Sustain.cpp

//------------------------------------------------------------------------------
/*
    This file is part of rippled: https://github.com/ripple/rippled
    Copyright (c) 2012, 2013 Ripple Labs Inc.
 
    Permission to use, copy, modify, and/or distribute this software for any
    purpose  with  or without fee is hereby granted, provided that the above
    copyright notice and this permission notice appear in all copies.
 
    THE  SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
    WITH  REGARD  TO  THIS  SOFTWARE  INCLUDING  ALL  IMPLIED  WARRANTIES  OF
    MERCHANTABILITY  AND  FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
    ANY  SPECIAL ,  DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
    WHATSOEVER  RESULTING  FROM  LOSS  OF USE, DATA OR PROFITS, WHETHER IN AN
    ACTION  OF  CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
//==============================================================================
 
#include <ripple/basics/Sustain.h>
#include <ripple/basics/safe_cast.h>
#include <ripple/beast/core/CurrentThreadName.h>
#include <boost/format.hpp>
 
// For Sustain Linux variants
// VFALCO TODO Rewrite Sustain to use beast::Process
#ifdef __linux__
#include <sys/prctl.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#endif
#ifdef __FreeBSD__
#include <sys/types.h>
#include <sys/wait.h>
#endif
 
namespace ripple {
 
#ifdef __unix__
 
static auto const sleepBeforeWaiting = 10;
static auto const sleepBetweenWaits = 1;
 
static pid_t pManager = safe_cast<pid_t>(0);
static pid_t pChild = safe_cast<pid_t>(0);
 
static void
pass_signal(int a)
{
    kill(pChild, a);
}
 
static void
stop_manager(int)
{
    kill(pChild, SIGINT);
    _exit(0);
}
 
bool
HaveSustain()
{
    return true;
}
 
std::string
StopSustain()
{
    if (getppid() != pManager)
        return "";
 
    kill(pManager, SIGHUP);
    return "Terminating monitor";
}
 
static bool
checkChild(pid_t pid, int options)
{
    int i;
 
    if (waitpid(pChild, &i, options) == -1)
        return false;
 
    return kill(pChild, 0) == 0;
}
 
std::string
DoSustain()
{
    pManager = getpid();
    signal(SIGINT, stop_manager);
    signal(SIGHUP, stop_manager);
    signal(SIGUSR1, pass_signal);
    signal(SIGUSR2, pass_signal);
 
    // Number of times the child has exited in less than
    // 15 seconds.
    int fastExit = 0;
 
    for (auto childCount = 1;; ++childCount)
    {
        pChild = fork();
 
        if (pChild == -1)
            _exit(0);
 
        auto cc = std::to_string(childCount);
        if (pChild == 0)
        {
            beast::setCurrentThreadName("rippled: main");
            signal(SIGINT, SIG_DFL);
            signal(SIGHUP, SIG_DFL);
            signal(SIGUSR1, SIG_DFL);
            signal(SIGUSR2, SIG_DFL);
            return "Launching child " + cc;
        }
 
        beast::setCurrentThreadName(("rippled: #" + cc).c_str());
 
        sleep(sleepBeforeWaiting);
 
        // If the child has already terminated count this
        // as a fast exit and an indication that something
        // went wrong:
        if (!checkChild(pChild, WNOHANG))
        {
            if (++fastExit == 5)
                _exit(0);
        }
        else
        {
            fastExit = 0;
 
            while (checkChild(pChild, 0))
                sleep(sleepBetweenWaits);
 
            (void)rename("core", ("core." + std::to_string(pChild)).c_str());
        }
    }
}
 
#else
 
bool
HaveSustain()
{
    return false;
}
 
std::string
DoSustain()
{
    return "";
}
 
std::string
StopSustain()
{
    return "";
}
 
#endif
 
}  // namespace ripple