1 /*
2  * Copyright 2016-17, OpenCensus Authors
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *     http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 package io.opencensus.stats;
18 
19 import io.opencensus.internal.DefaultVisibilityForTesting;
20 import io.opencensus.internal.Provider;
21 import java.util.logging.Level;
22 import java.util.logging.Logger;
23 import javax.annotation.Nullable;
24 
25 /**
26  * Class for accessing the default {@link StatsComponent}.
27  *
28  * @since 0.8
29  */
30 public final class Stats {
31   private static final Logger logger = Logger.getLogger(Stats.class.getName());
32 
33   private static final StatsComponent statsComponent =
34       loadStatsComponent(StatsComponent.class.getClassLoader());
35 
36   /**
37    * Returns the default {@link StatsRecorder}.
38    *
39    * @since 0.8
40    */
getStatsRecorder()41   public static StatsRecorder getStatsRecorder() {
42     return statsComponent.getStatsRecorder();
43   }
44 
45   /**
46    * Returns the default {@link ViewManager}.
47    *
48    * @since 0.8
49    */
getViewManager()50   public static ViewManager getViewManager() {
51     return statsComponent.getViewManager();
52   }
53 
54   /**
55    * Returns the current {@code StatsCollectionState}.
56    *
57    * <p>When no implementation is available, {@code getState} always returns {@link
58    * StatsCollectionState#DISABLED}.
59    *
60    * <p>Once {@link #getState()} is called, subsequent calls to {@link
61    * #setState(StatsCollectionState)} will throw an {@code IllegalStateException}.
62    *
63    * @return the current {@code StatsCollectionState}.
64    * @since 0.8
65    */
getState()66   public static StatsCollectionState getState() {
67     return statsComponent.getState();
68   }
69 
70   /**
71    * Sets the current {@code StatsCollectionState}.
72    *
73    * <p>When no implementation is available, {@code setState} does not change the state.
74    *
75    * <p>If state is set to {@link StatsCollectionState#DISABLED}, all stats that are previously
76    * recorded will be cleared.
77    *
78    * @param state the new {@code StatsCollectionState}.
79    * @throws IllegalStateException if {@link #getState()} was previously called.
80    * @deprecated This method is deprecated because other libraries could cache the result of {@link
81    *     #getState()}, use a stale value, and behave incorrectly. It is only safe to call early in
82    *     initialization. This method throws {@link IllegalStateException} after {@code getState()}
83    *     has been called, in order to limit changes to the result of {@code getState()}.
84    * @since 0.8
85    */
86   @Deprecated
setState(StatsCollectionState state)87   public static void setState(StatsCollectionState state) {
88     statsComponent.setState(state);
89   }
90 
91   // Any provider that may be used for StatsComponent can be added here.
92   @DefaultVisibilityForTesting
loadStatsComponent(@ullable ClassLoader classLoader)93   static StatsComponent loadStatsComponent(@Nullable ClassLoader classLoader) {
94     try {
95       // Call Class.forName with literal string name of the class to help shading tools.
96       return Provider.createInstance(
97           Class.forName(
98               "io.opencensus.impl.stats.StatsComponentImpl", /*initialize=*/ true, classLoader),
99           StatsComponent.class);
100     } catch (ClassNotFoundException e) {
101       logger.log(
102           Level.FINE,
103           "Couldn't load full implementation for StatsComponent, now trying to load lite "
104               + "implementation.",
105           e);
106     }
107     try {
108       // Call Class.forName with literal string name of the class to help shading tools.
109       return Provider.createInstance(
110           Class.forName(
111               "io.opencensus.impllite.stats.StatsComponentImplLite",
112               /*initialize=*/ true,
113               classLoader),
114           StatsComponent.class);
115     } catch (ClassNotFoundException e) {
116       logger.log(
117           Level.FINE,
118           "Couldn't load lite implementation for StatsComponent, now using "
119               + "default implementation for StatsComponent.",
120           e);
121     }
122     return NoopStats.newNoopStatsComponent();
123   }
124 
Stats()125   private Stats() {}
126 }
127