Merge pull request #26 from go-pkgz/pubsub

Basic support for distributed cache for LRU and Expirable caches

.github/workflows/ci.yml

@@ -20,6 +20,9 @@ jobs:
       - name: checkout
         uses: actions/checkout@v2
 
+      - name: start Redis
+        uses: supercharge/[email protected]
+
       - name: build and test
         run: |
           go get -v
@@ -29,6 +32,7 @@ jobs:
         env:
           GO111MODULE: "on"
           TZ: "America/Chicago"
+          ENABLE_REDIS_TESTS: "true"
 
       - name: install golangci-lint and goveralls
         run: |

README.md

@@ -27,8 +27,11 @@ Main features:
 
 ## Usage
 
-```
-cache := lcw.NewLruCache(lcw.MaxKeys(500), lcw.MaxCacheSize(65536), lcw.MaxValSize(200), lcw.MaxKeySize(32))
+```go
+cache, err := lcw.NewLruCache(lcw.MaxKeys(500), lcw.MaxCacheSize(65536), lcw.MaxValSize(200), lcw.MaxKeySize(32))
+if err != nil {
+    panic("failed to create cache")
+}
 defer cache.Close()
 
 val, err := cache.Get("key123", func() (lcw.Value, error) {
@@ -59,7 +62,7 @@ Cache can be created with URIs:
 1. Key is not a string, but a composed type made from partition, key-id and list of scopes (tags). 
 1. Value type limited to `[]byte`
 1. Added `Flush` method for scoped/tagged invalidation of multiple records in a given partition
-1. A simplified interface with Get, Stat and Flush only.
+1. A simplified interface with Get, Stat, Flush and Close only.
 
 ## Details
 

cache.go

@@ -6,6 +6,8 @@
 // 3 flavors of cache provided - NoP (do-nothing cache), ExpirableCache (TTL based), and LruCache
 package lcw
 
+//go:generate sh -c "mockery -inpkg -name LoadingCache -print > /tmp/cache-mock.tmp && mv /tmp/cache-mock.tmp cache_mock.go"
+
 import (
 	"fmt"
 )
@@ -81,3 +83,4 @@ func (n *Nop) Stat() CacheStat {
 func (n *Nop) Close() error {
 	return nil
 }
+

cache_test.go

@@ -656,3 +656,39 @@ func (s sizedString) Size() int { return len(s) }
 func (s sizedString) MarshalBinary() (data []byte, err error) {
 	return []byte(s), nil
 }
+
+type mockPubSub struct {
+	calledKeys []string
+	fns        []func(fromID, key string)
+	sync.Mutex
+	sync.WaitGroup
+}
+
+func (m *mockPubSub) CalledKeys() []string {
+	m.Lock()
+	defer m.Unlock()
+	return m.calledKeys
+}
+
+func (m *mockPubSub) Subscribe(fn func(fromID, key string)) error {
+	m.Lock()
+	defer m.Unlock()
+	m.fns = append(m.fns, fn)
+	return nil
+}
+
+func (m *mockPubSub) Publish(fromID, key string) error {
+	m.Lock()
+	defer m.Unlock()
+	m.calledKeys = append(m.calledKeys, key)
+	for _, fn := range m.fns {
+		fn := fn
+		m.Add(1)
+		// run in goroutine to prevent deadlock
+		go func() {
+			fn(fromID, key)
+			m.Done()
+		}()
+	}
+	return nil
+}

eventbus/pubsub.go

@@ -0,0 +1,24 @@
+// Package eventbus provides PubSub interface used for distributed cache invalidation,
+// as well as NopPubSub and RedisPubSub implementations.
+package eventbus
+
+// PubSub interface is used for distributed cache invalidation.
+// Publish is called on each entry invalidation,
+// Subscribe is used for subscription for these events.
+type PubSub interface {
+	Publish(fromID, key string) error
+	Subscribe(fn func(fromID, key string)) error
+}
+
+// NopPubSub implements default do-nothing pub-sub (event bus)
+type NopPubSub struct{}
+
+// Subscribe does nothing for NopPubSub
+func (n *NopPubSub) Subscribe(fn func(fromID, key string)) error {
+	return nil
+}
+
+// Publish does nothing for NopPubSub
+func (n *NopPubSub) Publish(fromID, key string) error {
+	return nil
+}

eventbus/pubsub_test.go

@@ -0,0 +1,13 @@
+package eventbus
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestNopPubSub(t *testing.T) {
+	nopPubSub := NopPubSub{}
+	assert.NoError(t, nopPubSub.Subscribe(nil))
+	assert.NoError(t, nopPubSub.Publish("", ""))
+}

eventbus/redis.go

@@ -0,0 +1,71 @@
+package eventbus
+
+import (
+	"strings"
+	"time"
+
+	"github.com/go-redis/redis/v7"
+	"github.com/hashicorp/go-multierror"
+	"github.com/pkg/errors"
+)
+
+// NewRedisPubSub creates new RedisPubSub with given parameters.
+// Returns an error in case of problems with creating PubSub client for specified channel.
+func NewRedisPubSub(addr, channel string) (*RedisPubSub, error) {
+	client := redis.NewClient(&redis.Options{Addr: addr})
+	pubSub := client.Subscribe(channel)
+	// wait for subscription to be created and ignore the message
+	if _, err := pubSub.Receive(); err != nil {
+		return nil, errors.Wrapf(err, "problem subscribing to channel %s on address %s", channel, addr)
+	}
+	return &RedisPubSub{client: client, pubSub: pubSub, channel: channel, done: make(chan struct{})}, nil
+}
+
+// RedisPubSub provides Redis implementation for PubSub interface
+type RedisPubSub struct {
+	client  *redis.Client
+	pubSub  *redis.PubSub
+	channel string
+
+	done chan struct{}
+}
+
+// Subscribe calls provided function on subscription channel provided on new RedisPubSub instance creation.
+// Should not be called more than once. Spawns a goroutine and does not return an error.
+func (m *RedisPubSub) Subscribe(fn func(fromID, key string)) error {
+	go func(done <-chan struct{}, pubsub *redis.PubSub) {
+		for {
+			select {
+			case <-done:
+				return
+			default:
+			}
+			msg, err := pubsub.ReceiveTimeout(time.Second * 10)
+			if err != nil {
+				continue
+			}
+
+			// Process the message
+			if msg, ok := msg.(*redis.Message); ok {
+				payload := strings.Split(msg.Payload, "$")
+				fn(payload[0], strings.Join(payload[1:], "$"))
+			}
+		}
+	}(m.done, m.pubSub)
+
+	return nil
+}
+
+// Publish publishes provided message to channel provided on new RedisPubSub instance creation
+func (m *RedisPubSub) Publish(fromID, key string) error {
+	return m.client.Publish(m.channel, fromID+"$"+key).Err()
+}
+
+// Close cleans up running goroutines and closes Redis clients
+func (m *RedisPubSub) Close() error {
+	close(m.done)
+	errs := new(multierror.Error)
+	errs = multierror.Append(errs, errors.Wrap(m.pubSub.Close(), "problem closing pubSub client"))
+	errs = multierror.Append(errs, errors.Wrap(m.client.Close(), "problem closing redis client"))
+	return errs.ErrorOrNil()
+}

eventbus/redis_test.go

@@ -0,0 +1,38 @@
+package eventbus
+
+import (
+	"math/rand"
+	"os"
+	"strconv"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestNewRedisPubSub_Error(t *testing.T) {
+	redisPubSub, err := NewRedisPubSub("127.0.0.1:99999", "test")
+	require.Error(t, err)
+	require.Nil(t, redisPubSub)
+}
+
+func TestRedisPubSub(t *testing.T) {
+	if _, ok := os.LookupEnv("ENABLE_REDIS_TESTS"); !ok {
+		t.Skip("ENABLE_REDIS_TESTS env variable is not set, not expecting Redis to be ready at 127.0.0.1:6379")
+	}
+
+	channel := "lcw-test-" + strconv.Itoa(rand.Intn(1000000))
+	redisPubSub, err := NewRedisPubSub("127.0.0.1:6379", channel)
+	require.NoError(t, err)
+	require.NotNil(t, redisPubSub)
+	var called []string
+	assert.Nil(t, redisPubSub.Subscribe(func(fromID, key string) {
+		called = append(called, fromID, key)
+	}))
+	assert.NoError(t, redisPubSub.Publish("test_fromID", "$test$key$"))
+	// Sleep which waits for Subscribe goroutine to pick up published changes
+	time.Sleep(time.Second)
+	assert.NoError(t, redisPubSub.Close())
+	assert.Equal(t, []string{"test_fromID", "$test$key$"}, called)
+}

expirable_cache.go

@@ -4,8 +4,10 @@ import (
 	"sync/atomic"
 	"time"
 
+	"github.com/google/uuid"
 	"github.com/pkg/errors"
 
+	"github.com/go-pkgz/lcw/eventbus"
 	"github.com/go-pkgz/lcw/internal/cache"
 )
 
@@ -14,6 +16,7 @@ type ExpirableCache struct {
 	options
 	CacheStat
 	currentSize int64
+	id          string
 	backend     *cache.LoadingCache
 }
 
@@ -24,7 +27,9 @@ func NewExpirableCache(opts ...Option) (*ExpirableCache, error) {
 			maxKeys:      1000,
 			maxValueSize: 0,
 			ttl:          5 * time.Minute,
+			eventBus:     &eventbus.NopPubSub{},
 		},
+		id: uuid.New().String(),
 	}
 
 	for _, opt := range opts {
@@ -33,6 +38,10 @@ func NewExpirableCache(opts ...Option) (*ExpirableCache, error) {
 		}
 	}
 
+	if err := res.eventBus.Subscribe(res.onBusEvent); err != nil {
+		return nil, errors.Wrapf(err, "can't subscribe to event bus")
+	}
+
 	backend, err := cache.NewLoadingCache(
 		cache.MaxKeys(res.maxKeys),
 		cache.TTL(res.ttl),
@@ -45,6 +54,10 @@ func NewExpirableCache(opts ...Option) (*ExpirableCache, error) {
 				size := s.Size()
 				atomic.AddInt64(&res.currentSize, -1*int64(size))
 			}
+			// ignore the error on Publish as we don't have log inside the module and
+			// there is no other way to handle it: we publish the cache invalidation
+			// and hope for the best
+			_ = res.eventBus.Publish(res.id, key)
 		}),
 	)
 	if err != nil {
@@ -128,6 +141,13 @@ func (c *ExpirableCache) Close() error {
 	return nil
 }
 
+// onBusEvent reacts on invalidation message triggered by event bus from another cache instance
+func (c *ExpirableCache) onBusEvent(id, key string) {
+	if id != c.id {
+		c.backend.Invalidate(key)
+	}
+}
+
 func (c *ExpirableCache) size() int64 {
 	return atomic.LoadInt64(&c.currentSize)
 }

expirable_cache_test.go

@@ -37,7 +37,11 @@ func TestExpirableCache(t *testing.T) {
 	assert.Equal(t, 5, lc.Stat().Keys)
 	assert.Equal(t, int64(6), lc.Stat().Misses)
 
-	time.Sleep(55 * time.Millisecond)
+	// let key-0 expire, GitHub Actions friendly way
+	for lc.Stat().Keys > 4 {
+		lc.backend.DeleteExpired() // enforce DeleteExpired for GitHub earlier than TTL/2
+		time.Sleep(time.Millisecond * 10)
+	}
 	assert.Equal(t, 4, lc.Stat().Keys)
 
 	time.Sleep(210 * time.Millisecond)
@@ -112,3 +116,52 @@ func TestExpirableCache_BadOptions(t *testing.T) {
 	_, err = NewExpirableCache(TTL(-1))
 	assert.EqualError(t, err, "failed to set cache option: negative ttl")
 }
+
+func TestExpirableCacheWithBus(t *testing.T) {
+	ps := &mockPubSub{}
+	lc1, err := NewExpirableCache(MaxKeys(5), TTL(time.Millisecond*100), EventBus(ps))
+	require.NoError(t, err)
+	defer lc1.Close()
+
+	lc2, err := NewExpirableCache(MaxKeys(50), TTL(time.Millisecond*5000), EventBus(ps))
+	require.NoError(t, err)
+	defer lc2.Close()
+
+	// add 5 keys to the first node cache
+	for i := 0; i < 5; i++ {
+		i := i
+		_, e := lc1.Get(fmt.Sprintf("key-%d", i), func() (Value, error) {
+			return fmt.Sprintf("result-%d", i), nil
+		})
+		assert.NoError(t, e)
+		time.Sleep(10 * time.Millisecond)
+	}
+
+	assert.Equal(t, 0, len(ps.CalledKeys()), "no events")
+	assert.Equal(t, 5, lc1.Stat().Keys)
+	assert.Equal(t, int64(5), lc1.Stat().Misses)
+
+	// add key-1 key to the second node
+	_, e := lc2.Get("key-1", func() (Value, error) {
+		return "result-111", nil
+	})
+	assert.NoError(t, e)
+	assert.Equal(t, 1, lc2.Stat().Keys)
+	assert.Equal(t, int64(1), lc2.Stat().Misses, lc2.Stat())
+
+	// let key-0 expire, GitHub Actions friendly way
+	for lc1.Stat().Keys > 4 {
+		lc1.backend.DeleteExpired() // enforce DeleteExpired for GitHub earlier than TTL/2
+		ps.Wait()                   // wait for onBusEvent goroutines to finish
+		time.Sleep(time.Millisecond * 10)
+	}
+	assert.Equal(t, 4, lc1.Stat().Keys)
+	assert.Equal(t, 1, lc2.Stat().Keys, "key-1 still in cache2")
+	assert.Equal(t, 1, len(ps.CalledKeys()))
+
+	time.Sleep(210 * time.Millisecond) // let all keys expire
+	ps.Wait()                          // wait for onBusEvent goroutines to finish
+	assert.Equal(t, 6, len(ps.CalledKeys()), "6 events, key-1 expired %+v", ps.calledKeys)
+	assert.Equal(t, 0, lc1.Stat().Keys)
+	assert.Equal(t, 0, lc2.Stat().Keys, "key-1 removed from cache2")
+}

go.mod

@@ -3,6 +3,7 @@ module github.com/go-pkgz/lcw
 require (
 	github.com/alicebob/miniredis/v2 v2.11.4
 	github.com/go-redis/redis/v7 v7.2.0
+	github.com/google/uuid v1.1.1
 	github.com/hashicorp/go-multierror v1.1.0
 	github.com/hashicorp/golang-lru v0.5.4
 	github.com/pkg/errors v0.9.1

go.sum

@@ -16,6 +16,8 @@ github.com/golang/protobuf v1.3.2 h1:6nsPYzhq5kReh6QImI3k5qWzO4PEbvbIW2cwSfR/6xs
 github.com/golang/protobuf v1.3.2/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
 github.com/gomodule/redigo v1.7.1-0.20190322064113-39e2c31b7ca3 h1:6amM4HsNPOvMLVc2ZnyqrjeQ92YAVWn7T4WBKK87inY=
 github.com/gomodule/redigo v1.7.1-0.20190322064113-39e2c31b7ca3/go.mod h1:B4C85qUVwatsJoIUNIfCRsp7qO0iAmpGFZ4EELWSbC4=
+github.com/google/uuid v1.1.1 h1:Gkbcsh/GbpXz7lPftLA3P6TYMwjCLYm83jiFQZF/3gY=
+github.com/google/uuid v1.1.1/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
 github.com/hashicorp/errwrap v1.0.0 h1:hLrqtEDnRye3+sgx6z4qVLNuviH3MR5aQ0ykNJa/UYA=
 github.com/hashicorp/errwrap v1.0.0/go.mod h1:YH+1FKiLXxHSkmPseP+kNlulaMuP3n2brvKWEqk/Jc4=
 github.com/hashicorp/go-multierror v1.1.0 h1:B9UzwGQJehnUY1yNrnwREHc3fGbC2xefo8g4TbElacI=