Improve cluster state manager

- Support stop cluster mode (`NOT-STARTED` mode)
- Fix bug when updating cluster state via command API (should modify via state property)

Signed-off-by: Eric Zhao <sczyh16@gmail.com>

sentinel-core/src/main/java/com/alibaba/csp/sentinel/cluster/ClusterStateManager.java

@@ -27,7 +27,10 @@ import com.alibaba.csp.sentinel.property.SentinelProperty;
 import com.alibaba.csp.sentinel.util.TimeUtil;
 
 /**
- * <p>Global tate manager for Sentinel cluster. This enables switching between cluster client and server.</p>
+ * <p>
+ * Global state manager for Sentinel cluster.
+ * This enables switching between cluster token client and server mode.
+ * </p>
  *
  * @author Eric Zhao
  * @since 1.4.0
@@ -36,15 +39,14 @@ public final class ClusterStateManager {
 
     public static final int CLUSTER_CLIENT = 0;
     public static final int CLUSTER_SERVER = 1;
+    public static final int CLUSTER_NOT_STARTED = -1;
 
-    private static volatile int mode = -1;
+    private static volatile int mode = CLUSTER_NOT_STARTED;
     private static volatile long lastModified = -1;
 
     private static volatile SentinelProperty<Integer> stateProperty = new DynamicSentinelProperty<Integer>();
     private static final PropertyListener<Integer> PROPERTY_LISTENER = new ClusterStatePropertyListener();
 
-    private static final Object UPDATE_LOCK = new Object();
-
     static {
         InitExecutor.doInit();
         stateProperty.addListener(PROPERTY_LISTENER);
@@ -206,33 +208,61 @@ public final class ClusterStateManager {
     private static class ClusterStatePropertyListener implements PropertyListener<Integer> {
         @Override
         public synchronized void configLoad(Integer value) {
-            applyState(value);
+            applyStateInternal(value);
         }
 
         @Override
         public synchronized void configUpdate(Integer value) {
-            applyState(value);
+            applyStateInternal(value);
         }
     }
 
-    public static boolean applyState(Integer state) {
-        if (state == null || state < 0) {
+    private static boolean applyStateInternal(Integer state) {
+        if (state == null || state < CLUSTER_NOT_STARTED) {
             return false;
         }
         if (state == mode) {
             return true;
         }
-        synchronized (UPDATE_LOCK) {
-            switch (state) {
-                case CLUSTER_CLIENT:
-                    return setToClient();
-                case CLUSTER_SERVER:
-                    return setToServer();
-                default:
-                    RecordLog.warn("[ClusterStateManager] Ignoring unknown cluster state: " + state);
-                    return false;
-            }
+        switch (state) {
+            case CLUSTER_CLIENT:
+                return setToClient();
+            case CLUSTER_SERVER:
+                return setToServer();
+            case CLUSTER_NOT_STARTED:
+                setStop();
+                return true;
+            default:
+                RecordLog.warn("[ClusterStateManager] Ignoring unknown cluster state: " + state);
+                return false;
+        }
+    }
+
+    private static void setStop() {
+        if (mode == CLUSTER_NOT_STARTED) {
+            return;
         }
+        RecordLog.info("[ClusterStateManager] Changing cluster mode to not-started");
+        mode = CLUSTER_NOT_STARTED;
+
+        sleepIfNeeded();
+        lastModified = TimeUtil.currentTimeMillis();
+
+        stopClient();
+        stopServer();
+    }
+
+    /**
+     * Apply given state to cluster mode.
+     *
+     * @param state valid state to apply
+     */
+    public static void applyState(Integer state) {
+        stateProperty.updateValue(state);
+    }
+
+    public static void markToServer() {
+        mode = CLUSTER_SERVER;
     }
 
     private static final int MIN_INTERVAL = 5 * 1000;

sentinel-core/src/main/java/com/alibaba/csp/sentinel/cluster/client/TokenClientProvider.java

@@ -49,5 +49,9 @@ public final class TokenClientProvider {
         }
     }
 
+    public static boolean isClientSpiAvailable() {
+        return getClient() != null;
+    }
+
     private TokenClientProvider() {}
 }

sentinel-core/src/main/java/com/alibaba/csp/sentinel/cluster/server/EmbeddedClusterTokenServerProvider.java

@@ -44,5 +44,9 @@ public final class EmbeddedClusterTokenServerProvider {
         return server;
     }
 
+    public static boolean isServerSpiAvailable() {
+        return getServer() != null;
+    }
+
     private EmbeddedClusterTokenServerProvider() {}
 }

sentinel-transport/sentinel-transport-common/src/main/java/com/alibaba/csp/sentinel/command/handler/cluster/ModifyClusterModeCommandHandler.java

@@ -16,6 +16,8 @@
 package com.alibaba.csp.sentinel.command.handler.cluster;
 
 import com.alibaba.csp.sentinel.cluster.ClusterStateManager;
+import com.alibaba.csp.sentinel.cluster.client.TokenClientProvider;
+import com.alibaba.csp.sentinel.cluster.server.EmbeddedClusterTokenServerProvider;
 import com.alibaba.csp.sentinel.command.CommandHandler;
 import com.alibaba.csp.sentinel.command.CommandRequest;
 import com.alibaba.csp.sentinel.command.CommandResponse;
@@ -33,16 +35,24 @@ public class ModifyClusterModeCommandHandler implements CommandHandler<String> {
     public CommandResponse<String> handle(CommandRequest request) {
         try {
             int mode = Integer.valueOf(request.getParam("mode"));
-            RecordLog.info("[ModifyClusterModeCommandHandler] Modifying cluster mode to: " + mode);
-            if (ClusterStateManager.applyState(mode)) {
-                return CommandResponse.ofSuccess("success");
-            } else {
-                return CommandResponse.ofSuccess("failed");
+            if (mode == ClusterStateManager.CLUSTER_CLIENT && !TokenClientProvider.isClientSpiAvailable()) {
+                return CommandResponse.ofFailure(new IllegalStateException("token client mode not available: no SPI found"));
+            }
+            if (mode == ClusterStateManager.CLUSTER_SERVER && !isClusterServerSpiAvailable()) {
+                return CommandResponse.ofFailure(new IllegalStateException("token server mode not available: no SPI found"));
             }
+            RecordLog.info("[ModifyClusterModeCommandHandler] Modifying cluster mode to: " + mode);
+
+            ClusterStateManager.applyState(mode);
+            return CommandResponse.ofSuccess("success");
         } catch (NumberFormatException ex) {
-            return CommandResponse.ofFailure(new IllegalArgumentException("invalid mode"));
+            return CommandResponse.ofFailure(new IllegalArgumentException("invalid parameter"));
         } catch (Exception ex) {
             return CommandResponse.ofFailure(ex);
         }
     }
+
+    private boolean isClusterServerSpiAvailable() {
+        return EmbeddedClusterTokenServerProvider.isServerSpiAvailable();
+    }
 }