pdns/dolog.hh

   1 /*
   2  * This file is part of PowerDNS or dnsdist.
   3  * Copyright -- PowerDNS.COM B.V. and its contributors
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of version 2 of the GNU General Public License as
   7  * published by the Free Software Foundation.
   8  *
   9  * In addition, for the avoidance of any doubt, permission is granted to
  10  * link this program with OpenSSL and to (re)distribute the binaries
  11  * produced as the result of such linking.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License
  19  * along with this program; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  21  */
  22 #pragma once
  23 #include <iostream>
  24 #include <sstream>
  25 #include <syslog.h>
  26
  27 /* This file is intended not to be metronome specific, and is simple example of C++2011
  28    variadic templates in action.
  29
  30    The goal is rapid easy to use logging to console & syslog.
  31
  32    Usage:
  33           string address="localhost";
  34           vinfolog("Got TCP connection from %s", remote);
  35           infolog("Bound to %s port %d", address, port);
  36           warnlog("Query took %d milliseconds", 1232.4); // yes, %d
  37           errlog("Unable to bind to %s: %s", ca.toStringWithPort(), strerr(errno));
  38
  39    Will log to stdout. Will syslog in any case with LOG_INFO,
  40    LOG_WARNING, LOG_ERR respectively. If g_verbose=false, vinfolog is a noop.
  41    More generically, dolog(someiostream, "Hello %s", stream) will log to someiostream
  42
  43    This will happily print a string to %d! Doesn't do further format processing.
  44 */
  45
  46 inline void dolog(std::ostream& os, const char*s)
  47 {
  48   os<<s;
  49 }
  50
  51 template<typename T, typename... Args>
  52 void dolog(std::ostream& os, const char* s, T value, Args... args)
  53 {
  54   while (*s) {
  55     if (*s == '%') {
  56       if (*(s + 1) == '%') {
  57         ++s;
  58       }
  59       else {
  60         os << value;
  61         s += 2;
  62         dolog(os, s, args...);
  63         return;
  64       }
  65     }
  66     os << *s++;
  67   }
  68 }
  69
  70 extern bool g_verbose;
  71 extern bool g_syslog;
  72
  73 inline void setSyslogFacility(int facility)
  74 {
  75   /* we always call openlog() right away at startup */
  76   closelog();
  77   openlog("dnsdist", LOG_PID|LOG_NDELAY, facility);
  78 }
  79
  80 template<typename... Args>
  81 void genlog(int level, const char* s, Args... args)
  82 {
  83   std::ostringstream str;
  84   dolog(str, s, args...);
  85   if(g_syslog)
  86     syslog(level, "%s", str.str().c_str());
  87   std::cout<<str.str()<<std::endl;
  88 }
  89
  90
  91 #define vinfolog if(g_verbose)infolog
  92
  93 template<typename... Args>
  94 void infolog(const char* s, Args... args)
  95 {
  96   genlog(LOG_INFO, s, args...);
  97 }
  98
  99 template<typename... Args>
 100 void warnlog(const char* s, Args... args)
 101 {
 102   genlog(LOG_WARNING, s, args...);
 103 }
 104
 105 template<typename... Args>
 106 void errlog(const char* s, Args... args)
 107 {
 108   genlog(LOG_ERR, s, args...);
 109 }
 110