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updater.go
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updater.go
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// Copyright 2016 Michal Witkowski. All Rights Reserved.
// See LICENSE for licensing terms.
// Package kubernetes provides an a K8S ConfigMap watcher for the jobs systems.
package configmap
import (
"fmt"
"io/ioutil"
"path"
"strings"
"github.com/fsnotify/fsnotify"
flag "github.com/spf13/pflag"
"github.com/mwitkow/go-flagz"
)
const (
k8sInternalsPrefix = ".."
k8sDataSymlink = "..data"
)
var (
errFlagNotDynamic = fmt.Errorf("flag is not dynamic")
errFlagNotFound = fmt.Errorf("flag not found")
)
// Minimum logger interface needed.
// Default "log" and "logrus" should support these.
type loggerCompatible interface {
Printf(format string, v ...interface{})
}
type Updater struct {
started bool
dirPath string
watcher *fsnotify.Watcher
flagSet *flag.FlagSet
logger loggerCompatible
done chan bool
}
func New(flagSet *flag.FlagSet, dirPath string, logger loggerCompatible) (*Updater, error) {
watcher, err := fsnotify.NewWatcher()
if err != nil {
return nil, fmt.Errorf("flagz: error initializing fsnotify watcher.")
}
return &Updater{
flagSet: flagSet,
logger: logger,
dirPath: dirPath,
watcher: watcher,
}, nil
}
func (u *Updater) Initialize() error {
if u.started {
return fmt.Errorf("flagz: already initialized updater.")
}
return u.readAll(/* allowNonDynamic */ false)
}
// Start kicks off the go routine that watches the directory for updates of values.
func (u *Updater) Start() error {
if u.started {
return fmt.Errorf("flagz: updater already started.")
}
u.watcher.Add(path.Join(u.dirPath, "..")) // add parent in case the dirPath is a symlink itself
u.watcher.Add(u.dirPath) // add the dir itself.
u.done = make(chan bool)
go u.watchForUpdates()
return nil
}
// Stops the auto-updating go-routine.
func (u *Updater) Stop() error {
if !u.started {
return fmt.Errorf("flagz: not updating")
}
u.done <- true
u.watcher.Remove(u.dirPath)
return nil
}
func (u *Updater) readAll(dynamicOnly bool) error {
files, err := ioutil.ReadDir(u.dirPath)
if err != nil {
return fmt.Errorf("flagz: updater initialization: %v", err)
}
errorStrings := []string{}
for _, f := range files {
if strings.HasPrefix(path.Base(f.Name()), "..") {
// skip random ConfigMap internals
continue
}
fullPath := path.Join(u.dirPath, f.Name())
if err := u.readFlagFile(fullPath, dynamicOnly); err != nil {
if err == errFlagNotDynamic && dynamicOnly {
// ignore
} else {
errorStrings = append(errorStrings, fmt.Sprintf("flag %v: %v", f.Name(), err.Error()))
}
}
}
if len(errorStrings) > 0 {
return fmt.Errorf("encountered %d errors while parsing flags from directory \n %v",
len(errorStrings), strings.Join(errorStrings, "\n"))
}
return nil
}
func (u *Updater) readFlagFile(fullPath string, dynamicOnly bool) error {
flagName := path.Base(fullPath)
flag := u.flagSet.Lookup(flagName)
if flag == nil {
return errFlagNotFound
}
if dynamicOnly && !flagz.IsFlagDynamic(flag) {
return errFlagNotDynamic
}
content, err := ioutil.ReadFile(fullPath)
if err != nil {
return err
}
// do not call flag.Value.Set, instead go through flagSet.Set to change "changed" state.
return u.flagSet.Set(flagName, string(content))
}
func (u *Updater) watchForUpdates() {
u.logger.Printf("starting watching")
for {
select {
case event := <-u.watcher.Events:
if event.Name == u.dirPath || event.Name == path.Join(u.dirPath, k8sDataSymlink) {
// case of the whole directory being re-symlinked
switch event.Op {
case fsnotify.Create:
u.watcher.Add(u.dirPath)
u.logger.Printf("flagz: Re-reading flags after ConfigMap update.")
if err := u.readAll(/* dynamicOnly */ true); err != nil {
u.logger.Printf("flagz: directory reload yielded errors: %v", err.Error())
}
case fsnotify.Remove:
}
} else if strings.HasPrefix(event.Name, u.dirPath) && !isK8sInternalDirectory(event.Name) {
switch event.Op {
case fsnotify.Create, fsnotify.Write, fsnotify.Rename:
if err := u.readFlagFile(event.Name, true); err != nil {
flagName := path.Base(event.Name)
u.logger.Printf("flagz: failed setting flag %s: %v", flagName, err.Error())
}
}
}
case <-u.done:
return
}
}
}
func isK8sInternalDirectory(filePath string) bool {
basePath := path.Base(filePath)
return strings.HasPrefix(basePath, k8sInternalsPrefix)
}