1 /**
2 * Licensed to the Apache Software Foundation (ASF) under one
3 * or more contributor license agreements. See the NOTICE file
4 * distributed with this work for additional information
5 * regarding copyright ownership. The ASF licenses this file
6 * to you under the Apache License, Version 2.0 (the
7 * "License"); you may not use this file except in compliance
8 * with the License. You may obtain a copy of the License at
9 *
10 * http://www.apache.org/licenses/LICENSE-2.0
11 *
12 * Unless required by applicable law or agreed to in writing, software
13 * distributed under the License is distributed on an "AS IS" BASIS,
14 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15 * See the License for the specific language governing permissions and
16 * limitations under the License.
17 */
18 package org.apache.hadoop.hbase.metrics;
19
20 import org.apache.hadoop.hbase.HBaseInterfaceAudience;
21 import org.apache.hadoop.hbase.classification.InterfaceAudience;
22 import org.apache.hadoop.hbase.classification.InterfaceStability;
23
24 /**
25 * A mutable number optimized for high concurrency counting.
26 */
27 @InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.COPROC)
28 @InterfaceStability.Evolving
29 public interface Counter extends Metric {
30
31 /**
32 * Increment {@code this} by 1.
33 */
34 void increment();
35
36 /**
37 * Increment {@code this} by {@code n}.
38 *
39 * @param n The amount to increment.
40 */
41 void increment(long n);
42
43 /**
44 * Decrement {@code this} by 1.
45 */
46 void decrement();
47
48 /**
49 * Decrement {@code this} by {@code n}.
50 *
51 * @param n The amount to decrement.
52 */
53 void decrement(long n);
54
55 /**
56 * Returns the current value.
57 * @return the current value.
58 */
59 long getCount();
60 }