ReactiveCouchbaseTemplate can overwrite PseudoArgs. (#1685)

* ReactiveCouchbaseTemplate can overwrite PseudoArgs under heavy concurrency.

Raised as issue #1684

* Added author

Author: SkyAndyToone

src/main/java/org/springframework/data/couchbase/core/ReactiveCouchbaseTemplate.java

@@ -37,6 +37,7 @@
  * @author Michael Reiche
  * @author Jorge Rodriguez Martin
  * @author Carlos Espinaco
+ * @author Andy Toone
  */
 public class ReactiveCouchbaseTemplate implements ReactiveCouchbaseOperations, ApplicationContextAware {
 
@@ -186,7 +187,14 @@ public PseudoArgs<?> getPseudoArgs() {
 	 * set the ThreadLocal field
 	 */
 	public void setPseudoArgs(PseudoArgs<?> threadLocalArgs) {
-		this.threadLocalArgs = new ThreadLocal<>();
+		if (this.threadLocalArgs == null) {
+			synchronized (this) {
+				if (this.threadLocalArgs == null) {
+					this.threadLocalArgs = new ThreadLocal<>();
+				}
+			}
+		}
+
 		this.threadLocalArgs.set(threadLocalArgs);
 	}
 

src/test/java/org/springframework/data/couchbase/core/ReactiveCouchbaseTemplateConcurrencyTests.java

@@ -0,0 +1,63 @@
+package org.springframework.data.couchbase.core;
+
+import java.util.concurrent.Semaphore;
+import org.springframework.data.couchbase.core.support.PseudoArgs;
+import org.springframework.data.couchbase.domain.Config;
+import org.springframework.data.couchbase.util.ClusterType;
+import org.springframework.data.couchbase.util.IgnoreWhen;
+
+import org.junit.jupiter.api.Test;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.springframework.beans.factory.annotation.Autowired;
+
+import org.springframework.test.context.junit.jupiter.SpringJUnitConfig;
+
+@IgnoreWhen(clusterTypes = ClusterType.MOCKED)
+@SpringJUnitConfig(Config.class)
+public class ReactiveCouchbaseTemplateConcurrencyTests {
+
+    @Autowired public CouchbaseTemplate couchbaseTemplate;
+
+    @Autowired public ReactiveCouchbaseTemplate reactiveCouchbaseTemplate;
+
+    @Test
+    public void shouldStoreArgsForLocalThread() throws InterruptedException {
+        // These will consume any args set on the current thread
+        PseudoArgs<?> args1 = new PseudoArgs<>(reactiveCouchbaseTemplate, "aScope", "aCollection", null, Object.class);
+        PseudoArgs<?> args2 = new PseudoArgs<>(reactiveCouchbaseTemplate, "aScope", "aCollection", null, Object.class);
+
+        // Store args1 on this thread
+        reactiveCouchbaseTemplate.setPseudoArgs(args1);
+
+        final PseudoArgs<?>[] threadArgs = {null};
+
+        Semaphore awaitingArgs1 = new Semaphore(0);
+        Semaphore checkingArgs2 = new Semaphore(0);
+
+        Thread t = new Thread(() -> {
+            // Store args2 on separate thread
+            reactiveCouchbaseTemplate.setPseudoArgs(args2);
+            awaitingArgs1.release();
+            try {
+                // Wait to check args2
+                checkingArgs2.acquire();
+            } catch (InterruptedException e) {
+                throw new RuntimeException(e);
+            }
+            threadArgs[0] = reactiveCouchbaseTemplate.getPseudoArgs();
+        });
+        t.start();
+
+        // Wait for separate thread to have set args2
+        awaitingArgs1.acquire();
+
+        assertEquals(args1, reactiveCouchbaseTemplate.getPseudoArgs());
+        checkingArgs2.release();
+        t.join();
+
+        assertEquals(args2, threadArgs[0]);
+
+    }
+
+}