1 /*
2  * Copyright (c) Facebook, Inc. and its affiliates.
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *     http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 #pragma once
18 
19 #include <chrono>
20 
21 #include <folly/experimental/observer/Observer.h>
22 
23 namespace folly {
24 namespace observer {
25 
26 /**
27  * The returned Observer will proxy updates from the input observer but will
28  * delay the propagation of each update by some duration between 0 ms and
29  * lag + jitter. In addition, if an update arrives while no preceding jittered
30  * updates are still in flight, then the delay applied to the latest update will
31  * be a uniformly random duration between lag - jitter and lag + jitter.
32  */
33 template <typename T>
34 Observer<T> withJitter(
35     Observer<T> observer,
36     std::chrono::milliseconds lag,
37     std::chrono::milliseconds jitter);
38 
39 } // namespace observer
40 } // namespace folly
41 
42 #include <folly/experimental/observer/WithJitter-inl.h>
43