From 1ae04cf2bb1d4a2defc91633c7a453e02a0f8fea Mon Sep 17 00:00:00 2001
From: qxo <49526356@qq.com>
Date: Tue, 6 Aug 2019 08:30:29 +0800
Subject: [PATCH] improve AsyncSpan API: make #asyncFinish and #prepareForAsync
 can not invoke more than once (#3201)

* improve AsyncSpan API: make #asyncFinish and #prepareForAsync can not invoke more than once
make the API more strong: make the plugin code bug fail-fast
---
 .../core/context/trace/AbstractTracingSpan.java | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/apm-sniffer/apm-agent-core/src/main/java/org/apache/skywalking/apm/agent/core/context/trace/AbstractTracingSpan.java b/apm-sniffer/apm-agent-core/src/main/java/org/apache/skywalking/apm/agent/core/context/trace/AbstractTracingSpan.java
index 4c14aa2b1..b5ece98f0 100644
--- a/apm-sniffer/apm-agent-core/src/main/java/org/apache/skywalking/apm/agent/core/context/trace/AbstractTracingSpan.java
+++ b/apm-sniffer/apm-agent-core/src/main/java/org/apache/skywalking/apm/agent/core/context/trace/AbstractTracingSpan.java
@@ -40,7 +40,14 @@ public abstract class AbstractTracingSpan implements AbstractSpan {
     protected String operationName;
     protected int operationId;
     protected SpanLayer layer;
-    protected boolean isInAsyncMode = false;
+    /**
+     * The span has been tagged in async mode, required async stop to finish.
+     */
+    protected volatile boolean isInAsyncMode = false;
+    /**
+     * The flag represents whether the span has been async stopped
+     */
+    private volatile boolean isAsyncStopped = false;
     protected volatile AbstractTracerContext context;
 
     /**
@@ -322,6 +329,9 @@ public abstract class AbstractTracingSpan implements AbstractSpan {
     }
 
     @Override public AbstractSpan prepareForAsync() {
+        if (isInAsyncMode) {
+            throw new RuntimeException("Prepare for async repeatedly. Span is already in async mode.");
+        }
         context = ContextManager.awaitFinishAsync(this);
         isInAsyncMode = true;
         return this;
@@ -331,9 +341,12 @@ public abstract class AbstractTracingSpan implements AbstractSpan {
         if (!isInAsyncMode) {
             throw new RuntimeException("Span is not in async mode, please use '#prepareForAsync' to active.");
         }
-
+        if (isAsyncStopped) {
+            throw new RuntimeException("Can not do async finish for the span repeately.");
+        }
         this.endTime = System.currentTimeMillis();
         context.asyncStop(this);
+        isAsyncStopped = true;
         return this;
     }
 }