Built-in Redis cache store

* Supports vanilla Redis, hiredis, and Redis::Distributed.
* Supports Memcached-like sharding across Redises with Redis::Distributed.
* Fault tolerant. If the Redis server is unavailable, no exceptions are
  raised. Cache fetches are treated as misses and writes are dropped.
* Local cache. Hot in-memory primary cache within block/middleware scope.
* `read_/write_multi` support for Redis mget/mset. Use Redis::Distributed
  4.0.1+ for distributed mget support.
* `delete_matched` support for Redis KEYS globs.

3 files changed, 162 insertions, 3 deletions

diff --git a/activesupport/test/cache/behaviors/cache_increment_decrement_behavior.rb b/activesupport/test/cache/behaviors/cache_increment_decrement_behavior.rb
index 2fa2d7af88..16b7abc679 100644
--- a/activesupport/test/cache/behaviors/cache_increment_decrement_behavior.rb
+++ b/activesupport/test/cache/behaviors/cache_increment_decrement_behavior.rb
@@ -8,7 +8,9 @@ module CacheIncrementDecrementBehavior
     assert_equal 2, @cache.read("foo").to_i
     assert_equal 3, @cache.increment("foo")
     assert_equal 3, @cache.read("foo").to_i
-    assert_nil @cache.increment("bar")
+
+    missing = @cache.increment("bar")
+    assert(missing.nil? || missing == 1)
   end
 
   def test_decrement
@@ -18,6 +20,8 @@ module CacheIncrementDecrementBehavior
     assert_equal 2, @cache.read("foo").to_i
     assert_equal 1, @cache.decrement("foo")
     assert_equal 1, @cache.read("foo").to_i
-    assert_nil @cache.decrement("bar")
+
+    missing = @cache.decrement("bar")
+    assert(missing.nil? || missing == -1)
   end
 end
diff --git a/activesupport/test/cache/behaviors/local_cache_behavior.rb b/activesupport/test/cache/behaviors/local_cache_behavior.rb
index 8dec8090b1..f7302df4c8 100644
--- a/activesupport/test/cache/behaviors/local_cache_behavior.rb
+++ b/activesupport/test/cache/behaviors/local_cache_behavior.rb
@@ -20,7 +20,11 @@ module LocalCacheBehavior
   end
 
   def test_cleanup_clears_local_cache_but_not_remote_cache
-    skip unless @cache.class.instance_methods(false).include?(:cleanup)
+    begin
+      @cache.cleanup
+    rescue NotImplementedError
+      skip
+    end
 
     @cache.with_local_cache do
       @cache.write("foo", "bar")
diff --git a/activesupport/test/cache/stores/redis_cache_store_test.rb b/activesupport/test/cache/stores/redis_cache_store_test.rb
new file mode 100644
index 0000000000..988de9207f
--- /dev/null
+++ b/activesupport/test/cache/stores/redis_cache_store_test.rb
@@ -0,0 +1,151 @@
+# frozen_string_literal: true
+
+require "abstract_unit"
+require "active_support/cache"
+require "active_support/cache/redis_cache_store"
+require_relative "../behaviors"
+
+module ActiveSupport::Cache::RedisCacheStoreTests
+  class LookupTest < ActiveSupport::TestCase
+    test "may be looked up as :redis_cache_store" do
+      assert_kind_of ActiveSupport::Cache::RedisCacheStore,
+        ActiveSupport::Cache.lookup_store(:redis_cache_store)
+    end
+  end
+
+  class InitializationTest < ActiveSupport::TestCase
+    test "omitted URL uses Redis client with default settings" do
+      assert_called_with Redis, :new, [
+        url: nil,
+        connect_timeout: 20, read_timeout: 1, write_timeout: 1,
+        reconnect_attempts: 0,
+      ] do
+        build
+      end
+    end
+
+    test "no URLs uses Redis client with default settings" do
+      assert_called_with Redis, :new, [
+        url: nil,
+        connect_timeout: 20, read_timeout: 1, write_timeout: 1,
+        reconnect_attempts: 0,
+      ] do
+        build url: []
+      end
+    end
+
+    test "singular URL uses Redis client" do
+      assert_called_with Redis, :new, [
+        url: "redis://localhost:6379/0",
+        connect_timeout: 20, read_timeout: 1, write_timeout: 1,
+        reconnect_attempts: 0,
+      ] do
+        build url: "redis://localhost:6379/0"
+      end
+    end
+
+    test "one URL uses Redis client" do
+      assert_called_with Redis, :new, [
+        url: "redis://localhost:6379/0",
+        connect_timeout: 20, read_timeout: 1, write_timeout: 1,
+        reconnect_attempts: 0,
+      ] do
+        build url: %w[ redis://localhost:6379/0 ]
+      end
+    end
+
+    test "multiple URLs uses Redis::Distributed client" do
+      assert_called_with Redis, :new, [
+        [ url: "redis://localhost:6379/0",
+          connect_timeout: 20, read_timeout: 1, write_timeout: 1,
+          reconnect_attempts: 0 ],
+        [ url: "redis://localhost:6379/1",
+          connect_timeout: 20, read_timeout: 1, write_timeout: 1,
+          reconnect_attempts: 0 ],
+      ], returns: Redis.new do
+        @cache = build url: %w[ redis://localhost:6379/0 redis://localhost:6379/1 ]
+        assert_kind_of ::Redis::Distributed, @cache.redis
+      end
+    end
+
+    test "block argument uses yielded client" do
+      block = -> { :custom_redis_client }
+      assert_called block, :call do
+        build redis: block
+      end
+    end
+
+    private
+      def build(**kwargs)
+        ActiveSupport::Cache::RedisCacheStore.new(**kwargs).tap do |cache|
+          cache.redis
+        end
+      end
+  end
+
+  class StoreTest < ActiveSupport::TestCase
+    setup do
+      @namespace = "namespace"
+
+      @cache = ActiveSupport::Cache::RedisCacheStore.new(timeout: 0.1, namespace: @namespace, expires_in: 60)
+      #@cache.logger = Logger.new($stdout)  # For test debugging
+
+      # For LocalCacheBehavior tests
+      @peek = ActiveSupport::Cache::RedisCacheStore.new(timeout: 0.1, namespace: @namespace)
+    end
+
+    teardown do
+      @cache.clear
+      @cache.redis.disconnect!
+    end
+  end
+
+  class RedisCacheStoreCommonBehaviorTest < StoreTest
+    include CacheStoreBehavior
+    include CacheStoreVersionBehavior
+    include LocalCacheBehavior
+    include CacheIncrementDecrementBehavior
+    include AutoloadingCacheBehavior
+  end
+
+  # Separate test class so we can omit the namespace which causes expected,
+  # appropriate complaints about incompatible string encodings.
+  class KeyEncodingSafetyTest < StoreTest
+    include EncodedKeyCacheBehavior
+
+    setup do
+      @cache = ActiveSupport::Cache::RedisCacheStore.new(timeout: 0.1)
+      @cache.logger = nil
+    end
+  end
+
+  class StoreAPITest < StoreTest
+  end
+
+  class FailureSafetyTest < StoreTest
+    test "fetch read failure returns nil" do
+    end
+
+    test "fetch read failure does not attempt to write" do
+    end
+
+    test "write failure returns nil" do
+    end
+  end
+
+  class DeleteMatchedTest < StoreTest
+    test "deletes keys matching glob" do
+      @cache.write("foo", "bar")
+      @cache.write("fu", "baz")
+      @cache.delete_matched("foo*")
+      assert !@cache.exist?("foo")
+      assert @cache.exist?("fu")
+    end
+
+    test "fails with regexp matchers" do
+      assert_raise ArgumentError do
+        @cache.delete_matched(/OO/i)
+      end
+    end
+  end
+end