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watcher.go
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watcher.go
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package workloadapi
import (
"context"
"sync"
"github.com/spiffe/go-spiffe/v2/bundle/jwtbundle"
"github.com/spiffe/go-spiffe/v2/svid/jwtsvid"
"github.com/zeebo/errs"
)
type sourceClient interface {
WatchX509Context(context.Context, X509ContextWatcher) error
WatchJWTBundles(context.Context, JWTBundleWatcher) error
FetchJWTSVID(context.Context, jwtsvid.Params) (*jwtsvid.SVID, error)
FetchJWTSVIDs(context.Context, jwtsvid.Params) ([]*jwtsvid.SVID, error)
Close() error
}
type watcherConfig struct {
client sourceClient
clientOptions []ClientOption
}
type watcher struct {
updatedCh chan struct{}
client sourceClient
ownsClient bool
cancel func()
wg sync.WaitGroup
closeMtx sync.Mutex
closed bool
closeErr error
x509ContextFn func(*X509Context)
x509ContextSet chan struct{}
x509ContextSetOnce sync.Once
jwtBundlesFn func(*jwtbundle.Set)
jwtBundlesSet chan struct{}
jwtBundlesSetOnce sync.Once
}
func newWatcher(ctx context.Context, config watcherConfig, x509ContextFn func(*X509Context), jwtBundlesFn func(*jwtbundle.Set)) (_ *watcher, err error) {
w := &watcher{
updatedCh: make(chan struct{}, 1),
client: config.client,
cancel: func() {},
x509ContextFn: x509ContextFn,
x509ContextSet: make(chan struct{}),
jwtBundlesFn: jwtBundlesFn,
jwtBundlesSet: make(chan struct{}),
}
// If this function fails, we need to clean up the source.
defer func() {
if err != nil {
err = errs.Combine(err, w.Close())
}
}()
// Initialize a new client unless one is provided by the options
if w.client == nil {
client, err := New(ctx, config.clientOptions...)
if err != nil {
return nil, err
}
w.client = client
w.ownsClient = true
}
errCh := make(chan error, 2)
waitFor := func(has <-chan struct{}) error {
select {
case <-has:
return nil
case err := <-errCh:
return err
case <-ctx.Done():
return ctx.Err()
}
}
// Kick up a background goroutine that watches the Workload API for
// updates.
var watchCtx context.Context
watchCtx, w.cancel = context.WithCancel(context.Background())
if w.x509ContextFn != nil {
w.wg.Add(1)
go func() {
defer w.wg.Done()
errCh <- w.client.WatchX509Context(watchCtx, w)
}()
if err := waitFor(w.x509ContextSet); err != nil {
return nil, err
}
}
if w.jwtBundlesFn != nil {
w.wg.Add(1)
go func() {
defer w.wg.Done()
errCh <- w.client.WatchJWTBundles(watchCtx, w)
}()
if err := waitFor(w.jwtBundlesSet); err != nil {
return nil, err
}
}
// Drain the update channel since this function blocks until an update and
// don't want callers to think there was an update on the source right
// after it was initialized. If we ever allow the watcher to be initialzed
// without waiting, this reset should be removed.
w.drainUpdated()
return w, nil
}
// Close closes the watcher, dropping the connection to the Workload API.
func (w *watcher) Close() error {
w.closeMtx.Lock()
defer w.closeMtx.Unlock()
if !w.closed {
w.cancel()
w.wg.Wait()
// Close() can be called by New() to close a partially initialized source.
// Only close the client if it has been set and the source owns it.
if w.client != nil && w.ownsClient {
w.closeErr = w.client.Close()
}
w.closed = true
}
return w.closeErr
}
func (w *watcher) OnX509ContextUpdate(x509Context *X509Context) {
w.x509ContextFn(x509Context)
w.triggerUpdated()
w.x509ContextSetOnce.Do(func() {
close(w.x509ContextSet)
})
}
func (w *watcher) OnX509ContextWatchError(err error) {
// The watcher doesn't do anything special with the error. If logging is
// desired, it should be provided to the Workload API client.
}
func (w *watcher) OnJWTBundlesUpdate(jwtBundles *jwtbundle.Set) {
w.jwtBundlesFn(jwtBundles)
w.triggerUpdated()
w.jwtBundlesSetOnce.Do(func() {
close(w.jwtBundlesSet)
})
}
func (w *watcher) OnJWTBundlesWatchError(error) {
// The watcher doesn't do anything special with the error. If logging is
// desired, it should be provided to the Workload API client.
}
func (w *watcher) WaitUntilUpdated(ctx context.Context) error {
select {
case <-w.updatedCh:
return nil
case <-ctx.Done():
return ctx.Err()
}
}
func (w *watcher) Updated() <-chan struct{} {
return w.updatedCh
}
func (w *watcher) drainUpdated() {
select {
case <-w.updatedCh:
default:
}
}
func (w *watcher) triggerUpdated() {
w.drainUpdated()
w.updatedCh <- struct{}{}
}