Fixes #453: Support tracing exception count for specific entry or context in Tracer

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

sentinel-core/src/main/java/com/alibaba/csp/sentinel/Tracer.java

@@ -22,18 +22,30 @@ import com.alibaba.csp.sentinel.node.DefaultNode;
 import com.alibaba.csp.sentinel.slots.block.BlockException;
 
 /**
- * This class is used to record other exception except block exception.
+ * This class is used to record other exceptions except block exception.
  *
  * @author jialiang.linjl
+ * @author Eric Zhao
  */
 public final class Tracer {
 
+    /**
+     * Trace provided {@link Throwable} and increment exception count to entry in current context.
+     *
+     * @param e exception to record
+     */
     public static void trace(Throwable e) {
         trace(e, 1);
     }
 
+    /**
+     * Trace provided {@link Throwable} and add exception count to entry in current context.
+     *
+     * @param e     exception to record
+     * @param count exception count to add
+     */
     public static void trace(Throwable e, int count) {
-        if (e instanceof BlockException) {
+        if (e == null || e instanceof BlockException) {
             return;
         }
 
@@ -43,6 +55,58 @@ public final class Tracer {
         }
 
         DefaultNode curNode = (DefaultNode)context.getCurNode();
+        traceExceptionToNode(e, count, curNode);
+    }
+
+    /**
+     * Trace provided {@link Throwable} and add exception count to current entry in provided context.
+     *
+     * @param e     exception to record
+     * @param count exception count to add
+     * @since 1.4.2
+     */
+    public static void traceContext(Throwable e, int count, Context context) {
+        if (e == null || e instanceof BlockException) {
+            return;
+        }
+        if (context == null) {
+            return;
+        }
+
+        DefaultNode curNode = (DefaultNode)context.getCurNode();
+        traceExceptionToNode(e, count, curNode);
+    }
+
+    /**
+     * Trace provided {@link Throwable} and increment exception count to provided entry.
+     *
+     * @param e exception to record
+     * @since 1.4.2
+     */
+    public static void traceEntry(Throwable e, Entry entry) {
+        traceEntry(e, 1, entry);
+    }
+
+    /**
+     * Trace provided {@link Throwable} and add exception count to provided entry.
+     *
+     * @param e     exception to record
+     * @param count exception count to add
+     * @since 1.4.2
+     */
+    public static void traceEntry(Throwable e, int count, Entry entry) {
+        if (e == null || e instanceof BlockException) {
+            return;
+        }
+        if (entry == null || entry.getCurNode() == null) {
+            return;
+        }
+
+        DefaultNode curNode = (DefaultNode)entry.getCurNode();
+        traceExceptionToNode(e, count, curNode);
+    }
+
+    private static void traceExceptionToNode(Throwable t, int count, DefaultNode curNode) {
         if (curNode == null) {
             return;
         }
@@ -52,7 +116,8 @@ public final class Tracer {
         if (clusterNode == null) {
             return;
         }
-        clusterNode.trace(e, count);
+        clusterNode.trace(t, count);
     }
 
+    private Tracer() {}
 }