-record(state, {
          host :: string() | undefined,
          port :: integer() | undefined,
          database :: binary() | undefined,
          auth_cmd :: iodata() | undefined,
          reconnect_sleep :: integer() | undefined | no_reconnect,
          connect_timeout :: integer() | undefined,
          socket_options :: list(),
          tls_options :: list(),

          transport :: gen_tcp | ssl,
          socket :: gen_tcp:socket() | ssl:sslsocket() | undefined,
          parser_state :: #pstate{} | undefined,

          %% Channels we should subscribe to
          channels = [] :: [channel()],
          pchannels = [] :: [channel()], % psubscribe

          %% The process we send pubsub and connection state messages to.
          controlling_process :: undefined | {reference(), pid()},

          %% This is the queue of messages to send to the controlling process.
          msg_queue :: eredis_queue(),

          %% When the queue reaches this size, either drop all
          %% messages or exit.
          max_queue_size :: integer() | inifinity,
          queue_behaviour :: drop | exit,

          %% The msg_state keeps track of whether we are waiting for the
          %% controlling process to acknowledge the last message.
          msg_state = need_ack :: ready | need_ack
}).