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diff --git a/Firestore/Source/Remote/FSTExponentialBackoff.h b/Firestore/Source/Remote/FSTExponentialBackoff.h
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+++ b/Firestore/Source/Remote/FSTExponentialBackoff.h
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+/*
+ * Copyright 2017 Google
+ *
+ * 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.
+ */
+
+#import <Foundation/Foundation.h>
+
+@class FSTDispatchQueue;
+
+NS_ASSUME_NONNULL_BEGIN
+
+/**
+ * Helper to implement exponential backoff.
+ *
+ * In general, call -reset after each successful round-trip. Call -backoffAndRunBlock before
+ * retrying after an error. Each backoffAndRunBlock will increase the delay between retries.
+ */
+@interface FSTExponentialBackoff : NSObject
+
+/**
+ * Creates and returns a helper for running delayed tasks following an exponential backoff curve
+ * between attempts.
+ *
+ * Each delay is made up of a "base" delay which follows the exponential backoff curve, and a
+ * +/- 50% "jitter" that is calculated and added to the base delay. This prevents clients from
+ * accidentally synchronizing their delays causing spikes of load to the backend.
+ *
+ * @param dispatchQueue The dispatch queue to run tasks on.
+ * @param initialDelay The initial delay (used as the base delay on the first retry attempt).
+ *     Note that jitter will still be applied, so the actual delay could be as little as
+ *     0.5*initialDelay.
+ * @param backoffFactor The multiplier to use to determine the extended base delay after each
+ *     attempt.
+ * @param maxDelay The maximum base delay after which no further backoff is performed. Note that
+ *     jitter will still be applied, so the actual delay could be as much as 1.5*maxDelay.
+ */
++ (instancetype)exponentialBackoffWithDispatchQueue:(FSTDispatchQueue *)dispatchQueue
+                                       initialDelay:(NSTimeInterval)initialDelay
+                                      backoffFactor:(double)backoffFactor
+                                           maxDelay:(NSTimeInterval)maxDelay;
+
+- (instancetype)init
+    __attribute__((unavailable("Use exponentialBackoffWithDispatchQueue constructor method.")));
+
+/**
+ * Resets the backoff delay.
+ *
+ * The very next backoffAndRunBlock: will have no delay. If it is called again (i.e. due to an
+ * error), initialDelay (plus jitter) will be used, and subsequent ones will increase according
+ * to the backoffFactor.
+ */
+- (void)reset;
+
+/**
+ * Resets the backoff to the maximum delay (e.g. for use after a RESOURCE_EXHAUSTED error).
+ */
+- (void)resetToMax;
+
+/**
+ * Waits for currentDelay seconds, increases the delay and runs the specified block.
+ *
+ * @param block The block to run.
+ */
+- (void)backoffAndRunBlock:(void (^)())block;
+
+@end
+
+NS_ASSUME_NONNULL_END