Home | History | Annotate | Download | only in stats 
      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    */
     41   public static StatsRecorder getStatsRecorder() {
     42     return statsComponent.getStatsRecorder();
     43   }
     44 
     45   /**
     46    * Returns the default {@link ViewManager}.
     47    *
     48    * @since 0.8
     49    */
     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    */
     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
     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
     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 
    125   private Stats() {}
    126 }
    127