From c1ff9135ee6e9013863f7d64102870cab27da2d5 Mon Sep 17 00:00:00 2001
From: cdfive <31885791+cdfive@users.noreply.github.com>
Date: Fri, 21 Feb 2020 09:21:30 +0800
Subject: [PATCH] Fix NPE in Tracer when context size exceeds the limit (#1293)

---
 .../java/com/alibaba/csp/sentinel/Tracer.java | 16 +++------
 .../alibaba/csp/sentinel/context/Context.java |  2 +-
 .../com/alibaba/csp/sentinel/TracerTest.java  | 34 +++++++++++++++++++
 3 files changed, 39 insertions(+), 13 deletions(-)

diff --git a/sentinel-core/src/main/java/com/alibaba/csp/sentinel/Tracer.java b/sentinel-core/src/main/java/com/alibaba/csp/sentinel/Tracer.java
index 08df6b2c..4d0e6da3 100755
--- a/sentinel-core/src/main/java/com/alibaba/csp/sentinel/Tracer.java
+++ b/sentinel-core/src/main/java/com/alibaba/csp/sentinel/Tracer.java
@@ -17,6 +17,7 @@ package com.alibaba.csp.sentinel;
 
 import com.alibaba.csp.sentinel.context.Context;
 import com.alibaba.csp.sentinel.context.ContextUtil;
+import com.alibaba.csp.sentinel.context.NullContext;
 import com.alibaba.csp.sentinel.metric.extension.MetricExtensionProvider;
 import com.alibaba.csp.sentinel.node.ClusterNode;
 import com.alibaba.csp.sentinel.node.DefaultNode;
@@ -53,17 +54,7 @@ public class Tracer {
      * @param count exception count to add
      */
     public static void trace(Throwable e, int count) {
-        if (!shouldTrace(e)) {
-            return;
-        }
-
-        Context context = ContextUtil.getContext();
-        if (context == null) {
-            return;
-        }
-
-        DefaultNode curNode = (DefaultNode)context.getCurNode();
-        traceExceptionToNode(e, count, context.getCurEntry(), curNode);
+        traceContext(e, count, ContextUtil.getContext());
     }
 
     /**
@@ -77,7 +68,8 @@ public class Tracer {
         if (!shouldTrace(e)) {
             return;
         }
-        if (context == null) {
+
+        if (context == null || context instanceof NullContext) {
             return;
         }
 
diff --git a/sentinel-core/src/main/java/com/alibaba/csp/sentinel/context/Context.java b/sentinel-core/src/main/java/com/alibaba/csp/sentinel/context/Context.java
index 0e857b72..54d5d497 100755
--- a/sentinel-core/src/main/java/com/alibaba/csp/sentinel/context/Context.java
+++ b/sentinel-core/src/main/java/com/alibaba/csp/sentinel/context/Context.java
@@ -109,7 +109,7 @@ public class Context {
     }
 
     public Node getCurNode() {
-        return curEntry.getCurNode();
+        return curEntry == null ? null : curEntry.getCurNode();
     }
 
     public Context setCurNode(Node node) {
diff --git a/sentinel-core/src/test/java/com/alibaba/csp/sentinel/TracerTest.java b/sentinel-core/src/test/java/com/alibaba/csp/sentinel/TracerTest.java
index 4b2352e1..2a0e21a6 100644
--- a/sentinel-core/src/test/java/com/alibaba/csp/sentinel/TracerTest.java
+++ b/sentinel-core/src/test/java/com/alibaba/csp/sentinel/TracerTest.java
@@ -1,6 +1,10 @@
 package com.alibaba.csp.sentinel;
 
+import com.alibaba.csp.sentinel.context.ContextTestUtil;
+import com.alibaba.csp.sentinel.context.ContextUtil;
+import org.junit.After;
 import org.junit.Assert;
+import org.junit.Before;
 import org.junit.Test;
 
 /**
@@ -8,6 +12,36 @@ import org.junit.Test;
  */
 public class TracerTest extends Tracer {
 
+    @Before
+    public void setUp() {
+        ContextTestUtil.cleanUpContext();
+        ContextTestUtil.resetContextMap();
+    }
+
+    @After
+    public void tearDown() {
+        ContextTestUtil.cleanUpContext();
+        ContextTestUtil.resetContextMap();
+    }
+
+    @Test
+    public void testTraceWhenContextSizeExceedsThreshold() {
+        int i = 0;
+        for (; i < Constants.MAX_CONTEXT_NAME_SIZE; i++) {
+            ContextUtil.enter("test-context-" + i);
+            ContextUtil.exit();
+        }
+
+        try {
+            ContextUtil.enter("test-context-" + i);
+            throw new RuntimeException("test");
+        } catch (Exception e) {
+            Tracer.trace(e);
+        } finally {
+            ContextUtil.exit();
+        }
+    }
+
     @Test
     public void setExceptionsToTrace() {
         Tracer.ignoreClasses = null;