Enhance log and null check for rule managers

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

sentinel-core/src/main/java/com/alibaba/csp/sentinel/slots/block/degrade/DegradeRuleManager.java

@@ -56,6 +56,7 @@ public class DegradeRuleManager {
      */
     public static void register2Property(SentinelProperty<List<DegradeRule>> property) {
         synchronized (listener) {
+            RecordLog.info("[DegradeRuleManager] Registering new property to degrade rule manager");
             currentProperty.removeListener(listener);
             property.addListener(listener);
             currentProperty = property;
@@ -122,7 +123,7 @@ public class DegradeRuleManager {
                 degradeRules.clear();
                 degradeRules.putAll(rules);
             }
-            RecordLog.info("receive degrade config: " + degradeRules);
+            RecordLog.info("[DegradeRuleManager] Degrade rules received: " + degradeRules);
         }
 
         @Override
@@ -132,16 +133,22 @@ public class DegradeRuleManager {
                 degradeRules.clear();
                 degradeRules.putAll(rules);
             }
-            RecordLog.info("init degrade config: " + degradeRules);
+            RecordLog.info("[DegradeRuleManager] Degrade rules loaded: " + degradeRules);
         }
 
         private Map<String, List<DegradeRule>> loadDegradeConf(List<DegradeRule> list) {
-            if (list == null) {
-                return null;
-            }
             Map<String, List<DegradeRule>> newRuleMap = new ConcurrentHashMap<String, List<DegradeRule>>();
 
+            if (list == null || list.isEmpty()) {
+                return newRuleMap;
+            }
+
             for (DegradeRule rule : list) {
+                if (!isValidRule(rule)) {
+                    RecordLog.warn("[DegradeRuleManager] Ignoring invalid degrade rule when loading new rules: " + rule);
+                    continue;
+                }
+
                 if (StringUtil.isBlank(rule.getLimitApp())) {
                     rule.setLimitApp(FlowRule.LIMIT_APP_DEFAULT);
                 }
@@ -160,4 +167,7 @@ public class DegradeRuleManager {
 
     }
 
+    private static boolean isValidRule(DegradeRule rule) {
+        return rule != null && !StringUtil.isBlank(rule.getResource()) && rule.getCount() >= 0;
+    }
 }

sentinel-core/src/main/java/com/alibaba/csp/sentinel/slots/block/flow/FlowRuleManager.java

@@ -51,7 +51,6 @@ import com.alibaba.csp.sentinel.slots.block.flow.controller.WarmUpController;
  *
  * @author jialiang.linjl
  */
-
 public class FlowRuleManager {
 
     private static final Map<String, List<FlowRule>> flowRules = new ConcurrentHashMap<String, List<FlowRule>>();
@@ -105,12 +104,13 @@ public class FlowRuleManager {
     private static Map<String, List<FlowRule>> loadFlowConf(List<FlowRule> list) {
         Map<String, List<FlowRule>> newRuleMap = new ConcurrentHashMap<String, List<FlowRule>>();
 
-        if (list == null) {
+        if (list == null || list.isEmpty()) {
             return newRuleMap;
         }
 
         for (FlowRule rule : list) {
-            if (!isValid(rule)) {
+            if (!isValidRule(rule)) {
+                RecordLog.warn("[FlowRuleManager] Ignoring invalid flow rule when loading new flow rules: " + rule);
                 continue;
             }
             if (StringUtil.isBlank(rule.getLimitApp())) {
@@ -202,7 +202,7 @@ public class FlowRuleManager {
 
     }
 
-    private static boolean isValid(FlowRule rule) {
+    private static boolean isValidRule(FlowRule rule) {
         return rule != null && !StringUtil.isBlank(rule.getResource());
     }
 }