com.google.idea.blaze.base.experiments.ExperimentServiceImpl.java Source code

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Here is the source code for com.google.idea.blaze.base.experiments.ExperimentServiceImpl.java

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/*
 * Copyright 2016 The Bazel Authors. All rights reserved.
 *
 * 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 com.google.idea.blaze.base.experiments;

import com.google.common.annotations.VisibleForTesting;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Lists;
import com.google.common.collect.Maps;
import com.intellij.openapi.diagnostic.Logger;
import com.intellij.util.SystemProperties;

import org.jetbrains.annotations.NotNull;

import java.io.File;
import java.util.List;
import java.util.Map;
import java.util.concurrent.atomic.AtomicInteger;

/**
 * An experiment service that delegates to {@link ExperimentLoader ExperimentLoaders}, in a
 * specific order.
 *
 * It will check system properties first, then an experiment file in the user's home directory, then
 * finally all files specified by the system property blaze.experiments.file.
 */
public class ExperimentServiceImpl implements ExperimentService {
    private static final Logger LOG = Logger.getInstance(ExperimentServiceImpl.class);

    private static final String USER_EXPERIMENT_OVERRIDES_FILE = SystemProperties.getUserHome() + File.separator
            + ".blaze-experiments";

    private final List<ExperimentLoader> services;
    private Map<String, String> experiments;
    private AtomicInteger experimentScopeCounter = new AtomicInteger(0);

    public ExperimentServiceImpl() {
        this(new SystemPropertyExperimentLoader(), new FileExperimentLoader(USER_EXPERIMENT_OVERRIDES_FILE),
                new WebExperimentLoader());
    }

    @VisibleForTesting
    protected ExperimentServiceImpl(ExperimentLoader... loaders) {
        services = ImmutableList.copyOf(loaders);
    }

    @Override
    public synchronized void reloadExperiments() {
        if (experimentScopeCounter.get() > 0) {
            return;
        }

        Map<String, String> experiments = Maps.newHashMap();
        for (ExperimentLoader loader : Lists.reverse(services)) {
            experiments.putAll(loader.getExperiments());
        }
        this.experiments = experiments;
    }

    @Override
    public synchronized void startExperimentScope() {
        this.experimentScopeCounter.incrementAndGet();
    }

    @Override
    public synchronized void endExperimentScope() {
        int value = this.experimentScopeCounter.decrementAndGet();
        LOG.assertTrue(value >= 0);
    }

    @Override
    public boolean getExperiment(@NotNull String key, boolean defaultValue) {
        String property = getExperiment(key);
        return property != null ? property.equals("1") : defaultValue;
    }

    @Override
    public String getExperimentString(@NotNull String key, String defaultValue) {
        String property = getExperiment(key);
        return property != null ? property : defaultValue;
    }

    @Override
    public int getExperimentInt(@NotNull String key, int defaultValue) {
        String property = getExperiment(key);
        try {
            return property != null ? Integer.parseInt(property) : defaultValue;
        } catch (NumberFormatException e) {
            LOG.warn("Could not parse int for experiment: " + key, e);
            return defaultValue;
        }
    }

    String getExperiment(@NotNull String key) {
        if (experiments == null) {
            reloadExperiments();
        }
        LOG.assertTrue(experiments != null, "Failure to load experiments.");
        return experiments.get(key);
    }
}