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/*
* Copyright (C) 2022 The Android Open Source Project
*
* 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.android.adservices.service.common;
import android.annotation.NonNull;
import android.util.Pair;
import com.android.internal.annotations.VisibleForTesting;
import com.google.common.util.concurrent.RateLimiter;
import java.util.concurrent.ConcurrentHashMap;
/** Class to throttle PPAPI requests. */
public class Throttler {
// Enum for each PP API or entry point that will be throttled.
public enum ApiKey {
UNKNOWN,
// Key to throttle Topics API based on the App Package Name.
TOPICS_API_APP_PACKAGE_NAME,
// Key to throttle Topics API based on the Sdk Name.
TOPICS_API_SDK_NAME,
// Key to throttle Measurement Register Source API
MEASUREMENT_API_REGISTER_SOURCE,
// Key to throttle Measurement Register Web Source API
MEASUREMENT_API_REGISTER_WEB_SOURCE,
// Key to throttle Measurement Register Trigger API
MEASUREMENT_API_REGISTER_TRIGGER,
// Key to throttle Measurement Register Web Trigger API
MEASUREMENT_API_REGISTER_WEB_TRIGGER,
// Key to throttle Measurement Deletion Registration API
MEASUREMENT_API_DELETION_REGISTRATION,
// Key to throttle Select Ads API
FLEDGE_API_SELECT_ADS,
// Key to throttle Join Custom Audience API
FLEDGE_API_JOIN_CUSTOM_AUDIENCE,
// Key to throttle Leave Custom Audience API
FLEDGE_API_LEAVE_CUSTOM_AUDIENCE,
// Key to throttle Report impressions API
FLEDGE_API_REPORT_IMPRESSIONS
}
private static volatile Throttler sSingleton;
private final double mSdkRequestPermitsPerSecond;
// A Map from a Pair<ApiKey, Requester> to its RateLimiter.
// The Requester could be a SdkName or an AppPackageName depending on the rate limiting needs.
// Example Pair<TOPICS_API, "SomeSdkName">, Pair<TOPICS_API, "SomePackageName">.
private final ConcurrentHashMap<Pair<ApiKey, String>, RateLimiter> mSdkRateLimitMap =
new ConcurrentHashMap<>();
/**
* Returns the singleton instance of the Throttler. Note: Request for a new instance, even with
* changed rate limits, is ignored if the Throttler was already instantiated.
*/
@NonNull
public static Throttler getInstance(double sdkRequestPermitsPerSecond) {
synchronized (Throttler.class) {
if (null == sSingleton) {
sSingleton = new Throttler(sdkRequestPermitsPerSecond);
}
return sSingleton;
}
}
@VisibleForTesting
Throttler(double sdkRequestPermitsPerSecond) {
mSdkRequestPermitsPerSecond = sdkRequestPermitsPerSecond;
}
/**
* The throttler is a Singleton and does not allow changing the rate limits once initialised,
* therefore it is not feasible to test different throttling policies across tests without
* destroying the previous instance. Intended to be used in test cases only.
*/
@VisibleForTesting
public static void destroyExistingThrottler() {
sSingleton = null;
}
/**
* Acquires a permit for an API and a Requester if it can be acquired immediately without delay.
* Example: {@code tryAcquire(TOPICS_API, "SomeSdkName") }
*
* @return {@code true} if the permit was acquired, {@code false} otherwise
*/
public boolean tryAcquire(ApiKey apiKey, String requester) {
// Negative Permits Per Second turns off rate limiting.
if (mSdkRequestPermitsPerSecond <= 0) {
return true;
}
RateLimiter rateLimiter =
mSdkRateLimitMap.computeIfAbsent(
Pair.create(apiKey, requester),
ignored -> RateLimiter.create(mSdkRequestPermitsPerSecond));
return rateLimiter.tryAcquire();
}
}
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