cache : add cache service (#457)

Signed-off-by: Bobby DeSimone <bobbydesimone@gmail.com>

cache/cache.go

@@ -0,0 +1,68 @@
+package cache // import "github.com/pomerium/pomerium/cache"
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	stdlog "log"
+
+	"github.com/pomerium/pomerium/config"
+	"github.com/pomerium/pomerium/internal/kv"
+	"github.com/pomerium/pomerium/internal/kv/autocache"
+	"github.com/pomerium/pomerium/internal/kv/bolt"
+	"github.com/pomerium/pomerium/internal/kv/redis"
+	"github.com/pomerium/pomerium/internal/log"
+)
+
+// Cache represents the cache service. The cache service is a simple interface
+// for storing keyed blobs (bytes) of unstructured data.
+type Cache struct {
+	cache kv.Store
+}
+
+// New creates a new cache service.
+func New(opts config.Options) (*Cache, error) {
+	cache, err := NewCacheStore(opts.CacheStore, &opts)
+	if err != nil {
+		return nil, err
+	}
+	return &Cache{
+		cache: cache,
+	}, nil
+}
+
+// NewCacheStore creates a new cache store by name and given a set of
+// configuration options.
+func NewCacheStore(name string, o *config.Options) (s kv.Store, err error) {
+	switch name {
+	case bolt.Name:
+		s, err = bolt.New(&bolt.Options{Path: o.CacheStorePath})
+	case redis.Name:
+		// todo(bdd): make path configurable in config.Options
+		s, err = redis.New(&redis.Options{
+			Addr:     o.CacheStoreAddr,
+			Password: o.CacheStorePassword,
+		})
+	case autocache.Name:
+		acLog := log.Logger.With().Str("service", "autocache").Logger()
+		s, err = autocache.New(&autocache.Options{
+			SharedKey:     o.SharedKey,
+			Log:           stdlog.New(acLog, "", 0),
+			ClusterDomain: o.CacheURL.Hostname(),
+		})
+	default:
+		return nil, fmt.Errorf("cache: unknown store: %s", name)
+	}
+	if err != nil {
+		return nil, err
+	}
+	return s, nil
+}
+
+// Close shuts down the underlying cache store, services, or both -- if any.
+func (c *Cache) Close() error {
+	if c.cache == nil {
+		return errors.New("cache: cannot close nil cache")
+	}
+	return c.cache.Close(context.TODO())
+}