4 changed files with 1085 additions and 0 deletions
@ -0,0 +1,64 @@ |
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package reverseproxy |
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|
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import ( |
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"net/http" |
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"time" |
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) |
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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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|
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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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|
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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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|
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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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|
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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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|
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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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|
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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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|
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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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|
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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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} |
@ -0,0 +1,46 @@ |
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package reverseproxy |
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|
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import ( |
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"fmt" |
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|
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"bitbucket.org/lightcodelabs/caddy2" |
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) |
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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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|
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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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|
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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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|
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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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} |
@ -0,0 +1,562 @@ |
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package reverseproxy |
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|
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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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|
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"golang.org/x/net/http/httpguts" |
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) |
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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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|
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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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|
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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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|
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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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|
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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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|
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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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|
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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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|
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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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|
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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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|
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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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|
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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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|
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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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|
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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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|
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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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|
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p.handleUpgradeResponse(rw, outreq, res) |
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return res, nil |
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} |
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|
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removeConnectionHeaders(res.Header) |
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|
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for _, h := range hopHeaders { |
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res.Header.Del(h) |
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} |
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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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|
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copyHeader(rw.Header(), res.Header) |
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|
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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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|
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rw.WriteHeader(res.StatusCode) |
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|
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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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|
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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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|
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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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|
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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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|
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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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|
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return res, nil |
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} |
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|
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var inOurTests bool // whether we're in our own tests
|
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|
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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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|
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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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|
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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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|
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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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|
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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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|
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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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|
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var buf []byte |
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if p.BufferPool != nil { |
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buf = p.BufferPool.Get() |
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defer p.BufferPool.Put(buf) |
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} |
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_, err := p.copyBuffer(dst, src, buf) |
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return err |
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} |
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|
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// copyBuffer returns any write errors or non-EOF read errors, and the amount
|
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// of bytes written.
|
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func (p *ReverseProxy) copyBuffer(dst io.Writer, src io.Reader, buf []byte) (int64, error) { |
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if len(buf) == 0 { |
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buf = make([]byte, 32*1024) |
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} |
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var written int64 |
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for { |
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nr, rerr := src.Read(buf) |
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if rerr != nil && rerr != io.EOF && rerr != context.Canceled { |
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p.logf("httputil: ReverseProxy read error during body copy: %v", rerr) |
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} |
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if nr > 0 { |
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nw, werr := dst.Write(buf[:nr]) |
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if nw > 0 { |
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written += int64(nw) |
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} |
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if werr != nil { |
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return written, werr |
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} |
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if nr != nw { |
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return written, io.ErrShortWrite |
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} |
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} |
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if rerr != nil { |
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if rerr == io.EOF { |
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rerr = nil |
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} |
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return written, rerr |
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} |
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} |
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} |
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|
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func (p *ReverseProxy) logf(format string, args ...interface{}) { |
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if p.ErrorLog != nil { |
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p.ErrorLog.Printf(format, args...) |
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} else { |
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log.Printf(format, args...) |
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} |
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} |
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|
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type writeFlusher interface { |
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io.Writer |
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http.Flusher |
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} |
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|
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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