envconst: queryable report of resolved variables + integration inot zrepl status --raw

fixes #299
refs #186

daemon/control.go

@@ -120,7 +120,13 @@ func (j *controlJob) Run(ctx context.Context) {
 		jsonResponder{log, func() (interface{}, error) {
 			jobs := j.jobs.status()
 			globalZFS := zfscmd.GetReport()
-			s := Status{Jobs: jobs, Global: GlobalStatus{ZFSCmds: globalZFS}}
+			envconstReport := envconst.GetReport()
+			s := Status{
+				Jobs: jobs,
+				Global: GlobalStatus{
+					ZFSCmds:  globalZFS,
+					Envconst: envconstReport,
+				}}
 			return s, nil
 		}})
 

daemon/daemon.go

@@ -14,6 +14,7 @@ import (
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/zrepl/zrepl/daemon/logging/trace"
 	"github.com/zrepl/zrepl/endpoint"
+	"github.com/zrepl/zrepl/util/envconst"
 
 	"github.com/zrepl/zrepl/config"
 	"github.com/zrepl/zrepl/daemon/job"
@@ -150,7 +151,8 @@ type Status struct {
 }
 
 type GlobalStatus struct {
-	ZFSCmds *zfscmd.Report
+	ZFSCmds  *zfscmd.Report
+	Envconst *envconst.Report
 }
 
 func (s *jobs) status() map[string]*job.Status {

util/envconst/envconst.go

@@ -12,84 +12,100 @@ import (
 
 var cache sync.Map
 
-func Duration(varname string, def time.Duration) time.Duration {
+func Reset() {
+	cache.Range(func(key, _ interface{}) bool {
+		cache.Delete(key)
+		return true
+	})
+}
+
+func Duration(varname string, def time.Duration) (d time.Duration) {
+	var err error
 	if v, ok := cache.Load(varname); ok {
 		return v.(time.Duration)
 	}
 	e := os.Getenv(varname)
 	if e == "" {
-		return def
-	}
-	d, err := time.ParseDuration(e)
-	if err != nil {
-		panic(err)
+		d = def
+	} else {
+		d, err = time.ParseDuration(e)
+		if err != nil {
+			panic(err)
+		}
 	}
 	cache.Store(varname, d)
 	return d
 }
 
-func Int(varname string, def int) int {
+func Int(varname string, def int) (d int) {
 	if v, ok := cache.Load(varname); ok {
 		return v.(int)
 	}
 	e := os.Getenv(varname)
 	if e == "" {
-		return def
+		d = def
+	} else {
+		d64, err := strconv.ParseInt(e, 10, strconv.IntSize)
+		if err != nil {
+			panic(err)
+		}
+		d = int(d64)
 	}
-	d64, err := strconv.ParseInt(e, 10, strconv.IntSize)
-	if err != nil {
-		panic(err)
-	}
-	d := int(d64)
 	cache.Store(varname, d)
 	return d
 }
 
-func Int64(varname string, def int64) int64 {
+func Int64(varname string, def int64) (d int64) {
+	var err error
 	if v, ok := cache.Load(varname); ok {
 		return v.(int64)
 	}
 	e := os.Getenv(varname)
 	if e == "" {
-		return def
-	}
-	d, err := strconv.ParseInt(e, 10, 64)
-	if err != nil {
-		panic(err)
+		d = def
+	} else {
+		d, err = strconv.ParseInt(e, 10, 64)
+		if err != nil {
+			panic(err)
+		}
 	}
 	cache.Store(varname, d)
 	return d
 }
 
-func Bool(varname string, def bool) bool {
+func Bool(varname string, def bool) (d bool) {
+	var err error
 	if v, ok := cache.Load(varname); ok {
 		return v.(bool)
 	}
 	e := os.Getenv(varname)
 	if e == "" {
-		return def
-	}
-	d, err := strconv.ParseBool(e)
-	if err != nil {
-		panic(err)
+		d = def
+	} else {
+		d, err = strconv.ParseBool(e)
+		if err != nil {
+			panic(err)
+		}
 	}
 	cache.Store(varname, d)
 	return d
 }
 
-func String(varname string, def string) string {
+func String(varname string, def string) (d string) {
 	if v, ok := cache.Load(varname); ok {
 		return v.(string)
 	}
 	e := os.Getenv(varname)
 	if e == "" {
-		return def
+		d = def
+	} else {
+		d = e
 	}
-	cache.Store(varname, e)
-	return e
+	cache.Store(varname, d)
+	return d
 }
 
-func Var(varname string, def flag.Value) interface{} {
+func Var(varname string, def flag.Value) (d interface{}) {
 
 	// use def's type to instantiate a new object of that same type
 	// and call flag.Value.Set() on it
@@ -100,19 +116,43 @@ func Var(varname string, def flag.Value) interface{} {
 	defElemType := defType.Elem()
 
 	if v, ok := cache.Load(varname); ok {
-		return v.(string)
+		return v
 	}
+
 	e := os.Getenv(varname)
 	if e == "" {
-		return def
+		d = def
+	} else {
+		newInstance := reflect.New(defElemType)
+		if err := newInstance.Interface().(flag.Value).Set(e); err != nil {
+			panic(err)
+		}
+		d = newInstance.Interface()
 	}
 
-	newInstance := reflect.New(defElemType)
-	if err := newInstance.Interface().(flag.Value).Set(e); err != nil {
-		panic(err)
-	}
-
-	res := newInstance.Interface()
-	cache.Store(varname, res)
-	return res
+	cache.Store(varname, d)
+	return d
+}
+
+type Report struct {
+	Entries []EntryReport
+}
+
+type EntryReport struct {
+	Var         string
+	Value       string
+	ValueGoType string
+}
+
+func GetReport() *Report {
+	var r Report
+	cache.Range(func(key, value interface{}) bool {
+		r.Entries = append(r.Entries, EntryReport{
+			Var:         key.(string),
+			Value:       fmt.Sprintf("%v", value),
+			ValueGoType: fmt.Sprintf("%T", value),
+		})
+		return true
+	})
+	return &r
 }

util/envconst/envconst_test.go

@@ -32,19 +32,27 @@ func (m *ExampleVarType) Set(s string) error {
 
 const EnvVarName = "ZREPL_ENVCONST_UNIT_TEST_VAR"
 
-func TestVar(t *testing.T) {
+func TestVarDefaultValue(t *testing.T) {
+	envconst.Reset()
 	_, set := os.LookupEnv(EnvVarName)
 	require.False(t, set)
 	defer os.Unsetenv(EnvVarName)
 
 	val := envconst.Var(EnvVarName, &Var1)
 	if &Var1 != val {
-		t.Errorf("default value shut be same address")
+		t.Errorf("default value should be same address")
 	}
+}
+
+func TestVarOverriddenValue(t *testing.T) {
+	envconst.Reset()
+	_, set := os.LookupEnv(EnvVarName)
+	require.False(t, set)
+	defer os.Unsetenv(EnvVarName)
 
 	err := os.Setenv(EnvVarName, "var2")
 	require.NoError(t, err)
 
-	val = envconst.Var(EnvVarName, &Var1)
+	val := envconst.Var(EnvVarName, &Var1)
 	require.Equal(t, &Var2, val, "only structural identity is required for non-default vars")
 }