javascript - 客户端可以访问套接字分配吗？

Question

我知道在 Phoenix Channel 中，服务器可以通过套接字分配来保持状态，例如

def join("room:lobby", payload, socket) do
  socket = socket
    |> assign(:message, Enum.random(@messages))
    |> assign(:albums, [])
  {:ok, socket}
end

但是，我无法确定客户是否可以通过任何方式访问这些分配。

我的困惑是，如果套接字连接应该在服务器和客户端之间保持直到终止，那么客户端不应该也能够访问此连接中的内容吗？

或者所有这些分配都只保存在服务器端进程中，因此客户端无法访问，即使客户端在某些情况下确实保持与服务器的连接怎么办？

如果是这样，服务器似乎必须明确地向客户端广播它存储的任何分配，如果它愿意的话？

Answer 1

My confusion is that, if a socket connection is supposedly kept between the server and the client until it's terminated, shouldn't the client be able to access what's in this connection as well?

assigns 只是结构中的一个键:

defmodule Phoenix.Socket
  ...
  ...
  defstruct assigns: %{},
            channel: nil,
            channel_pid: nil,
            endpoint: nil,
            handler: nil,
            id: nil,
            joined: false,
            join_ref: nil,
            private: %{},
            pubsub_server: nil,
            ref: nil,
            serializer: nil,
            topic: nil,
            transport: nil,
            transport_pid: nil

https://github.com/phoenixframework/phoenix/blob/v1.4.0/lib/phoenix/socket.ex#L181

该结构不在连接中。相反，该结构是服务器用来存储有关特定连接的相关信息的暂存器。根据Channels docs :

To start communicating, a client connects to a node (a Phoenix server) using a transport (eg, Websockets or long polling) and joins one or more channels using that single network connection. One channel server process is created per client, per topic. The appropriate socket handler initializes a %Phoenix.Socket for the channel server (possibly after authenticating the client). The channel server then holds onto the %Phoenix.Socket{} and can maintain any state it needs within its socket.assigns.

Once the connection is established, each incoming message from a client is routed, based on its topic, to the correct channel server. If the channel server asks to broadcast a message, that message is sent to the local PubSub, which sends it out to any clients connected to the same server and subscribed to that topic.

--

It seems the server must explicitly broadcast to the client whatever assigns it has stored, if it wants to?

是的。

您可以在此 ElixirCasts.io video 中查看服务器如何使用分配(从 4:15 开始)。