1 /*
   2  * Copyright (c) 2016, 2019, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package jdk.jfr;
  27 
  28 import java.lang.annotation.ElementType;
  29 import java.lang.annotation.Inherited;
  30 import java.lang.annotation.Retention;
  31 import java.lang.annotation.RetentionPolicy;
  32 import java.lang.annotation.Target;
  33 
  34 /**
  35  * Event annotation, specifies the default setting value for a periodic event.
  36  *
  37  * @since 9
  38  */
  39 @MetadataDefinition
  40 @Retention(RetentionPolicy.RUNTIME)
  41 @Inherited
  42 @Target(ElementType.TYPE)
  43 public @interface Period {
  44     /**
  45      * Settings name {@code "period"} for configuring periodic events
  46      */
  47     public final static String NAME = "period";
  48 
  49     /**
  50      * Returns the default setting value for a periodic setting.
  51      * <p>
  52      * String representation of a positive {@code Long} value followed by an empty
  53      * space and one of the following units:<br>
  54      * <br>
  55      * {@code "ns"} (nanoseconds)<br>
  56      * {@code "us"} (microseconds)<br>
  57      * {@code "ms"} (milliseconds)<br>
  58      * {@code "s"} (seconds)<br>
  59      * {@code "m"} (minutes)<br>
  60      * {@code "h"} (hours)<br>
  61      * {@code "d"} (days)<br>
  62      * <p>
  63      * Example values: {@code "0 ns"}, {@code "10 ms"}, and {@code "1 s"}.
  64      * <p>
  65      * A period may also bes <code>"everyChunk"</code> to specify that it occurs at
  66      * least once for every recording file. The number of events that are emitted
  67      * depends on how many times the file rotations occur when data is recorded.
  68      *
  69      * @return the default setting value, not {@code null}
  70      */
  71     String value() default "everyChunk";
  72 }