Add redis-backed cache implementation.

Resolves #54.

Author: ghbutton

redis/redis.go

@@ -0,0 +1,43 @@
+// Package redis provides a redis interface for http caching.
+package redis
+
+import (
+	"github.com/garyburd/redigo/redis"
+	"github.com/gregjones/httpcache"
+)
+
+// cache is an implementation of httpcache.Cache that caches responses in a
+// redis server.
+type cache struct {
+	redis.Conn
+}
+
+// cacheKey modifies an httpcache key for use in redis. Specifically, it
+// prefixes keys to avoid collision with other data stored in redis.
+func cacheKey(key string) string {
+	return "rediscache:" + key
+}
+
+// Get returns the response corresponding to key if present.
+func (c cache) Get(key string) (resp []byte, ok bool) {
+	item, err := redis.Bytes(c.Do("GET", cacheKey(key)))
+	if err != nil {
+		return nil, false
+	}
+	return item, true
+}
+
+// Set saves a response to the cache as key.
+func (c cache) Set(key string, resp []byte) {
+	c.Do("SET", cacheKey(key), resp)
+}
+
+// Delete removes the response with key from the cache.
+func (c cache) Delete(key string) {
+	c.Do("DEL", cacheKey(key))
+}
+
+// NewWithClient returns a new Cache with the given redis connection.
+func NewWithClient(client redis.Conn) httpcache.Cache {
+	return cache{client}
+}

redis/redis_test.go

@@ -0,0 +1,43 @@
+package redis
+
+import (
+	"bytes"
+	"testing"
+
+	"github.com/garyburd/redigo/redis"
+)
+
+func TestRedisCache(t *testing.T) {
+	conn, err := redis.Dial("tcp", "localhost:6379")
+	if err != nil {
+		// TODO: rather than skip the test, fall back to a faked redis server
+		t.Skipf("skipping test; no server running at localhost:6379")
+	}
+	conn.Do("FLUSHALL")
+
+	cache := NewWithClient(conn)
+
+	key := "testKey"
+	_, ok := cache.Get(key)
+	if ok {
+		t.Fatal("retrieved key before adding it")
+	}
+
+	val := []byte("some bytes")
+	cache.Set(key, val)
+
+	retVal, ok := cache.Get(key)
+	if !ok {
+		t.Fatal("could not retrieve an element we just added")
+	}
+	if !bytes.Equal(retVal, val) {
+		t.Fatal("retrieved a different value than what we put in")
+	}
+
+	cache.Delete(key)
+
+	_, ok = cache.Get(key)
+	if ok {
+		t.Fatal("deleted key still present")
+	}
+}