Documentation
¶
Overview ¶
Package loadbalance defines an http.RoundTripper that load balances requests across a group of hosts.
// select from two servers
var client http.Client
selector := roundrobin.SelectFrom("localhost:8000", "localhost:8001")
client.Transport = loadbalance.With(http.DefaultTransport, selector)
// create a new request (to any host)
req, _ := http.NewRequest("GET", "http://replaced/foo/bar", nil)
// make the request, which will be routed to one of the two servers
resp, _ := client.Do(req)
Index ¶
Examples ¶
Constants ¶
This section is empty.
Variables ¶
View Source
var ( // NoHosts is returned RoundTrip when no hosts have been set. NoHosts = errors.New("No hosts to choose from") )
Functions ¶
func With ¶
func With(another http.RoundTripper, s Selector) http.RoundTripper
With returns an http.RoundTripper that will change the request's host based on the result from the provided Selector and call another RoundTripper.
Example ¶
Send requests using the round-robin algorithm.
package main
import (
"fmt"
"io"
"net/http"
"net/http/httptest"
"net/url"
"os"
"github.com/go-goo/http/loadbalance"
"github.com/go-goo/http/loadbalance/roundrobin"
)
func main() {
// example only: create 2 test servers that will return their identifier
// and the requested path
serverA := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
fmt.Fprintf(w, "A: %s", r.URL)
}))
serverB := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
fmt.Fprintf(w, "B: %s", r.URL)
}))
defer serverA.Close()
defer serverB.Close()
// example only: extract the host:port from the test server URLs
hosts := []string{serverA.URL, serverB.URL}
for i, host := range hosts {
url, _ := url.Parse(host)
hosts[i] = url.Host
}
// create a new client that will load balance across hosts using the
// RoundRobin algorithm.
var client http.Client
selector := roundrobin.SelectFrom(hosts...)
client.Transport = loadbalance.With(http.DefaultTransport, selector)
// make multiple requests, which are distributed across A/B hosts
keys := "abc"
for _, key := range keys {
req, _ := http.NewRequest("GET", "http://replace.me/foo/bar?key="+string(key), nil)
resp, _ := client.Do(req)
io.Copy(os.Stdout, resp.Body)
fmt.Println()
resp.Body.Close()
}
}
Output: A: /foo/bar?key=a B: /foo/bar?key=b A: /foo/bar?key=c
Types ¶
type Selector ¶
type Selector interface {
// Select the host to send the request to using properties of an http.Request.
Select(*http.Request) (host string)
// Complete is called once the response is received from the underlying
// http.RoundTripper. The host value is the same as what was returned by
// Select. This is used in algorithms that require tracking the number
// of pending requests.
Complete(host string)
}
Selector defines an interface capable of choosing a host. Implementations must be safe for concurrent access.
type Transport ¶
type Transport struct {
http.RoundTripper
Selector
}
Transport implements http.Transport that will change the request's host based on the result from a Selector and call the embedded Transport.
Source Files
Directories
¶
| Path | Synopsis |
|---|---|
|
Package hashring implements a loadbalance.Selector that selects hosts using groupcache's consistenthash package.
|
Package hashring implements a loadbalance.Selector that selects hosts using groupcache's consistenthash package. |
|
Package least implements a loadbalance.Selector that selects hosts using a weighted least connection algorithm.
|
Package least implements a loadbalance.Selector that selects hosts using a weighted least connection algorithm. |
|
Package random implements a loadbalance.Selector that selects hosts randomly using math/rand.
|
Package random implements a loadbalance.Selector that selects hosts randomly using math/rand. |
|
Package roundrobin implements a loadbalance.Selector that selects hosts using a round-robin algorithm.
|
Package roundrobin implements a loadbalance.Selector that selects hosts using a round-robin algorithm. |
|
Package single implements a loadbalance.Selector that uses a single host.
|
Package single implements a loadbalance.Selector that uses a single host. |
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