Add support for systemd daemon

CMakeLists.txt

@@ -29,6 +29,7 @@ set(SRC_FILES
 	src/grpc_service.cpp
 	protos/yess.grpc.pb.cc
 	protos/yess.pb.cc
+	src/daemonizer.cpp
 )
 set(INC_FILES
 	src/server.hpp
@@ -45,6 +46,7 @@ set(INC_FILES
 	src/grpc_service.hpp
 	protos/yess.grpc.pb.h
 	protos/yess.pb.h
+	src/daemonizer.hpp
 )
 add_library(${PROJECT_NAME}_objects OBJECT ${SRC_FILES} ${INCL_FILES})
 add_subdirectory(utils)
@@ -69,6 +71,7 @@ target_link_libraries(${PROJECT_NAME} PRIVATE ${CONAN_LIBS} yessutils
 	gRPC::grpc++
 	gRPC::grpc++_reflection
 	protobuf::libprotobuf
+	-lsystemd
 )
 
 add_custom_target(

src/daemonizer.cpp

@@ -0,0 +1,34 @@
+#include <exception>
+#include <iostream>
+#include <signal.h>
+#include <systemd/sd-daemon.h>
+
+#include "daemonizer.hpp"
+
+namespace yess
+{
+int Daemonizer::run(int (*cb)(int argc, char **argv), int argc, char **argv)
+{
+    int result = 1;
+    try {
+        sd_notify(0, "READY=1");
+        std::cerr << std::string("Yess daemon has successfully started up.")
+                  << std::endl
+                  << std::flush;
+
+        // start program
+        result = cb(argc, argv);
+
+        sd_notify(0, "STOPPING=1");
+        std::cerr << std::string("Yess daemon has been successfully shut down.")
+                  << std::endl
+                  << std::flush;
+    } catch (std::exception &ex) {
+        sd_notifyf(
+            0, "STATUS=Failed to start up: %s\n ERRNO=%i", ex.what(), result);
+        return result;
+    }
+    result = 0;
+    return result;
+}
+} // namespace yess

src/daemonizer.hpp

@@ -0,0 +1,16 @@
+#pragma once
+
+namespace yess
+{
+class Daemonizer
+{
+  public:
+    // static int run(int (*cb)(const int &argc, const char **arbv));
+    static int run(int (*cb)(int argc, char **argv), int argc, char **argv);
+    /*
+static int run(int (*cb)(const int &argc, const char **arbv),
+             const int &argc,
+             const char **argv);
+             */
+};
+} // namespace yess

src/main.cpp

@@ -1,8 +1,28 @@
+#include "daemonizer.hpp"
 #include "server.hpp"
+#include <iostream>
+
+void sayhello_loop()
+{
+    while (1) {
+        std::cout << "hello\n";
+    }
+}
 
 int main(int argc, char **argv)
 {
-    yess::Server server(argc, argv);
-    return server.run();
+    /*
+yess::Server server(argc, argv);
+return server.run();
+*/
+    // daemonize(sayhello_loop, "yess");
+    yess::Daemonizer::run(
+        [](int argc, char **argv) {
+            yess::Server server(argc, argv);
+            return server.run();
+        },
+        argc,
+        argv);
+    return 0;
 }
 

src/server.cpp

@@ -1,6 +1,7 @@
 #include <iostream>
 #include <stdexcept>
 #include <string>
+#include <systemd/sd-daemon.h>
 
 #include "argparse.hpp"
 #include "db/repositories/sqlite_stream_repo.hpp"
@@ -12,6 +13,42 @@
 using namespace yess;
 using namespace db;
 
+#include <atomic>
+#include <chrono>
+#include <iostream>
+#include <thread>
+
+#include <signal.h>
+#include <unistd.h>
+
+namespace
+{
+// In the GNUC Library, sig_atomic_t is a typedef for int,
+// which is atomic on all systems that are supported by the
+// GNUC Library
+volatile sig_atomic_t do_shutdown = 0;
+
+// std::atomic is safe, as long as it is lock-free
+std::atomic<bool> shutdown_requested = false;
+static_assert(std::atomic<bool>::is_always_lock_free);
+// or, at runtime: assert( shutdown_requested.is_lock_free() );
+} // namespace
+
+void my_signal_handler(int /*signum*/)
+{
+    // ok, lock-free atomics
+    do_shutdown = 1;
+    shutdown_requested = true;
+
+    const char str[] = "received signal\n";
+    // ok, write is signal-safe
+    write(STDERR_FILENO, str, sizeof(str) - 1);
+
+    // UB, unsafe, internal buffers: std::cout << "received signal\n";
+    // UB, unsafe, allocates: std::vector<T>(20);
+    // unsafe, internal buffers: printf("received signal\n");
+}
+
 Server::Server(int argc, char **argv)
 {
     log::init_logger();
@@ -57,6 +94,10 @@ void Server::parse_args(int argc, char **argv)
         exit(0);
     }
 
+    if (argparser_["--daemon"] == true) {
+        daemon_ = true;
+    }
+
     auto log_path = argparser_.get<std::string>("--log-path");
     bool file_only = argparser_.get<bool>("--file-only");
     if (!log_path.empty()) {
@@ -92,8 +133,19 @@ void Server::display_version()
 
 std::string Server::conn_str() { return conn_str_; }
 
+#include <thread>
+
 int Server::run()
 {
+    // setup signal handler
+    {
+        struct sigaction action;
+        action.sa_handler = my_signal_handler;
+        sigemptyset(&action.sa_mask);
+        action.sa_flags = 0;
+        sigaction(SIGTERM, &action, NULL);
+    }
+
     std::string server_address("0.0.0.0:" + std::to_string(port_));
     Grpc_service service(conn_str_);
 
@@ -109,8 +161,26 @@ int Server::run()
     std::unique_ptr<grpc::Server> server(builder.BuildAndStart());
     log::info("yess listening on {}...", server_address);
 
-    // Wait for the server to shutdown. Note that some other thread must be
-    // responsible for shutting down the server for this call to ever return.
-    server->Wait();
+    if (daemon_) {
+        // Watchdog thread (for systemd notification)
+        std::thread w_th([&]() {
+            // TODO: remove 5s delay for SIGTERM handling
+            while (!do_shutdown && !shutdown_requested.load()) {
+                // log::info("Notify systemd");
+                sd_notify(0, "WATCHDOG=1");
+                // WatchdogSec=6 (systemd) -> notify every 5 sec
+                std::this_thread::sleep_for(std::chrono::seconds(5));
+            }
+            server->Shutdown();
+            log::info("Server has been shut down.");
+        });
+        w_th.join();
+    }
+    std::thread grpc_th([&]() {
+        // Other thread is responsible for shutting down the server
+        server->Wait();
+    });
+    grpc_th.join();
+
     return 0;
 }

src/server.hpp

@@ -28,7 +28,9 @@ class Server
   private:
     void parse_args(int argc, char **argv);
     bool is_config_loaded_ = false;
+    bool daemon_ = false;
     std::string log_path_;
     argparse::ArgumentParser argparser_;
+    void daemon();
 };
 } // namespace yess

yess.service

@@ -0,0 +1,12 @@
+[Unit]
+Description=Yess service
+
+[Service]
+Type=simple
+ExecStart=/usr/bin/yess --daemon
+Restart=on-failure
+KillMode=process
+WatchdogSec=6
+
+[Install]
+WantedBy=multi-user.target