ZYppFactory.cc

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extern "C"
{
#include <sys/file.h>
}
#include <iostream>
#include <fstream>

#include "zypp/base/Logger.h"
#include "zypp/base/Gettext.h"
#include "zypp/base/IOStream.h"
#include "zypp/base/Functional.h"
#include "zypp/PathInfo.h"

#include "zypp/ZYppFactory.h"
#include "zypp/zypp_detail/ZYppImpl.h"
#include "zypp/zypp_detail/ZYppReadOnlyHack.h"

#include <boost/interprocess/sync/file_lock.hpp>
#include <boost/interprocess/sync/scoped_lock.hpp>
#include <boost/interprocess/sync/sharable_lock.hpp>

using boost::interprocess::file_lock;
using boost::interprocess::scoped_lock;
using boost::interprocess::sharable_lock;

using std::endl;

namespace zypp
{ 

  namespace env
  {
    inline Pathname ZYPP_LOCKFILE_ROOT()
    { return getenv("ZYPP_LOCKFILE_ROOT") ? getenv("ZYPP_LOCKFILE_ROOT") : "/"; }
  }

  namespace zypp_readonly_hack
  { 

    static bool active = false;

    void IWantIt()
    {
      active = true;
      MIL << "ZYPP_READONLY promised." <<  endl;
    }

    bool IGotIt()
    {
      return active;
    }

  } // namespace zypp_readonly_hack

  class ZYppGlobalLock
  {
  public:
    ZYppGlobalLock()
    : _cleanLock( false )
    , _zyppLockFilePath( env::ZYPP_LOCKFILE_ROOT() / "/var/run/zypp.pid" )
    , _zyppLockFile( NULL )
    , _lockerPid( 0 )
    {
      filesystem::assert_dir(_zyppLockFilePath.dirname() );
    }

    ~ZYppGlobalLock()
    {
        if ( _cleanLock )
        try {
          // Exception safe access to the lockfile.
          ScopedGuard closeOnReturn( accessLockFile() );
          {
            scoped_lock<file_lock> flock( _zyppLockFileLock );  // aquire write lock
            // Truncate the file rather than deleting it. Other processes may
            // still use it to synchronsize.
            ftruncate( fileno(_zyppLockFile), 0 );
          }
          MIL << "Cleanned lock file. (" << getpid() << ")" << std::endl;
        }
        catch(...) {} // let no exception escape.
    }

    pid_t lockerPid() const
    { return _lockerPid; }

    const std::string & lockerName() const
    { return _lockerName; }

    const Pathname & zyppLockFilePath() const
    { return _zyppLockFilePath; }


  private:
    Pathname    _zyppLockFilePath;
    file_lock   _zyppLockFileLock;
    FILE *      _zyppLockFile;

    pid_t       _lockerPid;
    std::string _lockerName;
    bool        _cleanLock;

  private:
    typedef shared_ptr<void> ScopedGuard;

    ScopedGuard accessLockFile()
    {
      _openLockFile();
      return ScopedGuard( static_cast<void*>(0),
                          bind( mem_fun_ref( &ZYppGlobalLock::_closeLockFile ), ref(*this) ) );
    }

    void _openLockFile()
    {
      if ( _zyppLockFile != NULL )
        return; // is open

      // open pid file rw so we are sure it exist when creating the flock
      _zyppLockFile = fopen( _zyppLockFilePath.c_str(), "a+" );
      if ( _zyppLockFile == NULL )
        ZYPP_THROW( Exception( "Cant open " + _zyppLockFilePath.asString() ) );
      _zyppLockFileLock = _zyppLockFilePath.c_str();
      MIL << "Open lockfile " << _zyppLockFilePath << endl;
    }

    void _closeLockFile()
    {
      if ( _zyppLockFile == NULL )
        return; // is closed

      clearerr( _zyppLockFile );
      fflush( _zyppLockFile );
      // http://www.boost.org/doc/libs/1_50_0/doc/html/interprocess/synchronization_mechanisms.html
      // If you are using a std::fstream/native file handle to write to the file
      // while using file locks on that file, don't close the file before releasing
      // all the locks of the file.
      _zyppLockFileLock = file_lock();
      fclose( _zyppLockFile );
      _zyppLockFile = NULL;
      MIL << "Close lockfile " << _zyppLockFilePath << endl;
    }


    bool isProcessRunning( pid_t pid_r )
    {
      // it is another program, not me, see if it is still running
      Pathname procdir( "/proc"/str::numstring(pid_r) );
      PathInfo status( procdir );
      MIL << "Checking " <<  status << endl;

      if ( ! status.isDir() )
      {
        DBG << "No such process." << endl;
        return false;
      }

      static char buffer[513];
      buffer[0] = buffer[512] = 0;
      // man proc(5): /proc/[pid]/cmdline is empty if zombie.
      if ( std::ifstream( (procdir/"cmdline").c_str() ).read( buffer, 512 ).gcount() > 0 )
      {
        _lockerName = buffer;
        DBG << "Is running: " <<  _lockerName << endl;
        return true;
      }

      DBG << "In zombie state." << endl;
      return false;
    }

    pid_t readLockFile()
    {
      clearerr( _zyppLockFile );
      fseek( _zyppLockFile, 0, SEEK_SET );
      long readpid = 0;
      fscanf( _zyppLockFile, "%ld", &readpid );
      MIL << "read: Lockfile " << _zyppLockFilePath << " has pid " << readpid << " (our pid: " << getpid() << ") "<< std::endl;
      return (pid_t)readpid;
    }

    void writeLockFile()
    {
      clearerr( _zyppLockFile );
      fseek( _zyppLockFile, 0, SEEK_SET );
      ftruncate( fileno(_zyppLockFile), 0 );
      fprintf(_zyppLockFile, "%ld\n", (long)getpid() );
      fflush( _zyppLockFile );
      _cleanLock = true; // cleanup on exit
      MIL << "write: Lockfile " << _zyppLockFilePath << " got pid " <<  getpid() << std::endl;
    }

  public:

    bool zyppLocked()
    {
      if ( geteuid() != 0 )
        return false;   // no lock as non-root

      // Exception safe access to the lockfile.
      ScopedGuard closeOnReturn( accessLockFile() );
      {
        scoped_lock<file_lock> flock( _zyppLockFileLock );      // aquire write lock

        _lockerPid = readLockFile();
        if ( _lockerPid == 0 )
        {
          // no or empty lock file
          writeLockFile();
          return false;
        }
        else if ( _lockerPid == getpid() )
        {
          // keep my own lock
          return false;
        }
        else
        {
          // a foreign pid in lock
          if ( isProcessRunning( _lockerPid ) )
          {
            WAR << _lockerPid << " is running and has a ZYpp lock. Sorry." << std::endl;
            return true;
          }
          else
          {
            MIL << _lockerPid << " is dead. Taking the lock file." << std::endl;
            writeLockFile();
            return false;
          }
        }
      }
      INT << "Oops! We should not be here!" << std::endl;
      return true;
    }

  };

  namespace
  {
    static ZYppGlobalLock & globalLock()
    {
      static ZYppGlobalLock lock;
      return lock;
    }
    bool           _haveZYpp = false;
  }

  //
  //    CLASS NAME : ZYppFactoryException
  //

  ZYppFactoryException::ZYppFactoryException( const std::string & msg_r, pid_t lockerPid_r, const std::string & lockerName_r )
    : Exception( msg_r )
    , _lockerPid( lockerPid_r )
    , _lockerName( lockerName_r )
  {}

  ZYppFactoryException::~ZYppFactoryException() throw ()
  {}

  //
  //    CLASS NAME : ZYppFactory
  //

  //
  //    METHOD NAME : ZYppFactory::instance
  //    METHOD TYPE : ZYppFactory
  //
  ZYppFactory ZYppFactory::instance()
  {
    return ZYppFactory();
  }

  //
  //    METHOD NAME : ZYppFactory::ZYppFactory
  //    METHOD TYPE : Ctor
  //
  ZYppFactory::ZYppFactory()
  {

  }

  //
  //    METHOD NAME : ZYppFactory::~ZYppFactory
  //    METHOD TYPE : Dtor
  //
  ZYppFactory::~ZYppFactory()
  {}

  //
  ZYpp::Ptr ZYppFactory::getZYpp() const
  {
    static ZYpp::Ptr _instance;

    if ( ! _instance )
    {
      if ( geteuid() != 0 )
      {
        MIL << "Running as user. Skip creating " << globalLock().zyppLockFilePath() << std::endl;
      }
      else if ( zypp_readonly_hack::active )
      {
        MIL << "ZYPP_READONLY active." << endl;
      }
      else if ( globalLock().zyppLocked() )
      {
        bool failed = true;
        const long LOCK_TIMEOUT = str::strtonum<long>( getenv( "ZYPP_LOCK_TIMEOUT" ) );
        if ( LOCK_TIMEOUT > 0 )
        {
          MIL << "Waiting whether pid " << globalLock().lockerPid() << " ends within $LOCK_TIMEOUT=" << LOCK_TIMEOUT << " sec." << endl;
          unsigned delay = 1;
          Pathname procdir( "/proc"/str::numstring(globalLock().lockerPid()) );
          for ( long i = 0; i < LOCK_TIMEOUT; i += delay )
          {
            if ( PathInfo( procdir ).isDir() )  // wait for /proc/pid to disapear
              sleep( delay );
            else
            {
              MIL << "Retry after " << i << " sec." << endl;
              failed = globalLock().zyppLocked();
              if ( failed )
              {
                // another proc locked faster. maybe it ends fast as well....
                MIL << "Waiting whether pid " << globalLock().lockerPid() << " ends within " << (LOCK_TIMEOUT-i) << " sec." << endl;
                procdir = Pathname( "/proc"/str::numstring(globalLock().lockerPid()) );
              }
              else
              {
                MIL << "Finally got the lock!" << endl;
                break;  // gotcha
              }
            }
          }

        }
        if ( failed )
        {
          std::string t = str::form(_("System management is locked by the application with pid %d (%s).\n"
                                      "Close this application before trying again."),
                                      globalLock().lockerPid(),
                                      globalLock().lockerName().c_str()
                                    );
          ZYPP_THROW(ZYppFactoryException(t, globalLock().lockerPid(), globalLock().lockerName() ));
        }
      }
      // Here we go...
      _instance = new ZYpp( ZYpp::Impl_Ptr(new ZYpp::Impl) );
      if ( _instance )
        _haveZYpp = true;
    }

    return _instance;
  }

  //
  bool ZYppFactory::haveZYpp() const
  { return _haveZYpp; }

  /******************************************************************
  **
  **    FUNCTION NAME : operator<<
  **    FUNCTION TYPE : std::ostream &
  */
  std::ostream & operator<<( std::ostream & str, const ZYppFactory & obj )
  {
    return str << "ZYppFactory";
  }

} // namespace zypp