blob: e1078320b5a98e6978773be94798c12f0292524d [file] [log] [blame]
// Copyright 2014 The Chromium OS Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include <string>
#include <base/at_exit.h>
#include <base/macros.h>
#include <base/message_loop/message_loop.h>
#include <brillo/asynchronous_signal_handler.h>
#include <brillo/brillo_export.h>
#include <brillo/message_loops/base_message_loop.h>
struct signalfd_siginfo;
namespace brillo {
// Daemon is a simple base class for system daemons. It provides a lot
// of useful facilities such as a message loop, handling of SIGTERM, SIGINT, and
// SIGHUP system signals.
// You can use this class directly to implement your daemon or you can
// specialize it by creating your own class and deriving it from
// brillo::Daemon. Override some of the virtual methods provide to fine-tune
// its behavior to suit your daemon's needs.
class BRILLO_EXPORT Daemon : public AsynchronousSignalHandlerInterface {
virtual ~Daemon();
// Performs proper initialization of the daemon and runs the message loop.
// Blocks until the daemon is finished. The return value is the error
// code that should be returned from daemon's main(). Returns EX_OK (0) on
// success.
virtual int Run();
// Can be used by call-backs to trigger shut-down of a running message loop.
// Calls QuiteWithExitCode(EX_OK);
// WARNING: This method (as well as QuitWithExitCode) can only be called when
// the message loop is running (that is, during Daemon::Run() call). Calling
// these methods before (e.g. during OnInit()) or after (e.g in OnShutdown())
// will lead to abnormal process termination.
void Quit();
// |exit_code| is the status code to be returned when the daemon process
// quits. See the warning for Quit() above regarding the allowed scope for
// this method.
void QuitWithExitCode(int exit_code);
// AsynchronousSignalHandlerInterface overrides.
// Register/unregister custom signal handlers for the daemon. The semantics
// are identical to AsynchronousSignalHandler::RegisterHandler and
// AsynchronousSignalHandler::UnregisterHandler, except that handlers for
// SIGTERM, SIGINT, and SIGHUP cannot be modified.
void RegisterHandler(
int signal, const
AsynchronousSignalHandlerInterface::SignalHandler& callback) override;
void UnregisterHandler(int signal) override;
// Overload to provide your own initialization code that should happen just
// before running the message loop. Return EX_OK (0) on success or any other
// non-zero error codes. If an error is returned, the message loop execution
// is aborted and Daemon::Run() exits early.
// When overloading, make sure you call the base implementation of OnInit().
virtual int OnInit();
// Called when the message loops exits and before Daemon::Run() returns.
// Overload to clean up the data that was set up during OnInit().
// |return_code| contains the current error code that will be returned from
// Run(). You can override this value with your own error code if needed.
// When overloading, make sure you call the base implementation of
// OnShutdown().
virtual void OnShutdown(int* exit_code);
// Called when the SIGHUP signal is received. In response to this call, your
// daemon could reset/reload the configuration and re-initialize its state
// as if the process has been reloaded.
// Return true if the signal was processed successfully and the daemon
// reset its configuration. Returning false will force the daemon to
// quit (and subsequently relaunched by an upstart job, if one is configured).
// The default implementation just returns false (unhandled), which terminates
// the daemon, so do not call the base implementation of OnRestart() from
// your overload.
virtual bool OnRestart();
// Returns a delegate to Quit() method in the base::RunLoop instance.
base::Closure QuitClosure() const {
return brillo_message_loop_.QuitClosure();
// Called when SIGTERM/SIGINT signals are received.
bool Shutdown(const signalfd_siginfo& info);
// Called when SIGHUP signal is received.
bool Restart(const signalfd_siginfo& info);
// |at_exit_manager_| must be first to make sure it is initialized before
// other members, especially the |message_loop_|.
base::AtExitManager at_exit_manager_;
// The main message loop for the daemon.
base::MessageLoopForIO message_loop_;
// The brillo wrapper for the main message loop.
BaseMessageLoop brillo_message_loop_{&message_loop_};
// A helper to dispatch signal handlers asynchronously, so that the main
// system signal handler returns as soon as possible.
AsynchronousSignalHandler async_signal_handler_;
// Process exit code specified in QuitWithExitCode() method call.
int exit_code_;
} // namespace brillo