std::exception, more information.
        try { __throw_exception_again; }
        catch (exception &E) {
          Msg << " (what(): " << E.what() << ")";         
        }
        catch (...) { }
  }
  else Msg << "Terminate() called without an active exception";

  This->Message(FATAL, Msg.str().c_str());
}


// Translates DIM data safely to string (assures no invalid memory accesses are made)
string EvidenceServer::ToString(char *Format, void *Data, int Size) {

  ostringstream Text;
  
  // 'Message' service format handled here
  if (strcmp(Format, "I:1;C") == 0 && Size >= (int) sizeof(struct Message)) {
        struct Message *Msg = (struct Message *) Data;
        // Safely extract string and limit to length of C string (padding might make it longer)
        string MsgText(Msg->Text, Size-sizeof(struct Message));
        Text << Msg->Severity << " " << MsgText.erase(strlen(MsgText.c_str()));

        return Text.str();
  }
  
  // Structure: print hex representation 
  if (strlen(Format) != 1) {
        for (int i=0; i<Size; i++) {
          Text << setw(2) << hex << *((char *) Data + i) << " ";
        } 
        return Text.str();
  }

  // String if format "C" and terminated with \0
  if (strcmp(Format, "C") == 0 && Size > 0 && *((char *) Data+Size-1)=='\0') {
        return string((char *) Data);
  }

  // Number array
  int ElementSize;
  switch (*Format) {
    case 'C': ElementSize = sizeof(char);               break;
    case 'I':
    case 'L': ElementSize = sizeof(int);                break;
    case 'S': ElementSize = sizeof(short);              break;
    case 'F': ElementSize = sizeof(float);              break;
    case 'D': ElementSize = sizeof(double);             break;
    case 'X': ElementSize = sizeof(long long);  break;
    default: return string();
  }

  for (int i=0; i<Size/ElementSize; i++) {
        // Space between entries
    if (i != 0) Text << " ";

        // Translate data
        switch (*Format) {
      case 'C': Text << *((char *) Data + i);           break;
      case 'I':
      case 'L': Text << *((int *) Data + i);            break;
      case 'S': Text << *((short *) Data + i);          break;
      case 'F': Text << *((float *) Data + i);          break;
      case 'D': Text << *((double *) Data + i);         break;
      case 'X': Text << *((long long *) Data + i);      break;
        }
  }
  
  return Text.str();
}


// Checks if service contents indicates not available
bool EvidenceServer::ServiceOK(DimInfo *Item) {

  return !((Item->getSize() == strlen(NO_LINK)+1) &&  
          (memcmp(Item->getData(), NO_LINK, Item->getSize()) == 0));
}

bool EvidenceServer::ServiceOK(DimRpcInfo *Item) {

  return !((Item->getSize() == strlen(NO_LINK)+1) &&  
          (memcmp(Item->getData(), NO_LINK, Item->getSize()) == 0));
}


// Tokenize std::string using given delimeter list
vector<string> EvidenceServer::Tokenize(const string &String, const string &Delimiters) {

  vector<string> Tokens;
  string::size_type Next, EndNext=0;
    
  while (EndNext != string::npos) {
    // Find next token
    Next = String.find_first_not_of(Delimiters, EndNext);
    EndNext = String.find_first_of(Delimiters, Next);

        // Stop if end of string reached
        if (Next == string::npos) break;

    // Add token to vector.
    Tokens.push_back(String.substr(Next, EndNext - Next));
  }
  
  return Tokens;
}


///////////////////////////
// EvidenceHistory Class //
///////////////////////////

// Organisaztion of history buffer
// F | T S D | T S D | 0 0 ......  | T S D | T S D | 0 -1
//
// F: Offset of oldest entry  T: Time  S: Size  D: Data
// F, T, S: int

// Marker for history buffer
const struct EvidenceHistory::Item EvidenceHistory::WrapMark = {0, -1, {}};
const struct EvidenceHistory::Item EvidenceHistory::EndMark = {0, 0, {}};

// Constructor
EvidenceHistory::EvidenceHistory(std::string Name):     Name(Name) {

  Buffer = NULL;
}

// Destructor
EvidenceHistory::~EvidenceHistory() {

  delete[] Buffer;
}

// Requests service history (returns true if data received OK)
bool EvidenceHistory::GetHistory() {

  DimRpcInfo R((char *) "ServiceHistory", NO_LINK);
  R.setData((char *) Name.c_str());

  // Check if data OK
  if (!EvidenceServer::ServiceOK(&R)) return false;
  if (R.getSize() == 0) return false;
  
  // Copy data to buffer
  delete[] Buffer;
  BufferSize = R.getSize();
  Buffer = new char [BufferSize];

  memcpy(Buffer, R.getData(), BufferSize);
  DataStart = Buffer + strlen(Buffer) + 1;
  Rewind();
  
  return true;
}

// Returns next item in history buffer
const struct EvidenceHistory::Item *EvidenceHistory::Next() {

  if (Buffer == NULL) return NULL;

  // Check for wrap around
  if (memcmp(Pointer, &WrapMark, sizeof(WrapMark)) == 0) Pointer = (struct Item *) (DataStart + sizeof(int));
  // Check if at end of ring buffer
  if (memcmp(Pointer, &EndMark, sizeof(EndMark)) == 0) return NULL;

  const struct Item *Ret = Pointer;
  Pointer = (struct Item *) ((char *) (Ret + 1) + Ret->Size);

  return Ret;
}

// Reset to start of buffer
void EvidenceHistory::Rewind() {

  if (Buffer != NULL) Pointer = (struct Item *) (DataStart + (*(int *) DataStart));
}

// Return DIM format string of service (NULL if no data)
char *EvidenceHistory::GetFormat() {

  return Buffer;
}