MCOL-4170 Refactor services/systemd units to finish their bootstrap ...

utils/common/service.h

@@ -0,0 +1,116 @@
+/* Copyright (C) 2020 MariaDB Corporation
+
+   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; version 2 of
+   the License.
+
+   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 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. */
+
+#ifndef SERVICE_H_INCLUDED
+#define SERVICE_H_INCLUDED
+
+#include <signal.h>
+#include "pipe.h"
+
+
+class Service
+{
+protected:
+    // The service name, for logging
+    const std::string m_name;
+    // The pipe to send messages from the child to the parent
+    Pipe m_pipe;
+
+
+    static void common_signal_handler_CHLD(int sig)
+    { }
+
+    void InitCommonSignalHandlers()
+    {
+        struct sigaction sa;
+        memset(&sa, 0, sizeof(sa));
+        sa.sa_handler = common_signal_handler_CHLD;
+        sigaction(SIGCHLD, &sa, NULL);
+    }
+
+    int RunForking()
+    {
+        int err;
+        InitCommonSignalHandlers();
+
+        if (m_pipe.open() || (err = fork()) < 0)
+        {
+            // Pipe or fork failed
+            LogErrno();
+            return 1;
+        }
+
+        if (err > 0) // Parent
+          return Parent();
+
+        return Child();
+    }
+
+    virtual int Parent()
+    {
+        char str[100];
+        // Read the message from the child
+        ssize_t nbytes= m_pipe.readtm({120,0}, str, sizeof(str));
+        if (nbytes >= 0)
+        {
+            ParentLogChildMessage(std::string(str, nbytes));
+        }
+        else
+        {
+            // read() failed
+            LogErrno();
+            return 1;
+        }
+        return 0;
+    }
+    
+
+public:
+    Service(const std::string &name)
+     :m_name(name)
+    { }
+    virtual ~Service() { }
+
+    void NotifyServiceStarted()
+    {
+        if (m_pipe.is_open_for_write())
+        {
+            std::ostringstream str;
+            str << m_name << " main process has started";
+            m_pipe.write(str.str());
+        }
+    }
+
+    void NotifyServiceInitializationFailed()
+    {
+        if (m_pipe.is_open_for_write())
+        {
+            std::ostringstream str;
+            str << m_name << " main process initialization failed";
+            m_pipe.write(str.str());
+        }
+    }
+
+    // Used by both Parent and Child to log errors
+    virtual void LogErrno()= 0;
+    // Used by Parent to log an initialization notification message from child
+    virtual void ParentLogChildMessage(const std::string &str)= 0;
+    // The main service process job
+    virtual int Child()= 0;
+};
+
+#endif // SERVICE_H_INCLUDED