THREESCALE-11061: Async mode: Add support for Redis logical DBs (#390)

* Add support for Redis logical DBs in async mode

lib/3scale/backend/async_redis/protocol/extended_resp2.rb

@@ -0,0 +1,30 @@
+# frozen_string_literal: true
+
+require 'async/redis/protocol/resp2'
+
+module ThreeScale
+  module Backend
+    module AsyncRedis
+      module Protocol
+
+        # Custom Redis Protocol supporting Redis logical DBs
+        class ExtendedRESP2
+          def initialize(db: nil)
+            @db = db
+          end
+
+          def client(stream)
+            client = Async::Redis::Protocol::RESP2.client(stream)
+
+            if @db
+              client.write_request(["SELECT", @db])
+              client.read_response
+            end
+
+            client
+          end
+        end
+      end
+    end
+  end
+end

lib/3scale/backend/storage_async/client.rb

@@ -1,6 +1,7 @@
 require 'async/io'
 require 'async/redis/client'
 require 'async/redis/sentinels'
+require '3scale/backend/async_redis/protocol/extended_resp2'
 
 module ThreeScale
   module Backend
@@ -71,20 +72,34 @@ def initialize_client(opts)
         end
 
         def init_host_client(opts)
-          uri = URI(opts[:url] || '')
-          host = uri.host || DEFAULT_HOST
-          port = uri.port || DEFAULT_PORT
-
-          endpoint = Async::IO::Endpoint.tcp(host, port)
-          Async::Redis::Client.new(endpoint, limit: opts[:max_connections])
+          endpoint = make_redis_endpoint(opts)
+          protocol = make_redis_protocol(opts)
+          Async::Redis::Client.new(endpoint, protocol: protocol, limit: opts[:max_connections])
         end
 
         def init_sentinels_client(opts)
           uri = URI(opts[:url] || '')
           name = uri.host
           role = opts[:role] || :master
+          protocol = make_redis_protocol(opts)
+
+          Async::Redis::SentinelsClient.new(name, opts[:sentinels], role, protocol)
+        end
+
+        # RESP2 with support for logical DBs
+        def make_redis_protocol(opts)
+          uri = URI(opts[:url] || "")
+          db = uri.path[1..-1]
+
+          ThreeScale::Backend::AsyncRedis::Protocol::ExtendedRESP2.new(db: db)
+        end
+
+        def make_redis_endpoint(opts)
+          uri = URI(opts[:url] || "")
+          host = uri.host || DEFAULT_HOST
+          port = uri.port || DEFAULT_PORT
 
-          Async::Redis::SentinelsClient.new(name, opts[:sentinels], role)
+          Async::IO::Endpoint.tcp(host, port)
         end
       end
     end