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+/*
+ * =========================================================================================
+ * Copyright © 2013-2015 the kamon project <http://kamon.io/>
+ *
+ * Licensed 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 kamon.annotation;
+
+import java.lang.annotation.*;
+
+/**
+ * A marker annotation to start a new Trace.
+ * <p>
+ * <p>
+ * Given a method like this:
+ * <pre><code>
+ * {@literal @}Trace("coolTraceName", tags="${'my-cool-tag':'my-cool-value'}")
+ * public String coolName(String name) {
+ * return "Hello " + name;
+ * }
+ * </code></pre>
+ * <p>
+ * <p>
+ * A new Trace will be created for the defining method with the name each time the
+ * {@code #coolName(String)} method is invoked.
+ */
+
+@Documented
+@Target(ElementType.METHOD)
+@Retention(RetentionPolicy.RUNTIME)
+public @interface Trace {
+ /**
+ * @return The Trace's name.
+ * <p>
+ * Also, the Trace name can be resolved with an EL expression that evaluates to a String:
+ * <p>
+ * <pre>
+ * {@code
+ * class Traced {
+ * private long id;
+ *
+ * public long getId() { return id; }
+ *
+ * {@literal @}Trace (name = "${'traceID:' += this.id}")
+ * void countedMethod() {} // create a Trace with name => traceID:[id]
+ * }
+ * }
+ * </pre>
+ */
+ String value();
+
+ /**
+ * Tags are a way of adding dimensions to metrics,
+ * these are constructed using EL syntax e.g. "${'algorithm':'1','env':'production'}"
+ *
+ * @return the tags associated to the trace
+ */
+ String tags() default "";
+}