mongodb/db/repl.h

// repl.h - replication

/**
*    Copyright (C) 2008 10gen Inc.
*  
*    This program is free software: you can redistribute it and/or  modify
*    it under the terms of the GNU Affero General Public License, version 3,
*    as published by the Free Software Foundation.
*  
*    This program 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 Affero General Public License for more details.
*  
*    You should have received a copy of the GNU Affero General Public License
*    along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

/* replication data overview

   at the slave: 
     local.sources { host: ..., source: ..., syncedTo: ..., dbs: { ... } }

   at the master:
     local.oplog.$<source>
     local.oplog.$main is the default
*/

#pragma once

class DBClientConnection;
class DBClientCursor;
extern bool slave;
extern bool master;

bool cloneFrom(const char *masterHost, string& errmsg, const string& fromdb);

#pragma pack(push,4)
class OpTime { 
	unsigned i;
	unsigned secs;
public:
	OpTime(unsigned long long date) { 
		reinterpret_cast<unsigned long long&>(*this) = date;
	}
	OpTime(unsigned a, unsigned b) { secs = a; i = b; }
	OpTime() { secs = 0; i = 0; }
	static OpTime now();

	  /* We store OpTime's in the database as Javascript Date datatype -- we needed some sort of 
	     64 bit "container" for these values.  While these are not really "Dates", that seems a 
		 better choice for now than say, Number, which is floating point.  Note the BinData type 
		 is perhaps the cleanest choice, lacking a true unsigned64 datatype, but BinData has a 
		 couple bytes of overhead.
	  */
	  unsigned long long asDate() const { return *((unsigned long long *) &i); } 
//	  unsigned long long& asDate() { return *((unsigned long long *) &i); } 

	  bool isNull() { return secs == 0; }
	  string toString() const { 
		  stringstream ss;
		  ss << hex << secs << ':' << i;
		  return ss.str();
	  }
	  bool operator==(const OpTime& r) const { 
		  return i == r.i && secs == r.secs;
	  }
	  bool operator!=(const OpTime& r) const { return !(*this == r); }
	  bool operator<(const OpTime& r) const { 
		  if( secs != r.secs ) 
			  return secs < r.secs;
		  return i < r.i;
	  }
};
#pragma pack(pop)

/* A replication exception */
struct SyncException { 
};

/* A Source is a source from which we can pull (replicate) data.
   stored in collection local.sources.

   Can be a group of things to replicate for several databases.

      { host: ..., source: ..., syncedTo: ..., dbs: { ... } }
*/
class ReplSource {
	bool resync(string db);
	void sync_pullOpLog();
	void sync_pullOpLog_applyOperation(JSObj& op);

	auto_ptr<DBClientConnection> conn;
	auto_ptr<DBClientCursor> cursor;

	set<string> addDbNextPass;

	ReplSource();
public:
	bool paired; // --pair in use
	string hostName;    // ip addr or hostname plus optionally, ":<port>" 
	string sourceName;  // a logical source name.
	string only; // only a certain db. note that in the sources collection, this may not be changed once you start replicating.

	/* the last time point we have already synced up to. */
	OpTime syncedTo;

	/* list of databases that we have synced. 
	   we need this so that if we encounter a new one, we know 
	   to go fetch the old data.
	*/
	set<string> dbs;

	int nClonedThisPass;

	static void loadAll(vector<ReplSource*>&);
	static void cleanup(vector<ReplSource*>&);
	ReplSource(JSObj);
	bool sync();
	void save(); // write ourself to local.sources
	void resetConnection() { 
        conn = auto_ptr<DBClientConnection>(0); 
        cursor = auto_ptr<DBClientCursor>(0);
    }

	// make a jsobj from our member fields of the form 
	//   { host: ..., source: ..., syncedTo: ... }
	JSObj jsobj(); 
	
	bool operator==(const ReplSource&r) const { 
		return hostName == r.hostName && sourceName == r.sourceName; 
	}
};

/* Write operation to the log (local.oplog.$main)
   "i" insert
   "u" update
   "d" delete
   "c" db cmd
   "db" declares presence of a database (ns is set to the db name + '.')
*/
void _logOp(const char *opstr, const char *ns, JSObj& obj, JSObj *patt, bool *b);
inline void logOp(const char *opstr, const char *ns, JSObj& obj, JSObj *patt = 0, bool *b = 0) {
	if( master )
		_logOp(opstr, ns, obj, patt, b);
}