Fix servers not responding to SIGTERM and SIGINT

Commons/core/src/main/java/tc/oc/commons/core/restart/RequestRestartEvent.java

@@ -1,5 +1,7 @@
 package tc.oc.commons.core.restart;
 
+import javax.annotation.Nullable;
+import java.time.Duration;
 import java.util.HashSet;
 import java.util.Set;
 import java.util.logging.Logger;
@@ -39,17 +41,23 @@ public class RequestRestartEvent {
     }
 
     public Deferral defer(String deferrerName) {
+        return defer(deferrerName, null);
+    }
+
+    public Deferral defer(String deferrerName, @Nullable Duration predictedDelay) {
         logger.info("Restart deferred by " + deferrerName);
-        Deferral deferral = new Deferral(deferrerName);
+        Deferral deferral = new Deferral(deferrerName, predictedDelay);
         deferrals.add(deferral);
         return deferral;
     }
 
     public class Deferral {
         private final String deferrerName;
+        private final Duration predictedDelay;
 
-        public Deferral(String deferrerName) {
+        public Deferral(String deferrerName, @Nullable Duration predictedDelay) {
             this.deferrerName = deferrerName;
+            this.predictedDelay = predictedDelay;
         }
 
         public RequestRestartEvent request() {
@@ -60,6 +68,10 @@ public class RequestRestartEvent {
             return deferrerName;
         }
 
+        public Duration predictedDelay() {
+            return predictedDelay;
+        }
+
         /**
          * Allow the deferred restart to proceed. After this method is called,
          * this object becomes useless and can be discarded.

Commons/core/src/main/java/tc/oc/commons/core/restart/RestartConfiguration.java

@@ -4,6 +4,9 @@ import javax.annotation.Nullable;
 import javax.inject.Inject;
 
 import java.time.Duration;
+import java.util.Set;
+
+import com.google.common.collect.Sets;
 import tc.oc.commons.core.configuration.ConfigUtils;
 import tc.oc.commons.core.exception.ExceptionHandler;
 import tc.oc.minecraft.api.configuration.Configuration;
@@ -55,4 +58,11 @@ public class RestartConfiguration {
     public int kickLimit() {
         return config.getInt("kick-limit", Integer.MAX_VALUE);
     }
+
+    /**
+     * Restart the server when any of the given stop signals are received from the system.
+     */
+    public Set<String> stopSignals() {
+        return ConfigUtils.getStringSet(config, "stop-signals", Sets.newHashSet("INT", "TERM"));
+    }
 }

Commons/core/src/main/java/tc/oc/commons/core/restart/RestartManager.java

@@ -2,6 +2,7 @@ package tc.oc.commons.core.restart;
 
 import java.time.Duration;
 import java.time.Instant;
+import java.util.Collection;
 import java.util.Collections;
 import java.util.Objects;
 import java.util.Set;
@@ -17,6 +18,7 @@ import com.google.common.eventbus.EventBus;
 import com.google.common.eventbus.Subscribe;
 import com.google.common.util.concurrent.Futures;
 import com.google.common.util.concurrent.ListenableFuture;
+import sun.misc.Signal;
 import tc.oc.api.docs.Server;
 import tc.oc.api.docs.virtual.ServerDoc;
 import tc.oc.api.minecraft.MinecraftService;
@@ -60,6 +62,7 @@ public class RestartManager implements PluginFacet, Tickable {
         this.eventBus = eventBus;
         this.threads = threads;
         this.startTime = Instant.now();
+        onSignal(this.config.stopSignals());
     }
 
     @Override
@@ -160,6 +163,15 @@ public class RestartManager implements PluginFacet, Tickable {
         }
     }
 
+    private void requestRestartInternal(Instant time, String reason, int priority) {
+        logger.info("Restart requested at " + time +
+                    ", with " + priority +
+                    " priority, because \"" + reason + '"');
+        currentRequest = new RequestRestartEvent(logger, reason, priority, this::restartIfRequested);
+        eventBus.post(currentRequest);
+        restartIfRequested();
+    }
+
     public ListenableFuture<?> cancelRestart() {
         if(this.isRestartRequested()) {
             return minecraftService.updateLocalServer(new ServerDoc.Restart() {
@@ -202,12 +214,7 @@ public class RestartManager implements PluginFacet, Tickable {
         }
 
         if(newTime != null) {
-            logger.info("Restart requested at " + newTime +
-                        ", with " + newPriority +
-                        " priority, because \"" + newReason + '"');
-            currentRequest = new RequestRestartEvent(logger, newReason, newPriority, this::restartIfRequested);
-            eventBus.post(currentRequest);
-            restartIfRequested();
+            requestRestartInternal(newTime, newReason, newPriority);
         }
     }
 
@@ -236,4 +243,28 @@ public class RestartManager implements PluginFacet, Tickable {
             return false;
         }
     }
+
+    private void onSignal(Collection<String> signals) {
+        signals.stream()
+               .map(Signal::new)
+               .forEach(signal -> Signal.handle(signal, s -> {
+                   requestRestartInternal(Instant.now(), "Received signal " + s.getName() + " (" + s.getNumber() + ") from system", Integer.MAX_VALUE);
+                   try {
+                       Thread.sleep(currentRequest.deferrals()
+                                                  .stream()
+                                                  .filter(deferral -> deferral.predictedDelay() != null)
+                                                  .map(RequestRestartEvent.Deferral::predictedDelay)
+                                                  .findFirst()
+                                                  .orElse(Duration.ZERO)
+                                                  .toMillis() + 1L);
+                   } catch(InterruptedException e) {
+                       if(!minecraftServer.isStopping()) {
+                           logger.severe(s.getName() + " signal is unable to wait for restart");
+                       }
+                   }
+                   if(!restartIfRequested() && !minecraftServer.isStopping()) {
+                       minecraftServer.stop();
+                   }
+               }));
+    }
 }

PGM/src/main/java/tc/oc/pgm/restart/RestartListener.java

@@ -142,7 +142,7 @@ public class RestartListener implements PluginFacet, Listener {
     public void onRequestRestart(RequestRestartEvent event) {
         if(!server.isSuspended()) {
             logger.info("Deferring restart");
-            deferral = event.defer(getClass().getName());
+            deferral = event.defer(getClass().getName(), config.time());
             checkCountdown(mm.needCurrentMatch());
         }
     }