Crate rpm_timer

Overview

RpmTimer (RequestPerMinute Timer) is a tool for limiting your processing speed to the requested number of items (e.g. requests) per minut.

It is designed to work with any rate-limited API.

Documentation

Repository

Getting Started

First of all you have to add this dependency to your Cargo.toml:

[dev-dependencies]
rpm-timer = "0.0.3"

Next include rpm_timer crate in your lib.rs or main.rs file:

extern crate rpm_timer;

Finally, use RpmTimer in the mods where you are going to limit your processing speed:

use rpm_timer::RpmTimer;

Examples

In order to avoid unnecessary memory alocations, run function has two version.

1. run_slices accepts slice and pass sub-slices to the processing function:

extern crate rpm_timer;

use rpm_timer::RpmTimer;

fn send_slice(requests: Vec<String>) {
    RpmTimer::default()
        .rpm_limit(100.0)
        .run_slice(&requests, send_http_requests);
}

fn send_http_requests(requests: &[&String]) {
    // process all requests here
}

2. run_iter accepts any iterator, collects items and pass every portion in Vec to the processing function:processing

extern crate rpm_timer;

use rpm_timer::RpmTimer;

fn send_slice(reader: BufReader) {
    let lines = reader.lines();

    RpmTimer::default()
        .rpm_limit(100.0)
        .run_iter(lines, send_http_requests);
}

fn send_http_requests(requests: Vec<Result<String, io::Error>>) {
    // process all requests here
}

Please check examples directory for more detailed, working examples.

Description

RpmTimer works in tick intervals. You can adjust tick length with tick method. Every tick it checks if there are any free worker threads (the number of threads can be adjusted with max_threads) and how many items should be processed in order to achieve requested speed. If any items should be processed, RpmTimer collects them to the either slice (in non-allocating version) or Vec (in allocating version) and fires processing function in the parallel. Every tick, RpmTimer tries to utilize all available worker threads. For example, when there are 100 items ready and 4 workers available, RpmTimer will pass 25 items to each worker in this single tick.

Visualization:

Assume 2 worker threads and 500 ms tick time. Also, imagine a lag (e.g. cpu busy with other processes) between 2nd and 3rd second:60

60 RPM = 1 RPS = 1 request every 1 second

Time                     0   0.5   1   1.5   2   2.5   3   3.5
Main Thread:             |....X....X....X....X.........X....X..
Number of items ready    1   0.5   1   0.5   1         2   0.5
Worker no. 1             1**********************.......1******.
Worker no. 2             ..........1**************.....1***....
                                             ^         ^
                                             |         |- 2 items sent to the threads
                                             |- an item is ready but no worker threads available

30 RPM = 0.5 RPS = 1 request every 2 seconds

Time                     0   0.5   1   1.5   2   2.5   3   3.5
Main Thread:             |....X....X....X..............X....X..
Number of items ready    1  0.25  0.5  0.75  1  0.25  0.5  0.75
Worker no. 1             1***********..........................
Worker no. 2             ....................1************.....

Legend:

• . - sleeping
• X - main thread’s tick
• * - busy with # requests

Contribution

All contributions and comments are more than welcome! Don’t be afraid to open an issue or PR whenever you find a bug or have an idea to improve this crate.

License

MIT License

Copyright (c) 2017 Marcin Sas-Szymański

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

Structs

• RpmTimer
  Use this struct to limit the speed of any items processing.