Use sd_notify to notify systemd of readiness

CMakeLists.txt

@@ -93,6 +93,7 @@ add_subdirectory(common)
 add_subdirectory(radio)
 
 if (MRC_BUILD)
+add_subdirectory(libsystemd)
 add_subdirectory(powerdistribution)
 add_subdirectory(expansionhub)
 endif()

common/CMakeLists.txt

@@ -2,6 +2,7 @@ project(Common)
 
 set (SOURCES
     version.cpp
+    systemd-utils.cpp
 )
 
 add_library(Common STATIC ${SOURCES})
@@ -11,3 +12,8 @@ target_include_directories(Common PUBLIC ${CMAKE_CURRENT_SOURCE_DIR})
 
 target_compile_definitions(Common PRIVATE MRC_BUILD_GIT_HASH=${BUILD_CURRENT_GIT_HASH})
 target_compile_definitions(Common PRIVATE MRC_BUILD_TIMESTAMP=${BUILD_CURRENT_TIMESTAMP})
+
+if (MRC_BUILD)
+target_compile_definitions(Common PRIVATE MRC_DAEMON_BUILD)
+target_link_libraries(Common PRIVATE systemd)
+endif()

common/systemd-utils.cpp

@@ -0,0 +1,23 @@
+#include "systemd-utils.h"
+
+#ifdef MRC_DAEMON_BUILD
+#include <systemd/sd-daemon.h>
+#endif
+
+void systemd_utils::notify_ready() {
+#ifdef MRC_DAEMON_BUILD
+    sd_notify(0, "READY=1");
+#endif
+}
+
+void systemd_utils::notify_stopping() {
+#ifdef MRC_DAEMON_BUILD
+    sd_notify(0, "STOPPING=1");
+#endif
+}
+
+void systemd_utils::notify_status(std::string_view status) {
+#ifdef MRC_DAEMON_BUILD
+    sd_notifyf(0, "STATUS=%s", status.data());
+#endif
+}

common/systemd-utils.h

@@ -0,0 +1,8 @@
+#pragma once
+
+#include <string_view>
+namespace systemd_utils {
+void notify_ready();
+void notify_stopping();
+void notify_status(std::string_view status);
+}  // namespace systemd_utils

expansionhub/CMakeLists.txt

@@ -1,7 +1,5 @@
 project(ExpansionHubDaemon)
 
-set(CMAKE_EXE_LINKER_FLAGS "-Wl,--allow-shlib-undefined")
-
 add_executable(ExpansionHubDaemon
     main.cpp
     PidConstants.cpp
@@ -16,9 +14,7 @@ add_executable(ExpansionHubDaemon
 target_compile_features(ExpansionHubDaemon PRIVATE cxx_std_20)
 target_compile_features(ExpansionHubDaemon PRIVATE c_std_17)
 wpilib_target_warnings(ExpansionHubDaemon)
-target_link_libraries(ExpansionHubDaemon PRIVATE Common wpimath ntcore wpinet wpiutil)
-target_link_libraries(ExpansionHubDaemon PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/libsystemd.so.0.37.0)
-target_include_directories(ExpansionHubDaemon PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/rhsp/include)
+target_link_libraries(ExpansionHubDaemon PRIVATE Common wpimath ntcore wpinet wpiutil systemd)
 
 if (MRC_BUILD)
 target_compile_definitions(ExpansionHubDaemon PRIVATE MRC_DAEMON_BUILD)

expansionhub/main.cpp

@@ -48,6 +48,8 @@
 #include "EnabledState.h"
 #include "SystemDUsbMonitor.h"
 
+#include "systemd-utils.h"
+
 struct ExpansionHubState {
     uint64_t lastLoop = wpi::util::Now();
 
@@ -413,6 +415,8 @@ int main() {
         return -1;
     }
 
+    systemd_utils::notify_ready();
+
     {
 #if defined(__linux__) && defined(MRC_DAEMON_BUILD)
         int sig = 0;
@@ -421,6 +425,9 @@ int main() {
         (void)getchar();
 #endif
     }
+
+    systemd_utils::notify_stopping();
+
     ntInst.StopClient();
     wpi::nt::NetworkTableInstance::Destroy(ntInst);
 

libsystemd/CMakeLists.txt

@@ -0,0 +1,14 @@
+add_library(systemd SHARED IMPORTED GLOBAL)
+
+set_target_properties(systemd PROPERTIES
+    IMPORTED_LOCATION "${CMAKE_CURRENT_SOURCE_DIR}/libsystemd.so.0.37.0"
+    IMPORTED_SONAME "libsystemd.so.0"
+)
+
+target_include_directories(systemd INTERFACE
+    "${CMAKE_CURRENT_SOURCE_DIR}"
+)
+
+target_link_options(systemd INTERFACE
+    "LINKER:--unresolved-symbols=ignore-in-shared-libs"
+)

powerdistribution/main.cpp

@@ -17,6 +17,8 @@
 #include "wpi/nt/RawTopic.hpp"
 #include "wpi/nt/IntegerTopic.hpp"
 
+#include "systemd-utils.h"
+
 #define NUM_CAN_BUSES 2
 
 static constexpr uint32_t deviceTypeMask = 0x3F000000;
@@ -226,6 +228,8 @@ int main() {
         return -1;
     }
 
+    systemd_utils::notify_ready();
+
     {
 #if defined(__linux__) && defined(MRC_DAEMON_BUILD)
         int sig = 0;
@@ -234,6 +238,9 @@ int main() {
         (void)getchar();
 #endif
     }
+
+    systemd_utils::notify_stopping();
+
     ntInst.StopClient();
     wpi::nt::NetworkTableInstance::Destroy(ntInst);
 

radio/main.cpp

@@ -16,6 +16,8 @@
 #include "wpi/nt/StringTopic.hpp"
 #include "wpi/util/StringExtras.hpp"
 
+#include "systemd-utils.h"
+
 struct DataStorage {
     wpi::util::Logger logger;
     wpi::nt::StringSubscriber teamSubscriber;
@@ -59,6 +61,8 @@ int main() {
         return -1;
     }
 
+    systemd_utils::notify_ready();
+
     {
 #if defined(__linux__) && defined(MRC_DAEMON_BUILD)
         int sig = 0;
@@ -67,6 +71,9 @@ int main() {
         (void)getchar();
 #endif
     }
+
+    systemd_utils::notify_stopping();
+
     loopRunner.Stop();
     ntInst.StopClient();
     wpi::nt::NetworkTableInstance::Destroy(ntInst);