add some hacky experiments for inotify event parsing

docker/Dockerfile

@@ -1,9 +1,15 @@
 FROM golang:1.9-stretch
 
-RUN useradd -ms /bin/bash myuser
+RUN apt-get update && apt-get -y install cron sudo
+COPY docker/etc/cron.d /etc/cron.d
+COPY docker/scripts /scripts
 
+RUN useradd -ms /bin/bash myuser && \
+    adduser myuser sudo && \
+    echo 'myuser ALL=(ALL) NOPASSWD:ALL' >> /etc/sudoers
 USER myuser
 
+
 WORKDIR /go/src/github.com/dominicbreuker
 
 

docker/etc/cron.d/myjob

@@ -0,0 +1 @@
+* * * * * root echo 'this is some text' >> /tmp/myjob.log

docker/etc/cron.d/print

@@ -0,0 +1 @@
+* * * * * root python /scripts/print_stuff.py >> /tmp/print.log

docker/scripts/print_stuff.py

@@ -0,0 +1,9 @@
+#!/usr/bin/python
+
+user = "myusername"
+password = "thepw"
+
+for i in range(100):
+    print("a"*i)
+
+print("done")

internal/dev/plist.go

@@ -6,6 +6,7 @@ import (
 
 	"github.com/dominicbreuker/pspy/internal/inotify"
 	"github.com/dominicbreuker/pspy/internal/process"
+	"github.com/dominicbreuker/pspy/internal/walker"
 )
 
 type Process struct {
@@ -19,32 +20,36 @@ type Process struct {
 }
 
 func Monitor() {
-	// procList := make(map[int]string)
-
 	watch()
-
-	// for {
-	// 	refresh(procList)
-	// }
 }
 
 func watch() {
+	maxWatchers, err := inotify.WatcherLimit()
+	if err != nil {
+		log.Printf("Can't get inotify watcher limit...: %v\n", err)
+	}
+	log.Printf("Watcher limit: %d\n", maxWatchers)
+
 	ping := make(chan struct{})
 	in, err := inotify.NewInotify(ping)
 	if err != nil {
 		log.Fatalf("Can't init inotify: %v", err)
 	}
+	defer in.Close()
 
-	dirs := []string{
+	dirCh, errCh := walker.Walk("/tmp")
-		"/proc",
+loop:
-		"/var/log",
+	for {
-		"/home",
+		select {
-		"/tmp",
+		case dir, ok := <-dirCh:
+			if !ok {
+				break loop
 			}
-
-	for _, dir := range dirs {
 			if err := in.Watch(dir); err != nil {
-			log.Fatalf("Can't create watcher: %v", err)
+				log.Printf("Can't create watcher: %v", err)
+			}
+		case err := <-errCh:
+			log.Printf("Error walking filesystem: %v", err)
 		}
 	}
 
@@ -52,14 +57,13 @@ func watch() {
 
 	procList := process.NewProcList()
 
-	ticker := time.NewTicker(50 * time.Millisecond).C
+	ticker := time.NewTicker(100 * time.Millisecond).C
 
 	for {
 		select {
 		case <-ticker:
 			refresh(in, procList)
 		case <-ping:
-			log.Printf("PING")
 			refresh(in, procList)
 		}
 	}
@@ -70,6 +74,6 @@ func refresh(in *inotify.Inotify, pl *process.ProcList) {
 	if err := pl.Refresh(); err != nil {
 		log.Printf("ERROR refreshing process list: %v", err)
 	}
-	time.Sleep(50 * time.Millisecond)
+	time.Sleep(10 * time.Millisecond)
 	in.UnPause()
 }

internal/inotify/inotify.go

@@ -2,13 +2,16 @@ package inotify
 
 import (
 	"fmt"
+	"log"
+	"strings"
+	"unsafe"
 
 	"golang.org/x/sys/unix"
 )
 
 type Inotify struct {
 	fd       int
-	watchers []*watcher
+	watchers map[int]*watcher
 	ping     chan struct{}
 	paused   bool
 }
@@ -21,6 +24,7 @@ func NewInotify(ping chan struct{}) (*Inotify, error) {
 
 	i := &Inotify{
 		fd:       fd,
+		watchers: make(map[int]*watcher),
 		ping:     ping,
 		paused:   false,
 	}
@@ -34,7 +38,14 @@ func (i *Inotify) Watch(dir string) error {
 	if err != nil {
 		return fmt.Errorf("creating watcher: %v", err)
 	}
-	i.watchers = append(i.watchers, w)
+	i.watchers[w.wd] = w
+	return nil
+}
+
+func (i *Inotify) Close() error {
+	if err := unix.Close(i.fd); err != nil {
+		return fmt.Errorf("closing inotify file descriptor: %v", err)
+	}
 	return nil
 }
 
@@ -47,19 +58,104 @@ func (i *Inotify) UnPause() {
 }
 
 func (i *Inotify) String() string {
+	if len(i.watchers) < 20 {
 		dirs := make([]string, 0)
 		for _, w := range i.watchers {
 			dirs = append(dirs, w.dir)
 		}
 		return fmt.Sprintf("Watching: %v", dirs)
+	} else {
+		return fmt.Sprintf("Watching %d directories", len(i.watchers))
+	}
+}
+
+type bufRead struct {
+	n   int
+	buf []byte
 }
 
 func watch(i *Inotify) {
-	buf := make([]byte, 1024)
+	buf := make([]byte, 20*unix.SizeofInotifyEvent)
+	buffers := make(chan bufRead)
+	go verboseWatcher(i, buffers)
 	for {
-		_, _ = unix.Read(i.fd, buf)
+		n, _ := unix.Read(i.fd, buf)
 		if !i.paused {
 			i.ping <- struct{}{}
 		}
+		buffers <- bufRead{
+			n:   n,
+			buf: buf,
 		}
 	}
+}
+
+func verboseWatcher(i *Inotify, buffers chan bufRead) {
+	for bf := range buffers {
+		n := bf.n
+		buf := bf.buf
+
+		if n < unix.SizeofInotifyEvent {
+			if n == 0 {
+				// If EOF is received. This should really never happen.
+				panic(fmt.Sprintf("No bytes read from fd"))
+			} else if n < 0 {
+				// If an error occurred while reading.
+				log.Printf("ERROR: reading from inotify: %d", n)
+			} else {
+				// Read was too short.
+				log.Printf("ERROR: Short read")
+			}
+			continue
+		}
+
+		var offset uint32
+		for offset <= uint32(n-unix.SizeofInotifyEvent) {
+			raw := (*unix.InotifyEvent)(unsafe.Pointer(&buf[offset]))
+
+			mask := uint32(raw.Mask)
+			nameLen := uint32(raw.Len)
+
+			name := i.watchers[int(raw.Wd)].dir
+			if nameLen > 0 {
+				bytes := (*[unix.PathMax]byte)(unsafe.Pointer(&buf[offset+unix.SizeofInotifyEvent]))
+				if uint32(len(bytes)) > nameLen {
+					name += "/" + strings.TrimRight(string(bytes[0:nameLen]), "\000")
+				}
+			}
+			ev := newEvent(name, mask)
+			log.Printf("### %+v", ev)
+
+			offset += unix.SizeofInotifyEvent + nameLen
+		}
+	}
+}
+
+type Event struct {
+	name string
+	op   string
+}
+
+func (e Event) String() string {
+	return fmt.Sprintf("%10s | %s", e.op, e.name)
+}
+
+func newEvent(name string, mask uint32) Event {
+	e := Event{name: name}
+	if mask&unix.IN_CREATE == unix.IN_CREATE || mask&unix.IN_MOVED_TO == unix.IN_MOVED_TO {
+		e.op = "CREATE"
+	}
+	if mask&unix.IN_DELETE_SELF == unix.IN_DELETE_SELF || mask&unix.IN_DELETE == unix.IN_DELETE {
+		e.op = "REMOVE"
+	}
+	if mask&unix.IN_MODIFY == unix.IN_MODIFY {
+		e.op = "WRITE"
+	}
+	if mask&unix.IN_MOVE_SELF == unix.IN_MOVE_SELF || mask&unix.IN_MOVED_FROM == unix.IN_MOVED_FROM {
+		e.op = "RENAME"
+	}
+	if mask&unix.IN_ATTRIB == unix.IN_ATTRIB {
+		e.op = "CHMOD"
+	}
+	return e
+}

internal/inotify/watcher.go

@@ -2,11 +2,15 @@ package inotify
 
 import (
 	"fmt"
+	"io/ioutil"
+	"strconv"
+	"strings"
 
 	"golang.org/x/sys/unix"
 )
 
 const events = unix.IN_ALL_EVENTS
+const MaximumWatchersFile = "/proc/sys/fs/inotify/max_user_watches"
 
 type watcher struct {
 	wd  int
@@ -23,3 +27,18 @@ func newWatcher(fd int, dir string, ping chan struct{}) (*watcher, error) {
 		dir: dir,
 	}, nil
 }
+
+func WatcherLimit() (int, error) {
+	b, err := ioutil.ReadFile(MaximumWatchersFile)
+	if err != nil {
+		return 0, fmt.Errorf("reading from %s: %v", MaximumWatchersFile, err)
+	}
+
+	s := strings.TrimSpace(string(b))
+	m, err := strconv.Atoi(s)
+	if err != nil {
+		return 0, fmt.Errorf("converting to integer: %v", err)
+	}
+
+	return m, nil
+}

internal/walker/walker.go

@@ -0,0 +1,47 @@
+package walker
+
+import (
+	"fmt"
+	"io/ioutil"
+)
+
+func Walk(root string) (dirCh chan string, errCh chan error) {
+	dirCh = make(chan string)
+	errCh = make(chan error)
+	dirs := make([]string, 1)
+	dirs[0] = root
+
+	go func() {
+		dirCh <- root
+	}()
+	go func() {
+		for {
+			if len(dirs) == 0 {
+				break
+			}
+			dirs = descent(dirs, dirCh, errCh)
+		}
+		close(dirCh)
+		close(errCh)
+	}()
+	return dirCh, errCh
+}
+
+func descent(dirs []string, dirCh chan string, errCh chan error) []string {
+	next := make([]string, 0)
+	for _, dir := range dirs {
+		ls, err := ioutil.ReadDir(dir)
+		if err != nil {
+			errCh <- fmt.Errorf("opening dir %s: %v", dir, err)
+		}
+
+		for _, e := range ls {
+			if e.IsDir() {
+				newDir := dir + e.Name() + "/"
+				dirCh <- newDir
+				next = append(next, newDir)
+			}
+		}
+	}
+	return next
+}