For the events i created these hooks:

import { SKIP } from '@feathersjs/feathers';

function stackTransactionEvents(context) {
  const { params, service } = context;
  if(!params.sequelize || !params.sequelize.transaction) {
    return context;
  }

  if(!params.stackedEvents) params.stackedEvents = [];
  let event;
  switch(context.method) {
    case 'create':
    case 'update':
    case 'remove':
      event = context.method + 'd';
      break;
    case 'patch':
      event = 'patched';
      break;
  }
  if(event) {
    params.stackedEvents.push({
      service,
      event,
      data: context.dispatch ? context.dispatch : context.result,
      context
    });
  }
  return SKIP;
}

function unstackTransactionEvents(context) {
  const { params } = context;
  if(!params.sequelize || !params.sequelize.transaction || !params.stackedEvents) {
    return context;
  }
  params.stackedEvents.forEach(function(stackedEvent) {
    const {service, event, context} = stackedEvent;
    let { data } = stackedEvent;
    if(!Array.isArray(data)) {
      data = [data];
    }
    console.log('EMITTING ' + event);
    service.emit(event, data, context);
  });
  return context;
}

Use something like this as a patch before hook:
(Where content and route are associated models with respective services)

function patchTransaction(context) {
  const { data , app, service, params } = context;
  if(params.sequelize && params.sequelize.transaction) {
    return context;
  }
  // If the associated content ad route are sent with the data, then a transaction is created
  if(data.content && data.route) {
    const seq = app.get('sequelizeClient');
    return seq.transaction(function(t) {
      const paramsWithTransaction = {sequelize: {transaction: t}};
      return app.service('content').patch(data.contentId, data.content, paramsWithTransaction)
      .then(function() {
        return app.service('route').patch(data.routeId, data.route, paramsWithTransaction)
        .then(function() {
          return service.patch(data.id, data, paramsWithTransaction)
        });
      });
    }).then(async function() {
      context.result = await service.get(data.id);
      return SKIP;
    });
  }
  return context;
}

You have to use the stackTransactionEvents as the last after hook on your services which are called in your transaction. With returning SKIP the automatic event dispatching is disabled.

You have to use the unstackTransactionEvents as the last after hook on your service which creating the transaction.

Please keep inn mind, that I'm not a feathers expert. Maybe the code has some flaws, or design misconceptions.

It would be nice, if someone from the core team could take a look at it, and confirm this is a right approach.

@daffl What do you think?

Transactions support #188

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