Monetization Programmatic Quotas

Beta Feature

The monetization feature is currently in beta and is subject to change. There may be bugs and issues that are not yet resolved. Use with caution and please report any issues to support.

When adding monetization to your API, you would usually set the number of meters a request will consume in the settings of the Monetization Policy. For example, the policy below specifies that each request will consume 1 requests meter and 5 computeUnits meters.

{
  "export": "MonetizationInboundPolicy",
  "module": "$import(@zuplo/runtime)",
  "options": {
    "allowRequestsOverQuota": false,
    "allowedSubscriptionStatuses": ["active", "incomplete"],
    "meterOnStatusCodes": "200-399",
    "meters": {
      "requests": 1,
      "computeUnits": 5
    }
  }
}

However, in some cases, you may not know up front how many units of a particular meter will be consumed until after the response is sent. For example, maybe your backend is responsible for computing the computeUnits on a request and send the result in the response in the compute-units header.

In Zuplo, you can support these dynamic meters by writing a little code. To make the computeUnits meter dynamic, first update the policy by setting the computeUnits meter to 0 as shown below.

{
  "export": "MonetizationInboundPolicy",
  "module": "$import(@zuplo/runtime)",
  "options": {
    "allowRequestsOverQuota": false,
    "allowedSubscriptionStatuses": ["active", "incomplete"],
    "meterOnStatusCodes": "200-399",
    "meters": {
      "requests": 1,
      "computeUnits": 0
    }
  }
}

Next you can create a custom code outbound policy that reads data from the Response (in this case the compute-units header) and sets the meter programmatically.

/modules/set-compute-units-outbound.ts

import {
  MonetizationInboundPolicy,
  ZuploRequest,
  ZuploContext,
} from "@zuplo/runtime";
 
export default async function (
  response: Response,
  request: ZuploRequest,
  context: ZuploContext,
  options: any,
  policyName: string,
) {
  const headerValue = response.headers.get("compute-units");
  let computeUnitsValue;
  if (headerValue && typeof headerValue === "string") {
    computeUnitsValue = parseInt(headerValue);
  }
 
  // Throw an error if the server doesn't send compute units
  // Alternatively, you could have a default value
  if (!computeUnitsValue) {
    throw new Error("Invalid response, no compute units sent.");
  }
 
  // Set the compute units for the request
  MonetizationInboundPolicy.setMeters(context, {
    computeUnits: computeUnitsValue,
  });
 
  return response;
}