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http.go
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/*
* Copyright (c) 2020 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package vanity
import (
"bytes"
"context"
"html/template"
"net/http"
"strings"
"time"
"github.com/prometheus/client_golang/prometheus"
"github.com/prometheus/client_golang/prometheus/promauto"
)
const (
xForwardedHost = "X-Forwarded-Host"
// DefaultDocURL is the default Go doc URL.
// It can MockBackend replaced with https://https://godoc.org/.
DefaultDocURL = "https://pkg.go.dev/"
)
type data struct {
ImportRoot string
VCS string
VCSRoot string
}
var tmpl = template.Must(template.New("main").Parse(`<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
<meta name="go-import" content="{{.ImportRoot}} {{.VCS}} {{.VCSRoot}}">
<meta name="go-source" content="{{.ImportRoot}} {{.VCSRoot}} {{.VCSRoot}}/tree/master{/dir} {{.VCSRoot}}/blob/master{/dir}/{file}#L{line}">
</head>
</html>
`))
var (
// APICalls is a Prometheus counter that tracks the total vanity Backend calls.
APICalls = promauto.NewCounter(prometheus.CounterOpts{
Namespace: "vanity",
Subsystem: "api",
Name: "calls_total",
Help: "The total vanity Backend calls",
})
// APIErrors is a Prometheus counter that tracks the total vanity Backend errors.
APIErrors = promauto.NewCounter(prometheus.CounterOpts{
Namespace: "vanity",
Subsystem: "api",
Name: "errors_total",
Help: "The total vanity Backend errors",
})
// APINotFound is a Prometheus counter that tracks the total vanity Backend not found calls.
APINotFound = promauto.NewCounter(prometheus.CounterOpts{
Namespace: "vanity",
Subsystem: "api",
Name: "not_found_total",
Help: "The total vanity Backend not found calls",
})
// APIDocRedirects is a Prometheus counter that tracks the total vanity Backend doc redirects.
APIDocRedirects = promauto.NewCounter(prometheus.CounterOpts{
Namespace: "vanity",
Subsystem: "api",
Name: "doc_total",
Help: "The total vanity Backend doc redirects",
})
// APIErrTemplates is a Prometheus counter that tracks the total templating errors.
APIErrTemplates = promauto.NewCounter(prometheus.CounterOpts{
Namespace: "vanity",
Subsystem: "api",
Name: "error_templates_total",
Help: "The total templating errors",
})
// SummaryVec is a Prometheus histogram to track the Backend duration in seconds.
SummaryVec = promauto.NewHistogram(prometheus.HistogramOpts{
Namespace: "vanity",
Subsystem: "api",
Name: "duration_seconds",
Help: "The Backend duration in seconds",
})
)
// Handler is a http.Handler that services vanity URLs using api
// as a backend service.
type Handler struct {
api Backend
// DocURL is the base URL browsers are redirected to - default is https://pkg.go.dev/
DocURL string
// Duration is the timeout duration for the calls to the backend implementation.
// Default is five seconds.
Duration time.Duration
}
// NewVanityHandler creates a new http.Handler that services vanity URLs using api
// as a backend service.
func NewVanityHandler(api Backend) http.Handler {
return &Handler{
api: api,
DocURL: DefaultDocURL,
Duration: 5 * time.Second, // nolint
}
}
func (s *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
if r.Method != http.MethodGet {
status := http.StatusMethodNotAllowed
http.Error(w, http.StatusText(status), status)
return
}
APICalls.Inc()
ctx, _ := context.WithTimeout(r.Context(), s.Duration) // nolint
root := r.URL.Path
paths := strings.FieldsFunc(root, func(c rune) bool { return c == '/' })
if len(paths) > 0 {
root = "/" + paths[0]
}
importPath := host(r) + root
vcs, repoRoot, err := s.timedGet(ctx, importPath)
if err != nil {
if err == ErrNotFound {
APINotFound.Inc()
http.NotFound(w, r)
} else {
logger.Printf("Unable to get %s: %s", importPath, err)
APIErrors.Inc()
http.Error(w, err.Error(), http.StatusInternalServerError)
}
return
}
vcsRoot := repoRoot + root
if r.FormValue("go-get") != "1" {
APIDocRedirects.Inc()
url := "https://pkg.go.dev/" + importPath
http.Redirect(w, r, url, http.StatusTemporaryRedirect)
return
}
body, err := templatize(host(r)+r.URL.Path, vcs, vcsRoot)
if err != nil {
logger.Printf("Unable to templatize %s: %s", importPath, err)
APIErrTemplates.Inc()
http.Error(w, err.Error(), http.StatusInternalServerError)
return
}
w.Header().Set("Cache-Control", "public, max-age=300")
_, err = w.Write(body)
if err != nil {
logger.Printf("Error writing body for %s: %s", importPath, err)
}
}
func (s *Handler) timedGet(ctx context.Context, importPath string) (vcs, vcsPath string, err error) {
start := time.Now()
defer SummaryVec.Observe(time.Since(start).Seconds())
vcs, vcsPath, err = s.api.Get(ctx, importPath)
return
}
func host(r *http.Request) string {
if r.Header.Get(xForwardedHost) == "" {
return r.Host
}
return r.Header.Get(xForwardedHost)
}
func templatize(importRoot, vcs, vcsRoot string) (body []byte, err error) {
logger.Printf("%s %s %s", importRoot, vcs, vcsRoot)
d := &data{
ImportRoot: importRoot,
VCS: vcs,
VCSRoot: vcsRoot,
}
var buf bytes.Buffer
err = tmpl.Execute(&buf, d)
if err != nil {
return
}
body = buf.Bytes()
return
}