Client Cache

client/cache.go

@@ -0,0 +1,64 @@
+package client
+
+import (
+	"context"
+	"crypto/sha1"
+	"encoding/json"
+	"fmt"
+	"sync"
+	"time"
+
+	"github.com/micro/go-micro/v2/metadata"
+)
+
+// NewCache returns an initialised cache.
+// TODO: Setup a go routine to expire records in the cache.
+func NewCache() *Cache {
+	return &Cache{
+		values: make(map[string]interface{}),
+	}
+}
+
+// Cache for responses
+type Cache struct {
+	values map[string]interface{}
+	mutex  sync.Mutex
+}
+
+// Get a response from the cache
+func (c *Cache) Get(ctx context.Context, req *Request) interface{} {
+	md, _ := metadata.FromContext(ctx)
+	ck := cacheKey{req, md}
+
+	c.mutex.Lock()
+	defer c.mutex.Unlock()
+
+	if val, ok := c.values[ck.Hash()]; ok {
+		return val
+	}
+
+	return nil
+}
+
+// Set a response in the cache
+func (c *Cache) Set(ctx context.Context, req *Request, rsp interface{}, expiry time.Duration) {
+	md, _ := metadata.FromContext(ctx)
+	ck := cacheKey{req, md}
+
+	c.mutex.Lock()
+	c.values[ck.Hash()] = rsp
+	defer c.mutex.Unlock()
+}
+
+type cacheKey struct {
+	Request  *Request
+	Metadata metadata.Metadata
+}
+
+// Source: https://gobyexample.com/sha1-hashes
+func (k *cacheKey) Hash() string {
+	bytes, _ := json.Marshal(k)
+	h := sha1.New()
+	h.Write(bytes)
+	return fmt.Sprintf("%x", h.Sum(nil))
+}

client/options.go

@@ -29,6 +29,9 @@ type Options struct {
 	PoolSize int
 	PoolTTL  time.Duration
 
+	// Response cache
+	Cache *Cache
+
 	// Middleware for client
 	Wrappers []Wrapper
 
@@ -59,6 +62,8 @@ type CallOptions struct {
 	StreamTimeout time.Duration
 	// Use the services own auth token
 	ServiceToken bool
+	// Duration to cache the response for
+	CacheExpiry time.Duration
 
 	// Middleware for low level call func
 	CallWrappers []CallWrapper
@@ -91,6 +96,7 @@ type RequestOptions struct {
 
 func NewOptions(options ...Option) Options {
 	opts := Options{
+		Cache:       NewCache(),
 		Context:     context.Background(),
 		ContentType: DefaultContentType,
 		Codecs:      make(map[string]codec.NewCodec),
@@ -324,6 +330,14 @@ func WithServiceToken() CallOption {
 	}
 }
 
+// WithCache is a CallOption which sets the duration the response
+// shoull be cached for
+func WithCache(c time.Duration) CallOption {
+	return func(o *CallOptions) {
+		o.CacheExpiry = c
+	}
+}
+
 func WithMessageContentType(ct string) MessageOption {
 	return func(o *MessageOptions) {
 		o.ContentType = ct