Add functionality to notify systemd on olad startup and config reload

configure.ac

@@ -748,6 +748,21 @@ AC_ARG_ENABLE(
   [AS_HELP_STRING([--disable-doxygen-version],
   [Substitute the Doxygen version with latest, for the website])])
 
+# systemd support
+AC_ARG_ENABLE(
+  [systemd],
+  [AS_HELP_STRING([--enable-systemd], [Enable systemd support])])
+
+have_libsystemd="no"
+AS_IF([test "x$enable_systemd" = "xyes"],
+  [PKG_CHECK_MODULES([libsystemd], [libsystemd >= 38], [have_libsystemd="yes"])
+   AC_CHECK_HEADER([systemd/sd-daemon.h], [], [have_libsystemd="no"])])
+
+AS_IF([test "x$have_libsystemd" = xyes],
+      [AC_DEFINE([HAVE_LIBSYSTEMD], [1], [define if systemd support wanted])])
+
+AM_CONDITIONAL([HAVE_LIBSYSTEMD], [test "x$have_libsystemd" = xyes])
+
 # UUCP Lock directory
 AC_ARG_WITH([uucp-lock],
             [AS_HELP_STRING([--with-uucp-lock],

olad/Makefile.mk

@@ -42,6 +42,11 @@ ola_server_sources += olad/HttpServerActions.cpp \
 ola_server_additional_libs += common/http/libolahttp.la
 endif
 
+if HAVE_LIBSYSTEMD
+ola_server_sources += olad/NotifySystemd.cpp olad/Systemd.h
+ola_server_additional_libs += $(libsystemd_LIBS)
+endif
+
 # lib olaserver
 lib_LTLIBRARIES += olad/libolaserver.la
 

olad/NotifySystemd.cpp

@@ -0,0 +1,51 @@
+/*
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * NotifySystemd.cpp
+ * Provides wrapped access to the systemd notification interface.
+ * Copyright (C) 2018 Shenghao Yang
+ */
+
+#if HAVE_CONFIG_H
+#include <config.h>
+#endif  // HAVE_CONFIG_H
+
+#if HAVE_LIBSYSTEMD
+#include <systemd/sd-daemon.h>
+#include <errno.h>
+#include <string.h>
+#endif  // HAVE_LIBSYSTEMD
+
+#include "ola/Logging.h"
+
+#include "olad/Systemd.h"
+
+namespace ola {
+
+int notify_systemd(int unset_environment, const char *state) {
+  int rtn = sd_notify(unset_environment, state);
+  if (rtn < 0) {
+    char buf[1024];
+    OLA_WARN << "Error sending notification to systemd: " <<
+      strerror_r(-rtn, buf, sizeof(buf));
+  }
+  return rtn;
+}
+
+bool notify_available() {
+  return (sd_notify(0, "") != 0);
+}
+
+}  // namespace ola

olad/OlaServer.cpp

@@ -63,6 +63,10 @@
 #include "olad/OladHTTPServer.h"
 #endif  // HAVE_LIBMICROHTTPD
 
+#ifdef HAVE_LIBSYSTEMD
+#include "olad/Systemd.h"
+#endif  // HAVE_LIBSYSTEMD
+
 DEFINE_s_uint16(rpc_port, r, ola::OlaServer::DEFAULT_RPC_PORT,
                 "The port to listen for RPCs on. Defaults to 9010.");
 DEFINE_default_bool(register_with_dns_sd, true,
@@ -472,9 +476,15 @@ bool OlaServer::InternalNewConnection(
 }
 
 void OlaServer::ReloadPluginsInternal() {
+#ifdef HAVE_LIBSYSTEMD
+  ola::notify_systemd(0, "RELOADING=1\nSTATUS=Reloading plugins\n");
+#endif  // HAVE_LIBSYSTEMD
   OLA_INFO << "Reloading plugins";
   StopPlugins();
   m_plugin_manager->LoadAll();
+#ifdef HAVE_LIBSYSTEMD
+  ola::notify_systemd(0, "READY=1\nSTATUS=Plugin reload complete\n");
+#endif  // HAVE_LIBSYSTEMD
 }
 
 void OlaServer::UpdatePidStore(const RootPidStore *pid_store) {

olad/Olad.cpp

@@ -36,6 +36,10 @@
 // which needs to be after WinSock2.h, hence this order
 #include "olad/OlaDaemon.h"
 
+#if HAVE_LIBSYSTEMD
+#include "olad/Systemd.h"
+#endif  // HAVE_LIBSYSTEMD
+
 #include "ola/Logging.h"
 #include "ola/base/Credentials.h"
 #include "ola/base/Flags.h"
@@ -171,6 +175,16 @@ int main(int argc, char *argv[]) {
       ola::NewCallback(olad->GetOlaServer(), &ola::OlaServer::ReloadPlugins));
 #endif  // _WIN32
 
+#if HAVE_LIBSYSTEMD
+  if (ola::notify_available()) {
+    OLA_INFO << "Systemd notification socket present. Sending notifications.";
+  } else {
+    OLA_WARN << "Systemd notification socket not present";
+  }
+  // Does not need to be guarded. sd_notify does its own internal check on
+  // the socket's presence, as well.
+  ola::notify_systemd(0, "READY=1\nSTATUS=Startup complete\n");
+#endif  // HAVE_LIBSYSTEMD
   olad->Run();
   return ola::EXIT_OK;
 }

olad/Systemd.h

@@ -0,0 +1,46 @@
+/*
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Systemd.h
+ * Interface to systemd functionality.
+ * Copyright (C) 2018 Shenghao Yang
+ */
+
+#ifndef OLAD_SYSTEMD_H_
+#define OLAD_SYSTEMD_H_
+
+namespace ola {
+
+/*
+ * @brief Notify systemd about daemon state changes.
+ *  
+ * This function logs on failures to queue notifications, but only if the
+ * notification socket environment variable is set.
+ *  
+ * @param unset_environment whether to unset the notification socket environment
+ *        variable so child processes cannot utilize it.
+ * @param state state block to pass to systemd.
+ * @return value returned from \ref sd_notify()
+ */
+int notify_systemd(int unset_environment, const char *state);
+
+/* 
+ * @brief Tests whether the systemd notification socket is available.
+ * @return @c true if the socket is available, @c false if not.
+ */
+bool notify_available();
+
+}  // namespace ola
+#endif  // OLAD_SYSTEMD_H_