Refactor debug into debug module

debug/debug.go

@@ -0,0 +1,162 @@
+// +build debug
+
+package debug
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"path"
+	"runtime"
+	"strings"
+	"sync"
+	"syscall"
+)
+
+var opts struct {
+	tags   map[string]bool
+	breaks map[string]bool
+	m      sync.Mutex
+}
+
+var debugLogger = initDebugLogger()
+
+func initDebugLogger() (lgr *log.Logger) {
+	opts.tags = make(map[string]bool)
+	opts.breaks = make(map[string]bool)
+
+	fmt.Fprintf(os.Stderr, "debug enabled\n")
+
+	debugfile := os.Getenv("DEBUG_LOG")
+	if debugfile != "" {
+		fmt.Fprintf(os.Stderr, "debug log file %v\n", debugfile)
+
+		// open logfile
+		f, err := os.OpenFile(debugfile, os.O_WRONLY|os.O_APPEND, 0600)
+
+		if err != nil && os.IsNotExist(err) {
+			// create logfile
+			f, err = os.OpenFile(debugfile, os.O_WRONLY|os.O_CREATE, 0600)
+		}
+
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "unable to open debug log file: %v\n", err)
+			os.Exit(2)
+		}
+
+		// seek to the end
+		_, err = f.Seek(2, 0)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "unable to seek to the end of %v: %v\n", debugfile, err)
+			os.Exit(3)
+		}
+
+		// open logger
+		lgr = log.New(f, "", log.LstdFlags)
+	}
+
+	// defaults
+	opts.tags["break"] = true
+
+	// initialize tags
+	env := os.Getenv("DEBUG_TAGS")
+	if len(env) > 0 {
+		tags := []string{}
+
+		for _, tag := range strings.Split(env, ",") {
+			t := strings.TrimSpace(tag)
+			val := true
+			if t[0] == '-' {
+				val = false
+				t = t[1:]
+			} else if t[0] == '+' {
+				val = true
+				t = t[1:]
+			}
+
+			// test pattern
+			_, err := path.Match(t, "")
+			if err != nil {
+				fmt.Fprintf(os.Stderr, "error: invalid pattern %q: %v\n", t, err)
+				os.Exit(5)
+			}
+
+			opts.tags[t] = val
+			tags = append(tags, tag)
+		}
+
+		fmt.Fprintf(os.Stderr, "debug log enabled for: %v\n", tags)
+	}
+
+	// initialize break tags
+	env = os.Getenv("DEBUG_BREAK")
+	if len(env) > 0 {
+		breaks := []string{}
+
+		for _, tag := range strings.Split(env, ",") {
+			t := strings.TrimSpace(tag)
+			opts.breaks[t] = true
+			breaks = append(breaks, t)
+		}
+
+		fmt.Fprintf(os.Stderr, "debug breaks enabled for: %v\n", breaks)
+	}
+
+	return
+}
+
+func Log(tag string, f string, args ...interface{}) {
+	// synchronize log writes
+	opts.m.Lock()
+	defer opts.m.Unlock()
+
+	dbgprint := func() {
+		fmt.Fprintf(os.Stderr, "DEBUG["+tag+"]: "+f, args...)
+	}
+
+	if debugLogger != nil {
+		debugLogger.Printf("["+tag+"] "+f, args...)
+	}
+
+	// check if tag is enabled directly
+	if v, ok := opts.tags[tag]; ok {
+		if v {
+			dbgprint()
+		}
+		return
+	}
+
+	// check for globbing
+	for k, v := range opts.tags {
+		if m, _ := path.Match(k, tag); m {
+			if v {
+				dbgprint()
+			}
+			return
+		}
+	}
+
+	// check if tag "all" is enabled
+	if v, ok := opts.tags["all"]; ok && v {
+		dbgprint()
+	}
+}
+
+func Break(tag string) {
+	// check if breaking is enabled
+	if v, ok := opts.breaks[tag]; !ok || !v {
+		return
+	}
+
+	_, file, line, _ := runtime.Caller(1)
+	Log("break", "stopping process %d at %s (%v:%v)\n", os.Getpid(), tag, file, line)
+	p, err := os.FindProcess(os.Getpid())
+	if err != nil {
+		panic(err)
+	}
+
+	err = p.Signal(syscall.SIGSTOP)
+	if err != nil {
+		panic(err)
+	}
+}