Jobs Parameters Serialization

When you pass an Adonis.js model instance as an argument to a job, you can’t use it to perform database operations directly inside the job because the instance is serialized before being stored in the queue and then deserialized when the job is processed. This serialization process loses the active database connection and other internal state that the model instance needs to interact with the database.

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Why this Happens

Adonis.js jobs, by default, use a queuing system (like Redis or a database table) to store the job’s data. To be stored, the job data, including any arguments passed to it, must be converted into a flat, storable format like a JSON string. This process is called serialization.

1. Serialization: The model instance, which is a complex JavaScript object with methods, getters, and setters, and an active database connection, is converted into a plain object or a string. During this process, the methods and the connection to the database are discarded.

2. Storage: The serialized data is then stored in the queue (e.g., Redis).

3. Deserialization: When the worker process picks up the job, it retrieves the data from the queue and converts it back into a JavaScript object. This newly created object is just a plain data object; it is not a live Adonis.js model instance. It lacks the internal magic and database connection required to perform queries like save(), update(), or delete().

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How to Fix It

Instead of passing the entire model instance, you should pass a unique identifier for that model, such as its primary key (ID).

Here’s a step-by-step example:

1. In your controller or service, get the model instance and pass its ID to the job:

   const user = await User.findOrFail(1);
   // Pass only the user's ID to the job
   await DriveJob.dispatch([user.id]); 
   

2. In your job handler, use the ID to fetch a fresh instance of the model from the database:

   'use strict'
   
   const User = use('App/Models/User')
   
   class DriveJob {
       static get key() {
           return 'drive-job'
       }
   
       async handle(userId) {
           // Fetch a fresh instance of the user model
           const user = await User.findOrFail(userId);
               
           // Now you can work with the database using this fresh instance
           user.name = 'New Name';
           await user.save();
       }
   }
   
   module.exports = DriveJob
   

By following this pattern, you ensure that your job is working with a live, fully functional model instance that has the necessary database connection to perform all model operations.