mirror of
https://github.com/firebase/firebase-ios-sdk
synced 2026-11-11 22:55:59 +05:45
Gil
530437ea7a
* Move sources into firebase::firestore and internal namespaces Combine support and core/util packages; this distinction wasn't really paying its freight.
106 lines
3.6 KiB
Plaintext
106 lines
3.6 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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- (instancetype)initWithDispatchQueue:(FSTDispatchQueue *)dispatchQueue
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initialDelay:(NSTimeInterval)initialDelay
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backoffFactor:(double)backoffFactor
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maxDelay:(NSTimeInterval)maxDelay NS_DESIGNATED_INITIALIZER;
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@property(nonatomic, strong) FSTDispatchQueue *dispatchQueue;
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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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@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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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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_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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+ (instancetype)exponentialBackoffWithDispatchQueue:(FSTDispatchQueue *)dispatchQueue
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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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return [[FSTExponentialBackoff alloc] initWithDispatchQueue:dispatchQueue
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initialDelay:initialDelay
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backoffFactor:backoffFactor
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maxDelay:maxDelay];
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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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// 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.dispatchQueue dispatchAfterDelay:delayWithJitter 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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