pdns/delaypipe.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 <map>
  24 #include <time.h>
  25 #include <thread>
  26
  27 /**
  28    General idea: many threads submit work to this class, but only one executes it. The work should therefore be entirely trivial.
  29    The implementation is that submitter threads create an object that represents the work, and it gets sent over a pipe
  30    to the worker thread.
  31
  32    The worker thread meanwhile listens on this pipe (non-blocking), with a delay set to the next object that needs to be executed.
  33    If meanwhile new work comes in, all objects who's time has come are executed, a new sleep time is calculated.
  34 */
  35
  36
  37 /* ObjectPipe facilitates the type-safe passing of types over a pipe */
  38
  39 template<class T>
  40 class ObjectPipe
  41 {
  42 public:
  43   ObjectPipe();
  44   ~ObjectPipe();
  45   void write(T& t);
  46   bool read(T* t); // returns false on EOF
  47   int readTimeout(T* t, double msec); //!< -1 is timeout, 0 is no data, 1 is data. msec<0 waits infinitely wrong. msec==0 = undefined
  48   void close();
  49 private:
  50   int d_fds[2];
  51 };
  52
  53 template<class T>
  54 class DelayPipe
  55 {
  56 public:
  57   DelayPipe();
  58   ~DelayPipe();
  59   void submit(T& t, int msec); //!< don't try for more than 4294 msec
  60
  61 private:
  62   void worker();
  63   struct Combo
  64   {
  65     T what;
  66     struct timespec when;
  67   };
  68
  69   double tsdelta(const struct timespec& a, const struct timespec& b) // read as a-b
  70   {
  71     return 1.0*(a.tv_sec-b.tv_sec)+1.0*(a.tv_nsec-b.tv_nsec)/1000000000.0;
  72   }
  73
  74   ObjectPipe<Combo> d_pipe;
  75   struct tscomp {
  76     bool operator()(const struct timespec& a, const struct timespec& b) const
  77     {
  78       return std::tie(a.tv_sec, a.tv_nsec) < std::tie(b.tv_sec, b.tv_nsec);
  79     }
  80   };
  81   std::multimap<struct timespec, T, tscomp> d_work;
  82   void gettime(struct timespec* ts);
  83   std::thread d_thread;
  84 };
  85
  86 #include "delaypipe.cc"