README
¶
Congestion
A congestion control limiter with priorities. Useful if you are working with a service that implements dynamic rate limits with a way of signaling when you're over the rate limit, e.g. HTTP 429.
It works by limiting the number of outstanding concurrent requests. It gradually increments concurrency, until it hits a limit, at which point, it decreases concurrency by 25%.
Installation
$ go get github.com/joshbohde/congestion
Usage
import (
"context"
"log"
"github.com/joshbohde/congestion"
)
func Example() {
const (
HighPriority = 100
)
// A limiter can be used to manage concurrent access to a rate limited resource
limiter := congestion.New(congestion.Config{
Capacity: 10,
MaxLimit: 10,
})
// backoff manages a single retryable request with priority
backoff := congestion.Backoff{
Step: 100 * time.Millisecond,
Limiter: &limiter,
Priority: HighPriority,
}
defer backoff.Close()
// Try the request until either it succeeds, or the context is canceled
for backoff.Try(context.Background()) {
// Make some sort of request to the rate limited resource
err := doRequest()
// If this error signals we are overloading the server, we'll retry
if err != nil {
continue
}
// Otherwise return
return
}
}
Documentation
¶
Overview ¶
Example ¶
package main
import (
"context"
"time"
"github.com/joshbohde/congestion"
)
func doRequest() error {
return nil
}
func main() {
const (
HighPriority = 100
)
// A limiter can be used to manage concurrent access to a rate limited resource
limiter := congestion.New(congestion.Config{
Capacity: 10,
MaxLimit: 10,
})
// backoff manages a single retryable request with priority
backoff := congestion.Backoff{
Step: 100 * time.Millisecond,
Limiter: &limiter,
Priority: HighPriority,
}
defer backoff.Close()
// Try the request until either it succeeds, or the context is canceled
for backoff.Try(context.Background()) {
// Make some sort of request to the rate limited resource
err := doRequest()
// If this error signals we are overloading the server, we'll retry
if err != nil {
continue
}
// Otherwise return
return
}
}
Output:
Index ¶
Examples ¶
Constants ¶
This section is empty.
Variables ¶
View Source
var Dropped = errors.New("dropped")
Dropped is the error that will be returned if this token is dropped
Functions ¶
This section is empty.
Types ¶
type Backoff ¶
type Backoff struct {
Step time.Duration
Limiter *Limiter
Priority int
Error error
// contains filtered or unexported fields
}
Backoff implements exponential backoff retries on top of a Limiter
type Limiter ¶
type Limiter struct {
// contains filtered or unexported fields
}
func (*Limiter) Acquire ¶
Acquire a Lock with FIFO ordering, respecting the context. Returns an error it fails to acquire.
Source Files
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