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// Copyright 2019 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package frontend provides functionality for running the pkg.go.dev site.
package frontend
import (
"bytes"
"context"
"errors"
"fmt"
"io"
"net/http"
"strings"
"sync"
"time"
"github.com/go-redis/redis/v8"
"github.com/google/safehtml"
"github.com/google/safehtml/template"
"golang.org/x/pkgsite/internal"
"golang.org/x/pkgsite/internal/derrors"
"golang.org/x/pkgsite/internal/experiment"
"golang.org/x/pkgsite/internal/godoc/dochtml"
"golang.org/x/pkgsite/internal/licenses"
"golang.org/x/pkgsite/internal/log"
"golang.org/x/pkgsite/internal/middleware"
"golang.org/x/pkgsite/internal/queue"
)
// Server can be installed to serve the go discovery frontend.
type Server struct {
// getDataSource should never be called from a handler. It is called only in Server.errorHandler.
getDataSource func(context.Context) internal.DataSource
queue queue.Queue
// cmplClient is a redis client that has access to the "completions" sorted
// set.
cmplClient *redis.Client
taskIDChangeInterval time.Duration
staticPath template.TrustedSource
thirdPartyPath string
templateDir template.TrustedSource
devMode bool
errorPage []byte
appVersionLabel string
googleTagManagerID string
serveStats bool
mu sync.Mutex // Protects all fields below
templates map[string]*template.Template
}
// ServerConfig contains everything needed by a Server.
type ServerConfig struct {
// DataSourceGetter should return a DataSource on each call.
// It should be goroutine-safe.
DataSourceGetter func(context.Context) internal.DataSource
Queue queue.Queue
CompletionClient *redis.Client
TaskIDChangeInterval time.Duration
StaticPath template.TrustedSource
ThirdPartyPath string
DevMode bool
AppVersionLabel string
GoogleTagManagerID string
ServeStats bool
}
// NewServer creates a new Server for the given database and template directory.
func NewServer(scfg ServerConfig) (_ *Server, err error) {
defer derrors.Wrap(&err, "NewServer(...)")
templateDir := template.TrustedSourceJoin(scfg.StaticPath, template.TrustedSourceFromConstant("html"))
ts, err := parsePageTemplates(templateDir)
if err != nil {
return nil, fmt.Errorf("error parsing templates: %v", err)
}
docTemplateDir := template.TrustedSourceJoin(templateDir, template.TrustedSourceFromConstant("doc"))
dochtml.LoadTemplates(docTemplateDir)
s := &Server{
getDataSource: scfg.DataSourceGetter,
queue: scfg.Queue,
cmplClient: scfg.CompletionClient,
staticPath: scfg.StaticPath,
thirdPartyPath: scfg.ThirdPartyPath,
templateDir: templateDir,
devMode: scfg.DevMode,
templates: ts,
taskIDChangeInterval: scfg.TaskIDChangeInterval,
appVersionLabel: scfg.AppVersionLabel,
googleTagManagerID: scfg.GoogleTagManagerID,
serveStats: scfg.ServeStats,
}
errorPageBytes, err := s.renderErrorPage(context.Background(), http.StatusInternalServerError, "error.tmpl", nil)
if err != nil {
return nil, fmt.Errorf("s.renderErrorPage(http.StatusInternalServerError, nil): %v", err)
}
s.errorPage = errorPageBytes
return s, nil
}
// Install registers server routes using the given handler registration func.
// authValues is the set of values that can be set on authHeader to bypass the
// cache.
func (s *Server) Install(handle func(string, http.Handler), redisClient *redis.Client, authValues []string) {
var (
detailHandler http.Handler = s.errorHandler(s.serveDetails)
fetchHandler http.Handler = s.errorHandler(s.serveFetch)
searchHandler http.Handler = s.errorHandler(s.serveSearch)
)
if redisClient != nil {
detailHandler = middleware.Cache("details", redisClient, detailsTTL, authValues)(detailHandler)
searchHandler = middleware.Cache("search", redisClient, middleware.TTL(defaultTTL), authValues)(searchHandler)
}
// Each AppEngine instance is created in response to a start request, which
// is an empty HTTP GET request to /_ah/start when scaling is set to manual
// or basic, and /_ah/warmup when scaling is automatic and min_instances is
// set. AppEngine sends this request to bring an instance into existence.
// See details for /_ah/start at
// https://cloud.google.com/appengine/docs/standard/go/how-instances-are-managed#startup
// and for /_ah/warmup at
// https://cloud.google.com/appengine/docs/standard/go/configuring-warmup-requests.
handle("/_ah/", http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
log.Infof(r.Context(), "Request made to %q", r.URL.Path)
}))
handle("/static/", http.StripPrefix("/static/", http.FileServer(http.Dir(s.staticPath.String()))))
handle("/third_party/", http.StripPrefix("/third_party", http.FileServer(http.Dir(s.thirdPartyPath))))
handle("/favicon.ico", http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
http.ServeFile(w, r, fmt.Sprintf("%s/img/favicon.ico", http.Dir(s.staticPath.String())))
}))
handle("/mod/", http.HandlerFunc(s.handleModuleDetailsRedirect))
handle("/pkg/", http.HandlerFunc(s.handlePackageDetailsRedirect))
handle("/fetch/", fetchHandler)
handle("/play/", http.HandlerFunc(s.handlePlay))
handle("/search", searchHandler)
handle("/search-help", s.staticPageHandler("search_help.tmpl", "Search Help"))
handle("/license-policy", s.licensePolicyHandler())
handle("/about", http.RedirectHandler("https://go.dev/about", http.StatusFound))
handle("/badge/", http.HandlerFunc(s.badgeHandler))
handle("/C", http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
// Package "C" is a special case: redirect to /cmd/cgo.
// (This is what golang.org/C does.)
http.Redirect(w, r, "/cmd/cgo", http.StatusMovedPermanently)
}))
handle("/", detailHandler)
if s.serveStats {
handle("/detail-stats/",
middleware.Stats()(http.StripPrefix("/detail-stats", s.errorHandler(s.serveDetails))))
}
handle("/robots.txt", http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
w.Header().Set("Content-Type", "text/plain; charset=utf-8")
http.ServeContent(w, r, "", time.Time{}, strings.NewReader(`User-agent: *
Disallow: /search?*
Disallow: /fetch/*
`))
}))
}
const (
// defaultTTL is used when details tab contents are subject to change, or when
// there is a problem confirming that the details can be permanently cached.
defaultTTL = 1 * time.Hour
// shortTTL is used for volatile content, such as the latest version of a
// package or module.
shortTTL = 10 * time.Minute
// longTTL is used when details content is essentially static.
longTTL = 24 * time.Hour
// tinyTTL is used to cache crawled pages.
tinyTTL = 1 * time.Minute
)
var crawlers = []string{
"+http://www.google.com/bot.html",
"+http://www.bing.com/bingbot.htm",
"+http://ahrefs.com/robot",
}
// detailsTTL assigns the cache TTL for package detail requests.
func detailsTTL(r *http.Request) time.Duration {
userAgent := r.Header.Get("User-Agent")
for _, c := range crawlers {
if strings.Contains(userAgent, c) {
return tinyTTL
}
}
return detailsTTLForPath(r.Context(), r.URL.Path, r.FormValue("tab"))
}
func detailsTTLForPath(ctx context.Context, urlPath, tab string) time.Duration {
if urlPath == "/" {
return defaultTTL
}
info, err := parseDetailsURLPath(urlPath)
if err != nil {
log.Errorf(ctx, "falling back to default TTL: %v", err)
return defaultTTL
}
if info.requestedVersion == internal.LatestVersion {
return shortTTL
}
if tab == "importedby" || tab == "versions" {
return defaultTTL
}
return longTTL
}
// TagRoute categorizes incoming requests to the frontend for use in
// monitoring.
func TagRoute(route string, r *http.Request) string {
tag := strings.Trim(route, "/")
if tab := r.FormValue("tab"); tab != "" {
// Verify that the tab value actually exists, otherwise this is unsanitized
// input and could result in unbounded cardinality in our metrics.
if _, ok := unitTabLookup[tab]; ok {
if tag != "" {
tag += "-"
}
tag += tab
}
}
return tag
}
// staticPageHandler handles requests to a template that contains no dynamic
// content.
func (s *Server) staticPageHandler(templateName, title string) http.HandlerFunc {
return func(w http.ResponseWriter, r *http.Request) {
s.servePage(r.Context(), w, templateName, s.newBasePage(r, title))
}
}
// basePage contains fields shared by all pages when rendering templates.
type basePage struct {
// HTMLTitle is the value to use in the page’s <title> tag.
HTMLTitle string
// MetaDescription is the html used for rendering the <meta name="Description"> tag.
MetaDescription safehtml.HTML
// Query is the current search query (if applicable).
Query string
// Experiments contains the experiments currently active.
Experiments *experiment.Set
// DevMode indicates whether the server is running in development mode.
DevMode bool
// AppVersionLabel contains the current version of the app.
AppVersionLabel string
// GoogleTagManagerID is the ID used to load Google Tag Manager.
GoogleTagManagerID string
// AllowWideContent indicates whether the content should be displayed in a
// way that’s amenable to wider viewports.
AllowWideContent bool
}
// licensePolicyPage is used to generate the static license policy page.
type licensePolicyPage struct {
basePage
LicenseFileNames []string
LicenseTypes []licenses.AcceptedLicenseInfo
}
func (s *Server) licensePolicyHandler() http.HandlerFunc {
lics := licenses.AcceptedLicenses()
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
page := licensePolicyPage{
basePage: s.newBasePage(r, "Licenses"),
LicenseFileNames: licenses.FileNames,
LicenseTypes: lics,
}
s.servePage(r.Context(), w, "license_policy.tmpl", page)
})
}
// newBasePage returns a base page for the given request and title.
func (s *Server) newBasePage(r *http.Request, title string) basePage {
return basePage{
HTMLTitle: title,
Query: searchQuery(r),
Experiments: experiment.FromContext(r.Context()),
DevMode: s.devMode,
AppVersionLabel: s.appVersionLabel,
GoogleTagManagerID: s.googleTagManagerID,
}
}
// errorPage contains fields for rendering a HTTP error page.
type errorPage struct {
basePage
templateName string
messageTemplate template.TrustedTemplate
MessageData interface{}
}
// PanicHandler returns an http.HandlerFunc that can be used in HTTP
// middleware. It returns an error if something goes wrong pre-rendering the
// error template.
func (s *Server) PanicHandler() (_ http.HandlerFunc, err error) {
defer derrors.Wrap(&err, "PanicHandler")
status := http.StatusInternalServerError
buf, err := s.renderErrorPage(context.Background(), status, "error.tmpl", nil)
if err != nil {
return nil, err
}
return func(w http.ResponseWriter, r *http.Request) {
w.WriteHeader(status)
if _, err := io.Copy(w, bytes.NewReader(buf)); err != nil {
log.Errorf(r.Context(), "Error copying panic template to ResponseWriter: %v", err)
}
}, nil
}
type serverError struct {
status int // HTTP status code
responseText string // Response text to the user
epage *errorPage
err error // wrapped error
}
func (s *serverError) Error() string {
return fmt.Sprintf("%d (%s): %v (epage=%v)", s.status, http.StatusText(s.status), s.err, s.epage)
}
func (s *serverError) Unwrap() error {
return s.err
}
func (s *Server) errorHandler(f func(w http.ResponseWriter, r *http.Request, ds internal.DataSource) error) http.HandlerFunc {
return func(w http.ResponseWriter, r *http.Request) {
// Obtain a DataSource to use for this request.
ds := s.getDataSource(r.Context())
if err := f(w, r, ds); err != nil {
s.serveError(w, r, err)
}
}
}
func (s *Server) serveError(w http.ResponseWriter, r *http.Request, err error) {
ctx := r.Context()
var serr *serverError
if !errors.As(err, &serr) {
serr = &serverError{status: http.StatusInternalServerError, err: err}
}
if serr.status == http.StatusInternalServerError {
log.Error(ctx, err)
} else {
log.Infof(ctx, "returning %d (%s) for error %v", serr.status, http.StatusText(serr.status), err)
}
if serr.responseText == "" {
serr.responseText = http.StatusText(serr.status)
}
if r.Method == http.MethodPost {
http.Error(w, serr.responseText, serr.status)
return
}
s.serveErrorPage(w, r, serr.status, serr.epage)
}
func (s *Server) serveErrorPage(w http.ResponseWriter, r *http.Request, status int, page *errorPage) {
template := "error.tmpl"
if page != nil {
if page.AppVersionLabel == "" || page.GoogleTagManagerID == "" {
// If the basePage was properly created using newBasePage, both
// AppVersionLabel and GoogleTagManagerID should always be set.
page.basePage = s.newBasePage(r, "")
}
if page.templateName != "" {
template = page.templateName
}
} else {
page = &errorPage{
basePage: s.newBasePage(r, ""),
}
}
buf, err := s.renderErrorPage(r.Context(), status, template, page)
if err != nil {
log.Errorf(r.Context(), "s.renderErrorPage(w, %d, %v): %v", status, page, err)
buf = s.errorPage
status = http.StatusInternalServerError
}
w.WriteHeader(status)
if _, err := io.Copy(w, bytes.NewReader(buf)); err != nil {
log.Errorf(r.Context(), "Error copying template %q buffer to ResponseWriter: %v", template, err)
}
}
// renderErrorPage executes error.tmpl with the given errorPage
func (s *Server) renderErrorPage(ctx context.Context, status int, templateName string, page *errorPage) ([]byte, error) {
statusInfo := fmt.Sprintf("%d %s", status, http.StatusText(status))
if page == nil {
page = &errorPage{}
}
if page.messageTemplate.String() == "" {
page.messageTemplate = template.MakeTrustedTemplate(`<h3 class="Error-message">{{.}}</h3>`)
}
if page.MessageData == nil {
page.MessageData = statusInfo
}
if page.HTMLTitle == "" {
page.HTMLTitle = statusInfo
}
if templateName == "" {
templateName = "error.tmpl"
}
etmpl, err := s.findTemplate(templateName)
if err != nil {
return nil, err
}
tmpl, err := etmpl.Clone()
if err != nil {
return nil, err
}
_, err = tmpl.New("message").ParseFromTrustedTemplate(page.messageTemplate)
if err != nil {
return nil, err
}
return executeTemplate(ctx, templateName, tmpl, page)
}
// servePage is used to execute all templates for a *Server.
func (s *Server) servePage(ctx context.Context, w http.ResponseWriter, templateName string, page interface{}) {
defer middleware.ElapsedStat(ctx, "servePage")()
buf, err := s.renderPage(ctx, templateName, page)
if err != nil {
log.Errorf(ctx, "s.renderPage(%q, %+v): %v", templateName, page, err)
w.WriteHeader(http.StatusInternalServerError)
buf = s.errorPage
}
if _, err := io.Copy(w, bytes.NewReader(buf)); err != nil {
log.Errorf(ctx, "Error copying template %q buffer to ResponseWriter: %v", templateName, err)
w.WriteHeader(http.StatusInternalServerError)
}
}
// renderPage executes the given templateName with page.
func (s *Server) renderPage(ctx context.Context, templateName string, page interface{}) ([]byte, error) {
defer middleware.ElapsedStat(ctx, "renderPage")()
tmpl, err := s.findTemplate(templateName)
if err != nil {
return nil, err
}
return executeTemplate(ctx, templateName, tmpl, page)
}
func (s *Server) findTemplate(templateName string) (*template.Template, error) {
if s.devMode {
s.mu.Lock()
defer s.mu.Unlock()
var err error
s.templates, err = parsePageTemplates(s.templateDir)
if err != nil {
return nil, fmt.Errorf("error parsing templates: %v", err)
}
}
tmpl := s.templates[templateName]
if tmpl == nil {
return nil, fmt.Errorf("BUG: s.templates[%q] not found", templateName)
}
return tmpl, nil
}
func executeTemplate(ctx context.Context, templateName string, tmpl *template.Template, data interface{}) ([]byte, error) {
var buf bytes.Buffer
if err := tmpl.Execute(&buf, data); err != nil {
log.Errorf(ctx, "Error executing page template %q: %v", templateName, err)
return nil, err
}
return buf.Bytes(), nil
}
var templateFuncs = template.FuncMap{
"add": func(i, j int) int { return i + j },
"pluralize": func(i int, s string) string {
if i == 1 {
return s
}
return s + "s"
},
"commaseparate": func(s []string) string {
return strings.Join(s, ", ")
},
}
// parsePageTemplates parses html templates contained in the given base
// directory in order to generate a map of Name->*template.Template.
//
// Separate templates are used so that certain contextual functions (e.g.
// templateName) can be bound independently for each page.
func parsePageTemplates(base template.TrustedSource) (map[string]*template.Template, error) {
tsc := template.TrustedSourceFromConstant
join := template.TrustedSourceJoin
htmlSets := [][]template.TrustedSource{
{tsc("badge.tmpl")},
{tsc("error.tmpl")},
{tsc("fetch.tmpl")},
{tsc("index.tmpl")},
{tsc("license_policy.tmpl")},
{tsc("search.tmpl")},
{tsc("search_help.tmpl")},
{tsc("unit_details.tmpl"), tsc("unit.tmpl")},
{tsc("unit_importedby.tmpl"), tsc("unit.tmpl")},
{tsc("unit_imports.tmpl"), tsc("unit.tmpl")},
{tsc("unit_licenses.tmpl"), tsc("unit.tmpl")},
{tsc("unit_versions.tmpl"), tsc("unit.tmpl")},
}
templates := make(map[string]*template.Template)
for _, set := range htmlSets {
t, err := template.New("base.tmpl").Funcs(templateFuncs).ParseFilesFromTrustedSources(join(base, tsc("base.tmpl")))
if err != nil {
return nil, fmt.Errorf("ParseFiles: %v", err)
}
helperGlob := join(base, tsc("helpers"), tsc("*.tmpl"))
if _, err := t.ParseGlobFromTrustedSource(helperGlob); err != nil {
return nil, fmt.Errorf("ParseGlob(%q): %v", helperGlob, err)
}
var files []template.TrustedSource
for _, f := range set {
files = append(files, join(base, tsc("pages"), f))
}
if _, err := t.ParseFilesFromTrustedSources(files...); err != nil {
return nil, fmt.Errorf("ParseFilesFromTrustedSources(%v): %v", files, err)
}
templates[set[0].String()] = t
}
return templates, nil
}