tyler.durden
/
icinga2
mirror of https://github.com/Icinga/icinga2.git
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

Daemonize(): use one error convention, not three 

Standardize on exit() / _exit() (this depends whether we are considered
to be the "main" fork, which should run anything registered with atexit()).
Exclude `return false` and throwing exceptions.

This fixes the error path for fork().  Daemonize() would return false, but
the `return false` error convention was not tested in the caller.

It also fixes the error message for fork() to show the error code.
Everyone loves `strace`, but sysadmins should not have to rerun their
daemons under it just to see an error code.

Also in case an exception is thrown, show its diagnostic information
instead of dropping it on the floor.  In the log message, I mention why we
are uninitializing and then initializing the app at this point.

For the reader, it pushes all the weirdness into the error convention of
Daemonize().  This comes back to the exit() / _exit() distinction.  Once
we have forked, we technically don't want to allow the parent process to
exit(), so we don't want to return to the caller.
This commit is contained in:
Alan Jenkins 2018-05-30 12:21:39 +01:00
parent a0fb0bbfe3
commit 50463a6a10
1 changed files with 28 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

40
lib/cli/daemoncommand.cpp
View File

@ -52,14 +52,28 @@ static void SigHupHandler(int)
}
#endif /* _WIN32 */
static bool Daemonize()
/*
* Daemonize(). On error, this function logs by itself and exits (i.e. does not return).
*
* Implementation note: We're only supposed to call exit() in one of the forked processes.
* The other process calls _exit(). This prevents issues with exit handlers like atexit().
*/
static void Daemonize() noexcept
{
#ifndef _WIN32
Application::UninitializeBase();
try {
Application::UninitializeBase();
} catch (const std::exception& ex) {
Log(LogCritical, "cli")
<< "Failed to stop thread pool before daemonizing, unexpected error: " << DiagnosticInformation(ex);
exit(EXIT_FAILURE);
}
pid_t pid = fork();
if (pid == -1) {
return false;
Log(LogCritical, "cli")
<< "fork() failed with error code " << errno << ", \"" << Utility::FormatErrorNumber(errno) << "\"";
exit(EXIT_FAILURE);
}
if (pid) {
@ -91,10 +105,14 @@ static bool Daemonize()
Log(LogDebug, "Daemonize()")
<< "Child process with PID " << Utility::GetPid() << " continues; re-initializing base.";
Application::InitializeBase();
try {
Application::InitializeBase();
} catch (const std::exception& ex) {
Log(LogCritical, "cli")
<< "Failed to re-initialize thread pool after daemonizing: " << DiagnosticInformation(ex);
exit(EXIT_FAILURE);
}
#endif /* _WIN32 */
return true;
}
static bool SetDaemonIO(const String& stderrFile)
@ -245,12 +263,10 @@ int DaemonCommand::Run(const po::variables_map& vm, const std::vector<std::strin
if (vm.count("daemonize")) {
if (!vm.count("reload-internal")) {
// no additional fork neccessary on reload
try {
Daemonize();
} catch (std::exception&) {
Log(LogCritical, "cli", "Daemonize failed. Exiting.");
return EXIT_FAILURE;
}
// this subroutine either succeeds, or logs an error
// and terminates the process (does not return).
Daemonize();
}
}