mirror of
https://github.com/firebase/firebase-ios-sdk
synced 2026-11-11 22:55:59 +05:45
Michael Lehenbauer
81ee594e32
Basically a port of https://github.com/firebase/firebase-js-sdk/commit/a1e346ff93c6cbcc0a1b3b33f0fbc3a7b66e7e12 and https://github.com/firebase/firebase-js-sdk/commit/fce4168309f42aa038125f39818fbf654b65b05f * Introduces a DelayedCallback helper class in FSTDispatchQueue to encapsulate delayed callback logic. * Adds cancellation support. * Updates the idle timer in FSTStream to use new cancellation support. * Adds a FSTTimerId enum for identifying delayed operations on the queue and uses it to identify our existing backoff and idle timers. * Added containsDelayedCallback: and runDelayedCallbacksUntil: methods to FSTDispatchQueue which can be used from tests to check for the presence of a callback or to schedule them to run early. * Removes FSTTestDispatchQueue and changes idle tests to use new test methods.
100 lines
3.0 KiB
Plaintext
100 lines
3.0 KiB
Plaintext
/*
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* Copyright 2017 Google
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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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#import "Firestore/Source/Remote/FSTExponentialBackoff.h"
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#include <random>
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#include "Firestore/core/src/firebase/firestore/util/secure_random.h"
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#import "Firestore/Source/Util/FSTDispatchQueue.h"
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#import "Firestore/Source/Util/FSTLogger.h"
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using firebase::firestore::util::SecureRandom;
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@interface FSTExponentialBackoff ()
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@property(nonatomic, strong) FSTDispatchQueue *dispatchQueue;
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@property(nonatomic, assign, readonly) FSTTimerID timerID;
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@property(nonatomic) double backoffFactor;
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@property(nonatomic) NSTimeInterval initialDelay;
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@property(nonatomic) NSTimeInterval maxDelay;
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@property(nonatomic) NSTimeInterval currentBase;
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@property(nonatomic, strong, nullable) FSTDelayedCallback *timerCallback;
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@end
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@implementation FSTExponentialBackoff {
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SecureRandom _secureRandom;
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}
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- (instancetype)initWithDispatchQueue:(FSTDispatchQueue *)dispatchQueue
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timerID:(FSTTimerID)timerID
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initialDelay:(NSTimeInterval)initialDelay
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backoffFactor:(double)backoffFactor
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maxDelay:(NSTimeInterval)maxDelay {
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if (self = [super init]) {
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_dispatchQueue = dispatchQueue;
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_timerID = timerID;
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_initialDelay = initialDelay;
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_backoffFactor = backoffFactor;
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_maxDelay = maxDelay;
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[self reset];
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}
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return self;
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}
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- (void)reset {
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_currentBase = 0;
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}
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- (void)resetToMax {
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_currentBase = _maxDelay;
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}
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- (void)backoffAndRunBlock:(void (^)(void))block {
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if (self.timerCallback) {
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[self.timerCallback cancel];
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}
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// First schedule the block using the current base (which may be 0 and should be honored as such).
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NSTimeInterval delayWithJitter = _currentBase + [self jitterDelay];
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if (_currentBase > 0) {
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FSTLog(@"Backing off for %.2f seconds (base delay: %.2f seconds)", delayWithJitter,
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_currentBase);
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}
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self.timerCallback =
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[self.dispatchQueue dispatchAfterDelay:delayWithJitter timerID:self.timerID block:block];
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// Apply backoff factor to determine next delay and ensure it is within bounds.
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_currentBase *= _backoffFactor;
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if (_currentBase < _initialDelay) {
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_currentBase = _initialDelay;
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}
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if (_currentBase > _maxDelay) {
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_currentBase = _maxDelay;
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}
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}
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/** Returns a random value in the range [-currentBase/2, currentBase/2] */
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- (NSTimeInterval)jitterDelay {
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std::uniform_real_distribution<double> dist;
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double random_double = dist(_secureRandom);
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return (random_double - 0.5) * _currentBase;
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}
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@end
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