syncevo-dbus-server: restart when auto sync is enabled (BMC #14955)

This patch also covers the case that the server needs to restart
because it has to run automatic syncs. The restart is implemented as a
brute-force execve() after removing output redirection, using the
original argv and env arrays (Restart class).

src/syncevo-dbus-server.cpp

@@ -85,6 +85,55 @@ static GMainLoop *loop = NULL;
 static bool shutdownRequested = false;
 static LogRedirect *redirectPtr;
 
+/**
+ * Encapsulates startup environment from main() and can do execve()
+ * with it later on. Assumes that argv[0] is the executable to run.
+ */
+class Restart
+{
+    vector<string> m_argv;
+    vector<string> m_env;
+
+    void saveArray(vector<string> &array, char **p)
+    {
+        while(*p) {
+            array.push_back(*p);
+            p++;
+        }
+    }
+
+    const char **createArray(const vector<string> &array)
+    {
+        const char **res = new const char *[(array.size() + 1)];
+        size_t i;
+        for (i = 0; i < array.size(); i++) {
+            res[i] = array[i].c_str();
+        }
+        res[i] = NULL;
+        return res;
+    }
+
+public:
+    Restart(char **argv, char **env)
+    {
+        saveArray(m_argv, argv);
+        saveArray(m_env, env);
+    }
+
+    void restart()
+    {
+        const char **argv = createArray(m_argv);
+        const char **env = createArray(m_env);
+        LogRedirect::reset();
+        if (execve(argv[0], (char *const *)argv, (char *const *)env)) {
+            SE_THROW(StringPrintf("restarting syncevo-dbus-server failed: %s", strerror(errno)));
+        }
+    }
+};
+
+/** initialized in main() */
+static boost::shared_ptr<Restart> restart;
+
 /**
  * Anything that can be owned by a client, like a connection
  * or session.
@@ -827,9 +876,12 @@ class AutoSyncManager : public SessionListener
      */
     void update(const string &configName);
 
-    /* Is there any auto sync task in the queue? */
+    /* Is there anything ready to run? */
     bool hasTask() { return !m_workQueue.empty(); }
 
+    /* Is there anything with automatic syncing waiting for its time to run? */
+    bool hasAutoConfigs() { return !m_peerMap.empty(); }
+
     /** 
      * pick the front task from the working queue and create a session for it.
      * The session won't be used to do sync until it is active so 'prepare' is
@@ -3696,11 +3748,15 @@ void Session::shutdownFileModified()
 bool Session::shutdownServer()
 {
     Timespec now = Timespec::monotonic();
-    SE_LOG_DEBUG(NULL, NULL, "shut down server at %lu.%09lu because of file modifications",
-                 now.tv_sec, now.tv_nsec);
-    if (false /* restart? */) {
-        // TODO: suitable exec() call which restarts the server using the same environment it was in
+    bool autosync = m_server.getAutoSyncManager().hasTask() ||
+        m_server.getAutoSyncManager().hasAutoConfigs();
+    SE_LOG_DEBUG(NULL, NULL, "shut down server at %lu.%09lu because of file modifications, auto sync %s",
+                 now.tv_sec, now.tv_nsec,
+                 autosync ? "on" : "off");
+    if (autosync) {
+        // suitable exec() call which restarts the server using the same environment it was in
         // when it was started
+        restart->restart();
     } else {
         // leave server now
         shutdownRequested = true;
@@ -6594,8 +6650,11 @@ static bool parseDuration(int &duration, const char* value)
 
 SE_END_CXX
 
-int main(int argc, char **argv)
+int main(int argc, char **argv, char **envp)
 {
+    // remember environment for restart
+    restart.reset(new Restart(argv, envp));
+
     int duration = 600;
     int opt = 1;
     while(opt < argc) {

src/syncevo/LogRedirect.h

@@ -165,6 +165,14 @@ class LogRedirect : public LoggerStdout
     /** true if stderr is redirected */
     static bool redirectingStderr() { return m_redirect && m_redirect->m_stderr.m_read > 0; }
 
+    /** reset any redirection, if active */
+    static void reset() {
+        if (m_redirect) {
+            m_redirect->flush();
+            m_redirect->restore();
+        }
+    }
+
     const FDs &getStdout() { return m_stdout; }
     const FDs &getStderr() { return m_stderr; }
 

test/test-dbus.py

@@ -2595,5 +2595,25 @@ class TestFileNotify(unittest.TestCase, DBusUtil):
         time.sleep(4)
         self.failIf(self.isServerRunning())
 
+    @timeout(60)
+    def testRestart(self):
+        """set up auto sync, then check that server restarts"""
+        self.failUnless(self.isServerRunning())
+        self.setUpSession("memotoo")
+        config = self.session.GetConfig(True, utf8_strings=True)
+        config[""]["autoSync"] = "1"
+        self.session.SetConfig(False, False, config)
+        self.failUnless(self.isServerRunning())
+        self.session.Detach()
+        self.modifyServerFile()
+        bus_name = self.server.bus_name
+        # give server time to restart
+        time.sleep(15)
+        self.setUpServer()
+        self.failIfEqual(bus_name, self.server.bus_name)
+        # serverExecutable() will fail if the service wasn't properly
+        # with execve() because then the old process is dead.
+        self.failUnlessEqual(self.serverexe, self.serverExecutable())
+
 if __name__ == '__main__':
     unittest.main()