SAP BTP Feature Toggle Library

SAP BTP feature toggle library enables Node.js applications using the SAP Cloud Application Programming Model to maintain live-updatable feature toggles via Redis.

Getting Started (CAP Feature Toggles)

  • Set up project with @sap/cds.
  • Install library:

    npm install --save @cap-js-community/feature-toggle-library
    
  • For CAP Feature Toggles everything is configured automatically.
  • The library acts as a CDS-Plugin and registers a FeatureService, which can be used to check and update toggles.
  • For details see Example CAP Server.

Getting Started (Custom Configuration)

  • Same as previous section.
  • Write toggles.yaml configuration file:

    # info: check api priority; 0 means access is disabled
    /check/priority:
      type: number
      fallbackValue: 0
      validations:
        - scopes: [user, tenant]
        - regex: '^\d+$'
    
  • Add configuration path to package.json:

    {
      "cds": {
        "featureToggles": {
          "configFile": "./toggles.yaml"
        }
      }
    }
    
  • Write usage code in handlers:

    const toggles = require("@cap-js-community/feature-toggle-library");
    
    const priorityHandler = async (context) => {
      const user = context.user.id;
      const tenant = context.tenant;
      const value = toggles.getFeatureValue("/check/priority", { user, tenant });
      if (value <= 0) {
        return context.reject("blocked");
      } else if (value < 10) {
        return context.reply("welcome");
      } else {
        return context.reply("very welcome");
      }
    };
    

Features

  • Maintain feature toggle states consistently across multiple app instances.
  • Feature toggle changes are published from Redis to subscribed app instances with publish/subscribe pattern PUB/SUB.
  • Horizontal app scaling is supported and new app instances will start with the correct state, or fallback values, if they cannot connect to Redis.
  • Feature toggle values can be changed specifically for accessors with certain scopes, e.g., for specific tenants, users,…
  • Users can register change handler callbacks for specific toggles.
  • Users can register custom input validation callbacks for specific toggles.
  • Works as a CDS-Plugin and provides a REST service to read and manipulate toggles.

Peers

Further Topics