src/comm/AcceptLimiter.h

   1 /*
   2  * Copyright (C) 1996-2023 The Squid Software Foundation and contributors
   3  *
   4  * Squid software is distributed under GPLv2+ license and includes
   5  * contributions from numerous individuals and organizations.
   6  * Please see the COPYING and CONTRIBUTORS files for details.
   7  */
   8
   9 #ifndef _SQUID_SRC_COMM_ACCEPT_LIMITER_H
  10 #define _SQUID_SRC_COMM_ACCEPT_LIMITER_H
  11
  12 #include "comm/TcpAcceptor.h"
  13
  14 #include <deque>
  15
  16 namespace Comm
  17 {
  18
  19 /**
  20  * FIFO Queue holding listener socket handlers which have been activated
  21  * ready to dupe their FD and accept() a new client connection.
  22  * But when doing so there were not enough FD available to handle the
  23  * new connection. These handlers are awaiting some FD to become free.
  24  *
  25  * defer - used only by Comm layer ConnAcceptor adding themselves when FD are limited.
  26  * removeDead - used only by Comm layer ConnAcceptor to remove themselves when dying.
  27  * kick - used by Comm layer when FD are closed.
  28  */
  29 class AcceptLimiter
  30 {
  31
  32 public:
  33     /** retrieve the global instance of the queue. */
  34     static AcceptLimiter &Instance();
  35
  36     /** delay accepting a new client connection. */
  37     void defer(const TcpAcceptor::Pointer &afd);
  38
  39     /** remove all records of an acceptor. Only to be called by the ConnAcceptor::swanSong() */
  40     void removeDead(const TcpAcceptor::Pointer &afd);
  41
  42     /** try to accept and begin processing any delayed client connections. */
  43     void kick();
  44
  45 private:
  46     static AcceptLimiter Instance_;
  47
  48     /** FIFO queue */
  49     std::deque<TcpAcceptor::Pointer> deferred_;
  50 };
  51
  52 }; // namespace Comm
  53
  54 #endif /* _SQUID_SRC_COMM_ACCEPT_LIMITER_H */
  55