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dryrun_target.go
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/
dryrun_target.go
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package fi
import (
"fmt"
"bytes"
"github.com/golang/glog"
"io"
"k8s.io/kops/upup/pkg/fi/utils"
"reflect"
"strings"
)
// DryRunTarget is a special Target that does not execute anything, but instead tracks all changes.
// By running against a DryRunTarget, a list of changes that would be made can be easily collected,
// without any special support from the Tasks.
type DryRunTarget struct {
changes []*render
// The destination to which the final report will be printed on Finish()
out io.Writer
}
type render struct {
a Task
aIsNil bool
e Task
changes Task
}
var _ Target = &DryRunTarget{}
func NewDryRunTarget(out io.Writer) *DryRunTarget {
t := &DryRunTarget{}
t.out = out
return t
}
func (t *DryRunTarget) Render(a, e, changes Task) error {
valA := reflect.ValueOf(a)
aIsNil := valA.IsNil()
t.changes = append(t.changes, &render{
a: a,
aIsNil: aIsNil,
e: e,
changes: changes,
})
return nil
}
func IdForTask(taskMap map[string]Task, t Task) string {
for k, v := range taskMap {
if v == t {
return k
}
}
glog.Fatalf("unknown task: %v", t)
return "?"
}
func (t *DryRunTarget) PrintReport(taskMap map[string]Task, out io.Writer) error {
b := &bytes.Buffer{}
if len(t.changes) != 0 {
var creates []*render
var updates []*render
for _, r := range t.changes {
if r.aIsNil {
creates = append(creates, r)
} else {
updates = append(updates, r)
}
}
if len(creates) != 0 {
fmt.Fprintf(b, "Will create resources:\n")
for _, r := range creates {
taskName := getTaskName(r.changes)
fmt.Fprintf(b, " %s\t%s\n", taskName, IdForTask(taskMap, r.e))
}
}
if len(updates) != 0 {
fmt.Fprintf(b, "Will modify resources:\n")
// We can't use our reflection helpers here - we want corresponding values from a,e,c
for _, r := range updates {
var changeList []string
valC := reflect.ValueOf(r.changes)
valA := reflect.ValueOf(r.a)
valE := reflect.ValueOf(r.e)
if valC.Kind() == reflect.Ptr && !valC.IsNil() {
valC = valC.Elem()
}
if valA.Kind() == reflect.Ptr && !valA.IsNil() {
valA = valA.Elem()
}
if valE.Kind() == reflect.Ptr && !valE.IsNil() {
valE = valE.Elem()
}
if valC.Kind() == reflect.Struct {
for i := 0; i < valC.NumField(); i++ {
fieldValC := valC.Field(i)
changed := true
switch fieldValC.Kind() {
case reflect.Ptr, reflect.Interface, reflect.Slice, reflect.Map:
changed = !fieldValC.IsNil()
case reflect.String:
changed = fieldValC.Interface().(string) != ""
}
if !changed {
continue
}
if fieldValC.Kind() == reflect.String && fieldValC.Interface().(string) == "" {
// No change
continue
}
fieldValE := valE.Field(i)
description := ""
ignored := false
if fieldValE.CanInterface() {
fieldValA := valA.Field(i)
switch fieldValE.Interface().(type) {
//case SimpleUnit:
// ignored = true
default:
description = fmt.Sprintf(" %v -> %v", ValueAsString(fieldValA), ValueAsString(fieldValE))
}
}
if ignored {
continue
}
changeList = append(changeList, valC.Type().Field(i).Name+description)
}
} else {
return fmt.Errorf("unhandled change type: %v", valC.Type())
}
if len(changeList) == 0 {
continue
}
taskName := getTaskName(r.changes)
fmt.Fprintf(b, " %s\t%s\n", taskName, IdForTask(taskMap, r.e))
for _, f := range changeList {
fmt.Fprintf(b, " %s\n", f)
}
fmt.Fprintf(b, "\n")
}
}
}
_, err := out.Write(b.Bytes())
return err
}
func getTaskName(t Task) string {
s := fmt.Sprintf("%T", t)
lastDot := strings.LastIndexByte(s, '.')
if lastDot != -1 {
s = s[lastDot+1:]
}
return s
}
// asString returns a human-readable string representation of the passed value
func ValueAsString(value reflect.Value) string {
b := &bytes.Buffer{}
walker := func(path string, field *reflect.StructField, v reflect.Value) error {
if utils.IsPrimitiveValue(v) || v.Kind() == reflect.String {
fmt.Fprintf(b, "%v", v.Interface())
return utils.SkipReflection
}
switch v.Kind() {
case reflect.Ptr, reflect.Interface, reflect.Slice, reflect.Map:
if v.IsNil() {
fmt.Fprintf(b, "<nil>")
return utils.SkipReflection
}
}
switch v.Kind() {
case reflect.Ptr, reflect.Interface:
return nil // descend into value
case reflect.Slice:
len := v.Len()
fmt.Fprintf(b, "[")
for i := 0; i < len; i++ {
av := v.Index(i)
if i != 0 {
fmt.Fprintf(b, ", ")
}
fmt.Fprintf(b, "%s", ValueAsString(av))
}
fmt.Fprintf(b, "]")
return utils.SkipReflection
case reflect.Map:
keys := v.MapKeys()
fmt.Fprintf(b, "{")
for i, key := range keys {
mv := v.MapIndex(key)
if i != 0 {
fmt.Fprintf(b, ", ")
}
fmt.Fprintf(b, "%s: %s", ValueAsString(key), ValueAsString(mv))
}
fmt.Fprintf(b, "}")
return utils.SkipReflection
case reflect.Struct:
intf := v.Addr().Interface()
if _, ok := intf.(Resource); ok {
fmt.Fprintf(b, "<resource>")
} else if _, ok := intf.(*ResourceHolder); ok {
fmt.Fprintf(b, "<resource>")
} else if compareWithID, ok := intf.(CompareWithID); ok {
id := compareWithID.CompareWithID()
if id == nil {
fmt.Fprintf(b, "id:<nil>")
} else {
fmt.Fprintf(b, "id:%s", *id)
}
} else {
glog.V(4).Infof("Unhandled kind in asString for %q: %T", path, v.Interface())
fmt.Fprint(b, DebugAsJsonString(intf))
}
return utils.SkipReflection
default:
glog.Infof("Unhandled kind in asString for %q: %T", path, v.Interface())
return fmt.Errorf("Unhandled kind for %q: %v", path, v.Kind())
}
}
err := utils.ReflectRecursive(value, walker)
if err != nil {
glog.Fatalf("unexpected error during reflective walk: %v", err)
}
return b.String()
}
// Finish is called at the end of a run, and prints a list of changes to the configured Writer
func (t *DryRunTarget) Finish(taskMap map[string]Task) error {
return t.PrintReport(taskMap, t.out)
}
// HasChanges returns true iff any changes would have been made
func (t *DryRunTarget) HasChanges() bool {
return len(t.changes) != 0
}