Implement BACKEND_TYPE=memcache as an alternative k/v store to redis

Dockerfile.integration

@@ -1,7 +1,7 @@
 # Running this docker image runs the integration tests.
 FROM golang:1.14
 
-RUN apt-get update -y && apt-get install sudo stunnel4 redis -y && rm -rf /var/lib/apt/lists/*
+RUN apt-get update -y && apt-get install sudo stunnel4 redis memcached -y && rm -rf /var/lib/apt/lists/*
 
 WORKDIR /workdir
 

Makefile

@@ -97,6 +97,7 @@ tests_with_redis: bootstrap_redis_tls tests_unit
 	mkdir 6389 && cd 6389 && redis-server --port 6389 --cluster-enabled yes --requirepass password123 &
 	mkdir 6390 && cd 6390 && redis-server --port 6390 --cluster-enabled yes --requirepass password123 &
 	mkdir 6391 && cd 6391 && redis-server --port 6391 --cluster-enabled yes --requirepass password123 &
+	memcached -u root --port 6394 -m 64 &
 	sleep 2
 	echo "yes" | redis-cli --cluster create -a password123 127.0.0.1:6386 127.0.0.1:6387 127.0.0.1:6388 --cluster-replicas 0
 	echo "yes" | redis-cli --cluster create -a password123 127.0.0.1:6389 127.0.0.1:6390 127.0.0.1:6391 --cluster-replicas 0

README.md

@@ -31,6 +31,7 @@
   - [Pipelining](#pipelining)
   - [One Redis Instance](#one-redis-instance)
   - [Two Redis Instances](#two-redis-instances)
+- [Memcache](#memcache)
 - [Contact](#contact)
 
 <!-- END doctoc generated TOC please keep comment here to allow auto update -->
@@ -554,6 +555,21 @@ To configure two Redis instances use the following environment variables:
 This setup will use the Redis server configured with the `_PERSECOND_` vars for
 per second limits, and the other Redis server for all other limits.
 
+# Memcache
+
+Experimental Memcache support has been added as an alternative to Redis in v1.5.
+
+To configure a Memcache instance use the following environment variables instead of the Redis variables:
+
+1. `MEMCACHE_HOST_PORT=<host:port>`
+1. `BACKEND_TYPE=memcache`
+
+With memcache mode increments will happen asynchronously, so it's technically possible for
+a client to exceed quota briefly if multiple requests happen at exactly the same time.
+
+Note that Memcache has a max key length of 250 characters, so operations referencing very long
+descriptors will fail.
+
 # Contact
 
 * [envoy-announce](https://groups.google.com/forum/#!forum/envoy-announce): Low frequency mailing

docker-compose.yml

@@ -10,6 +10,15 @@ services:
     networks:
       - ratelimit-network
 
+  memcached:
+    image: memcached:alpine
+    expose:
+      - 11211
+    ports:
+      - 11211:11211
+    networks:
+      - ratelimit-network
+
   # minimal container that builds the ratelimit service binary and exits.
   ratelimit-build:
     image: golang:1.14-alpine
@@ -51,6 +60,7 @@ services:
       - REDIS_URL=redis:6379
       - RUNTIME_ROOT=/data
       - RUNTIME_SUBDIRECTORY=ratelimit
+      - MEMCACHE_HOST_PORT=memcached:11211
 
 networks:
   ratelimit-network:

go.mod

@@ -4,6 +4,7 @@ go 1.14
 
 require (
 	github.com/alicebob/miniredis/v2 v2.11.4
+	github.com/bradfitz/gomemcache v0.0.0-20190913173617-a41fca850d0b
 	github.com/cespare/xxhash v1.1.0 // indirect
 	github.com/coocood/freecache v1.1.0
 	github.com/envoyproxy/go-control-plane v0.9.7

go.sum

@@ -6,6 +6,8 @@ github.com/alicebob/gopher-json v0.0.0-20180125190556-5a6b3ba71ee6 h1:45bxf7AZMw
 github.com/alicebob/gopher-json v0.0.0-20180125190556-5a6b3ba71ee6/go.mod h1:SGnFV6hVsYE877CKEZ6tDNTjaSXYUk6QqoIK6PrAtcc=
 github.com/alicebob/miniredis/v2 v2.11.4 h1:GsuyeunTx7EllZBU3/6Ji3dhMQZDpC9rLf1luJ+6M5M=
 github.com/alicebob/miniredis/v2 v2.11.4/go.mod h1:VL3UDEfAH59bSa7MuHMuFToxkqyHh69s/WUbYlOAuyg=
+github.com/bradfitz/gomemcache v0.0.0-20190913173617-a41fca850d0b h1:L/QXpzIa3pOvUGt1D1lA5KjYhPBAN/3iWdP7xeFS9F0=
+github.com/bradfitz/gomemcache v0.0.0-20190913173617-a41fca850d0b/go.mod h1:H0wQNHz2YrLsuXOZozoeDmnHXkNCRmMW0gwFWDfEZDA=
 github.com/census-instrumentation/opencensus-proto v0.2.1/go.mod h1:f6KPmirojxKA12rnyqOA5BBL4O983OfeGPqjHWSTneU=
 github.com/cespare/xxhash v1.1.0 h1:a6HrQnmkObjyL+Gs60czilIUGqrzKutQD6XZog3p+ko=
 github.com/cespare/xxhash v1.1.0/go.mod h1:XrSqR1VqqWfGrhpAt58auRo0WTKS1nRRg3ghfAqPWnc=

src/limiter/cache.go

@@ -6,20 +6,6 @@ import (
 	"golang.org/x/net/context"
 )
 
-// Interface for a time source.
-type TimeSource interface {
-	// @return the current unix time in seconds.
-	UnixNow() int64
-}
-
-// Interface for a rand Source for expiration jitter.
-type JitterRandSource interface {
-	// @return a non-negative pseudo-random 63-bit integer as an int64.
-	Int63() int64
-	// @param seed initializes pseudo-random generator to a deterministic state.
-	Seed(seed int64)
-}
-
 // Interface for interacting with a cache backend for rate limiting.
 type RateLimitCache interface {
 	// Contact the cache and perform rate limiting for a set of descriptors and limits.
@@ -35,4 +21,8 @@ type RateLimitCache interface {
 		ctx context.Context,
 		request *pb.RateLimitRequest,
 		limits []*config.RateLimit) []*pb.RateLimitResponse_DescriptorStatus
+
+	// Waits for any unfinished asynchronous work. This may be used by unit tests,
+	// since the memcache cache does increments in a background gorountine.
+	Flush()
 }