request-cancelation.md

Cancelable request

Every Bauta.js operations (endpoints) are listening to the following events: req.on('abort') and to the req.on('timeout') (See Node.js request events.

When any of those events are emitted, the operation is canceled and the onCancel method is called for each Pipeline.StepFunction that are currently in execution or it was already executed.

Example

// resolvers/my-resolver.js
const { resolver } = require('@axa/bautajs-core');

module.exports = resolver((operations) => {
  operations.findCats.setup(
    pipe(
      // First step function
      async function step1(val, ctx) {
        ctx.token.onCancel(() => {
          console.log('The request was canceled');
        })
        return {
          id: '1'
        }
    },
    // Second step function
    async function step2(val, ctx) {
        ctx.token.onCancel(() => {
            console.log('The request was canceled fired on cancel 2');
        })
        return {
          id: '1'
        }
    },
    // Last step function
    async function step3(val, ctx) {
      return {
        id: '1'
      }
    })
  );
})

In the previous example, if the operation findCats is canceled or aborted by the requester before all the Pipeline.StepFunctions are finished, an error will be thrown and the pending Pipeline.StepFunctions won't be executed. The error

If the request was canceled before the execution of the second Pipeline.StepFunctions, step2, only the first ctx.token.onCancel() function will be executed.

If one of the steps are a dataSource execution, the request to the third party API will be discarded also.

Cancelling the pipeline programmaticaly

// resolvers/my-resolver.js
const { resolver } = require('@axa/bautajs-core');

module.exports = resolver((operations) => {
  operations.findCats.setup(
    pipe(
      // First step function
      async (val, ctx) => {
        ctx.token.onCancel(() => {
          console.log('The request was canceled');
        })
        return {
          id: '1'
        }
    },
    // Second step function
    async (val, ctx) => {
        ctx.token.onCancel(() => {
            console.log('The request was canceled fired on cancel 2');
        })
        return {
          id: '1'
        }
    },
    // Last step function
    async (val, ctx) => {
      return {
        id: '1'
      }
    })
  );
})

const { BautajsExpress } = require('@axa/bautajs-express');
const myAPIDefinitions = require('./my-api-definitions.json');

const bautajs = new BautajsExpress(myAPIDefinitions);

const promise = bautajs.operations.findCats.run();
// Cancelling the promise manually
promise.cancel();