How to make compensation if something went wrong during current saga step execution

[imissyouso]

Hi.
For example, on step 3 of my saga I sent a new command 'createTicket' but ticket microservice rejected it and thrown Error, I logged it and now want to undo all previous saga steps (by sending compensation commands like makeRefund, deleteMessage etc). How to implement such scenario?

by the way: your pack of libraries is awesome, it wonders me why it has so small amount of stars.

[imissyouso]

My current implementation:
I created Saga step named commandReject with the code

module.exports = require('cqrs-saga').defineSaga({// event to match..
    existing: true, // if true it will check if there is already a saga in the db and only if there is something it will continue...
    payload: 'payload', // if not defined it will pass the whole event...
    id: 'payload.command.payload.transactionId', // if not defined it will generate an id
    priority: 2 // optional, default Infinity, all sagas will be sorted by this value
}, function (evt, saga, callback) {
    console.log('saga compensation start');

    // I put my first compensation command here and execute all next by chain.

    saga.commit(callback);
});

Is that way is correct?

[imissyouso]

Or another way:
I execute all compensation command in parallel, pay attention on switch breaks.

module.exports = require('cqrs-saga').defineSaga({// event to match..
    existing: true, // if true it will check if there is already a saga in the db and only if there is something it will continue...
    payload: 'payload', // if not defined it will pass the whole event...
    id: 'payload.command.payload.transactionId', // if not defined it will generate an id
    priority: 2 // optional, default Infinity, all sagas will be sorted by this value
}, function (evt, saga, callback) {
    console.log('saga compensation start');

    switch (evt.command.command) {
        case 'attachMessageToTicket':
            saga.addCommandToSend({
                command: 'deleteTicket',
                payload: {
                    transactionId: saga.id,
                    id: saga.get('ticketId'),
                }
            });
        case 'createTicket':
            console.log(evt.command.payload);
            saga.addCommandToSend({
                command: 'deleteContact',
                payload: {
                    transactionId: saga.id,
                    id: saga.get('contactId'),
                }
            });
        case 'createContact':
            saga.addCommandToSend({
                command: 'deleteMessage',
                payload: {
                    transactionId: saga.id,
                    id: saga.get('messageId'),
                }
            });
            break;
        default:
            callback("No compensation event found for "+evt.command.command);
            return;
    }

    saga.destroy();
    saga.commit(callback);
});

[adrai]

Yes, I would recommend to handle a failed command as a new event...