hedgedhttp

Hedged HTTP client which helps to reduce tail latency at scale.

Rationale

See paper Tail at Scale by Jeffrey Dean, Luiz André Barroso. In short: the client first sends one request, but then sends an additional request after a timeout if the previous hasn't returned an answer in the expected time. The client cancels remaining requests once the first result is received.

Acknowledge

Thanks to Bohdan Storozhuk for the review and powerful hints.

Features

• Simple API.
• Easy to integrate.
• Optimized for speed.
• Clean and tested code.
• Supports http.Client and http.RoundTripper.
• Dependency-free.

Install

Go version 1.16+

go get github.com/cristalhq/hedgedhttp

Example

ctx := context.Background()
req, err := http.NewRequestWithContext(ctx, http.MethodGet, "https://google.com", http.NoBody)
if err != nil {
    panic(err)
}

timeout := 10 * time.Millisecond
upto := 7
client := &http.Client{Timeout: time.Second}
hedged, err := hedgedhttp.NewClient(timeout, upto, client)
if err != nil {
    panic(err)
}

// will take `upto` requests, with a `timeout` delay between them
resp, err := hedged.Do(req)
if err != nil {
    panic(err)
}
defer resp.Body.Close()

Also see examples: examples_test.go.

Documentation

See these docs.

License

MIT License.