@sap/cds/lib/req/spawn.js

SAP Cloud Application Programming Model - CDS for Node.js

const { EventEmitter } = require('events')
const EventContext = require('./context')

module.exports = function spawn (o, fn, /** @type {import('../index')} */ cds=this) {
  if (typeof o === 'function') [fn,o] = [o,fn] //> for compatibility
  if (o instanceof EventContext) throw cds.error `The passed options must not be an instance of cds.EventContext.`
  const fx = ()=>{
    const tx = cds.tx({...o}) // create a new detached transaction for each run of the background job
    return cds._with (tx, async ()=> {
      // REVISIT: The model must be set _after_ run to make sure that cds.context.tenant is correctly set.
      //          Otherwise, `model4` could query the wrong database to check for extensions.
      if (cds.model && (cds.env.requires.extensibility || cds.env.requires.toggles)) {
        const ctx = cds.context
        const ExtendedModels = require('../srv/srv-models') // the sentinel is automatically started when required
        cds.context.model = await ExtendedModels.model4(ctx.tenant, ctx.features)
        tx.model = cds.context.model
      }
      return Promise.resolve(fn(tx))
      .then (tx.commit, e => {
        cds.log().error(`ERROR occurred in background job:`, e)
        return tx.rollback(e)
      })
      .then (res => Promise.all(em.listeners('succeeded').map(each => each(res))))
      .catch (err => Promise.all(em.listeners('failed').map(each => each(err))))
      .finally (() => Promise.all(em.listeners('done').map(each => each())))
    })
  }
  const em = new EventEmitter
  em.timer = (
    o?.every ? setInterval(fx, o.every) :
    o?.after ? setTimeout(fx, o.after) :
    setImmediate(fx)
  ).unref()
  if (cds.env.server.shutdown_on_uncaught_errors) em.on ('failed', e => {
    if (cds.error.isSystemError(e)) cds.shutdown(e)
  })
  return em
}