115 lines
3.7 KiB
Java
115 lines
3.7 KiB
Java
/*
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* Copyright (C) 2017 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.android.internal.telephony;
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import android.annotation.NonNull;
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import android.os.Handler;
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import android.os.Looper;
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import com.android.internal.annotations.VisibleForTesting;
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/** The implementation of exponential backoff with jitter applied. */
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public class ExponentialBackoff {
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private int mRetryCounter;
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private long mStartDelayMs;
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private long mMaximumDelayMs;
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private long mCurrentDelayMs;
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private int mMultiplier;
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private final Runnable mRunnable;
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private final Handler mHandler;
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/**
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* Implementation of Handler methods, Adapter for testing (can't spy on final methods).
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*/
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private HandlerAdapter mHandlerAdapter = new HandlerAdapter() {
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@Override
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public boolean postDelayed(Runnable runnable, long delayMillis) {
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return mHandler.postDelayed(runnable, delayMillis);
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}
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@Override
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public void removeCallbacks(Runnable runnable) {
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mHandler.removeCallbacks(runnable);
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}
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};
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/**
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* Need to spy final methods for testing.
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*/
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public interface HandlerAdapter {
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boolean postDelayed(Runnable runnable, long delayMillis);
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void removeCallbacks(Runnable runnable);
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}
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public ExponentialBackoff(
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long initialDelayMs,
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long maximumDelayMs,
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int multiplier,
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@NonNull Looper looper,
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@NonNull Runnable runnable) {
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this(initialDelayMs, maximumDelayMs, multiplier, new Handler(looper), runnable);
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}
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public ExponentialBackoff(
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long initialDelayMs,
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long maximumDelayMs,
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int multiplier,
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@NonNull Handler handler,
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@NonNull Runnable runnable) {
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mRetryCounter = 0;
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mStartDelayMs = initialDelayMs;
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mMaximumDelayMs = maximumDelayMs;
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mMultiplier = multiplier;
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mHandler = handler;
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mRunnable = runnable;
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}
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/** Starts the backoff, the runnable will be executed after {@link #mStartDelayMs}. */
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public void start() {
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mRetryCounter = 0;
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mCurrentDelayMs = mStartDelayMs;
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mHandlerAdapter.removeCallbacks(mRunnable);
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mHandlerAdapter.postDelayed(mRunnable, mCurrentDelayMs);
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}
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/** Stops the backoff, all pending messages will be removed from the message queue. */
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public void stop() {
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mRetryCounter = 0;
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mHandlerAdapter.removeCallbacks(mRunnable);
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}
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/** Should call when the retry action has failed and we want to retry after a longer delay. */
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public void notifyFailed() {
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mRetryCounter++;
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long temp = Math.min(
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mMaximumDelayMs, (long) (mStartDelayMs * Math.pow(mMultiplier, mRetryCounter)));
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mCurrentDelayMs = (long) (((1 + Math.random()) / 2) * temp);
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mHandlerAdapter.removeCallbacks(mRunnable);
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mHandlerAdapter.postDelayed(mRunnable, mCurrentDelayMs);
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}
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/** Returns the delay for the most recently posted message. */
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public long getCurrentDelay() {
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return mCurrentDelayMs;
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}
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@VisibleForTesting
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public void setHandlerAdapter(HandlerAdapter a) {
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mHandlerAdapter = a;
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}
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}
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