XrdCmsManTree.cc

/******************************************************************************/
/*                                                                            */
/*                      X r d C m s M a n T r e e . c c                       */
/*                                                                            */
/* (c) 2007 by the Board of Trustees of the Leland Stanford, Jr., University  */
/*                            All Rights Reserved                             */
/*   Produced by Andrew Hanushevsky for Stanford University under contract    */
/*              DE-AC02-76-SFO0515 with the Department of Energy              */
/*                                                                            */
/* This file is part of the XRootD software suite.                            */
/*                                                                            */
/* XRootD is free software: you can redistribute it and/or modify it under    */
/* the terms of the GNU Lesser General Public License as published by the     */
/* Free Software Foundation, either version 3 of the License, or (at your     */
/* option) any later version.                                                 */
/*                                                                            */
/* XRootD is distributed in the hope that it will be useful, but WITHOUT      */
/* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or      */
/* FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public       */
/* License for more details.                                                  */
/*                                                                            */
/* You should have received a copy of the GNU Lesser General Public License   */
/* along with XRootD in a file called COPYING.LESSER (LGPL license) and file  */
/* COPYING (GPL license).  If not, see <http://www.gnu.org/licenses/>.        */
/*                                                                            */
/* The copyright holder's institutional names and contributor's names may not */
/* be used to endorse or promote products derived from this software without  */
/* specific prior written permission of the institution or contributor.       */
/******************************************************************************/

#include <stdio.h>

#include "XProtocol/YProtocol.hh"

#include "XrdCms/XrdCmsManTree.hh"
#include "XrdCms/XrdCmsNode.hh"
#include "XrdCms/XrdCmsTrace.hh"

using namespace XrdCms;

/******************************************************************************/
/*                           C o n s t r u c t o r                            */
/******************************************************************************/

XrdCmsManTree::XrdCmsManTree(int maxC) : maxTMI(0),  numConn(0), maxConn(maxC),
                                         atRoot(0), conLevel(0), conNID(-1),
                                         numWaiting(0), myStatus(Active)
{
    snprintf(buff, sizeof(buff), "%d", maxC);
}
  
/******************************************************************************/
/*                                 A b o r t                                  */
/******************************************************************************/

void XrdCmsManTree::Abort()
{
   XrdSysMutexHelper Monitor(myMutex);

// An abort may be issued to make sure no one is waiting to participate in
// tree construction. It's usually issued when the manager object has been
// permanently redirected.
//
   if (myStatus != Aborted && numWaiting)
      {for (int i = 0; i < maxTMI; i++)
           if (tmInfo[i].Status == Waiting) {tmInfo[i].Level = 0; Redrive(i);}
      }

// Indicate we have aborted
//
   myStatus = Aborted;
}
  
/******************************************************************************/
/*                               C o n n e c t                                */
/******************************************************************************/
  
int XrdCmsManTree::Connect(int nID, XrdCmsNode *nP)
{
   static CmsDiscRequest discRequest = {{0, kYR_disc, 0, 0}};
   XrdSysMutexHelper Monitor(myMutex);
   char mybuff[16];
   int i;

// Rule 0: If we aborted tell the client to just stop doing this
//
   if (myStatus == Aborted) return 0;

// Rule 1: If we are already connected, thell the caller to disband the
//         connection as we must have a connection to an interior node.
//
   if (myStatus == Connected) return 0;
   numConn++;
   tmInfo[nID].nodeP = nP;

// Rule 2: If we connected to a root node then consider ourselves connected
//         only if all connections are to the root.
//
   if (tmInfo[nID].Level == 0)
      {if (numConn == maxConn)
          {myStatus = Connected; conLevel = 0; atRoot = 1;
           Say.Emsg("ManTree", "Now connected to", buff, "root node(s)");
          }
       tmInfo[nID].Status = Connected;
       return 1;
      }

// Rule 3: We connected to an interior node. Disband all other existing
//         connections (these should only be to root nodes) and consider 
//         ourselves connected.
//
   for (i = 0; i < maxTMI; i++)
       if (i != nID && tmInfo[i].Status == Connected)
          {tmInfo[i].nodeP->Send((char *)&discRequest, sizeof(discRequest));
           tmInfo[i].Status = Pending;
          }
   myStatus = Connected;
   conLevel = tmInfo[nID].Level;
   conNID   = nID;
   atRoot   = 0;

// Document our connection configuration
//
   snprintf(mybuff, sizeof(mybuff), "%d", conLevel);
   Say.Emsg("ManTree", "Now connected to supervisor at level", mybuff);
   return 1;
}

/******************************************************************************/
/*                                  D i s c                                   */
/******************************************************************************/
  
void XrdCmsManTree::Disc(int nID)
{

// A connected caller has lost it's connection.
//
   myMutex.Lock();
   if (tmInfo[nID].Status == Connected || tmInfo[nID].Status == Pending)
      numConn--;
   tmInfo[nID].Status = Active;
   if (atRoot || (conLevel && conNID == nID)) myStatus = Active;
   tmInfo[nID].nodeP = 0;
   myMutex.UnLock();
}

/******************************************************************************/
/*                              R e g i s t e r                               */
/******************************************************************************/
  
int XrdCmsManTree::Register()
{
   int nID;

// Add this server to the tree table. Register is called only once and there
// can be no more than MTMax connections to a manager. Hence, we dispense with
// error checking (how optimistic :-)
//
   myMutex.Lock();
   tmInfo[maxTMI].Status= Active;
   nID = maxTMI; maxTMI++;
   myMutex.UnLock();
   return nID;
}

/******************************************************************************/
/*                                T r y i n g                                 */
/******************************************************************************/
  
// This method arranges server connections to a manager to form a minimal B-Tree
// free of phantom arcs. The rule is simple, either all connections are to the
// root of tree or there is only one connection to an interior node. Because
// node discovery is non-determinstic, we must make sure that all root nodes
// are tried so as to discover the full set of supervisor nodes we can contact.
// This method returns True if the caller may continue at the indicated level
// and False if the caller should restart at the root node.
//
int XrdCmsManTree::Trying(int nID, int lvl)
{
   int i;

// Set the current status of the connection
//
   myMutex.Lock();
   tmInfo[nID].Level  = lvl;

// Rule 0: If we aborted tell the client to just stop doing this
//
   if (myStatus == Aborted) return -1;

// Rule 1: If we are already connected at level >0 then the caller must wait
//
   if (myStatus == Connected && conLevel > 0) 
      {Pause(nID);
       return (lvl == tmInfo[nID].Level);
      }

// Rule 2: If the caller is trying level 0 then any waiting threads must be
//         allowed to continue but forced to level 0. This allows us to discover 
//         all the supervisors connected to the root.
//
   if (!lvl)
      {if (numWaiting)
          {for (i = 0; i < maxTMI; i++)
               if (i != nID && tmInfo[i].Status == Waiting)
                  {tmInfo[i].Level = 0; Redrive(i);}
          }
       myMutex.UnLock();
       return 1;
      }

// Rule 3: If the caller is trying at a non-zero level (interior node) and
//         someone else is trying at a non-zero level, then the caller must
//         wait.
//
   for (i = 0; i < maxTMI; i++)
        if (i != nID && tmInfo[i].Status == Active && tmInfo[i].Level) break;
   if (i < maxTMI) Pause(nID);
      else myMutex.UnLock();

// The caller may continue. Indicate whether the caller must restart at the
// root node. If the caller may continue trying to connect to an interior
// node then it's the only thread trying to do so.
//
   return (lvl == tmInfo[nID].Level);
}