diff --git a/sentinel-core/src/main/java/com/alibaba/csp/sentinel/node/metric/MetricWriter.java b/sentinel-core/src/main/java/com/alibaba/csp/sentinel/node/metric/MetricWriter.java
index 836d27b8f5..7cd6f735e6 100755
--- a/sentinel-core/src/main/java/com/alibaba/csp/sentinel/node/metric/MetricWriter.java
+++ b/sentinel-core/src/main/java/com/alibaba/csp/sentinel/node/metric/MetricWriter.java
@@ -86,7 +86,7 @@ public MetricWriter(long singleFileSize, int totalFileCount) {
         if (singleFileSize <= 0 || totalFileCount <= 0) {
             throw new IllegalArgumentException();
         }
-        RecordLog.info("new MetricWriter, singleFileSize=" + singleFileSize + ", totalFileCount=" + totalFileCount);
+        RecordLog.info("[MetricWriter] Creating new MetricWriter, singleFileSize=" + singleFileSize + ", totalFileCount=" + totalFileCount);
         this.baseDir = METRIC_BASE_DIR;
         File dir = new File(baseDir);
         if (!dir.exists()) {
@@ -100,7 +100,7 @@ public MetricWriter(long singleFileSize, int totalFileCount) {
         try {
             this.timeSecondBase = df.parse("1970-01-01 00:00:00").getTime() / 1000;
         } catch (Exception e) {
-            RecordLog.info("new MetricWriter error: ", e);
+            RecordLog.warn("[MetricWriter] Create new MetricWriter error", e);
         }
     }
 
@@ -286,9 +286,9 @@ private void removeMoreFiles() throws Exception {
             String fileName = list.get(i);
             String indexFile = formIndexFileName(fileName);
             new File(fileName).delete();
-            RecordLog.info("remove metric file: " + fileName);
+            RecordLog.info("[MetricWriter] Removing metric file: " + fileName);
             new File(indexFile).delete();
-            RecordLog.info("remove metric index file: " + indexFile);
+            RecordLog.info("[MetricWriter] Removing metric index file: " + indexFile);
         }
     }
 
@@ -307,8 +307,8 @@ private void closeAndNewFile(String fileName) throws Exception {
         ;
         curMetricIndexFile = new File(idxFile);
         outIndex = new DataOutputStream(new BufferedOutputStream(new FileOutputStream(idxFile, append)));
-        RecordLog.info("create new metric file: " + fileName);
-        RecordLog.info("create new metric index file: " + idxFile);
+        RecordLog.info("[MetricWriter] New metric file created: " + fileName);
+        RecordLog.info("[MetricWriter] New metric index file created: " + idxFile);
     }
 
     private boolean validSize() throws Exception {
diff --git a/sentinel-core/src/main/java/com/alibaba/csp/sentinel/property/DynamicSentinelProperty.java b/sentinel-core/src/main/java/com/alibaba/csp/sentinel/property/DynamicSentinelProperty.java
index 3b2bc0cdb6..a72c3d0ccf 100755
--- a/sentinel-core/src/main/java/com/alibaba/csp/sentinel/property/DynamicSentinelProperty.java
+++ b/sentinel-core/src/main/java/com/alibaba/csp/sentinel/property/DynamicSentinelProperty.java
@@ -50,7 +50,7 @@ public void updateValue(T newValue) {
         if (isEqual(value, newValue)) {
             return;
         }
-        RecordLog.info("SentinelProperty, config is real updated to: " + newValue);
+        RecordLog.info("[DynamicSentinelProperty] Config will be updated to: " + newValue);
 
         value = newValue;
         for (PropertyListener<T> listener : listeners) {
diff --git a/sentinel-core/src/main/java/com/alibaba/csp/sentinel/slots/block/AbstractRule.java b/sentinel-core/src/main/java/com/alibaba/csp/sentinel/slots/block/AbstractRule.java
index ea7e7a3f1c..9e160623f9 100755
--- a/sentinel-core/src/main/java/com/alibaba/csp/sentinel/slots/block/AbstractRule.java
+++ b/sentinel-core/src/main/java/com/alibaba/csp/sentinel/slots/block/AbstractRule.java
@@ -17,13 +17,23 @@
 
 /***
  * @author youji.zj
+ * @author Eric Zhao
  */
 public abstract class AbstractRule implements Rule {
 
-    /*** 规则的资源描述 ***/
+    /**
+     * Resource name.
+     */
     private String resource;
 
-    /*** 被限制的应用,授权时候为逗号分隔的应用集合，限流时为单个应用 ***/
+    /**
+     * <p>
+     * Application name that will be limited by origin.
+     * Multiple application name can be separated with comma (',').
+     * </p>
+     * <p>The default limitApp is `default`, which means allowing all origin apps.</p>
+     * <p>For example: limitApp = `appA,appB` will limit requests from appA and appB.</p>
+     */
     private String limitApp;
 
     public String getResource() {
diff --git a/sentinel-core/src/main/java/com/alibaba/csp/sentinel/slots/block/RuleConstant.java b/sentinel-core/src/main/java/com/alibaba/csp/sentinel/slots/block/RuleConstant.java
index a9208177ba..4ff261103c 100755
--- a/sentinel-core/src/main/java/com/alibaba/csp/sentinel/slots/block/RuleConstant.java
+++ b/sentinel-core/src/main/java/com/alibaba/csp/sentinel/slots/block/RuleConstant.java
@@ -19,7 +19,7 @@
  * @author youji.zj
  * @author jialiang.linjl
  */
-public class RuleConstant {
+public final class RuleConstant {
 
     public static final int FLOW_GRADE_THREAD = 0;
     public static final int FLOW_GRADE_QPS = 1;
@@ -38,4 +38,8 @@ public class RuleConstant {
     public static final int CONTROL_BEHAVIOR_WARM_UP = 1;
     public static final int CONTROL_BEHAVIOR_RATE_LIMITER = 2;
 
+    public static final String LIMIT_APP_DEFAULT = "default";
+    public static final String LIMIT_APP_OTHER = "other";
+
+    private RuleConstant() {}
 }
diff --git a/sentinel-core/src/main/java/com/alibaba/csp/sentinel/slots/block/authority/AuthorityRuleManager.java b/sentinel-core/src/main/java/com/alibaba/csp/sentinel/slots/block/authority/AuthorityRuleManager.java
index 50faef4386..613bde57e1 100755
--- a/sentinel-core/src/main/java/com/alibaba/csp/sentinel/slots/block/authority/AuthorityRuleManager.java
+++ b/sentinel-core/src/main/java/com/alibaba/csp/sentinel/slots/block/authority/AuthorityRuleManager.java
@@ -21,11 +21,11 @@
 import java.util.concurrent.ConcurrentHashMap;
 
 import com.alibaba.csp.sentinel.log.RecordLog;
+import com.alibaba.csp.sentinel.slots.block.RuleConstant;
 import com.alibaba.csp.sentinel.util.StringUtil;
 import com.alibaba.csp.sentinel.property.DynamicSentinelProperty;
 import com.alibaba.csp.sentinel.property.PropertyListener;
 import com.alibaba.csp.sentinel.property.SentinelProperty;
-import com.alibaba.csp.sentinel.slots.block.flow.FlowRule;
 
 /**
  * Manager for authority rules.
@@ -115,7 +115,7 @@ private Map<String, List<AuthorityRule>> loadAuthorityConf(List<AuthorityRule> l
                 }
 
                 if (StringUtil.isBlank(rule.getLimitApp())) {
-                    rule.setLimitApp(FlowRule.LIMIT_APP_DEFAULT);
+                    rule.setLimitApp(RuleConstant.LIMIT_APP_DEFAULT);
                 }
 
                 String identity = rule.getResource();
diff --git a/sentinel-core/src/main/java/com/alibaba/csp/sentinel/slots/block/degrade/DegradeRuleManager.java b/sentinel-core/src/main/java/com/alibaba/csp/sentinel/slots/block/degrade/DegradeRuleManager.java
index ec48942c26..7a79f66c90 100755
--- a/sentinel-core/src/main/java/com/alibaba/csp/sentinel/slots/block/degrade/DegradeRuleManager.java
+++ b/sentinel-core/src/main/java/com/alibaba/csp/sentinel/slots/block/degrade/DegradeRuleManager.java
@@ -28,7 +28,7 @@
 import com.alibaba.csp.sentinel.property.SentinelProperty;
 import com.alibaba.csp.sentinel.slotchain.ResourceWrapper;
 import com.alibaba.csp.sentinel.slots.block.BlockException;
-import com.alibaba.csp.sentinel.slots.block.flow.FlowRule;
+import com.alibaba.csp.sentinel.slots.block.RuleConstant;
 import com.alibaba.csp.sentinel.util.StringUtil;
 
 /***
@@ -150,7 +150,7 @@ private Map<String, List<DegradeRule>> loadDegradeConf(List<DegradeRule> list) {
                 }
 
                 if (StringUtil.isBlank(rule.getLimitApp())) {
-                    rule.setLimitApp(FlowRule.LIMIT_APP_DEFAULT);
+                    rule.setLimitApp(RuleConstant.LIMIT_APP_DEFAULT);
                 }
 
                 String identity = rule.getResource();
diff --git a/sentinel-core/src/main/java/com/alibaba/csp/sentinel/slots/block/flow/FlowRule.java b/sentinel-core/src/main/java/com/alibaba/csp/sentinel/slots/block/flow/FlowRule.java
index e63f459ab5..5ed7cf15ce 100755
--- a/sentinel-core/src/main/java/com/alibaba/csp/sentinel/slots/block/flow/FlowRule.java
+++ b/sentinel-core/src/main/java/com/alibaba/csp/sentinel/slots/block/flow/FlowRule.java
@@ -40,12 +40,9 @@
  */
 public class FlowRule extends AbstractRule {
 
-    public static final String LIMIT_APP_DEFAULT = "default";
-    public static final String LIMIT_APP_OTHER = "other";
-
     public FlowRule(){
         super();
-        setLimitApp(LIMIT_APP_DEFAULT);
+        setLimitApp(RuleConstant.LIMIT_APP_DEFAULT);
     }
 
     /**
@@ -196,7 +193,7 @@ private Node selectNodeByRequesterAndStrategy(String origin, Context context, De
                 return node;
             }
 
-        } else if (LIMIT_APP_DEFAULT.equals(limitApp)) {
+        } else if (RuleConstant.LIMIT_APP_DEFAULT.equals(limitApp)) {
             if (strategy == RuleConstant.STRATEGY_DIRECT) {
                 return node.getClusterNode();
             }
@@ -216,7 +213,7 @@ private Node selectNodeByRequesterAndStrategy(String origin, Context context, De
                 return node;
             }
 
-        } else if (LIMIT_APP_OTHER.equals(limitApp) && FlowRuleManager.isOtherOrigin(origin, getResource())) {
+        } else if (RuleConstant.LIMIT_APP_OTHER.equals(limitApp) && FlowRuleManager.isOtherOrigin(origin, getResource())) {
             if (strategy == RuleConstant.STRATEGY_DIRECT) {
                 return context.getOriginNode();
             }
diff --git a/sentinel-core/src/main/java/com/alibaba/csp/sentinel/slots/block/flow/FlowRuleComparator.java b/sentinel-core/src/main/java/com/alibaba/csp/sentinel/slots/block/flow/FlowRuleComparator.java
index b5d091c141..688bed9692 100755
--- a/sentinel-core/src/main/java/com/alibaba/csp/sentinel/slots/block/flow/FlowRuleComparator.java
+++ b/sentinel-core/src/main/java/com/alibaba/csp/sentinel/slots/block/flow/FlowRuleComparator.java
@@ -17,6 +17,8 @@
 
 import java.util.Comparator;
 
+import com.alibaba.csp.sentinel.slots.block.RuleConstant;
+
 public class FlowRuleComparator implements Comparator<FlowRule> {
 
     @Override
@@ -30,9 +32,9 @@ public int compare(FlowRule o1, FlowRule o2) {
             return 0;
         }
 
-        if (FlowRule.LIMIT_APP_DEFAULT.equals(o1.getLimitApp())) {
+        if (RuleConstant.LIMIT_APP_DEFAULT.equals(o1.getLimitApp())) {
             return 1;
-        } else if (FlowRule.LIMIT_APP_DEFAULT.equals(o2.getLimitApp())) {
+        } else if (RuleConstant.LIMIT_APP_DEFAULT.equals(o2.getLimitApp())) {
             return -1;
         } else {
             return 0;
diff --git a/sentinel-core/src/main/java/com/alibaba/csp/sentinel/slots/block/flow/FlowRuleManager.java b/sentinel-core/src/main/java/com/alibaba/csp/sentinel/slots/block/flow/FlowRuleManager.java
index 3f719e6c23..68295fc14f 100755
--- a/sentinel-core/src/main/java/com/alibaba/csp/sentinel/slots/block/flow/FlowRuleManager.java
+++ b/sentinel-core/src/main/java/com/alibaba/csp/sentinel/slots/block/flow/FlowRuleManager.java
@@ -114,7 +114,7 @@ private static Map<String, List<FlowRule>> loadFlowConf(List<FlowRule> list) {
                 continue;
             }
             if (StringUtil.isBlank(rule.getLimitApp())) {
-                rule.setLimitApp(FlowRule.LIMIT_APP_DEFAULT);
+                rule.setLimitApp(RuleConstant.LIMIT_APP_DEFAULT);
             }
 
             Controller rater = new DefaultController(rule.getCount(), rule.getGrade());
diff --git a/sentinel-core/src/main/java/com/alibaba/csp/sentinel/slots/system/SystemRuleManager.java b/sentinel-core/src/main/java/com/alibaba/csp/sentinel/slots/system/SystemRuleManager.java
index d5a8ccc7d9..f25155a100 100755
--- a/sentinel-core/src/main/java/com/alibaba/csp/sentinel/slots/system/SystemRuleManager.java
+++ b/sentinel-core/src/main/java/com/alibaba/csp/sentinel/slots/system/SystemRuleManager.java
@@ -77,7 +77,7 @@ public class SystemRuleManager {
     private static volatile boolean maxRtIsSet = false;
     private static volatile boolean maxThreadIsSet = false;
 
-    static AtomicBoolean checkSystemStatus = new AtomicBoolean(false);
+    private static AtomicBoolean checkSystemStatus = new AtomicBoolean(false);
 
     private static SystemStatusListener statusListener = null;
     private final static SystemPropertyListener listener = new SystemPropertyListener();
@@ -185,11 +185,9 @@ public void configUpdate(List<SystemRule> rules) {
                 checkSystemStatus.set(false);
             }
 
-            RecordLog.info("current system system status : " + checkSystemStatus.get());
-            RecordLog.info("current highestSystemLoad status : " + highestSystemLoad);
-            RecordLog.info("current maxRt : " + maxRt);
-            RecordLog.info("current maxThread : " + maxThread);
-            RecordLog.info("current qps : " + qps);
+
+            RecordLog.info(String.format("[SystemRuleManager] Current system check status: %s, highestSystemLoad: "
+                + highestSystemLoad + ", " + "maxRt: %d, maxThread: %d, maxQps: " + qps, checkSystemStatus.get(), maxRt, maxThread));
         }
 
         protected void restoreSetting() {
@@ -222,9 +220,8 @@ public static void setHighestSystemLoad(double highestSystemLoad) {
     }
 
     public static void loadSystemConf(SystemRule rule) {
-
         boolean checkStatus = false;
-        // 首先判断是否有效
+        // Check if it's valid.
 
         if (rule.getHighestSystemLoad() >= 0) {
             highestSystemLoad = Math.min(highestSystemLoad, rule.getHighestSystemLoad());
@@ -260,9 +257,8 @@ public static void loadSystemConf(SystemRule rule) {
      * @throws BlockException when any system rule's threshold is exceeded.
      */
     public static void checkSystem(ResourceWrapper resourceWrapper) throws BlockException {
-
-        // 确定开关开了
-        if (checkSystemStatus.get() == false) {
+        // Ensure the checking switch is on.
+        if (!checkSystemStatus.get()) {
             return;
         }
 
@@ -288,7 +284,7 @@ public static void checkSystem(ResourceWrapper resourceWrapper) throws BlockExce
             throw new SystemBlockException(resourceWrapper.getName(), "rt");
         }
 
-        // 完全按照RT,BBR算法来
+        // BBR algorithm.
         if (highestSystemLoadIsSet && getCurrentSystemAvgLoad() > highestSystemLoad) {
             if (currentThread > 1 &&
                 currentThread > Constants.ENTRY_NODE.maxSuccessQps() * Constants.ENTRY_NODE.minRt() / 1000) {
@@ -301,5 +297,4 @@ public static void checkSystem(ResourceWrapper resourceWrapper) throws BlockExce
     public static double getCurrentSystemAvgLoad() {
         return statusListener.getSystemAverageLoad();
     }
-
 }
diff --git a/sentinel-core/src/main/java/com/alibaba/csp/sentinel/util/AppNameUtil.java b/sentinel-core/src/main/java/com/alibaba/csp/sentinel/util/AppNameUtil.java
index 7a182bae5f..0cde3e85d2 100755
--- a/sentinel-core/src/main/java/com/alibaba/csp/sentinel/util/AppNameUtil.java
+++ b/sentinel-core/src/main/java/com/alibaba/csp/sentinel/util/AppNameUtil.java
@@ -57,7 +57,7 @@ private AppNameUtil() {
 
     static {
         resolveAppName();
-        RecordLog.info("app name resolved: " + appName);
+        RecordLog.info("App name resolved: " + appName);
     }
 
     public static void resolveAppName() {
diff --git a/sentinel-extension/sentinel-parameter-flow-control/src/main/java/com/alibaba/csp/sentinel/slots/block/flow/param/ParamFlowRuleManager.java b/sentinel-extension/sentinel-parameter-flow-control/src/main/java/com/alibaba/csp/sentinel/slots/block/flow/param/ParamFlowRuleManager.java
index 4700ddd70f..b10b260a7b 100644
--- a/sentinel-extension/sentinel-parameter-flow-control/src/main/java/com/alibaba/csp/sentinel/slots/block/flow/param/ParamFlowRuleManager.java
+++ b/sentinel-extension/sentinel-parameter-flow-control/src/main/java/com/alibaba/csp/sentinel/slots/block/flow/param/ParamFlowRuleManager.java
@@ -26,7 +26,7 @@
 import com.alibaba.csp.sentinel.property.DynamicSentinelProperty;
 import com.alibaba.csp.sentinel.property.PropertyListener;
 import com.alibaba.csp.sentinel.property.SentinelProperty;
-import com.alibaba.csp.sentinel.slots.block.flow.FlowRule;
+import com.alibaba.csp.sentinel.slots.block.RuleConstant;
 import com.alibaba.csp.sentinel.util.StringUtil;
 
 /**
@@ -169,7 +169,7 @@ private Map<String, List<ParamFlowRule>> aggregateHotParamRules(List<ParamFlowRu
                 }
 
                 if (StringUtil.isBlank(rule.getLimitApp())) {
-                    rule.setLimitApp(FlowRule.LIMIT_APP_DEFAULT);
+                    rule.setLimitApp(RuleConstant.LIMIT_APP_DEFAULT);
                 }
 
                 if (rule.getParamFlowItemList() == null) {