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Create a real-time log with Send Blocks and Streaming APIs


For general concepts around streaming in Superblocks, see Streaming Applications.

This guide explains how to create a real-time log of what is happening in a Superblocks backend API as it executes. This guide can also be augmented to build other useful frontend features such as a progress bar or more advanced loading messages. Note, this guide covers only the core concepts for connecting the backend to the frontend via Send Blocks and a Streaming API. The steps may need to be modified to support your specific data sources or backend APIs.

  1. Create a temporary frontend variable named LogHistory with a default value of an empty array [].

    temporary frontend variable for logs
  2. Add a Table component and set its Table Data property to the value of the frontend variable, {{LogHistory.value}}.

    Configure Table
  3. Create a backend API with a single Send block. Configure the Message to send to {time:moment(), message:"test"}

    Configure Send Block
  4. On the backend API, open the response block and set the Response Type to "Stream".

    Convert API to Stream
  5. Configure the onMessage event handler using an Action Type of "Set Frontend Variable". Set your frontend variable LogHistory to a value of {{[...LogHistory.value, message.value]}}. This will update LogHistory with the new message.

    Configure OnMessage
  6. Click "Run API" a few times to see the logs produced and populated within the Table component.

Run and test API

Other useful patterns

With this fundamental pattern, you can now expand your Backend API to log through many different patterns. Here are some examples.

Using "Show Alert" to display current message

For each message sent from a backend API's Send block, you can show an alert on the frontend.

Configure Show Alerts
Show Alerts

Progressive updates as backend APIs execute

As steps and blocks complete or fail to complete, send messages to the frontend to show progress of an API.

Baclkend API Progress

Progressive updates as Loop runs through records

Similarly, we can show progress of a Loop or Parallel block as it processes a batch of records.

Looping progress