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redertron.go
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/
redertron.go
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package rendertron
import (
"context"
"errors"
"fmt"
"io"
"net/http"
"net/url"
"regexp"
"strings"
"time"
"github.com/caddyserver/caddy/v2"
"github.com/caddyserver/caddy/v2/caddyconfig/caddyfile"
"github.com/caddyserver/caddy/v2/modules/caddyhttp"
"go.uber.org/zap"
)
var (
defaultUserAgentPatern = regexp.MustCompile(strings.Join(botUserAgents[:], "|"))
defaultExcludeUrlPattern = regexp.MustCompile("\\.(" + strings.Join(staticFileExtensions[:], "|") + ")$")
)
func init() {
caddy.RegisterModule(Rendertron{})
}
var (
_ caddy.Provisioner = (*Rendertron)(nil)
_ caddyhttp.MiddlewareHandler = (*Rendertron)(nil)
_ caddyfile.Unmarshaler = (*Rendertron)(nil)
_ caddy.Validator = (*Rendertron)(nil)
)
type Rendertron struct {
ExcludeUrlPattern string `json:"excludeUrlPattern,omitempty"`
UserAgentPattern string `json:"userAgentPattern,omitempty"`
Timeout caddy.Duration `json:"timeout,omitempty"`
Proxy string `json:"proxy"`
AllowedForwadedHosts []string `json:"allowedForwadedHosts,omitempty"`
ForwardedHostHeader string `json:"forwardedHostHeader,omitempty"`
log *zap.Logger
cli RendertronClient
excludeUrlPattern *regexp.Regexp
userAgentPattern *regexp.Regexp
}
func (Rendertron) CaddyModule() caddy.ModuleInfo {
return caddy.ModuleInfo{
ID: "http.handlers.rendertron",
New: func() caddy.Module { return new(Rendertron) },
}
}
func (c *Rendertron) Provision(ctx caddy.Context) error {
c.log = ctx.Logger(c)
pu, err := url.Parse(c.Proxy)
if err != nil {
return fmt.Errorf("specified proxy is not a valid url: %w", err)
}
if pu.Scheme != "chrome" {
c.cli = NewProxyRendertronClient(c.Proxy)
}
if c.ExcludeUrlPattern == "" {
c.excludeUrlPattern = defaultExcludeUrlPattern
} else {
re, err := regexp.Compile(c.ExcludeUrlPattern)
if err != nil {
return fmt.Errorf("unable to parse exclude pattern: %w", err)
}
c.excludeUrlPattern = re
}
if c.UserAgentPattern == "" {
c.userAgentPattern = defaultUserAgentPatern
} else {
re, err := regexp.Compile(c.UserAgentPattern)
if err != nil {
return fmt.Errorf("unable to parse user agent pattern: %w", err)
}
c.userAgentPattern = re
}
if c.Timeout == 0 {
// The Rendertron service itself has a hard limit of 10 seconds to render, so
// let's give a little more time than that by default.
c.Timeout = 11 * caddy.Duration(time.Second)
}
if c.ForwardedHostHeader == "" {
c.ForwardedHostHeader = "X-Forwarded-Host"
}
return nil
}
func (c *Rendertron) Validate() error {
if c.excludeUrlPattern == nil {
return errors.New("exclude pattern is nil")
}
if c.userAgentPattern == nil {
return errors.New("user agent pattern is nil")
}
if c.cli == nil {
return errors.New("render mechanishm is not selected please select it using the proxy option")
}
return nil
}
func (c *Rendertron) ServeHTTP(w http.ResponseWriter, r *http.Request, next caddyhttp.Handler) error {
ua := r.Header.Get("User-Agent")
if ua == "" || !c.userAgentPattern.MatchString(ua) || c.excludeUrlPattern.MatchString(ua) {
return next.ServeHTTP(w, r)
}
host := r.Host
hh := r.Header.Get(c.ForwardedHostHeader)
for _, h := range c.AllowedForwadedHosts {
if h == hh {
host = hh
break
}
}
scheme := "https"
if r.TLS == nil {
scheme = "http"
}
ctx, cancel := context.WithTimeout(context.Background(), time.Duration(c.Timeout))
defer cancel()
ru := scheme + "://" + host + r.RequestURI
res, err := c.cli.Render(ctx, ru, nil)
if err != nil {
c.log.Error("unable to render page", zap.String("url", ru), zap.Error(err))
return err
}
defer res.Body.Close()
// Copy headers
for k, vv := range res.Header {
for _, v := range vv {
w.Header().Add(k, v)
}
}
w.WriteHeader(res.StatusCode)
if _, err := io.Copy(w, res.Body); err != nil {
c.log.Error("error writing response to client", zap.Error(err))
return err
}
return nil
}
var (
botUserAgents = [...]string{
"Baiduspider",
"bingbot",
"Embedly",
"facebookexternalhit",
"LinkedInBot",
"outbrain",
"pinterest",
"quora link preview",
"rogerbot",
"showyoubot",
"Slackbot",
"TelegramBot",
"Twitterbot",
"vkShare",
"W3C_Validator",
"WhatsApp",
}
staticFileExtensions = [...]string{
"ai",
"avi",
"css",
"dat",
"dmg",
"doc",
"doc",
"exe",
"flv",
"gif",
"ico",
"iso",
"jpeg",
"jpg",
"js",
"less",
"m4a",
"m4v",
"mov",
"mp3",
"mp4",
"mpeg",
"mpg",
"pdf",
"png",
"ppt",
"psd",
"rar",
"rss",
"svg",
"swf",
"tif",
"torrent",
"ttf",
"txt",
"wav",
"wmv",
"woff",
"xls",
"xml",
"zip",
}
)