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matrix-spec-proposals/scripts/continuserv/main.go

230 lines
5.0 KiB
Go

// continuserv proactively re-generates the spec on filesystem changes, and serves it over HTTP.
// It will always serve the most recent version of the spec, and may block an HTTP request until regeneration is finished.
// It does not currently pre-empt stale generations, but will block until they are complete.
package main
import (
"bytes"
"flag"
"fmt"
"io/ioutil"
"log"
"net/http"
"os"
"os/exec"
"path"
"path/filepath"
"strings"
"sync"
"sync/atomic"
"time"
fsnotify "gopkg.in/fsnotify.v1"
)
var (
port = flag.Int("port", 8000, "Port on which to serve HTTP")
mu sync.Mutex // Prevent multiple updates in parallel.
toServe atomic.Value // Always contains a bytesOrErr. May be stale unless wg is zero.
wgMu sync.Mutex // Prevent multiple calls to wg.Wait() or wg.Add(positive number) in parallel.
wg sync.WaitGroup // Indicates how many updates are pending.
)
func main() {
flag.Parse()
w, err := fsnotify.NewWatcher()
if err != nil {
log.Fatalf("Error making watcher: %v", err)
}
dir, err := os.Getwd()
if err != nil {
log.Fatalf("Error getting wd: %v", err)
}
for ; !exists(path.Join(dir, ".git")); dir = path.Dir(dir) {
if dir == "/" {
log.Fatalf("Could not find git root")
}
}
walker := makeWalker(dir, w)
paths := []string{"api", "changelogs", "event-schemas", "scripts",
"specification", "templating"}
for _, p := range paths {
filepath.Walk(path.Join(dir, p), walker)
}
wg.Add(1)
populateOnce(dir)
ch := make(chan struct{}, 100) // Buffered to ensure we can multiple-increment wg for pending writes
go doPopulate(ch, dir)
go watchFS(ch, w)
fmt.Printf("Listening on port %d\n", *port)
http.HandleFunc("/", serve)
log.Fatal(http.ListenAndServe(fmt.Sprintf(":%d", *port), nil))
}
func watchFS(ch chan struct{}, w *fsnotify.Watcher) {
for {
select {
case e := <-w.Events:
if filter(e) {
fmt.Printf("Noticed change to %s, re-generating spec\n", e.Name)
ch <- struct{}{}
}
}
}
}
func makeWalker(base string, w *fsnotify.Watcher) filepath.WalkFunc {
return func(path string, _ os.FileInfo, err error) error {
if err != nil {
log.Fatalf("Error walking: %v", err)
}
rel, err := filepath.Rel(base, path)
if err != nil {
log.Fatalf("Failed to get relative path of %s: %v", path, err)
}
// skip a few things that we know don't form part of the spec
if rel == "api/node_modules" ||
rel == "scripts/gen" ||
rel == "scripts/tmp" {
return filepath.SkipDir
}
// log.Printf("Adding watch on %s", path)
if err := w.Add(path); err != nil {
log.Fatalf("Failed to add watch on %s: %v", path, err)
}
return nil
}
}
// Return true if event should trigger re-population
func filter(e fsnotify.Event) bool {
// vim is *really* noisy about how it writes files
if e.Op != fsnotify.Write {
return false
}
// Avoid some temp files that vim writes
if strings.HasSuffix(e.Name, "~") || strings.HasSuffix(e.Name, ".swp") || strings.HasPrefix(e.Name, ".") {
return false
}
return true
}
func serve(w http.ResponseWriter, req *http.Request) {
wgMu.Lock()
wg.Wait()
wgMu.Unlock()
file := req.URL.Path
if file[0] == '/' {
file = file[1:]
}
if file == "" {
file = "index.html"
}
m := toServe.Load().(bytesOrErr)
if m.err != nil {
w.Header().Set("Content-Type", "text/plain")
w.Write([]byte(m.err.Error()))
return
}
b, ok := m.bytes[file]
if ok {
w.Header().Set("Content-Type", "text/html")
w.Write([]byte(b))
return
}
w.Header().Set("Content-Type", "text/plain")
w.WriteHeader(404)
w.Write([]byte("Not found"))
}
func populateOnce(dir string) {
defer wg.Done()
mu.Lock()
defer mu.Unlock()
cmd := exec.Command("python", "gendoc.py")
cmd.Dir = path.Join(dir, "scripts")
var b bytes.Buffer
cmd.Stderr = &b
err := cmd.Run()
if err != nil {
toServe.Store(bytesOrErr{nil, fmt.Errorf("error generating spec: %v\nOutput from gendoc:\n%v", err, b.String())})
return
}
files := make(map[string][]byte)
base := path.Join(dir, "scripts", "gen")
walker := func(path string, info os.FileInfo, err error) error {
if err != nil {
return err
}
if info.IsDir() {
return nil
}
rel, err := filepath.Rel(base, path)
if err != nil {
return fmt.Errorf("Failed to get relative path of %s: %v", path, err)
}
bytes, err := ioutil.ReadFile(path)
if err != nil {
return err
}
files[rel] = bytes
return nil
}
err = filepath.Walk(base, walker)
if err != nil {
toServe.Store(bytesOrErr{nil, fmt.Errorf("error reading spec: %v", err)})
return
}
toServe.Store(bytesOrErr{files, nil})
}
func doPopulate(ch chan struct{}, dir string) {
var pending int
for {
select {
case <-ch:
if pending == 0 {
wgMu.Lock()
wg.Add(1)
wgMu.Unlock()
}
pending++
case <-time.After(10 * time.Millisecond):
if pending > 0 {
pending = 0
populateOnce(dir)
}
}
}
}
func exists(path string) bool {
_, err := os.Stat(path)
return !os.IsNotExist(err)
}
type bytesOrErr struct {
bytes map[string][]byte // filename -> contents
err error
}