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72 lines
1.9 KiB
Go
72 lines
1.9 KiB
Go
// <em>[Rate limiting](http://en.wikipedia.org/wiki/Rate_limiting)</em>
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// is an important mechanism for controlling resource
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// utilization and maintaining quality of service. Go
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// elegantly supports rate limiting with goroutines,
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// channels, and [tickers](tickers).
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package main
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import (
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"fmt"
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"time"
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)
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func main() {
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// First we'll look at basic rate limiting. Suppose
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// we want to limit our handling of incoming requests.
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// We'll serve these requests off a channel of the
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// same name.
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requests := make(chan int, 5)
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for i := 1; i <= 5; i++ {
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requests <- i
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}
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close(requests)
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// This `limiter` channel will receive a value
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// every 200 milliseconds. This is the regulator in
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// our rate limiting scheme.
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limiter := time.Tick(200 * time.Millisecond)
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// By blocking on a receive from the `limiter` channel
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// before serving each request, we limit ourselves to
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// 1 request every 200 milliseconds.
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for req := range requests {
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<-limiter
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fmt.Println("request", req, time.Now())
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}
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// We may want to allow short bursts of requests in
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// our rate limiting scheme while preserving the
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// overall rate limit. We can accomplish this by
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// buffering our limiter channel. This `burstyLimiter`
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// channel will allow bursts of up to 3 events.
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burstyLimiter := make(chan time.Time, 3)
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// Fill up the channel to represent allowed bursting.
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for i := 0; i < 3; i++ {
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burstyLimiter <- time.Now()
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}
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// Every 200 milliseconds we'll try to add a new
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// value to `burstyLimiter`, up to its limit of 3.
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go func() {
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for t := range time.Tick(200 * time.Millisecond) {
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burstyLimiter <- t
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}
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}()
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// Now simulate 5 more incoming requests. The first
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// 3 of these will benefit from the burst capability
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// of `burstyLimiter`.
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burstyRequests := make(chan int, 5)
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for i := 1; i <= 5; i++ {
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burstyRequests <- i
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}
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close(burstyRequests)
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for req := range burstyRequests {
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<-burstyLimiter
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fmt.Println("request", req, time.Now())
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}
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}
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