From 59ed0fc7da3f2e59115a203001b7e3ce7e5a6d91 Mon Sep 17 00:00:00 2001
From: Jordan Orelli <jordanorelli@gmail.com>
Date: Sat, 1 Nov 2014 19:09:30 -0400
Subject: [PATCH] request ids

---
 global.go    | 29 +++++++++++++++++++++++++++
 main.go      |  6 ++++--
 requestId.go | 55 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 wrappers.go  | 40 ++++++++++++++++++++++++++++++++++++++
 4 files changed, 128 insertions(+), 2 deletions(-)
 create mode 100644 global.go
 create mode 100644 requestId.go
 create mode 100644 wrappers.go

diff --git a/global.go b/global.go
new file mode 100644
index 0000000..5c3031c
--- /dev/null
+++ b/global.go
@@ -0,0 +1,29 @@
+package main
+
+import (
+	"crypto/md5"
+	"os"
+)
+
+var global struct {
+	hostname       string
+	machineId      []byte
+	pid            int
+	requestCounter uint32
+}
+
+func init() {
+	global.pid = os.Getpid()
+	var err error
+	global.hostname, err = os.Hostname()
+	if err != nil {
+		panic("failed to get hostname: " + err.Error())
+	}
+
+	hw := md5.New()
+	if _, err := hw.Write([]byte(global.hostname)); err != nil {
+		panic("unable to md5 hostname: " + err.Error())
+	}
+	global.machineId = make([]byte, 3)
+	copy(global.machineId, hw.Sum(nil))
+}
diff --git a/main.go b/main.go
index 6555402..e8025e5 100644
--- a/main.go
+++ b/main.go
@@ -3,6 +3,7 @@ package main
 import (
 	"flag"
 	"fmt"
+	"log"
 	"net/http"
 	"os"
 	"strings"
@@ -32,10 +33,10 @@ func main() {
 		bail(1, "unable to get working directory: %v", err)
 	}
 	dir := http.Dir(cwd)
-	http.Handle("/", http.FileServer(dir))
+	http.Handle("/", &logWrapper{http.FileServer(dir)})
 
 	addr := fmt.Sprintf("%s:%d", options.hostname, options.port)
-    fmt.Printf("serving %s on %s\n", cwd, addr)
+	log.Printf("init [pid: %d] [machineId: %x] [addr: %s] [cwd: %s]", global.pid, string(global.machineId), addr, cwd)
 	if err := http.ListenAndServe(addr, nil); err != nil {
 		bail(1, "unable to start server: %v", err)
 	}
@@ -44,4 +45,5 @@ func main() {
 func init() {
 	flag.IntVar(&options.port, "port", 8000, "port to serve on")
 	flag.StringVar(&options.hostname, "host", "", "hostname")
+	log.SetFlags(log.Ldate | log.Lmicroseconds)
 }
diff --git a/requestId.go b/requestId.go
new file mode 100644
index 0000000..d7b199c
--- /dev/null
+++ b/requestId.go
@@ -0,0 +1,55 @@
+package main
+
+import (
+	"encoding/binary"
+	"fmt"
+	"sync/atomic"
+	"time"
+)
+
+// NewObjectId returns a new unique ObjectId.
+// This function causes a runtime error if it fails to get the hostname
+// of the current machine.
+func newRequestId() RequestId {
+	b := make([]byte, 12)
+	// Timestamp, 4 bytes, big endian
+	binary.BigEndian.PutUint32(b, uint32(time.Now().Unix()))
+	b[4] = global.machineId[0]
+	b[5] = global.machineId[1]
+	b[6] = global.machineId[2]
+	// Pid, 2 bytes, specs don't specify endianness, but we use big endian.
+	b[7] = byte(global.pid >> 8)
+	b[8] = byte(global.pid)
+	// Increment, 3 bytes, big endian
+	i := atomic.AddUint32(&global.requestCounter, 1)
+	b[9] = byte(i >> 16)
+	b[10] = byte(i >> 8)
+	b[11] = byte(i)
+	return RequestId(b)
+}
+
+// RequestId is used for tagging each incoming http request for logging
+// purposes.  The actual implementation is just the ObjectId implementation
+// found in launchpad.net/mgo/bson.  This will most likely change and evolve
+// into its own format.
+type RequestId string
+
+func (id RequestId) String() string {
+	return fmt.Sprintf("%x", string(id))
+}
+
+// Time returns the timestamp part of the id.
+// It's a runtime error to call this method with an invalid id.
+func (id RequestId) Time() time.Time {
+	secs := int64(binary.BigEndian.Uint32(id.byteSlice(0, 4)))
+	return time.Unix(secs, 0)
+}
+
+// byteSlice returns byte slice of id from start to end.
+// Calling this function with an invalid id will cause a runtime panic.
+func (id RequestId) byteSlice(start, end int) []byte {
+	if len(id) != 12 {
+		panic(fmt.Sprintf("Invalid RequestId: %q", string(id)))
+	}
+	return []byte(string(id)[start:end])
+}
diff --git a/wrappers.go b/wrappers.go
new file mode 100644
index 0000000..1442458
--- /dev/null
+++ b/wrappers.go
@@ -0,0 +1,40 @@
+package main
+
+import (
+	"log"
+	"net/http"
+	"time"
+)
+
+type logWrapper struct {
+	http.Handler
+}
+
+func (l *logWrapper) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	id := newRequestId()
+	log.Println(id, r.Method, r.URL)
+	statsThing := &writerWatcher{ResponseWriter: w}
+	start := time.Now()
+	l.Handler.ServeHTTP(statsThing, r)
+	log.Println(id, statsThing.headerWritten, statsThing.written, time.Since(start))
+}
+
+type writerWatcher struct {
+	http.ResponseWriter
+	written       int
+	headerWritten int
+}
+
+func (w *writerWatcher) Write(b []byte) (int, error) {
+	n, err := w.ResponseWriter.Write(b)
+	w.written += n
+	return n, err
+}
+
+func (w *writerWatcher) WriteHeader(status int) {
+	if w.headerWritten != 0 {
+		log.Println("somehow we wrote two headers.")
+	}
+	w.headerWritten = status
+	w.ResponseWriter.WriteHeader(status)
+}