shmmonitor: distinguish daemon from monitor mode (orthogonal)

fairmq/shmem/Manager.h

@@ -215,7 +215,7 @@ class Manager
             boost::filesystem::path p = boost::process::search_path("fairmq-shmmonitor", ownPath);
 
             if (!p.empty()) {
-                boost::process::spawn(p, "-x", "--shmid", id, "-d", "-t", "2000", env);
+                boost::process::spawn(p, "-x", "-m", "--shmid", id, "-d", "-t", "2000", env);
                 int numTries = 0;
                 do {
                     try {

fairmq/shmem/Monitor.cxx

@@ -71,11 +71,11 @@ void signalHandler(int signal)
     gSignalStatus = signal;
 }
 
-Monitor::Monitor(const string& shmId, bool selfDestruct, bool interactive, bool viewOnly, unsigned int timeoutInMS, unsigned int intervalInMS, bool runAsDaemon, bool cleanOnExit)
+Monitor::Monitor(const string& shmId, bool selfDestruct, bool interactive, bool viewOnly, unsigned int timeoutInMS, unsigned int intervalInMS, bool monitor, bool cleanOnExit)
     : fSelfDestruct(selfDestruct)
     , fInteractive(interactive)
     , fViewOnly(viewOnly)
-    , fIsDaemon(runAsDaemon)
+    , fMonitor(monitor)
     , fSeenOnce(false)
     , fCleanOnExit(cleanOnExit)
     , fTimeoutInMS(timeoutInMS)
@@ -90,12 +90,12 @@ Monitor::Monitor(const string& shmId, bool selfDestruct, bool interactive, bool
     , fSignalThread()
     , fDeviceHeartbeats()
 {
-    if (!fViewOnly) {
+    if (fMonitor) {
         try {
             bipc::named_mutex monitorStatus(bipc::create_only, string("fmq_" + fShmId + "_ms").c_str());
         } catch (bie&) {
-            cout << "fairmq-shmmonitor for shared memory id " << fShmId << " already started or not properly exited. Try `fairmq-shmmonitor --cleanup --shmid " << fShmId << "`" << endl;
-            throw DaemonPresent(tools::ToString("fairmq-shmmonitor for shared memory id ", fShmId, " already started or not properly exited."));
+            cout << "fairmq-shmmonitor (in monitoring mode) for shared memory id " << fShmId << " already started or did not not properly exited. Try `fairmq-shmmonitor --cleanup --shmid " << fShmId << "`" << endl;
+            throw DaemonPresent(tools::ToString("fairmq-shmmonitor (in monitoring mode) for shared memory id ", fShmId, " already started or did not not properly exited."));
         }
     }
 
@@ -140,7 +140,7 @@ void Monitor::Run()
         CheckSegment();
     } else {
         while (!fTerminating) {
-            this_thread::sleep_for(chrono::milliseconds(fIntervalInMS));
+            this_thread::sleep_for(chrono::milliseconds(500));
             CheckSegment();
         }
     }
@@ -288,11 +288,12 @@ void Monitor::CheckSegment()
         unsigned int duration = chrono::duration_cast<chrono::milliseconds>(now - fLastHeartbeat).count();
 
         if (fHeartbeatTriggered && duration > fTimeoutInMS) {
+            // memory is present, but no heartbeats since timeout duration
             cout << "no heartbeats since over " << fTimeoutInMS << " milliseconds, cleaning..." << endl;
             Cleanup(ShmId{fShmId});
             fHeartbeatTriggered = false;
             if (fSelfDestruct) {
-                cout << "\nself destructing" << endl;
+                cout << "self destructing (segment has been observed and cleaned up by the monitor)" << endl;
                 fTerminating = true;
             }
         }
@@ -329,23 +330,23 @@ void Monitor::CheckSegment()
     } catch (bie&) {
         fHeartbeatTriggered = false;
 
+        if (fSelfDestruct) {
+            if (fSeenOnce) {
+                // segment has been observed at least once, can self-destruct
+                cout << "self destructing (segment has been observed and cleaned up orderly)" << endl;
+                fTerminating = true;
+            } else {
+                // if self-destruct is requested, and no segment has ever been observed, quit after double timeout duration
                 auto now = chrono::high_resolution_clock::now();
                 unsigned int duration = chrono::duration_cast<chrono::milliseconds>(now - fLastHeartbeat).count();
 
-        if (fIsDaemon && duration > fTimeoutInMS * 2) {
+                if (fMonitor && duration > fTimeoutInMS * 2) {
+                    // clean just in case any other artifacts are left.
                     Cleanup(ShmId{fShmId});
-            fHeartbeatTriggered = false;
-            if (fSelfDestruct) {
-                cout << "\nself destructing" << endl;
+                    cout << "self destructing (no segments observed within (timeout * 2) since start)" << endl;
                     fTerminating = true;
                 }
             }
-
-        if (fSelfDestruct) {
-            if (fSeenOnce) {
-                cout << "self destructing" << endl;
-                fTerminating = true;
-            }
         }
     }
 }

fairmq/shmem/Monitor.h

@@ -100,7 +100,7 @@ class Monitor
     bool fSelfDestruct; // will self-destruct after the memory has been closed
     bool fInteractive; // running in interactive mode
     bool fViewOnly; // view only mode
-    bool fIsDaemon;
+    bool fMonitor;
     bool fSeenOnce; // true is segment has been opened successfully at least once
     bool fCleanOnExit;
     unsigned int fTimeoutInMS;

fairmq/shmem/runMonitor.cxx

@@ -78,6 +78,7 @@ int main(int argc, char** argv)
         unsigned int timeoutInMS = 5000;
         unsigned int intervalInMS = 100;
         bool runAsDaemon = false;
+        bool monitor = false;
         bool debug = false;
         bool cleanOnExit = false;
         bool getShmId = false;
@@ -93,11 +94,12 @@ int main(int argc, char** argv)
             ("view,v"         , value<bool>(&viewOnly)->implicit_value(true),           "Run in view only mode")
             ("timeout,t"      , value<unsigned int>(&timeoutInMS)->default_value(5000), "Heartbeat timeout in milliseconds")
             ("daemonize,d"    , value<bool>(&runAsDaemon)->implicit_value(true),        "Daemonize the monitor")
+            ("monitor,m"      , value<bool>(&monitor)->implicit_value(true),            "Run in monitoring mode")
             ("debug,b"        , value<bool>(&debug)->implicit_value(true),              "Debug - Print a list of messages)")
             ("clean-on-exit,e", value<bool>(&cleanOnExit)->implicit_value(true),        "Perform cleanup on exit")
             ("interval"       , value<unsigned int>(&intervalInMS)->default_value(100), "Output interval for interactive/view-only mode")
             ("get-shmid"      , value<bool>(&getShmId)->implicit_value(true),           "Translate given session id and user id to a shmem id (uses current user id if none provided)")
-            ("user-id"        , value<int>(&userId)->default_value(-1),                  "User id")
+            ("user-id"        , value<int>(&userId)->default_value(-1),                 "User id (used with --get-shmid)")
             ("help,h", "Print help");
 
         variables_map vm;
@@ -141,12 +143,17 @@ int main(int argc, char** argv)
 
         cout << "Starting shared memory monitor for session: \"" << sessionName << "\" (shmId: " << shmId << ")..." << endl;
 
-        Monitor monitor(shmId, selfDestruct, interactive, viewOnly, timeoutInMS, intervalInMS, runAsDaemon, cleanOnExit);
+        if (!viewOnly && !interactive && !monitor) {
+            // if neither of the run modes are selected, use view only mode.
+            viewOnly = true;
+        }
+
+        Monitor shmmonitor(shmId, selfDestruct, interactive, viewOnly, timeoutInMS, intervalInMS, monitor, cleanOnExit);
 
         if (interactive || !viewOnly) {
-            monitor.CatchSignals();
+            shmmonitor.CatchSignals();
         }
-        monitor.Run();
+        shmmonitor.Run();
     } catch (Monitor::DaemonPresent& dp) {
         return 0;
     } catch (exception& e) {