storage: dynamically register drivers

cmd/chihaya/config.go

@@ -13,7 +13,10 @@ import (
 	"github.com/chihaya/chihaya/middleware/clientapproval"
 	"github.com/chihaya/chihaya/middleware/jwt"
 	"github.com/chihaya/chihaya/middleware/varinterval"
-	"github.com/chihaya/chihaya/storage/memory"
+
+	// Imported to register as Storage Drivers.
+	_ "github.com/chihaya/chihaya/storage/memory"
+	_ "github.com/chihaya/chihaya/storage/memorybysubnet"
 )
 
 type hookConfig struct {
@@ -33,13 +36,18 @@ func (hookCfgs hookConfigs) Names() (hookNames []string) {
 	return
 }
 
+type storageConfig struct {
+	Name   string      `yaml:"name"`
+	Config interface{} `yaml:"config"`
+}
+
 // Config represents the configuration used for executing Chihaya.
 type Config struct {
 	middleware.Config `yaml:",inline"`
 	PrometheusAddr    string              `yaml:"prometheus_addr"`
 	HTTPConfig        httpfrontend.Config `yaml:"http"`
 	UDPConfig         udpfrontend.Config  `yaml:"udp"`
-	Storage           memory.Config       `yaml:"storage"`
+	Storage           storageConfig       `yaml:"storage"`
 	PreHooks          hookConfigs         `yaml:"prehooks"`
 	PostHooks         hookConfigs         `yaml:"posthooks"`
 }

cmd/chihaya/main.go

@@ -17,7 +17,6 @@ import (
 	"github.com/chihaya/chihaya/pkg/prometheus"
 	"github.com/chihaya/chihaya/pkg/stop"
 	"github.com/chihaya/chihaya/storage"
-	"github.com/chihaya/chihaya/storage/memory"
 )
 
 // Run represents the state of a running instance of Chihaya.
@@ -54,7 +53,7 @@ func (r *Run) Start(ps storage.PeerStore) error {
 
 	if ps == nil {
 		log.WithFields(cfg.Storage.LogFields()).Info("starting storage")
-		ps, err = memory.New(cfg.Storage)
+		ps, err = storage.NewPeerStore(cfg.Storage.Name, cfg.Storage.Config)
 		if err != nil {
 			return errors.New("failed to create memory storage: " + err.Error())
 		}

example_config.yaml

@@ -67,16 +67,18 @@ chihaya:
 
   # This block defines configuration used for the storage of peer data.
   storage:
-    # The frequency which stale peers are removed.
-    gc_interval: 14m
+    name: memory
+    config:
+      # The frequency which stale peers are removed.
+      gc_interval: 14m
 
-    # The amount of time until a peer is considered stale.
-    # To avoid churn, keep this slightly larger than `announce_interval`
-    peer_lifetime: 16m
+      # The amount of time until a peer is considered stale.
+      # To avoid churn, keep this slightly larger than `announce_interval`
+      peer_lifetime: 16m
 
-    # The number of partitions data will be divided into in order to provide a
-    # higher degree of parallelism.
-    shard_count: 1024
+      # The number of partitions data will be divided into in order to provide a
+      # higher degree of parallelism.
+      shards: 1024
 
     # The interval at which metrics about the number of infohashes and peers
     # are collected and posted to Prometheus.

storage/memory/peer_store.go

@@ -11,15 +11,20 @@ import (
 
 	log "github.com/Sirupsen/logrus"
 	"github.com/prometheus/client_golang/prometheus"
+	"gopkg.in/yaml.v2"
 
 	"github.com/chihaya/chihaya/bittorrent"
 	"github.com/chihaya/chihaya/storage"
 )
 
 func init() {
+	// Register Prometheus metrics.
 	prometheus.MustRegister(promGCDurationMilliseconds)
 	prometheus.MustRegister(promInfohashesCount)
 	prometheus.MustRegister(promSeedersCount, promLeechersCount)
+
+	// Register the storage driver.
+	storage.RegisterDriver("memory", driver{})
 }
 
 var promGCDurationMilliseconds = prometheus.NewHistogram(prometheus.HistogramOpts{
@@ -48,6 +53,30 @@ func recordGCDuration(duration time.Duration) {
 	promGCDurationMilliseconds.Observe(float64(duration.Nanoseconds()) / float64(time.Millisecond))
 }
 
+// recordInfohashesDelta records a change in the number of Infohashes tracked.
+func recordInfohashesDelta(delta float64) {
+	promInfohashesCount.Add(delta)
+}
+
+type driver struct{}
+
+func (d driver) NewPeerStore(icfg interface{}) (storage.PeerStore, error) {
+	// Marshal the config back into bytes.
+	bytes, err := yaml.Marshal(icfg)
+	if err != nil {
+		return nil, err
+	}
+
+	// Unmarshal the bytes into the proper config type.
+	var cfg Config
+	err = yaml.Unmarshal(bytes, &cfg)
+	if err != nil {
+		return nil, err
+	}
+
+	return New(cfg)
+}
+
 // ErrInvalidGCInterval is returned for a GarbageCollectionInterval that is
 // less than or equal to zero.
 var ErrInvalidGCInterval = errors.New("invalid garbage collection interval")

storage/memorybysubnet/peer_store.go

@@ -13,6 +13,7 @@ import (
 
 	log "github.com/Sirupsen/logrus"
 	"github.com/prometheus/client_golang/prometheus"
+	"gopkg.in/yaml.v2"
 
 	"github.com/chihaya/chihaya/bittorrent"
 	"github.com/chihaya/chihaya/storage"
@@ -21,6 +22,9 @@ import (
 func init() {
 	prometheus.MustRegister(promGCDurationMilliseconds)
 	prometheus.MustRegister(promInfohashesCount)
+
+	// Register the storage driver.
+	storage.RegisterDriver("memorybysubnet", driver{})
 }
 
 var promGCDurationMilliseconds = prometheus.NewHistogram(prometheus.HistogramOpts{
@@ -44,6 +48,25 @@ func recordInfohashesDelta(delta float64) {
 	promInfohashesCount.Add(delta)
 }
 
+type driver struct{}
+
+func (d driver) NewPeerStore(icfg interface{}) (storage.PeerStore, error) {
+	// Marshal the config back into bytes.
+	bytes, err := yaml.Marshal(icfg)
+	if err != nil {
+		return nil, err
+	}
+
+	// Unmarshal the bytes into the proper config type.
+	var cfg Config
+	err = yaml.Unmarshal(bytes, &cfg)
+	if err != nil {
+		return nil, err
+	}
+
+	return New(cfg)
+}
+
 // ErrInvalidGCInterval is returned for a GarbageCollectionInterval that is
 // less than or equal to zero.
 var ErrInvalidGCInterval = errors.New("invalid garbage collection interval")

storage/storage.go

@@ -1,14 +1,31 @@
 package storage
 
 import (
+	"errors"
+	"sync"
+
 	"github.com/chihaya/chihaya/bittorrent"
 	"github.com/chihaya/chihaya/pkg/stop"
 )
 
+var (
+	driversM sync.RWMutex
+	drivers  = make(map[string]Driver)
+)
+
+// Driver is the interface used to initalize a new type of PeerStore.
+type Driver interface {
+	NewPeerStore(cfg interface{}) (PeerStore, error)
+}
+
 // ErrResourceDoesNotExist is the error returned by all delete methods in the
 // store if the requested resource does not exist.
 var ErrResourceDoesNotExist = bittorrent.ClientError("resource does not exist")
 
+// ErrDriverDoesNotExist is the error returned by NewPeerStore when a peer
+// store driver with that name does not exist.
+var ErrDriverDoesNotExist = errors.New("peer store driver with that name does not exist")
+
 // PeerStore is an interface that abstracts the interactions of storing and
 // manipulating Peers such that it can be implemented for various data stores.
 type PeerStore interface {
@@ -70,3 +87,42 @@ type PeerStore interface {
 	// For more details see the documentation in the stop package.
 	stop.Stopper
 }
+
+// RegisterDriver makes a Driver available by the provided name.
+//
+// If called twice with the same name, the name is blank, or if the provided
+// Driver is nil, this function panics.
+func RegisterDriver(name string, d Driver) {
+	if name == "" {
+		panic("storage: could not register a Driver with an empty name")
+	}
+	if d == nil {
+		panic("storage: could not register a nil Driver")
+	}
+
+	driversM.Lock()
+	defer driversM.Unlock()
+
+	if _, dup := drivers[name]; dup {
+		panic("storage: RegisterDriver called twice for " + name)
+	}
+
+	drivers[name] = d
+}
+
+// NewPeerStore attempts to initialize a new PeerStore with given a name from
+// the list of registered Drivers.
+//
+// If a driver does not exist, returns ErrDriverDoesNotExist.
+func NewPeerStore(name string, cfg interface{}) (ps PeerStore, err error) {
+	driversM.RLock()
+	defer driversM.RUnlock()
+
+	var d Driver
+	d, ok := drivers[name]
+	if !ok {
+		return nil, ErrDriverDoesNotExist
+	}
+
+	return d.NewPeerStore(cfg)
+}