Add minimum online checks for a server to be considered online

shared/src/main/java/net/pistonmaster/pistonqueue/shared/config/Config.java

@@ -67,6 +67,9 @@ public final class Config {
   @Comment("It is not recommended to decrease this number (milliseconds)")
   private int serverOnlineCheckDelay = 500;
 
+  @Comment("How many online checks need to be successful before we consider the server online")
+  private int minOnlineChecks = 3;
+
   @Comment("Where to send the queue position message and what to send.")
   private boolean positionMessageChat = true;
   private boolean positionMessageHotBar = false;
@@ -207,6 +210,7 @@ public void copyFrom(Config source) {
     registerTab = source.registerTab;
     serverIsFullMessage = source.serverIsFullMessage;
     serverOnlineCheckDelay = source.serverOnlineCheckDelay;
+    minOnlineChecks = source.minOnlineChecks;
     positionMessageChat = source.positionMessageChat;
     positionMessageHotBar = source.positionMessageHotBar;
     queuePosition = source.queuePosition;
@@ -278,6 +282,10 @@ public int serverOnlineCheckDelay() {
     return serverOnlineCheckDelay;
   }
 
+  public int minOnlineChecks() {
+    return minOnlineChecks;
+  }
+
   public boolean positionMessageChat() {
     return positionMessageChat;
   }
@@ -527,6 +535,10 @@ public void setServerIsFullMessage(String message) {
     this.serverIsFullMessage = message;
   }
 
+  public void setMinOnlineChecks(int minOnlineChecks) {
+    this.minOnlineChecks = minOnlineChecks;
+  }
+
   public void setServerDownKickMessage(String message) {
     this.serverDownKickMessage = message;
   }

shared/src/main/java/net/pistonmaster/pistonqueue/shared/plugin/PistonQueuePlugin.java

@@ -85,7 +85,7 @@ default void scheduleTasks(QueueListenerShared queueListener) {
     final QueueGroup defaultGroup = resolvedDefaultGroup;
     // Sends the position message and updates tab on an interval in chat
     schedule(() -> {
-      boolean targetsOnline = defaultGroup.targetServers().stream().anyMatch(queueListener.getOnlineServers()::contains);
+      boolean targetsOnline = defaultGroup.targetServers().stream().anyMatch(queueListener.getServerStatusManager().getOnlineServers()::contains);
       if (targetsOnline) {
         for (QueueType type : config.getAllQueueTypes()) {
           if (config.positionMessageChat()) {
@@ -126,25 +126,24 @@ default void scheduleTasks(QueueListenerShared queueListener) {
       List<String> servers = new ArrayList<>(config.kickWhenDownServers());
       CountDownLatch latch = new CountDownLatch(servers.size());
       for (String server : servers) {
-        CompletableFuture<Void> future = CompletableFuture.runAsync(() -> {
+        CompletableFuture.runAsync(() -> {
           try {
             Optional<ServerInfoWrapper> serverInfoWrapper = getServer(server);
 
             if (serverInfoWrapper.isPresent()) {
               if (serverInfoWrapper.get().isOnline()) {
-                queueListener.getOnlineServers().add(server);
+                queueListener.getServerStatusManager().online(server);
               } else {
                 warning("Server %s is down!!!".formatted(server));
-                queueListener.getOnlineServers().remove(server);
+                queueListener.getServerStatusManager().offline(server);
               }
             } else {
               warning("Server \"%s\" not set up!!! Check out: https://github.com/AlexProgrammerDE/PistonQueue/wiki/FAQ#server-not-set-up-error".formatted(server));
             }
           } finally {
             latch.countDown();
           }
-        });
-        future.exceptionally(ex -> {
+        }).exceptionally(ex -> {
           error("Failed to check status of server " + server + ": " + ex.getMessage());
           return null;
         });

shared/src/main/java/net/pistonmaster/pistonqueue/shared/queue/QueueListenerShared.java

@@ -47,7 +47,7 @@
 public abstract class QueueListenerShared {
   private final PistonQueuePlugin plugin;
   @Getter
-  private final Set<String> onlineServers = ConcurrentHashMap.newKeySet();
+  private final ServerStatusManager serverStatusManager;
   private final QueueEnvironment queueEnvironment;
   private final QueuePlacementCoordinator queuePlacementCoordinator;
   private final QueueMoveProcessor queueMoveProcessor;
@@ -57,8 +57,9 @@ public abstract class QueueListenerShared {
 
   protected QueueListenerShared(PistonQueuePlugin plugin) {
     this.plugin = plugin;
-    this.queueEnvironment = new QueueEnvironment(plugin, this::currentConfig, onlineServers);
     Config config = currentConfig();
+    this.serverStatusManager = new ServerStatusManager(this::currentConfig);
+    this.queueEnvironment = new QueueEnvironment(plugin, this::currentConfig, serverStatusManager::getOnlineServers);
     this.usernameValidator = new UsernameValidator(config);
     this.shadowBanKickHandler = new ShadowBanKickHandler(config);
 

shared/src/main/java/net/pistonmaster/pistonqueue/shared/queue/ServerStatusManager.java

@@ -0,0 +1,46 @@
+package net.pistonmaster.pistonqueue.shared.queue;
+
+import net.pistonmaster.pistonqueue.shared.config.Config;
+
+import java.util.Map;
+import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.function.Supplier;
+import java.util.stream.Collectors;
+
+public class ServerStatusManager {
+  private final Supplier<Config> configSupplier;
+
+  private final Map<String, Integer> onlinePingCounts = new ConcurrentHashMap<>();
+
+  public ServerStatusManager(Supplier<Config> configSupplier) {
+    this.configSupplier = configSupplier;
+  }
+
+  public void online(String server) {
+    onlinePingCounts.merge(server, 1, (oldValue, newValue) -> {
+      //this prevents overflows, count never goes over the configured amount
+      final int sum = Integer.sum(oldValue, newValue);
+      if (sum > configSupplier.get().minOnlineChecks()) {
+        return oldValue;
+      }
+      return sum;
+    });
+  }
+
+  public void offline(String server) {
+    onlinePingCounts.remove(server);
+  }
+
+  public Set<String> getOnlineServers() {
+    return onlinePingCounts.entrySet().stream()
+      .filter(entry -> entry.getValue() >= configSupplier.get().minOnlineChecks())
+      .map(Map.Entry::getKey)
+      .collect(Collectors.toSet());
+  }
+
+  // For testing purposes so we can assert there is no overflow risk
+  public int getOnlinePingCount(String server) {
+    return onlinePingCounts.getOrDefault(server, 0);
+  }
+}

shared/src/main/java/net/pistonmaster/pistonqueue/shared/queue/logic/QueueEnvironment.java

@@ -21,9 +21,9 @@
 
 import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
 import net.pistonmaster.pistonqueue.shared.config.Config;
+import net.pistonmaster.pistonqueue.shared.plugin.PistonQueuePlugin;
 import net.pistonmaster.pistonqueue.shared.queue.QueueGroup;
 import net.pistonmaster.pistonqueue.shared.queue.QueueType;
-import net.pistonmaster.pistonqueue.shared.plugin.PistonQueuePlugin;
 
 import java.util.List;
 import java.util.Objects;
@@ -35,12 +35,12 @@
 public final class QueueEnvironment {
   private final PistonQueuePlugin plugin;
   private final Supplier<Config> configSupplier;
-  private final Set<String> onlineServers;
+  private final Supplier<Set<String>> onlineServersSupplier;
 
-  public QueueEnvironment(PistonQueuePlugin plugin, Supplier<Config> configSupplier, Set<String> onlineServers) {
+  public QueueEnvironment(PistonQueuePlugin plugin, Supplier<Config> configSupplier, Supplier<Set<String>> onlineServersSupplier) {
     this.plugin = Objects.requireNonNull(plugin, "plugin");
     this.configSupplier = Objects.requireNonNull(configSupplier, "configSupplier");
-    this.onlineServers = Objects.requireNonNull(onlineServers, "onlineServers");
+    this.onlineServersSupplier = Objects.requireNonNull(onlineServersSupplier, "onlineServersSupplier");
   }
 
   @SuppressFBWarnings(value = "EI_EXPOSE_REP", justification = "Plugin API is immutable for consumers")
@@ -52,9 +52,8 @@ public Config config() {
     return configSupplier.get();
   }
 
-  @SuppressFBWarnings(value = "EI_EXPOSE_REP", justification = "Caller needs live view for synchronization")
   public Set<String> onlineServers() {
-    return onlineServers;
+    return onlineServersSupplier.get();
   }
 
   public QueueGroup defaultGroup() {
@@ -94,14 +93,14 @@ public String defaultTarget(QueueGroup group) {
   }
 
   public boolean isGroupTargetOnline(QueueGroup group) {
-    return group.targetServers().stream().anyMatch(onlineServers::contains);
+    return group.targetServers().stream().anyMatch(onlineServers()::contains);
   }
 
   /// Checks if at least one queue server in the group is online.
   ///
   /// @param group the queue group to check
   /// @return true if at least one queue server is online
   public boolean isGroupQueueServerOnline(QueueGroup group) {
-    return group.queueServers().stream().anyMatch(onlineServers::contains);
+    return group.queueServers().stream().anyMatch(onlineServers()::contains);
   }
 }

shared/src/test/java/net/pistonmaster/pistonqueue/shared/queue/logic/KickEventHandlerTest.java

@@ -41,7 +41,7 @@ void redirectsToQueueWhenKickedFromDownTargetServer() {
     QueueTestUtils.TestQueuePlugin plugin = new QueueTestUtils.TestQueuePlugin(config);
     QueueGroup group = QueueTestUtils.defaultGroup(config);
     Set<String> onlineServers = QueueTestUtils.onlineServers("queue", "target");
-    QueueEnvironment environment = new QueueEnvironment(plugin, plugin::getConfiguration, onlineServers);
+    QueueEnvironment environment = new QueueEnvironment(plugin, plugin::getConfiguration,  () -> onlineServers);
     QueueServerSelector selector = new QueueServerSelector(environment);
     KickEventHandler handler = new KickEventHandler(config, environment, selector);
 
@@ -65,7 +65,7 @@ void doesNotRedirectWhenQueueRedirectionDisabled() {
 
     QueueTestUtils.TestQueuePlugin plugin = new QueueTestUtils.TestQueuePlugin(config);
     Set<String> onlineServers = QueueTestUtils.onlineServers("queue", "target");
-    QueueEnvironment environment = new QueueEnvironment(plugin, plugin::getConfiguration, onlineServers);
+    QueueEnvironment environment = new QueueEnvironment(plugin, plugin::getConfiguration,  () -> onlineServers);
     QueueServerSelector selector = new QueueServerSelector(environment);
     KickEventHandler handler = new KickEventHandler(config, environment, selector);
 
@@ -87,7 +87,7 @@ void doesNotRedirectWhenKickedFromNonTargetServer() {
 
     QueueTestUtils.TestQueuePlugin plugin = new QueueTestUtils.TestQueuePlugin(config);
     Set<String> onlineServers = QueueTestUtils.onlineServers("queue", "target");
-    QueueEnvironment environment = new QueueEnvironment(plugin, plugin::getConfiguration, onlineServers);
+    QueueEnvironment environment = new QueueEnvironment(plugin, plugin::getConfiguration,  () -> onlineServers);
     QueueServerSelector selector = new QueueServerSelector(environment);
     KickEventHandler handler = new KickEventHandler(config, environment, selector);
 
@@ -109,7 +109,7 @@ void doesNotRedirectWhenKickReasonDoesNotMatch() {
 
     QueueTestUtils.TestQueuePlugin plugin = new QueueTestUtils.TestQueuePlugin(config);
     Set<String> onlineServers = QueueTestUtils.onlineServers("queue", "target");
-    QueueEnvironment environment = new QueueEnvironment(plugin, plugin::getConfiguration, onlineServers);
+    QueueEnvironment environment = new QueueEnvironment(plugin, plugin::getConfiguration,  () -> onlineServers);
     QueueServerSelector selector = new QueueServerSelector(environment);
     KickEventHandler handler = new KickEventHandler(config, environment, selector);
 
@@ -130,7 +130,7 @@ void setsCustomKickMessageWhenEnabledAndWillDisconnect() {
 
     QueueTestUtils.TestQueuePlugin plugin = new QueueTestUtils.TestQueuePlugin(config);
     Set<String> onlineServers = QueueTestUtils.onlineServers("queue", "target");
-    QueueEnvironment environment = new QueueEnvironment(plugin, plugin::getConfiguration, onlineServers);
+    QueueEnvironment environment = new QueueEnvironment(plugin, plugin::getConfiguration,  () -> onlineServers);
     QueueServerSelector selector = new QueueServerSelector(environment);
     KickEventHandler handler = new KickEventHandler(config, environment, selector);
 
@@ -151,7 +151,7 @@ void doesNotSetKickMessageWhenDisabled() {
 
     QueueTestUtils.TestQueuePlugin plugin = new QueueTestUtils.TestQueuePlugin(config);
     Set<String> onlineServers = QueueTestUtils.onlineServers("queue", "target");
-    QueueEnvironment environment = new QueueEnvironment(plugin, plugin::getConfiguration, onlineServers);
+    QueueEnvironment environment = new QueueEnvironment(plugin, plugin::getConfiguration,  () -> onlineServers);
     QueueServerSelector selector = new QueueServerSelector(environment);
     KickEventHandler handler = new KickEventHandler(config, environment, selector);
 
@@ -172,7 +172,7 @@ void doesNotSetKickMessageWhenNotDisconnecting() {
 
     QueueTestUtils.TestQueuePlugin plugin = new QueueTestUtils.TestQueuePlugin(config);
     Set<String> onlineServers = QueueTestUtils.onlineServers("queue", "target");
-    QueueEnvironment environment = new QueueEnvironment(plugin, plugin::getConfiguration, onlineServers);
+    QueueEnvironment environment = new QueueEnvironment(plugin, plugin::getConfiguration,  () -> onlineServers);
     QueueServerSelector selector = new QueueServerSelector(environment);
     KickEventHandler handler = new KickEventHandler(config, environment, selector);
 
@@ -194,7 +194,7 @@ void handlesKickWithoutReason() {
 
     QueueTestUtils.TestQueuePlugin plugin = new QueueTestUtils.TestQueuePlugin(config);
     Set<String> onlineServers = QueueTestUtils.onlineServers("queue", "target");
-    QueueEnvironment environment = new QueueEnvironment(plugin, plugin::getConfiguration, onlineServers);
+    QueueEnvironment environment = new QueueEnvironment(plugin, plugin::getConfiguration,  () -> onlineServers);
     QueueServerSelector selector = new QueueServerSelector(environment);
     KickEventHandler handler = new KickEventHandler(config, environment, selector);
 
@@ -217,7 +217,7 @@ void caseInsensitiveKickReasonMatching() {
     QueueTestUtils.TestQueuePlugin plugin = new QueueTestUtils.TestQueuePlugin(config);
     QueueGroup group = QueueTestUtils.defaultGroup(config);
     Set<String> onlineServers = QueueTestUtils.onlineServers("queue", "target");
-    QueueEnvironment environment = new QueueEnvironment(plugin, plugin::getConfiguration, onlineServers);
+    QueueEnvironment environment = new QueueEnvironment(plugin, plugin::getConfiguration,  () -> onlineServers);
     QueueServerSelector selector = new QueueServerSelector(environment);
     KickEventHandler handler = new KickEventHandler(config, environment, selector);
 

shared/src/test/java/net/pistonmaster/pistonqueue/shared/queue/logic/QueueCleanerTest.java

@@ -37,7 +37,7 @@ void removesStaleEntriesWhenPlayerDisconnected() {
     QueueTestUtils.TestQueuePlugin plugin = new QueueTestUtils.TestQueuePlugin(config);
     QueueGroup group = QueueTestUtils.defaultGroup(config);
     Set<String> onlineServers = QueueTestUtils.onlineServers(group.queueServers().toArray(String[]::new));
-    QueueEnvironment environment = new QueueEnvironment(plugin, plugin::getConfiguration, onlineServers);
+    QueueEnvironment environment = new QueueEnvironment(plugin, plugin::getConfiguration,  () -> onlineServers);
     QueueCleaner cleaner = new QueueCleaner(environment);
 
     QueueType type = QueueTestUtils.defaultQueueType(config);
@@ -56,7 +56,7 @@ void keepsActiveQueueEntries() {
     QueueTestUtils.TestQueuePlugin plugin = new QueueTestUtils.TestQueuePlugin(config);
     QueueGroup group = QueueTestUtils.defaultGroup(config);
     Set<String> onlineServers = QueueTestUtils.onlineServers(group.queueServers().toArray(String[]::new));
-    QueueEnvironment environment = new QueueEnvironment(plugin, plugin::getConfiguration, onlineServers);
+    QueueEnvironment environment = new QueueEnvironment(plugin, plugin::getConfiguration,  () -> onlineServers);
     QueueCleaner cleaner = new QueueCleaner(environment);
 
     QueueType type = QueueTestUtils.defaultQueueType(config);
@@ -76,7 +76,7 @@ void handlesEmptyQueue() {
     QueueTestUtils.TestQueuePlugin plugin = new QueueTestUtils.TestQueuePlugin(config);
     QueueGroup group = QueueTestUtils.defaultGroup(config);
     Set<String> onlineServers = QueueTestUtils.onlineServers(group.queueServers().toArray(String[]::new));
-    QueueEnvironment environment = new QueueEnvironment(plugin, plugin::getConfiguration, onlineServers);
+    QueueEnvironment environment = new QueueEnvironment(plugin, plugin::getConfiguration,  () -> onlineServers);
     QueueCleaner cleaner = new QueueCleaner(environment);
 
     cleaner.cleanGroup(group);
@@ -90,7 +90,7 @@ void removesMultipleStaleEntries() {
     QueueTestUtils.TestQueuePlugin plugin = new QueueTestUtils.TestQueuePlugin(config);
     QueueGroup group = QueueTestUtils.defaultGroup(config);
     Set<String> onlineServers = QueueTestUtils.onlineServers(group.queueServers().toArray(String[]::new));
-    QueueEnvironment environment = new QueueEnvironment(plugin, plugin::getConfiguration, onlineServers);
+    QueueEnvironment environment = new QueueEnvironment(plugin, plugin::getConfiguration,  () -> onlineServers);
     QueueCleaner cleaner = new QueueCleaner(environment);
 
     QueueType type = QueueTestUtils.defaultQueueType(config);