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server.go
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server.go
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package pixel
import (
"encoding/json"
"fmt"
"io"
"log"
"log/syslog"
"net/http"
"time"
)
type Server struct {
listenAddress string
httpServer *http.Server
syslogAddress string
syslogPriority syslog.Priority
logger *log.Logger
now func() time.Time
}
// Every pixel GET or JSON POST is an event.
type Event struct {
Time string `json:"t"`
// Params are client-supplied event attributes.
// Pixel events have params of form map[string]string.
// JSON POST events have arbitrary JSON.
Params interface{} `json:"params,omitempty"`
UserAgent string `json:"ua,omitempty"`
IP string `json:"ip,omitempty"`
Proto string `json:"proto,omitempty"`
// Error is a server-defined string reporting any error that
// occurred while constructing the event, such as parse failures.
Error string `json:"error,omitempty"`
}
const ISO8601Format = "2006-01-02T15:04:05Z"
var Transparent1PxGIF = []byte("\x47\x49\x46\x38\x39\x61\x01\x00" +
"\x01\x00\x80\x00\x00\xff\xff\xff\x00\x00\x00\x2c\x00\x00\x00\x00" +
"\x01\x00\x01\x00\x00\x02\x02\x44\x01\x00\x3b")
const UDPMaxBytes = 65507
var BadRequest = http.StatusText(http.StatusBadRequest)
const PostBodyMaxLen = 2048
var levelMap = map[string]syslog.Priority{
"LOG_EMERG": syslog.LOG_EMERG,
"LOG_ALERT": syslog.LOG_ALERT,
"LOG_CRIT": syslog.LOG_CRIT,
"LOG_ERR": syslog.LOG_ERR,
"LOG_WARNING": syslog.LOG_WARNING,
"LOG_NOTICE": syslog.LOG_NOTICE,
"LOG_INFO": syslog.LOG_INFO,
"LOG_DEBUG": syslog.LOG_DEBUG,
}
var facilityMap = map[string]syslog.Priority{
"LOG_KERN": syslog.LOG_KERN,
"LOG_USER": syslog.LOG_USER,
"LOG_MAIL": syslog.LOG_MAIL,
"LOG_DAEMON": syslog.LOG_DAEMON,
"LOG_AUTH": syslog.LOG_AUTH,
"LOG_SYSLOG": syslog.LOG_SYSLOG,
"LOG_LPR": syslog.LOG_LPR,
"LOG_NEWS": syslog.LOG_NEWS,
"LOG_UUCP": syslog.LOG_UUCP,
"LOG_CRON": syslog.LOG_CRON,
"LOG_AUTHPRIV": syslog.LOG_AUTHPRIV,
"LOG_FTP": syslog.LOG_FTP,
"LOG_LOCAL0": syslog.LOG_LOCAL0,
"LOG_LOCAL1": syslog.LOG_LOCAL1,
"LOG_LOCAL2": syslog.LOG_LOCAL2,
"LOG_LOCAL3": syslog.LOG_LOCAL3,
"LOG_LOCAL4": syslog.LOG_LOCAL4,
"LOG_LOCAL5": syslog.LOG_LOCAL5,
"LOG_LOCAL6": syslog.LOG_LOCAL6,
}
func NewSyslogPriority(level string, facility string) syslog.Priority {
p, ok := levelMap[level]
if !ok {
p = syslog.LOG_INFO
}
f, ok := facilityMap[facility]
if !ok {
f = syslog.LOG_LOCAL7
}
return p | f
}
func NewServer(syslogAddress string, syslogPriority syslog.Priority) (*Server, error) {
s := new(Server)
s.syslogAddress = syslogAddress
s.syslogPriority = syslogPriority
writer, err := syslog.Dial("udp", s.syslogAddress, s.syslogPriority, "pixel")
if err != nil {
return nil, err
}
s.logger = log.New(writer, "", 0)
s.now = time.Now
return s, err
}
// Returns true if an interface is a flat mapping of strings to strings
// or numbers.
func isFlatJSON(i interface{}) bool {
m, ok := i.(map[string]interface{})
if !ok {
return false
}
for _, v := range m {
switch v.(type) {
case string:
case int:
case float64:
continue
default:
return false
}
}
return true
}
// Returns a new *Event. *http.Request can be either a pixel or a
// JSON POST request.
func NewEvent(t time.Time, r *http.Request) (*Event, error) {
event := &Event{
Time: t.UTC().Format(ISO8601Format),
UserAgent: r.Header.Get("User-Agent"),
IP: r.Header.Get("X-Forwarded-For"),
Proto: r.Header.Get("X-Forwarded-Proto"),
}
var err error
switch r.Method {
case "GET":
err = r.ParseForm()
if err != nil {
err = fmt.Errorf("Malformed query string: %s", err)
break
}
params := make(map[string]string)
for key, values := range r.Form {
params[key] = values[0]
}
event.Params = params
case "POST":
if r.ContentLength == 0 {
err = fmt.Errorf("Empty POST body")
break
}
if r.ContentLength > PostBodyMaxLen {
err = fmt.Errorf("POST body exceeds max length: %d", r.ContentLength)
break
}
body := make([]byte, PostBodyMaxLen)
var n int
n, err = r.Body.Read(body)
if err != nil && err != io.EOF {
break
}
var params interface{}
err = json.Unmarshal(body[:n], ¶ms)
if err != nil {
break
}
event.Params = ¶ms
default:
err = fmt.Errorf("Invalid method %s", r.Method)
}
if err != nil {
event.Error = err.Error()
}
return event, err
}
func (s *Server) parseRequest(w http.ResponseWriter, r *http.Request) (*Event, error) {
event, err := NewEvent(s.now(), r)
if err != nil {
log.Printf("%s", err)
http.Error(w, BadRequest, http.StatusBadRequest)
}
return event, err
}
func (s *Server) logEvent(event *Event) {
jsondata, err := json.Marshal(event)
if err != nil {
log.Printf("json encode error: %s", err)
} else {
s.logger.Printf("%s", jsondata)
}
}
func (s *Server) trackPixel(w http.ResponseWriter, r *http.Request) {
event, err := s.parseRequest(w, r)
s.logEvent(event)
if err != nil {
return
}
w.Header().Set("Content-Type", "image/gif")
w.Write(Transparent1PxGIF)
}
func (s *Server) trackJSON(w http.ResponseWriter, r *http.Request) {
event, err := s.parseRequest(w, r)
s.logEvent(event)
if err != nil {
return
}
w.Header().Set("Content-Type", "application/json")
w.Write([]byte("{}"))
}
func (s *Server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
switch r.Method {
case "GET":
s.trackPixel(w, r)
return
case "POST":
s.trackJSON(w, r)
default:
http.Error(w, BadRequest, http.StatusBadRequest)
}
}
func (s *Server) ListenAndServe(address string) {
s.httpServer = &http.Server{
Addr: address,
Handler: s,
ReadTimeout: 10 * time.Second,
WriteTimeout: 10 * time.Second,
MaxHeaderBytes: 1 << 20,
}
log.Fatal(s.httpServer.ListenAndServe())
}