Some bug fixes and enhancement for async entry support

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

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

@@ -16,6 +16,8 @@
 package com.alibaba.csp.sentinel;
 
 import com.alibaba.csp.sentinel.context.Context;
+import com.alibaba.csp.sentinel.context.NullContext;
+import com.alibaba.csp.sentinel.log.RecordLog;
 import com.alibaba.csp.sentinel.slotchain.ProcessorSlot;
 import com.alibaba.csp.sentinel.slotchain.ResourceWrapper;
 
@@ -37,6 +39,9 @@ public class AsyncEntry extends CtEntry {
      * Remove current entry from local context, but does not exit.
      */
     void cleanCurrentEntryInLocal() {
+        if (context instanceof NullContext) {
+            return;
+        }
         Context originalContext = context;
         if (originalContext != null) {
             Entry curEntry = originalContext.getCurEntry();
@@ -61,11 +66,15 @@ public Context getAsyncContext() {
      */
     void initAsyncContext() {
         if (asyncContext == null) {
+            if (context instanceof NullContext) {
+                asyncContext = context;
+                return;
+            }
             this.asyncContext = Context.newAsyncContext(context.getEntranceNode(), context.getName())
                 .setOrigin(context.getOrigin())
                 .setCurEntry(this);
         } else {
-            throw new IllegalStateException("Duplicate initialize of async context");
+            RecordLog.warn("[AsyncEntry] Duplicate initialize of async context for entry: " + resourceWrapper.getName());
         }
     }
 

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

@@ -53,42 +53,56 @@ public class CtSph implements Sph {
 
     private static final Object LOCK = new Object();
 
+    private AsyncEntry asyncEntryWithNoChain(ResourceWrapper resourceWrapper, Context context) {
+        AsyncEntry entry = new AsyncEntry(resourceWrapper, null, context);
+        entry.initAsyncContext();
+        // The async entry will be removed from current context as soon as it has been created.
+        entry.cleanCurrentEntryInLocal();
+        return entry;
+    }
+
     private AsyncEntry asyncEntryInternal(ResourceWrapper resourceWrapper, int count, Object... args) throws BlockException {
         Context context = ContextUtil.getContext();
         if (context instanceof NullContext) {
             // The {@link NullContext} indicates that the amount of context has exceeded the threshold,
             // so here init the entry only. No rule checking will be done.
-            return new AsyncEntry(resourceWrapper, null, context);
+            return asyncEntryWithNoChain(resourceWrapper, context);
         }
         if (context == null) {
+            // Using default context.
             context = MyContextUtil.myEnter(Constants.CONTEXT_DEFAULT_NAME, "", resourceWrapper.getType());
         }
 
         // Global switch is turned off, so no rule checking will be done.
         if (!Constants.ON) {
-            return new AsyncEntry(resourceWrapper, null, context);
+            return asyncEntryWithNoChain(resourceWrapper, context);
         }
 
         ProcessorSlot<Object> chain = lookProcessChain(resourceWrapper);
 
         // Means processor cache size exceeds {@link Constants.MAX_SLOT_CHAIN_SIZE}, so no rule checking will be done.
         if (chain == null) {
-            return new AsyncEntry(resourceWrapper, null, context);
+            return asyncEntryWithNoChain(resourceWrapper, context);
         }
 
         AsyncEntry asyncEntry = new AsyncEntry(resourceWrapper, chain, context);
         try {
             chain.entry(context, resourceWrapper, null, count, args);
-            // Initiate the async context.
+            // Initiate the async context only when the entry successfully passed the slot chain.
             asyncEntry.initAsyncContext();
+            // The asynchronous call may take time in background, and current context should not be hanged on it.
+            // So we need to remove current async entry from current context.
+            asyncEntry.cleanCurrentEntryInLocal();
         } catch (BlockException e1) {
-            asyncEntry.exit(count, args);
+            // When blocked, the async entry will be exited on current context.
+            // The async context will not be initialized.
+            asyncEntry.exitForContext(context, count, args);
             throw e1;
         } catch (Throwable e1) {
-            RecordLog.info("Sentinel unexpected exception", e1);
-        } finally {
-            // The asynchronous call may take time in background, and current context should not be hanged on it.
-            // So we need to remove current async entry from current context.
+            // This should not happen, unless there are errors existing in Sentinel internal.
+            // When this happens, async context is not initialized.
+            RecordLog.warn("Sentinel unexpected exception in asyncEntryInternal", e1);
+
             asyncEntry.cleanCurrentEntryInLocal();
         }
         return asyncEntry;
@@ -119,6 +133,7 @@ public Entry entry(ResourceWrapper resourceWrapper, int count, Object... args) t
         }
 
         if (context == null) {
+            // Using default context.
             context = MyContextUtil.myEnter(Constants.CONTEXT_DEFAULT_NAME, "", resourceWrapper.getType());
         }
 
@@ -130,8 +145,8 @@ public Entry entry(ResourceWrapper resourceWrapper, int count, Object... args) t
         ProcessorSlot<Object> chain = lookProcessChain(resourceWrapper);
 
         /*
-         * Means processor cache size exceeds {@link Constants.MAX_SLOT_CHAIN_SIZE}, so no
-         * rule checking will be done.
+         * Means amount of resources (slot chain) exceeds {@link Constants.MAX_SLOT_CHAIN_SIZE},
+         * so no rule checking will be done.
          */
         if (chain == null) {
             return new CtEntry(resourceWrapper, null, context);
@@ -165,7 +180,7 @@ public Entry entry(ResourceWrapper resourceWrapper, int count, Object... args) t
      * @param resourceWrapper target resource
      * @return {@link ProcessorSlotChain} of the resource
      */
-    private ProcessorSlot<Object> lookProcessChain(ResourceWrapper resourceWrapper) {
+    ProcessorSlot<Object> lookProcessChain(ResourceWrapper resourceWrapper) {
         ProcessorSlotChain chain = chainMap.get(resourceWrapper);
         if (chain == null) {
             synchronized (LOCK) {
@@ -188,6 +203,24 @@ private ProcessorSlot<Object> lookProcessChain(ResourceWrapper resourceWrapper)
         return chain;
     }
 
+    /**
+     * Reset the slot chain map. Only for internal test.
+     *
+     * @since 0.2.0
+     */
+    static void resetChainMap() {
+        chainMap.clear();
+    }
+
+    /**
+     * Only for internal test.
+     *
+     * @since 0.2.0
+     */
+    static Map<ResourceWrapper, ProcessorSlotChain> getChainMap() {
+        return chainMap;
+    }
+
     /**
      * This class is used for skip context name checking.
      */