Welcome to SCRAM’s documentation!

Contents:

WebSockets

WebSockets are used in two places:

  1. Between SCRAM and the systems that act on the actions (the “translators.”). config.consumers.TranslatorConsumer

  2. Between the user’s web browser and SCRAM for asynchronous operations (currently just querying about an entry’s current status). config.consumers.WebUIConsumer

Architecture

SCRAM is the source of truth, and has one or more action types (e.g. block, redirect, etc.). When an entry is added to SCRAM, it has one action type assigned to it.

WebSocket messages are sent to the group called translator_<actiontype_name>, such as translator_block. All translators that implement a block action type subscribe to that group.

Three message types are defined: translator_add, translator_remove, and translator_check. The first two are sent as entries are added and removed (possibly due to expiration), and the last is to inquire if the Entry is currently active in the translator. The translator replies with a translator_check_resp message.

WebUIConsumer

When viewing an scram.route_manager.models.Entry in the web interface, we want to know if the entry is currently blocked, and by which translator(s). In the template for that page, some Javascript code sends a WebSocket query of type wui_check_req:

{# Open connection to the websocket #}
let socket = new WebSocket(wss_uri + "/ws/route_manager/webui_block/")

{# Send status request message #}
function getStatus(route, pk) {
  let data = {"type": "wui_check_req", "message": {"route": route, "row": pk}};
  sendMessage(socket, JSON.stringify(data))
}

wui_check_req messages are forwarded to the appropriate translator group, as a translator_check message. The translator_check_resp message is converted to a wui_check_resp message and returned to the browser.

Indices and tables