diff --git a/htrace-core/src/main/java/org/apache/htrace/TraceScope.java b/htrace-core/src/main/java/org/apache/htrace/TraceScope.java index 3546e69..943c83e 100644 --- a/htrace-core/src/main/java/org/apache/htrace/TraceScope.java +++ b/htrace-core/src/main/java/org/apache/htrace/TraceScope.java @@ -53,6 +53,9 @@ public class TraceScope implements Closeable { * @return the same Span object */ public Span detach() { + if (span == null) { + return null; + } if (detached) { Tracer.clientError("Tried to detach trace span " + span + " but " + "it has already been detached."); diff --git a/htrace-core/src/test/java/org/apache/htrace/TestNullScope.java b/htrace-core/src/test/java/org/apache/htrace/TestNullScope.java new file mode 100644 index 0000000..26b1cba --- /dev/null +++ b/htrace-core/src/test/java/org/apache/htrace/TestNullScope.java @@ -0,0 +1,37 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You under the Apache License, Version 2.0 + * (the "License"); you may not use this file except in compliance with + * the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ +package org.apache.htrace; + +import org.apache.htrace.Trace; +import org.apache.htrace.TraceScope; +import org.apache.htrace.NullScope; +import org.junit.Assert; +import org.junit.Test; + +public class TestNullScope { + @Test + public void testNullScope() { + Assert.assertTrue(!Trace.isTracing()); + TraceScope tc = Trace.startSpan("NullScopeSingleton"); + Assert.assertTrue(tc == NullScope.INSTANCE); + tc.detach(); + tc.detach(); // should not fail even if called multiple times. + Assert.assertFalse(tc.isDetached()); + tc.close(); + tc.close(); // should not fail even if called multiple times. + } +}