Add heartbeat timeout

src/main/java/net/frozenorb/apiv3/model/Server.java

@@ -12,6 +12,7 @@ import fr.javatic.mongo.jacksonCodec.objectId.Id;
 import lombok.Getter;
 import net.frozenorb.apiv3.APIv3;
 import net.frozenorb.apiv3.serialization.gson.ExcludeFromReplies;
+import net.frozenorb.apiv3.util.TimeUtils;
 import org.bson.Document;
 
 import java.time.Instant;
@@ -46,6 +47,7 @@ public final class Server {
     static {
         updateCache();
         APIv3.getVertxInstance().setPeriodic(TimeUnit.MINUTES.toMillis(1), (id) -> updateCache());
+        APIv3.getVertxInstance().setPeriodic(TimeUnit.MINUTES.toMillis(1), (id) -> updateTimedOutServers());
     }
 
     private static void updateCache() {
@@ -66,6 +68,42 @@ public final class Server {
         });
     }
 
+    // TODO: This code isn't multi-instance safe AND will send more
+    // db requests than needed.
+    private static void updateTimedOutServers() {
+        for (Server server : serverCache) {
+            int lastUpdatedAgo = TimeUtils.getSecondsBetween(server.getLastUpdatedAt(), Instant.now());
+
+            if (lastUpdatedAgo < TimeUnit.SECONDS.toSeconds(30)) {
+                return;
+            }
+
+            for (UUID online : server.getPlayers()) {
+                User.findById(online, (user, error) -> {
+                    if (error != null) {
+                        error.printStackTrace();
+                        return;
+                    }
+
+                    if (user.leftServer(server)) {
+                        user.save((ignored, error2) -> {
+                            if (error2 != null) {
+                                error2.printStackTrace();
+                            }
+                        });
+                    }
+                });
+            }
+
+            server.players = new HashSet<>();
+            server.save((ignored, error) -> {
+                if (error != null) {
+                    error.printStackTrace();
+                }
+            });
+        }
+    }
+
     private Server() {} // For Jackson
 
     public Server(String id, String displayName, String apiKey, ServerGroup serverGroup, String serverIp) {

src/main/java/net/frozenorb/apiv3/model/User.java

@@ -349,12 +349,16 @@ public final class User {
         return true;
     }
 
-    public void leftServer(Server server) {
+    // Returns if any change was actually made.
+    public boolean leftServer(Server server) {
         // We have this check to prevent issues where one server's
         // leave is processed after another server's login.
         if (server.getId().equals(lastSeenOn)) {
             this.lastSeenAt = Instant.now();
             this.online = false;
+            return true;
+        } else {
+            return false;
         }
     }