Add functionality to notify systemd on olad startup and config reload

common/base/Makefile.mk

@@ -9,6 +9,11 @@ common_libolacommon_la_SOURCES += \
     common/base/SysExits.cpp \
     common/base/Version.cpp
 
+if HAVE_STRERROR_R
+common_libolacommon_la_SOURCES += common/base/StrError_R.cpp \
+                                  common/base/StrError_R_XSI.cpp
+endif
+
 # TESTS
 ##################################################
 

common/base/StrError_R.cpp

@@ -0,0 +1,50 @@
+/*
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ *
+ * StrError_R.cpp
+ * Helper function for StrError_R_XSI().
+ * Copyright (C) 2018 Shenghao Yang
+ */
+
+#if HAVE_CONFIG_H
+#include <config.h>
+#endif  // HAVE_CONFIG_H
+
+#include <stdio.h>
+#include <string.h>
+
+#include <limits>
+#include <string>
+#include <sstream>
+
+#include "ola/base/StrError_R.h"
+#include "ola/strings/Format.h"
+
+namespace ola {
+
+const int StrError_R_BufSize = 1024;
+
+std::string StrError_R(int errnum) {
+  // Pre-allocate to prevent re-allocation.
+  std::string out(StrError_R_BufSize, '\0');
+  if (StrError_R_XSI(errnum, &(out[0]), out.size())) {
+    out.assign(std::string("errno = ") + ola::strings::IntToString(errnum));
+  } else {
+    out.resize(strlen(&(out[0])));
+  }
+  return out;
+}
+
+}  // namespace ola

common/base/StrError_R_XSI.cpp

@@ -0,0 +1,51 @@
+/*
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ *
+ * StrError_R_XSI.cpp
+ * Definition of strerror_r() that is XSI-compliant.
+ * This extra file is required because the header declaring the symbols
+ * for the C++ string library conflicts with the macros used to expose
+ * the XSI-compliant declaration of strerror_r().
+ * Copyright (C) 2018 Shenghao Yang
+ */
+
+#if HAVE_CONFIG_H
+#include <config.h>
+#endif  // HAVE_CONFIG_H
+
+// Required for string.h to declare the standards-compliant version of
+// strerror_r(), when compiling under glibc. Must come before the inclusion
+// of string.h.
+// These are conditional to avoid errors when not compiling with glibc, or
+// when compiling with a compiler that does not define _POSIX_C_SOURCE.
+// See strerror(3) as to why the macros are defined this way.
+#ifdef _GNU_SOURCE
+#undef _GNU_SOURCE
+#endif
+
+#ifdef _POSIX_C_SOURCE
+#undef _POSIX_C_SOURCE
+#endif
+#define _POSIX_C_SOURCE 200112L
+
+#include <string.h>
+
+namespace ola {
+
+int StrError_R_XSI(int errnum, char* buf, size_t buflen) {
+  return strerror_r(errnum, buf, buflen);
+}
+
+}  // namespace ola

configure.ac

@@ -190,8 +190,8 @@ AC_FUNC_CLOSEDIR_VOID
 AC_FUNC_VPRINTF
 AC_CHECK_FUNCS([bzero gettimeofday memmove memset mkdir strdup strrchr \
                 if_nametoindex inet_ntoa inet_ntop inet_aton inet_pton select \
-                socket strerror getifaddrs getloadavg getpwnam_r getpwuid_r \
-                getgrnam_r getgrgid_r secure_getenv])
+                socket strerror strerror_r getifaddrs getloadavg getpwnam_r \
+                getpwuid_r getgrnam_r getgrgid_r secure_getenv])
 
 AC_MSG_CHECKING(for readdir_r deprecation)
 old_cxxflags=$CXXFLAGS
@@ -234,6 +234,9 @@ AM_CONDITIONAL(HAVE_EPOLL, test "${ax_cv_have_epoll}" = "yes")
 AC_CHECK_FUNCS([kqueue])
 AM_CONDITIONAL(HAVE_KQUEUE, test "${ac_cv_func_kqueue}" = "yes")
 
+# strerror_r
+AM_CONDITIONAL([HAVE_STRERROR_R], [test "x$ac_cv_func_strerror_r" = "xyes"])
+
 # check if the compiler supports -rdynamic
 AC_MSG_CHECKING(for -rdynamic support)
 old_cppflags=$CPPFLAGS
@@ -756,6 +759,31 @@ 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([--disable-systemd], [Disable systemd support])])
+
+have_libsystemd="no"
+AS_IF([test "x$enable_systemd" != xno],
+  [PKG_CHECK_MODULES([libsystemd], [libsystemd >= 38], [have_libsystemd=yes], 
+                     [AC_MSG_WARN([disabling systemd support: can't find libsystemd])])
+   AC_CHECK_HEADER([systemd/sd-daemon.h], [],
+                   [have_libsystemd=no
+                    AC_MSG_WARN([disabling systemd support: can't find systemd/sd-daemon.h])])
+   AS_IF([test "x$ac_cv_func_strerror_r" = xno],
+         [have_libsystemd=no
+          AC_MSG_WARN([disabling systemd support: can't find strerror_r])])])
+
+AS_IF([test "x$have_libsystemd" = xyes],
+      [AC_DEFINE([HAVE_LIBSYSTEMD], [1],
+                 [define if systemd support is wanted and libsystemd is present])])
+
+AM_CONDITIONAL([HAVE_LIBSYSTEMD], [test "x$have_libsystemd" = xyes])
+
+AS_IF([test "x$enable_systemd" = xyes && test "x$have_libsystemd" = xno],
+      [AC_MSG_ERROR([could not enable systemd support])])
+
 # UUCP Lock directory
 AC_ARG_WITH([uucp-lock],
             [AS_HELP_STRING([--with-uucp-lock],

include/ola/base/Makefile.mk

@@ -9,5 +9,9 @@ olabaseinclude_HEADERS = \
     include/ola/base/Macro.h \
     include/ola/base/SysExits.h
 
+if HAVE_STRERROR_R
+olabaseinclude_HEADERS += include/ola/base/StrError_R.h
+endif
+
 nodist_olabaseinclude_HEADERS = \
     include/ola/base/Version.h

include/ola/base/StrError_R.h

@@ -0,0 +1,79 @@
+/*
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ *
+ * StrError_R.h
+ * Helper functions for strerror_r and a declaration of strerror_r that is
+ * XSI-compliant.
+ * Copyright (C) 2018 Shenghao Yang
+ */
+
+/**
+ * @defgroup strerror Description of system error codes
+ * @brief Error descriptions
+ * @details Convenience functions to obtain descriptions of system error codes.
+ * The functions and variables in this group are only defined if \c strerror_r()
+ * is available.
+ */
+
+/**
+ * @addtogroup strerror
+ * @{
+ * @file StrError_R.h
+ * @}
+ */
+
+#ifndef INCLUDE_OLA_BASE_STRERROR_R_H_
+#define INCLUDE_OLA_BASE_STRERROR_R_H_
+
+#include <string>
+
+namespace ola {
+
+/**
+ * @addtogroup strerror
+ * @{
+ */
+
+/**
+ * @brief Length of the internal buffer used for @ref StrError_R().
+ * 
+ * If the length of the system-provided error description exceeds the length
+ * of this buffer minus one, then the output of @ref StrError_R() will only
+ * include the numerical error value provided.
+ */
+extern const int StrError_R_BufSize;
+
+/**
+ * @brief XSI-compliant version of \c strerror_r().
+ *
+ * @see https://linux.die.net/man/3/strerror for more details.
+ */
+int StrError_R_XSI(int errnum, char* buf, size_t buflen);
+
+/**
+ * @brief Convenience function that wraps @ref StrError_R_XSI().
+ * 
+ * @param errnum error value to generate the textual description for.
+ * @return Textual description of the error value. If the description is
+ * truncated due to an insufficient buffer length, the description will
+ * be in the form: "errno = errnum".
+ * @sa StrError_R_BufSize for information regarding truncation.
+ */
+std::string StrError_R(int errnum);
+
+/**@}*/
+}  // namespace ola
+
+#endif  // INCLUDE_OLA_BASE_STRERROR_R_H_

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/Systemd.cpp olad/Systemd.h
+ola_server_additional_libs += $(libsystemd_LIBS)
+endif
+
 # lib olaserver
 lib_LTLIBRARIES += olad/libolaserver.la
 

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::SystemdNotify(0, "RELOADING=1\nSTATUS=Reloading plugins\n");
+#endif  // HAVE_LIBSYSTEMD
   OLA_INFO << "Reloading plugins";
   StopPlugins();
   m_plugin_manager->LoadAll();
+#ifdef HAVE_LIBSYSTEMD
+  ola::SystemdNotify(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"
@@ -172,6 +176,18 @@ int main(int argc, char *argv[]) {
       ola::NewCallback(olad->GetOlaServer(), &ola::OlaServer::ReloadPlugins));
 #endif  // _WIN32
 
+#if HAVE_LIBSYSTEMD
+  if (ola::SystemdNotifyAvailable()) {
+    OLA_INFO << "Systemd notification socket address present, "
+             << "sending notifications.";
+  } else {
+    OLA_WARN << "Systemd notification socket address not present, "
+             << "not sending notifications.";
+  }
+  // Does not need to be guarded. sd_notify does its own internal check on
+  // the socket's presence, as well.
+  ola::SystemdNotify(0, "READY=1\nSTATUS=Startup complete\n");
+#endif  // HAVE_LIBSYSTEMD
   olad->Run();
   return ola::EXIT_OK;
 }

olad/Systemd.cpp

@@ -0,0 +1,49 @@
+/*
+ * 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.cpp
+ * Provides wrapped access to systemd interfaces.
+ * Copyright (C) 2018 Shenghao Yang
+ */
+
+#if HAVE_CONFIG_H
+#include <config.h>
+#endif  // HAVE_CONFIG_H
+
+#if HAVE_LIBSYSTEMD
+#include <systemd/sd-daemon.h>
+#endif  // HAVE_LIBSYSTEMD
+
+#include "ola/Logging.h"
+#include "ola/base/StrError_R.h"
+
+#include "olad/Systemd.h"
+
+namespace ola {
+
+int SystemdNotify(int unset_environment, const char *state) {
+  int rtn = sd_notify(unset_environment, state);
+  if (rtn < 0) {
+    OLA_WARN << "Error sending notification to systemd: "
+             << ola::StrError_R(-rtn);
+  }
+  return rtn;
+}
+
+bool SystemdNotifyAvailable() {
+  return (sd_notify(0, "") != 0);
+}
+
+}  // namespace ola