emissary/internal/agent/controller/persistence/controller.go

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package persistence
import (
"context"
"encoding/json"
"fmt"
"io/ioutil"
"os"
"path/filepath"
"forge.cadoles.com/Cadoles/emissary/internal/agent"
"forge.cadoles.com/Cadoles/emissary/internal/spec"
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"github.com/getsentry/sentry-go"
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"github.com/pkg/errors"
"gitlab.com/wpetit/goweb/logger"
)
type Controller struct {
trackedSpecRevisions map[spec.Name]int
filename string
loaded bool
}
// Name implements node.Controller.
func (c *Controller) Name() string {
return "persistence-controller"
}
// Reconcile implements node.Controller.
func (c *Controller) Reconcile(ctx context.Context, state *agent.State) error {
specs := state.Specs()
changed := c.specChanged(state.Specs())
switch {
// If first cycle, load state from file system
case !c.loaded:
logger.Info(ctx, "first cycle, loading state", logger.F("stateFile", c.filename))
if err := c.loadState(ctx, state); err != nil {
if errors.Is(err, os.ErrNotExist) {
logger.Info(ctx, "state file not found", logger.F("stateFile", c.filename))
c.loaded = true
return nil
}
return errors.WithStack(err)
}
c.trackSpecsRevisions(specs)
c.loaded = true
return nil
// If specs did not change, return
case !changed:
logger.Info(ctx, "no changes detected, doing nothing")
return nil
// If specs has changed, save it
case changed:
logger.Info(ctx, "saving state", logger.F("stateFile", c.filename))
if err := c.writeState(ctx, state); err != nil {
return errors.WithStack(err)
}
c.trackSpecsRevisions(specs)
}
return nil
}
func (c *Controller) specChanged(specs agent.Specs) bool {
if len(specs) != len(c.trackedSpecRevisions) {
return true
}
for name, spec := range specs {
trackedRevision, exists := c.trackedSpecRevisions[name]
if !exists {
return true
}
if trackedRevision != spec.SpecRevision() {
return true
}
}
for trackedSpecName, trackedRevision := range c.trackedSpecRevisions {
spec, exists := specs[trackedSpecName]
if !exists {
return true
}
if trackedRevision != spec.SpecRevision() {
return true
}
}
return false
}
func (c *Controller) trackSpecsRevisions(specs agent.Specs) {
c.trackedSpecRevisions = make(map[spec.Name]int)
for name, spec := range specs {
c.trackedSpecRevisions[name] = spec.SpecRevision()
}
}
func (c *Controller) loadState(ctx context.Context, state *agent.State) error {
data, err := ioutil.ReadFile(c.filename)
if err != nil {
return errors.WithStack(err)
}
if err := json.Unmarshal(data, state); err != nil {
return errors.WithStack(err)
}
return nil
}
func (c *Controller) writeState(ctx context.Context, state *agent.State) error {
dir, file := filepath.Split(c.filename)
if dir == "" {
dir = "."
}
f, err := ioutil.TempFile(dir, file)
if err != nil {
return errors.Errorf("cannot create temp file: %v", err)
}
defer func() {
if err == nil {
return
}
if err := os.Remove(f.Name()); err != nil {
if errors.Is(err, os.ErrNotExist) {
return
}
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err = errors.WithStack(err)
logger.Error(ctx, "could not remove temporary file", logger.E(err))
sentry.CaptureException(err)
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}
}()
defer func() {
if err := f.Close(); err != nil {
if errors.Is(err, os.ErrClosed) {
return
}
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err = errors.WithStack(err)
logger.Error(ctx, "could not close temporary file", logger.E(err))
sentry.CaptureException(err)
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}
}()
data, err := json.Marshal(state)
if err != nil {
return errors.WithStack(err)
}
name := f.Name()
if err := ioutil.WriteFile(name, data, os.ModePerm); err != nil {
return errors.Errorf("cannot write data to temporary file %q: %v", name, err)
}
if err := f.Sync(); err != nil {
return errors.Errorf("can't flush temporary file %q: %v", name, err)
}
if err := f.Close(); err != nil {
return errors.Errorf("can't close temporary file %q: %v", name, err)
}
// get the file mode from the original file and use that for the replacement
// file, too.
destInfo, err := os.Stat(c.filename)
switch {
case os.IsNotExist(err):
// Do nothing
case err != nil:
return errors.WithStack(err)
default:
sourceInfo, err := os.Stat(name)
if err != nil {
return errors.WithStack(err)
}
if sourceInfo.Mode() != destInfo.Mode() {
if err := os.Chmod(name, destInfo.Mode()); err != nil {
return fmt.Errorf("can't set filemode on temporary file %q: %v", name, err)
}
}
}
if err := os.Rename(name, c.filename); err != nil {
return fmt.Errorf("cannot replace %q with temporary file %q: %v", c.filename, name, err)
}
return nil
}
func NewController(filename string) *Controller {
return &Controller{
filename: filename,
trackedSpecRevisions: make(map[spec.Name]int),
}
}
var _ agent.Controller = &Controller{}