submatview: rough outline of the Get and Notify methods.

agent/submatview/materializer.go

@@ -204,9 +204,8 @@ func (m *Materializer) notifyUpdateLocked(err error) {
 	m.updateCh = make(chan struct{})
 }
 
-// Fetch implements the logic a StreamingCacheType will need during it's Fetch
-// call. Cache types that use streaming should just be able to proxy to this
-// once they have a subscription object and return it's results directly.
+// Fetch the value stored in the View. Fetch blocks until the index of the View
+// is greater than opts.MinIndex, or the context is cancelled.
 func (m *Materializer) Fetch(done <-chan struct{}, opts cache.FetchOptions) (cache.FetchResult, error) {
 	var result cache.FetchResult
 

agent/submatview/store.go

@@ -12,26 +12,48 @@ import (
 
 type Store struct {
 	lock       sync.RWMutex
-	byKey      map[string]*Materializer
+	byKey      map[string]entry
 	expiryHeap *ttlcache.ExpiryHeap
 }
 
+type entry struct {
+	materializer *Materializer
+	expiry       *ttlcache.Entry
+}
+
+// TODO: start expiration loop
 func NewStore() *Store {
 	return &Store{
-		byKey:      make(map[string]*Materializer),
+		byKey:      make(map[string]entry),
 		expiryHeap: ttlcache.NewExpiryHeap(),
 	}
 }
 
+var ttl = 20 * time.Minute
+
 // Get a value from the store, blocking if the store has not yet seen the
 // req.Index value.
 // See agent/cache.Cache.Get for complete documentation.
 func (s *Store) Get(
 	ctx context.Context,
 	typ string,
-	req cache.Request,
-) (result interface{}, meta cache.ResultMeta, err error) {
-	return nil, cache.ResultMeta{}, nil
+	req Request,
+	// TODO: only the Index field of ResultMeta is relevant, return a result struct instead.
+) (interface{}, cache.ResultMeta, error) {
+	info := req.CacheInfo()
+	key := makeEntryKey(typ, info)
+	e := s.getEntry(key, req.NewMaterializer)
+
+	// TODO: requires a lock to update the heap.
+	s.expiryHeap.Update(e.expiry.Index(), ttl)
+
+	// TODO: no longer any need to return cache.FetchResult from Materializer.Fetch
+	// TODO: pass context instead of Done chan, also replaces Timeout param
+	result, err := e.materializer.Fetch(ctx.Done(), cache.FetchOptions{
+		MinIndex: info.MinIndex,
+		Timeout:  info.Timeout,
+	})
+	return result.Value, cache.ResultMeta{Index: result.Index}, err
 }
 
 // Notify the updateCh when there are updates to the entry identified by req.
@@ -39,60 +61,75 @@ func (s *Store) Get(
 func (s *Store) Notify(
 	ctx context.Context,
 	typ string,
-	req cache.Request,
+	req Request,
 	correlationID string,
 	updateCh chan<- cache.UpdateEvent,
 ) error {
+	// TODO: set entry to not expire until ctx is cancelled.
+
+	info := req.CacheInfo()
+	key := makeEntryKey(typ, info)
+	e := s.getEntry(key, req.NewMaterializer)
+
+	var index uint64
+
+	go func() {
+		for {
+			result, err := e.materializer.Fetch(ctx.Done(), cache.FetchOptions{MinIndex: index})
+			switch {
+			case ctx.Err() != nil:
+				return
+			case err != nil:
+				// TODO: cache.Notify sends errors on updateCh, should this do the same?
+				// It seems like only fetch errors would ever get sent along.
+				// TODO: log warning
+				continue
+			}
+
+			index = result.Index
+			u := cache.UpdateEvent{
+				CorrelationID: correlationID,
+				Result:        result.Value,
+				Meta:          cache.ResultMeta{Index: result.Index},
+				Err:           err,
+			}
+			select {
+			case updateCh <- u:
+			case <-ctx.Done():
+				return
+			}
+
+		}
+	}()
 	return nil
 }
 
-func (s *Store) getMaterializer(opts GetOptions) *Materializer {
-	// TODO: use makeEntryKey
-	var key string
-
+func (s *Store) getEntry(key string, newMat func() *Materializer) entry {
 	s.lock.RLock()
-	mat, ok := s.byKey[key]
+	e, ok := s.byKey[key]
 	s.lock.RUnlock()
-
 	if ok {
-		return mat
+		return e
 	}
 
 	s.lock.Lock()
-	mat, ok = s.byKey[key]
-	if !ok {
-		mat = opts.NewMaterializer()
-		s.byKey[opts.Key] = mat
+	defer s.lock.Unlock()
+	e, ok = s.byKey[key]
+	if ok {
+		return e
 	}
-	s.lock.Unlock()
-	return mat
+
+	e = entry{materializer: newMat()}
+	s.byKey[key] = e
+	return e
 }
 
 // makeEntryKey matches agent/cache.makeEntryKey, but may change in the future.
-func makeEntryKey(t, dc, token, key string) string {
-	return fmt.Sprintf("%s/%s/%s/%s", t, dc, token, key)
+func makeEntryKey(typ string, r cache.RequestInfo) string {
+	return fmt.Sprintf("%s/%s/%s/%s", typ, r.Datacenter, r.Token, r.Key)
 }
 
-type GetOptions struct {
-	// TODO: needs to use makeEntryKey
-	Key string
-
-	// MinIndex is the index previously seen by the caller. If MinIndex>0 Fetch
-	// will not return until the index is >MinIndex, or Timeout is hit.
-	MinIndex uint64
-
-	// TODO: maybe remove and use a context deadline.
-	Timeout time.Duration
-
-	// NewMaterializer returns a new Materializer to be used if the store does
-	// not have one already running for the given key.
-	NewMaterializer func() *Materializer
-}
-
-type FetchResult struct {
-	// Value is the result of the fetch.
-	Value interface{}
-
-	// Index is the corresponding index value for this data.
-	Index uint64
+type Request interface {
+	cache.Request
+	NewMaterializer() *Materializer
 }