mirror of https://github.com/caddyserver/caddy.git
Add reverse proxy
This commit is contained in:
Matthew Holt
parent
5859cd8dad
commit
1136e2cfee
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@ -0,0 +1,64 @@
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package reverseproxy
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import (
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"net/http"
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"time"
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)
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// Upstream represents the interface that must be satisfied to use the healthchecker.
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type Upstream interface {
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SetHealthiness(bool)
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}
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// HealthChecker represents a worker that periodically evaluates if proxy upstream host is healthy.
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type HealthChecker struct {
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upstream Upstream
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Ticker *time.Ticker
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HTTPClient *http.Client
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}
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// ScheduleChecks periodically runs health checks against an upstream host.
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func (h *HealthChecker) ScheduleChecks(url string) {
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// check if a host is healthy on start vs waiting for timer
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h.upstream.SetHealthiness(h.IsHealthy(url))
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for {
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select {
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case <-h.Ticker.C:
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h.upstream.SetHealthiness(h.IsHealthy(url))
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}
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}
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}
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// Stop stops the healthchecker from makeing further requests.
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func (h *HealthChecker) Stop() {
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h.Ticker.Stop()
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}
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// IsHealthy attempts to check if a upstream host is healthy.
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func (h *HealthChecker) IsHealthy(url string) bool {
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req, err := http.NewRequest(http.MethodGet, url, nil)
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if err != nil {
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return false
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}
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resp, err := h.HTTPClient.Do(req)
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if err != nil {
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return false
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}
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if resp.StatusCode < 200 || resp.StatusCode >= 400 {
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return false
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}
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return true
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}
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// NewHealthCheckWorker returns a new instance of a HealthChecker.
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func NewHealthCheckWorker(u Upstream, interval time.Duration, client *http.Client) *HealthChecker {
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return &HealthChecker{
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upstream: u,
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Ticker: time.NewTicker(interval),
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HTTPClient: client,
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}
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}
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@ -0,0 +1,46 @@
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package reverseproxy
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import (
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"fmt"
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"bitbucket.org/lightcodelabs/caddy2"
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)
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// Register caddy module.
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func init() {
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caddy2.RegisterModule(caddy2.Module{
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Name: "http.responders.reverse_proxy",
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New: func() (interface{}, error) { return new(LoadBalanced), nil },
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OnLoad: func(instances []interface{}, _ interface{}) (interface{}, error) {
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// we don't need to do anything with prior state because healthcheckers are
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// cleaned up in OnUnload.
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s := &State{
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HealthCheckers: []*HealthChecker{},
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}
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for _, i := range instances {
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lb := i.(*LoadBalanced)
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err := NewLoadBalancedReverseProxy(lb, s)
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if err != nil {
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return nil, err
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}
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}
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return s, nil
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},
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OnUnload: func(state interface{}) error {
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s, ok := state.(*State)
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if !ok {
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return fmt.Errorf("proxy OnLoad: prior state not expected proxy.State type")
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}
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// cleanup old healthcheckers
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for _, hc := range s.HealthCheckers {
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hc.Stop()
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}
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return nil
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},
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})
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}
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@ -0,0 +1,562 @@
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package reverseproxy
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import (
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"context"
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"fmt"
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"io"
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"log"
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"net"
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"net/http"
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"net/url"
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"strings"
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"sync"
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"time"
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"golang.org/x/net/http/httpguts"
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)
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// ReverseProxy is an HTTP Handler that takes an incoming request and
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// sends it to another server, proxying the response back to the
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// client.
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type ReverseProxy struct {
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// Director must be a function which modifies
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// the request into a new request to be sent
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// using Transport. Its response is then copied
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// back to the original client unmodified.
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// Director must not access the provided Request
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// after returning.
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Director func(*http.Request)
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// The transport used to perform proxy requests.
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// If nil, http.DefaultTransport is used.
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Transport http.RoundTripper
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// FlushInterval specifies the flush interval
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// to flush to the client while copying the
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// response body.
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// If zero, no periodic flushing is done.
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// A negative value means to flush immediately
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// after each write to the client.
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// The FlushInterval is ignored when ReverseProxy
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// recognizes a response as a streaming response;
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// for such responses, writes are flushed to the client
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// immediately.
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FlushInterval time.Duration
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// ErrorLog specifies an optional logger for errors
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// that occur when attempting to proxy the request.
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// If nil, logging goes to os.Stderr via the log package's
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// standard logger.
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ErrorLog *log.Logger
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// BufferPool optionally specifies a buffer pool to
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// get byte slices for use by io.CopyBuffer when
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// copying HTTP response bodies.
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BufferPool BufferPool
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// ModifyResponse is an optional function that modifies the
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// Response from the backend. It is called if the backend
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// returns a response at all, with any HTTP status code.
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// If the backend is unreachable, the optional ErrorHandler is
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// called without any call to ModifyResponse.
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//
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// If ModifyResponse returns an error, ErrorHandler is called
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// with its error value. If ErrorHandler is nil, its default
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// implementation is used.
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ModifyResponse func(*http.Response) error
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// ErrorHandler is an optional function that handles errors
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// reaching the backend or errors from ModifyResponse.
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//
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// If nil, the default is to log the provided error and return
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// a 502 Status Bad Gateway response.
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ErrorHandler func(http.ResponseWriter, *http.Request, error)
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}
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// A BufferPool is an interface for getting and returning temporary
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// byte slices for use by io.CopyBuffer.
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type BufferPool interface {
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Get() []byte
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Put([]byte)
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}
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func singleJoiningSlash(a, b string) string {
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aslash := strings.HasSuffix(a, "/")
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bslash := strings.HasPrefix(b, "/")
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switch {
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case aslash && bslash:
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return a + b[1:]
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case !aslash && !bslash:
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return a + "/" + b
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}
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return a + b
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}
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// NewSingleHostReverseProxy returns a new ReverseProxy that routes
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// URLs to the scheme, host, and base path provided in target. If the
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// target's path is "/base" and the incoming request was for "/dir",
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// the target request will be for /base/dir.
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// NewSingleHostReverseProxy does not rewrite the Host header.
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// To rewrite Host headers, use ReverseProxy directly with a custom
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// Director policy.
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func NewSingleHostReverseProxy(target *url.URL) *ReverseProxy {
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targetQuery := target.RawQuery
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director := func(req *http.Request) {
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req.URL.Scheme = target.Scheme
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req.URL.Host = target.Host
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req.URL.Path = singleJoiningSlash(target.Path, req.URL.Path)
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if targetQuery == "" || req.URL.RawQuery == "" {
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req.URL.RawQuery = targetQuery + req.URL.RawQuery
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} else {
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req.URL.RawQuery = targetQuery + "&" + req.URL.RawQuery
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}
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if _, ok := req.Header["User-Agent"]; !ok {
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// explicitly disable User-Agent so it's not set to default value
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req.Header.Set("User-Agent", "")
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}
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}
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return &ReverseProxy{Director: director}
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}
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func copyHeader(dst, src http.Header) {
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for k, vv := range src {
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for _, v := range vv {
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dst.Add(k, v)
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}
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}
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}
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func cloneHeader(h http.Header) http.Header {
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h2 := make(http.Header, len(h))
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for k, vv := range h {
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vv2 := make([]string, len(vv))
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copy(vv2, vv)
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h2[k] = vv2
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}
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return h2
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}
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// Hop-by-hop headers. These are removed when sent to the backend.
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// As of RFC 7230, hop-by-hop headers are required to appear in the
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// Connection header field. These are the headers defined by the
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// obsoleted RFC 2616 (section 13.5.1) and are used for backward
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// compatibility.
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var hopHeaders = []string{
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"Connection",
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"Proxy-Connection", // non-standard but still sent by libcurl and rejected by e.g. google
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"Keep-Alive",
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"Proxy-Authenticate",
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"Proxy-Authorization",
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"Te", // canonicalized version of "TE"
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"Trailer", // not Trailers per URL above; https://www.rfc-editor.org/errata_search.php?eid=4522
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"Transfer-Encoding",
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"Upgrade",
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}
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func (p *ReverseProxy) defaultErrorHandler(rw http.ResponseWriter, req *http.Request, err error) {
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p.logf("http: proxy error: %v", err)
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rw.WriteHeader(http.StatusBadGateway)
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}
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func (p *ReverseProxy) getErrorHandler() func(http.ResponseWriter, *http.Request, error) {
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if p.ErrorHandler != nil {
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return p.ErrorHandler
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}
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return p.defaultErrorHandler
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}
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// modifyResponse conditionally runs the optional ModifyResponse hook
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// and reports whether the request should proceed.
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func (p *ReverseProxy) modifyResponse(rw http.ResponseWriter, res *http.Response, req *http.Request) bool {
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if p.ModifyResponse == nil {
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return true
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}
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if err := p.ModifyResponse(res); err != nil {
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res.Body.Close()
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p.getErrorHandler()(rw, req, err)
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return false
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}
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return true
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}
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func (p *ReverseProxy) ServeHTTP(rw http.ResponseWriter, req *http.Request) (*http.Response, error) {
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transport := p.Transport
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if transport == nil {
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transport = http.DefaultTransport
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}
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ctx := req.Context()
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if cn, ok := rw.(http.CloseNotifier); ok {
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var cancel context.CancelFunc
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ctx, cancel = context.WithCancel(ctx)
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defer cancel()
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notifyChan := cn.CloseNotify()
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go func() {
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select {
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case <-notifyChan:
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cancel()
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case <-ctx.Done():
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}
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}()
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}
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outreq := req.WithContext(ctx) // includes shallow copies of maps, but okay
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if req.ContentLength == 0 {
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outreq.Body = nil // Issue 16036: nil Body for http.Transport retries
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}
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outreq.Header = cloneHeader(req.Header)
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p.Director(outreq)
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outreq.Close = false
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reqUpType := upgradeType(outreq.Header)
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removeConnectionHeaders(outreq.Header)
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// Remove hop-by-hop headers to the backend. Especially
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// important is "Connection" because we want a persistent
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// connection, regardless of what the client sent to us.
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for _, h := range hopHeaders {
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hv := outreq.Header.Get(h)
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if hv == "" {
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continue
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}
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if h == "Te" && hv == "trailers" {
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// Issue 21096: tell backend applications that
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// care about trailer support that we support
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// trailers. (We do, but we don't go out of
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// our way to advertise that unless the
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// incoming client request thought it was
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// worth mentioning)
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continue
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}
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outreq.Header.Del(h)
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}
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// After stripping all the hop-by-hop connection headers above, add back any
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// necessary for protocol upgrades, such as for websockets.
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if reqUpType != "" {
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outreq.Header.Set("Connection", "Upgrade")
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outreq.Header.Set("Upgrade", reqUpType)
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}
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if clientIP, _, err := net.SplitHostPort(req.RemoteAddr); err == nil {
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// If we aren't the first proxy retain prior
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// X-Forwarded-For information as a comma+space
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// separated list and fold multiple headers into one.
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if prior, ok := outreq.Header["X-Forwarded-For"]; ok {
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clientIP = strings.Join(prior, ", ") + ", " + clientIP
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}
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outreq.Header.Set("X-Forwarded-For", clientIP)
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}
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res, err := transport.RoundTrip(outreq)
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if err != nil {
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p.getErrorHandler()(rw, outreq, err)
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return nil, err
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}
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// Deal with 101 Switching Protocols responses: (WebSocket, h2c, etc)
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if res.StatusCode == http.StatusSwitchingProtocols {
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if !p.modifyResponse(rw, res, outreq) {
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return res, nil
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}
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p.handleUpgradeResponse(rw, outreq, res)
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return res, nil
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}
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removeConnectionHeaders(res.Header)
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for _, h := range hopHeaders {
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res.Header.Del(h)
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}
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if !p.modifyResponse(rw, res, outreq) {
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return res, nil
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}
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copyHeader(rw.Header(), res.Header)
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// The "Trailer" header isn't included in the Transport's response,
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// at least for *http.Transport. Build it up from Trailer.
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announcedTrailers := len(res.Trailer)
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if announcedTrailers > 0 {
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trailerKeys := make([]string, 0, len(res.Trailer))
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for k := range res.Trailer {
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trailerKeys = append(trailerKeys, k)
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}
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rw.Header().Add("Trailer", strings.Join(trailerKeys, ", "))
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}
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rw.WriteHeader(res.StatusCode)
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err = p.copyResponse(rw, res.Body, p.flushInterval(req, res))
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if err != nil {
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defer res.Body.Close()
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// Since we're streaming the response, if we run into an error all we can do
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// is abort the request. Issue 23643: ReverseProxy should use ErrAbortHandler
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// on read error while copying body.
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if !shouldPanicOnCopyError(req) {
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p.logf("suppressing panic for copyResponse error in test; copy error: %v", err)
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return nil, err
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}
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panic(http.ErrAbortHandler)
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}
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res.Body.Close() // close now, instead of defer, to populate res.Trailer
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if len(res.Trailer) > 0 {
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// Force chunking if we saw a response trailer.
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// This prevents net/http from calculating the length for short
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// bodies and adding a Content-Length.
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if fl, ok := rw.(http.Flusher); ok {
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fl.Flush()
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}
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}
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if len(res.Trailer) == announcedTrailers {
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copyHeader(rw.Header(), res.Trailer)
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return res, nil
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}
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for k, vv := range res.Trailer {
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k = http.TrailerPrefix + k
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for _, v := range vv {
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rw.Header().Add(k, v)
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}
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}
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return res, nil
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}
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var inOurTests bool // whether we're in our own tests
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// shouldPanicOnCopyError reports whether the reverse proxy should
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// panic with http.ErrAbortHandler. This is the right thing to do by
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// default, but Go 1.10 and earlier did not, so existing unit tests
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// weren't expecting panics. Only panic in our own tests, or when
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// running under the HTTP server.
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func shouldPanicOnCopyError(req *http.Request) bool {
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if inOurTests {
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// Our tests know to handle this panic.
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return true
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}
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if req.Context().Value(http.ServerContextKey) != nil {
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// We seem to be running under an HTTP server, so
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// it'll recover the panic.
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return true
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}
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// Otherwise act like Go 1.10 and earlier to not break
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// existing tests.
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return false
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}
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// removeConnectionHeaders removes hop-by-hop headers listed in the "Connection" header of h.
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// See RFC 7230, section 6.1
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func removeConnectionHeaders(h http.Header) {
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if c := h.Get("Connection"); c != "" {
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for _, f := range strings.Split(c, ",") {
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if f = strings.TrimSpace(f); f != "" {
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h.Del(f)
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}
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}
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}
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}
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// flushInterval returns the p.FlushInterval value, conditionally
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// overriding its value for a specific request/response.
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func (p *ReverseProxy) flushInterval(req *http.Request, res *http.Response) time.Duration {
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resCT := res.Header.Get("Content-Type")
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// For Server-Sent Events responses, flush immediately.
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// The MIME type is defined in https://www.w3.org/TR/eventsource/#text-event-stream
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if resCT == "text/event-stream" {
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return -1 // negative means immediately
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}
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// TODO: more specific cases? e.g. res.ContentLength == -1?
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return p.FlushInterval
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}
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func (p *ReverseProxy) copyResponse(dst io.Writer, src io.Reader, flushInterval time.Duration) error {
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if flushInterval != 0 {
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if wf, ok := dst.(writeFlusher); ok {
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mlw := &maxLatencyWriter{
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dst: wf,
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latency: flushInterval,
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}
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defer mlw.stop()
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dst = mlw
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}
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}
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var buf []byte
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if p.BufferPool != nil {
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buf = p.BufferPool.Get()
|
||||
defer p.BufferPool.Put(buf)
|
||||
}
|
||||
_, err := p.copyBuffer(dst, src, buf)
|
||||
return err
|
||||
}
|
||||
|
||||
// copyBuffer returns any write errors or non-EOF read errors, and the amount
|
||||
// of bytes written.
|
||||
func (p *ReverseProxy) copyBuffer(dst io.Writer, src io.Reader, buf []byte) (int64, error) {
|
||||
if len(buf) == 0 {
|
||||
buf = make([]byte, 32*1024)
|
||||
}
|
||||
var written int64
|
||||
for {
|
||||
nr, rerr := src.Read(buf)
|
||||
if rerr != nil && rerr != io.EOF && rerr != context.Canceled {
|
||||
p.logf("httputil: ReverseProxy read error during body copy: %v", rerr)
|
||||
}
|
||||
if nr > 0 {
|
||||
nw, werr := dst.Write(buf[:nr])
|
||||
if nw > 0 {
|
||||
written += int64(nw)
|
||||
}
|
||||
if werr != nil {
|
||||
return written, werr
|
||||
}
|
||||
if nr != nw {
|
||||
return written, io.ErrShortWrite
|
||||
}
|
||||
}
|
||||
if rerr != nil {
|
||||
if rerr == io.EOF {
|
||||
rerr = nil
|
||||
}
|
||||
return written, rerr
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
func (p *ReverseProxy) logf(format string, args ...interface{}) {
|
||||
if p.ErrorLog != nil {
|
||||
p.ErrorLog.Printf(format, args...)
|
||||
} else {
|
||||
log.Printf(format, args...)
|
||||
}
|
||||
}
|
||||
|
||||
type writeFlusher interface {
|
||||
io.Writer
|
||||
http.Flusher
|
||||
}
|
||||
|
||||
type maxLatencyWriter struct {
|
||||
dst writeFlusher
|
||||
latency time.Duration // non-zero; negative means to flush immediately
|
||||
|
||||
mu sync.Mutex // protects t, flushPending, and dst.Flush
|
||||
t *time.Timer
|
||||
flushPending bool
|
||||
}
|
||||
|
||||
func (m *maxLatencyWriter) Write(p []byte) (n int, err error) {
|
||||
m.mu.Lock()
|
||||
defer m.mu.Unlock()
|
||||
n, err = m.dst.Write(p)
|
||||
if m.latency < 0 {
|
||||
m.dst.Flush()
|
||||
return
|
||||
}
|
||||
if m.flushPending {
|
||||
return
|
||||
}
|
||||
if m.t == nil {
|
||||
m.t = time.AfterFunc(m.latency, m.delayedFlush)
|
||||
} else {
|
||||
m.t.Reset(m.latency)
|
||||
}
|
||||
m.flushPending = true
|
||||
return
|
||||
}
|
||||
|
||||
func (m *maxLatencyWriter) delayedFlush() {
|
||||
m.mu.Lock()
|
||||
defer m.mu.Unlock()
|
||||
if !m.flushPending { // if stop was called but AfterFunc already started this goroutine
|
||||
return
|
||||
}
|
||||
m.dst.Flush()
|
||||
m.flushPending = false
|
||||
}
|
||||
|
||||
func (m *maxLatencyWriter) stop() {
|
||||
m.mu.Lock()
|
||||
defer m.mu.Unlock()
|
||||
m.flushPending = false
|
||||
if m.t != nil {
|
||||
m.t.Stop()
|
||||
}
|
||||
}
|
||||
|
||||
func upgradeType(h http.Header) string {
|
||||
if !httpguts.HeaderValuesContainsToken(h["Connection"], "Upgrade") {
|
||||
return ""
|
||||
}
|
||||
return strings.ToLower(h.Get("Upgrade"))
|
||||
}
|
||||
|
||||
func (p *ReverseProxy) handleUpgradeResponse(rw http.ResponseWriter, req *http.Request, res *http.Response) {
|
||||
reqUpType := upgradeType(req.Header)
|
||||
resUpType := upgradeType(res.Header)
|
||||
if reqUpType != resUpType {
|
||||
p.getErrorHandler()(rw, req, fmt.Errorf("backend tried to switch protocol %q when %q was requested", resUpType, reqUpType))
|
||||
return
|
||||
}
|
||||
|
||||
copyHeader(res.Header, rw.Header())
|
||||
|
||||
hj, ok := rw.(http.Hijacker)
|
||||
if !ok {
|
||||
p.getErrorHandler()(rw, req, fmt.Errorf("can't switch protocols using non-Hijacker ResponseWriter type %T", rw))
|
||||
return
|
||||
}
|
||||
backConn, ok := res.Body.(io.ReadWriteCloser)
|
||||
if !ok {
|
||||
p.getErrorHandler()(rw, req, fmt.Errorf("internal error: 101 switching protocols response with non-writable body"))
|
||||
return
|
||||
}
|
||||
defer backConn.Close()
|
||||
conn, brw, err := hj.Hijack()
|
||||
if err != nil {
|
||||
p.getErrorHandler()(rw, req, fmt.Errorf("Hijack failed on protocol switch: %v", err))
|
||||
return
|
||||
}
|
||||
defer conn.Close()
|
||||
res.Body = nil // so res.Write only writes the headers; we have res.Body in backConn above
|
||||
if err := res.Write(brw); err != nil {
|
||||
p.getErrorHandler()(rw, req, fmt.Errorf("response write: %v", err))
|
||||
return
|
||||
}
|
||||
if err := brw.Flush(); err != nil {
|
||||
p.getErrorHandler()(rw, req, fmt.Errorf("response flush: %v", err))
|
||||
return
|
||||
}
|
||||
errc := make(chan error, 1)
|
||||
spc := switchProtocolCopier{user: conn, backend: backConn}
|
||||
go spc.copyToBackend(errc)
|
||||
go spc.copyFromBackend(errc)
|
||||
<-errc
|
||||
return
|
||||
}
|
||||
|
||||
// switchProtocolCopier exists so goroutines proxying data back and
|
||||
// forth have nice names in stacks.
|
||||
type switchProtocolCopier struct {
|
||||
user, backend io.ReadWriter
|
||||
}
|
||||
|
||||
func (c switchProtocolCopier) copyFromBackend(errc chan<- error) {
|
||||
_, err := io.Copy(c.user, c.backend)
|
||||
errc <- err
|
||||
}
|
||||
|
||||
func (c switchProtocolCopier) copyToBackend(errc chan<- error) {
|
||||
_, err := io.Copy(c.backend, c.user)
|
||||
errc <- err
|
||||
}
|
||||
|
|
@ -0,0 +1,413 @@
|
|||
// Package reverseproxy implements a load-balanced reverse proxy.
|
||||
package reverseproxy
|
||||
|
||||
import (
|
||||
"context"
|
||||
"encoding/json"
|
||||
"fmt"
|
||||
"math/rand"
|
||||
"net"
|
||||
"net/http"
|
||||
"net/url"
|
||||
"strings"
|
||||
"sync"
|
||||
"sync/atomic"
|
||||
"time"
|
||||
|
||||
"bitbucket.org/lightcodelabs/caddy2"
|
||||
)
|
||||
|
||||
// State represents the global state of a loadbalancer. It is used to store
|
||||
// references to health checkers.
|
||||
type State struct {
|
||||
HealthCheckers []*HealthChecker
|
||||
}
|
||||
|
||||
// CircuitBreaker defines the functionality of a circuit breaker module.
|
||||
type CircuitBreaker interface {
|
||||
Ok() bool
|
||||
RecordMetric(statusCode int, latency time.Duration)
|
||||
}
|
||||
|
||||
type noopCircuitBreaker struct{}
|
||||
|
||||
func (ncb noopCircuitBreaker) RecordMetric(statusCode int, latency time.Duration) {}
|
||||
func (ncb noopCircuitBreaker) Ok() bool {
|
||||
return true
|
||||
}
|
||||
|
||||
const (
|
||||
// TypeBalanceRoundRobin represents the value to use for configuring a load balanced reverse proxy to use round robin load balancing.
|
||||
TypeBalanceRoundRobin = iota
|
||||
|
||||
// TypeBalanceRandom represents the value to use for configuring a load balanced reverse proxy to use random load balancing.
|
||||
TypeBalanceRandom
|
||||
|
||||
// msgNoHealthyUpstreams is returned if there are no upstreams that are healthy to proxy a request to
|
||||
msgNoHealthyUpstreams = "No healthy upstreams."
|
||||
|
||||
// by default perform health checks every 30 seconds
|
||||
defaultHealthCheckDur = time.Second * 30
|
||||
|
||||
// used when an upstream is unhealthy, health checks can be configured to perform at a faster rate
|
||||
defaultFastHealthCheckDur = time.Second * 1
|
||||
)
|
||||
|
||||
var (
|
||||
// defaultTransport is the default transport to use for the reverse proxy.
|
||||
defaultTransport = &http.Transport{
|
||||
Dial: (&net.Dialer{
|
||||
Timeout: 5 * time.Second,
|
||||
}).Dial,
|
||||
TLSHandshakeTimeout: 5 * time.Second,
|
||||
}
|
||||
|
||||
// defaultHTTPClient is the default http client to use for the healthchecker.
|
||||
defaultHTTPClient = &http.Client{
|
||||
Timeout: time.Second * 10,
|
||||
Transport: defaultTransport,
|
||||
}
|
||||
|
||||
// typeMap maps caddy load balance configuration to the internal representation of the loadbalance algorithm type.
|
||||
typeMap = map[string]int{
|
||||
"round_robin": TypeBalanceRoundRobin,
|
||||
"random": TypeBalanceRandom,
|
||||
}
|
||||
)
|
||||
|
||||
// NewLoadBalancedReverseProxy returns a collection of Upstreams that are to be loadbalanced.
|
||||
func NewLoadBalancedReverseProxy(lb *LoadBalanced, state *State) error {
|
||||
// set defaults
|
||||
if lb.NoHealthyUpstreamsMessage == "" {
|
||||
lb.NoHealthyUpstreamsMessage = msgNoHealthyUpstreams
|
||||
}
|
||||
|
||||
if lb.TryInterval == "" {
|
||||
lb.TryInterval = "20s"
|
||||
}
|
||||
|
||||
// set request retry interval
|
||||
ti, err := time.ParseDuration(lb.TryInterval)
|
||||
if err != nil {
|
||||
return fmt.Errorf("NewLoadBalancedReverseProxy: %v", err.Error())
|
||||
}
|
||||
lb.tryInterval = ti
|
||||
|
||||
// set load balance algorithm
|
||||
t, ok := typeMap[lb.LoadBalanceType]
|
||||
if !ok {
|
||||
t = TypeBalanceRandom
|
||||
}
|
||||
lb.loadBalanceType = t
|
||||
|
||||
// setup each upstream
|
||||
var us []*upstream
|
||||
for _, uc := range lb.Upstreams {
|
||||
// pass the upstream decr and incr methods to keep track of unhealthy nodes
|
||||
nu, err := newUpstream(uc, lb.decrUnhealthy, lb.incrUnhealthy)
|
||||
if err != nil {
|
||||
return err
|
||||
}
|
||||
|
||||
// setup any configured circuit breakers
|
||||
var cbModule = "http.responders.reverse_proxy.circuit_breaker"
|
||||
var cb CircuitBreaker
|
||||
|
||||
if uc.CircuitBreaker != nil {
|
||||
if _, err := caddy2.GetModule(cbModule); err == nil {
|
||||
val, err := caddy2.LoadModule(cbModule, uc.CircuitBreaker)
|
||||
if err == nil {
|
||||
cbv, ok := val.(CircuitBreaker)
|
||||
if ok {
|
||||
cb = cbv
|
||||
} else {
|
||||
fmt.Printf("\nerr: %v; cannot load circuit_breaker, using noop", err.Error())
|
||||
cb = noopCircuitBreaker{}
|
||||
}
|
||||
} else {
|
||||
fmt.Printf("\nerr: %v; cannot load circuit_breaker, using noop", err.Error())
|
||||
cb = noopCircuitBreaker{}
|
||||
}
|
||||
} else {
|
||||
fmt.Println("circuit_breaker module not loaded, using noop")
|
||||
cb = noopCircuitBreaker{}
|
||||
}
|
||||
} else {
|
||||
cb = noopCircuitBreaker{}
|
||||
}
|
||||
nu.CB = cb
|
||||
|
||||
// start a healthcheck worker which will periodically check to see if an upstream is healthy
|
||||
// to proxy requests to.
|
||||
nu.healthChecker = NewHealthCheckWorker(nu, defaultHealthCheckDur, defaultHTTPClient)
|
||||
|
||||
// TODO :- if path is empty why does this empty the entire Target?
|
||||
// nu.Target.Path = uc.HealthCheckPath
|
||||
|
||||
go nu.healthChecker.ScheduleChecks(nu.Target.String())
|
||||
state.HealthCheckers = append(state.HealthCheckers, nu.healthChecker)
|
||||
|
||||
us = append(us, nu)
|
||||
}
|
||||
|
||||
lb.upstreams = us
|
||||
|
||||
return nil
|
||||
}
|
||||
|
||||
// LoadBalanced represents a collection of upstream hosts that are loadbalanced. It
|
||||
// contains multiple features like health checking and circuit breaking functionality
|
||||
// for upstreams.
|
||||
type LoadBalanced struct {
|
||||
mu sync.Mutex
|
||||
numUnhealthy int32
|
||||
selectedServer int // used during round robin load balancing
|
||||
loadBalanceType int
|
||||
tryInterval time.Duration
|
||||
upstreams []*upstream
|
||||
|
||||
// The following struct fields are set by caddy configuration.
|
||||
// TryInterval is the max duration for which request retrys will be performed for a request.
|
||||
TryInterval string `json:"try_interval"`
|
||||
|
||||
// Upstreams are the configs for upstream hosts
|
||||
Upstreams []*UpstreamConfig `json:"upstreams"`
|
||||
|
||||
// LoadBalanceType is the string representation of what loadbalancing algorithm to use. i.e. "random" or "round_robin".
|
||||
LoadBalanceType string `json:"load_balance_type"`
|
||||
|
||||
// NoHealthyUpstreamsMessage is returned as a response when there are no healthy upstreams to loadbalance to.
|
||||
NoHealthyUpstreamsMessage string `json:"no_healthy_upstreams_message"`
|
||||
}
|
||||
|
||||
// ServeHTTP implements the http.Handler interface to dispatch an http request to the proper
|
||||
// server.
|
||||
func (lb *LoadBalanced) ServeHTTP(w http.ResponseWriter, r *http.Request) error {
|
||||
// ensure requests don't hang if an upstream does not respond or is not eventually healthy
|
||||
var u *upstream
|
||||
var done bool
|
||||
|
||||
retryTimer := time.NewTicker(lb.tryInterval)
|
||||
defer retryTimer.Stop()
|
||||
|
||||
go func() {
|
||||
select {
|
||||
case <-retryTimer.C:
|
||||
done = true
|
||||
}
|
||||
}()
|
||||
|
||||
// keep trying to get an available upstream to process the request
|
||||
for {
|
||||
switch lb.loadBalanceType {
|
||||
case TypeBalanceRandom:
|
||||
u = lb.random()
|
||||
case TypeBalanceRoundRobin:
|
||||
u = lb.roundRobin()
|
||||
}
|
||||
|
||||
// if we can't get an upstream and our retry interval has ended return an error response
|
||||
if u == nil && done {
|
||||
w.WriteHeader(http.StatusBadGateway)
|
||||
fmt.Fprint(w, lb.NoHealthyUpstreamsMessage)
|
||||
|
||||
return fmt.Errorf(msgNoHealthyUpstreams)
|
||||
}
|
||||
|
||||
// attempt to get an available upstream
|
||||
if u == nil {
|
||||
continue
|
||||
}
|
||||
|
||||
start := time.Now()
|
||||
|
||||
// if we get an error retry until we get a healthy upstream
|
||||
res, err := u.ReverseProxy.ServeHTTP(w, r)
|
||||
if err != nil {
|
||||
if err == context.Canceled {
|
||||
return nil
|
||||
}
|
||||
|
||||
continue
|
||||
}
|
||||
|
||||
// record circuit breaker metrics
|
||||
go u.CB.RecordMetric(res.StatusCode, time.Now().Sub(start))
|
||||
|
||||
return nil
|
||||
}
|
||||
}
|
||||
|
||||
// incrUnhealthy increments the amount of unhealthy nodes in a loadbalancer.
|
||||
func (lb *LoadBalanced) incrUnhealthy() {
|
||||
atomic.AddInt32(&lb.numUnhealthy, 1)
|
||||
}
|
||||
|
||||
// decrUnhealthy decrements the amount of unhealthy nodes in a loadbalancer.
|
||||
func (lb *LoadBalanced) decrUnhealthy() {
|
||||
atomic.AddInt32(&lb.numUnhealthy, -1)
|
||||
}
|
||||
|
||||
// roundRobin implements a round robin load balancing algorithm to select
|
||||
// which server to forward requests to.
|
||||
func (lb *LoadBalanced) roundRobin() *upstream {
|
||||
if atomic.LoadInt32(&lb.numUnhealthy) == int32(len(lb.upstreams)) {
|
||||
return nil
|
||||
}
|
||||
|
||||
selected := lb.upstreams[lb.selectedServer]
|
||||
|
||||
lb.mu.Lock()
|
||||
lb.selectedServer++
|
||||
if lb.selectedServer >= len(lb.upstreams) {
|
||||
lb.selectedServer = 0
|
||||
}
|
||||
lb.mu.Unlock()
|
||||
|
||||
if selected.IsHealthy() && selected.CB.Ok() {
|
||||
return selected
|
||||
}
|
||||
|
||||
return nil
|
||||
}
|
||||
|
||||
// random implements a random server selector for load balancing.
|
||||
func (lb *LoadBalanced) random() *upstream {
|
||||
if atomic.LoadInt32(&lb.numUnhealthy) == int32(len(lb.upstreams)) {
|
||||
return nil
|
||||
}
|
||||
|
||||
n := rand.Int() % len(lb.upstreams)
|
||||
selected := lb.upstreams[n]
|
||||
|
||||
if selected.IsHealthy() && selected.CB.Ok() {
|
||||
return selected
|
||||
}
|
||||
|
||||
return nil
|
||||
}
|
||||
|
||||
// UpstreamConfig represents the config of an upstream.
|
||||
type UpstreamConfig struct {
|
||||
// Host is the host name of the upstream server.
|
||||
Host string `json:"host"`
|
||||
|
||||
// FastHealthCheckDuration is the duration for which a health check is performed when a node is considered unhealthy.
|
||||
FastHealthCheckDuration string `json:"fast_health_check_duration"`
|
||||
|
||||
CircuitBreaker json.RawMessage `json:"circuit_breaker"`
|
||||
|
||||
// // CircuitBreakerConfig is the config passed to setup a circuit breaker.
|
||||
// CircuitBreakerConfig *circuitbreaker.Config `json:"circuit_breaker"`
|
||||
circuitbreaker CircuitBreaker
|
||||
|
||||
// HealthCheckDuration is the default duration for which a health check is performed.
|
||||
HealthCheckDuration string `json:"health_check_duration"`
|
||||
|
||||
// HealthCheckPath is the path at the upstream host to use for healthchecks.
|
||||
HealthCheckPath string `json:"health_check_path"`
|
||||
}
|
||||
|
||||
// upstream represents an upstream host.
|
||||
type upstream struct {
|
||||
Healthy int32 // 0 = false, 1 = true
|
||||
Target *url.URL
|
||||
ReverseProxy *ReverseProxy
|
||||
Incr func()
|
||||
Decr func()
|
||||
CB CircuitBreaker
|
||||
healthChecker *HealthChecker
|
||||
healthCheckDur time.Duration
|
||||
fastHealthCheckDur time.Duration
|
||||
}
|
||||
|
||||
// newUpstream returns a new upstream.
|
||||
func newUpstream(uc *UpstreamConfig, d func(), i func()) (*upstream, error) {
|
||||
host := strings.TrimSpace(uc.Host)
|
||||
protoIdx := strings.Index(host, "://")
|
||||
if protoIdx == -1 || len(host[:protoIdx]) == 0 {
|
||||
return nil, fmt.Errorf("protocol is required for host")
|
||||
}
|
||||
|
||||
hostURL, err := url.Parse(host)
|
||||
if err != nil {
|
||||
return nil, err
|
||||
}
|
||||
|
||||
// parse healthcheck durations
|
||||
hcd, err := time.ParseDuration(uc.HealthCheckDuration)
|
||||
if err != nil {
|
||||
hcd = defaultHealthCheckDur
|
||||
}
|
||||
|
||||
fhcd, err := time.ParseDuration(uc.FastHealthCheckDuration)
|
||||
if err != nil {
|
||||
fhcd = defaultFastHealthCheckDur
|
||||
}
|
||||
|
||||
u := upstream{
|
||||
healthCheckDur: hcd,
|
||||
fastHealthCheckDur: fhcd,
|
||||
Target: hostURL,
|
||||
Decr: d,
|
||||
Incr: i,
|
||||
Healthy: int32(0), // assume is unhealthy on start
|
||||
}
|
||||
|
||||
u.ReverseProxy = newReverseProxy(hostURL, u.SetHealthiness)
|
||||
return &u, nil
|
||||
}
|
||||
|
||||
// SetHealthiness sets whether an upstream is healthy or not. The health check worker is updated to
|
||||
// perform checks faster if a node is unhealthy.
|
||||
func (u *upstream) SetHealthiness(ok bool) {
|
||||
h := atomic.LoadInt32(&u.Healthy)
|
||||
var wasHealthy bool
|
||||
if h == 1 {
|
||||
wasHealthy = true
|
||||
} else {
|
||||
wasHealthy = false
|
||||
}
|
||||
|
||||
if ok {
|
||||
u.healthChecker.Ticker = time.NewTicker(u.healthCheckDur)
|
||||
|
||||
if !wasHealthy {
|
||||
atomic.AddInt32(&u.Healthy, 1)
|
||||
u.Decr()
|
||||
}
|
||||
} else {
|
||||
u.healthChecker.Ticker = time.NewTicker(u.fastHealthCheckDur)
|
||||
|
||||
if wasHealthy {
|
||||
atomic.AddInt32(&u.Healthy, -1)
|
||||
u.Incr()
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
// IsHealthy returns whether an Upstream is healthy or not.
|
||||
func (u *upstream) IsHealthy() bool {
|
||||
i := atomic.LoadInt32(&u.Healthy)
|
||||
if i == 1 {
|
||||
return true
|
||||
}
|
||||
|
||||
return false
|
||||
}
|
||||
|
||||
// newReverseProxy returns a new reverse proxy handler.
|
||||
func newReverseProxy(target *url.URL, setHealthiness func(bool)) *ReverseProxy {
|
||||
errorHandler := func(w http.ResponseWriter, r *http.Request, err error) {
|
||||
// we don't need to worry about cancelled contexts since this doesn't necessarilly mean that
|
||||
// the upstream is unhealthy.
|
||||
if err != context.Canceled {
|
||||
setHealthiness(false)
|
||||
}
|
||||
}
|
||||
|
||||
rp := NewSingleHostReverseProxy(target)
|
||||
rp.ErrorHandler = errorHandler
|
||||
rp.Transport = defaultTransport // use default transport that times out in 5 seconds
|
||||
return rp
|
||||
}
|
||||
Loading…
Reference in New Issue