Add LogTest to show bad log behavior

common/src/test/java/io/druid/common/utils/LogTest.java

@@ -0,0 +1,67 @@
+/*
+ * Licensed to Metamarkets Group Inc. (Metamarkets) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  Metamarkets 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 io.druid.common.utils;
+
+import com.metamx.common.ISE;
+import com.metamx.common.logger.Logger;
+import org.junit.Ignore;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.ExpectedException;
+
+// The issue here is that parameters to the logging system are evaluated eagerly
+// So CPU or resource heavy clauses in the log parameters get evaluated even if there is no debug logging
+public class LogTest
+{
+  private static final Logger LOG = new Logger(LogTest.class);
+  @Rule
+  public ExpectedException expectedException = ExpectedException.none();
+
+  @Test
+  public void testGoodLog()
+  {
+    final ExpensiveClass expensiveClass = new ExpensiveClass();
+    if (LOG.isDebugEnabled()) {
+      expectedException.expect(ISE.class);
+    }
+    if (LOG.isDebugEnabled()) {
+      LOG.debug("Some error %s", expensiveClass.expensiveMethod());
+    }
+  }
+
+  @Test
+  @Ignore
+  public void testBadLog()
+  {
+    final ExpensiveClass expensiveClass = new ExpensiveClass();
+    if (LOG.isDebugEnabled()) {
+      expectedException.expect(ISE.class);
+    }
+    LOG.debug("Some error %s", expensiveClass.expensiveMethod());
+  }
+}
+
+class ExpensiveClass
+{
+  String expensiveMethod()
+  {
+    throw new ISE("Hogged up too much CPU time");
+  }
+}