httplb

httplb provides client-side load balancing for net/http clients. By default, clients are designed for server-to-server and RPC workloads:

• They support HTTP/1.1, HTTP/2, and H2C.
• They periodically re-resolve names using DNS.
• They use a round-robin load balancing policy.

Random, fewest-pending, and power-of-two load balancing policies are also available. Clients with more complex needs can customize the underlying transports, name resolution, and load balancing. They can also add subsetting and active health checking.

httplb takes care to build all this functionality underneath the standard library's *http.Client, so httplb is usable anywhere you're currently using net/http.

Example

Here's a quick example of how to get started with httplb:

package main

import (
	"log"
	"net"
	"time"

	"github.com/bufbuild/httplb"
	"github.com/bufbuild/httplb/picker"
)

func main() {
	client := httplb.NewClient(
		// Switch from the default round-robin policy to power-of-two.
		httplb.WithPicker(picker.NewPowerOfTwo),
	)
	defer client.Close()
	resp, err := client.Get("https://example.com")
	if err != nil {
		log.Fatalln(err)
	}
	defer resp.Body.Close()
	log.Println(resp.Status)
}

If you're using Connect, you can use httplb for your RPC clients:

func main() {
	client := httplb.NewClient()
	defer client.Close()
	pingClient := pingv1connect.NewPingServiceClient(
		client,
		"http://localhost:8080/",
	)
	req := connect.NewRequest(&pingv1.PingRequest{
		Number: 42,
	})
	res, err := pingClient.Ping(context.Background(), req)
	if err != nil {
		log.Fatalln(err)
	}
	log.Println(res.Msg)
}

If you know the server supports HTTP/2 without TLS (HTTP/2 over cleartext, or H2C for short), use the h2c scheme in your URLs instead of http:

	pingClient := pingv1connect.NewPingServiceClient(
		client,
		"h2c://localhost:8080/",
	)

For more information on how to use httplb, especially for advanced use cases, take a look at the full documentation.

Ecosystem

• connect-go: RPC library, compatible with httplb.

Status: Alpha

This project is currently in alpha. The API should be considered unstable and likely to change.

Legal

Offered under the Apache 2 license.