Using Typescript Objects

You can add DBOS workflow, step, and transaction decorators to your TypeScript class instance methods. To add DBOS decorators to your instance methods, their class must inherit from ConfiguredInstance, which will take an instance name and register the instance.

For example:

class MyClass extends ConfiguredInstance {
  cfg: MyConfig;
  constructor(name: string, config: MyConfig) {
    super(name);
    this.cfg = cfg;
  }

  async initialize(_ctx: InitContext) : Promise<void> {
    // ... Validate this.cfg
  }

  @DBOS.transaction()
  async testTransaction() {
    // ... Operations that use this.cfg
  }

  @DBOS.step()
  async testStep() {
    // ... Operations that use this.cfg
  }

  @DBOS.workflow()
  async testWorkflow(p: string): Promise<void> {
    // ... Operations that use this.cfg
  }
}

const myClassInstance = new MyClass('instanceA');

When you create a new instance of a DBOS-decorated class, the constructor for the base ConfiguredInstance must be called with a name. This name should be unique among instances of the same class. Additionally, all ConfiguredInstance classes must be instantiated before DBOS.launch() is called.

The reason for these requirements is to enable workflow recovery. When you create a new instance of, DBOS stores it in a global registry indexed by name. When DBOS needs to recover a workflow belonging to that class, it looks up the name so it can run the workflow using the right class instance. While names are used by DBOS Transact internally to find the correct object instance across system restarts, they are also potentially useful for monitoring, tracing, and debugging.

Using Configured Class Instances

Configured class instances should be created and named when the application starts, before any workflows run. This ensures that they will all be initialized before any processing begins.

Writing New Configured Classes

All configured classes must:

• Extend from the ConfiguredInstance base class
• Provide a constructor, which can take any arguments, but must provide a name to the base ConfiguredInstance constructor
• Have an initialize(ctx: InitContext) that will be called after all objects have been created, but before request handling commences

initialize() Method

The initialize(ctx: InitContext) method will be called during application initialization, after the code modules have been loaded, but before request and workflow processing commences. The InitContext argument provides configuration file, logging, and database access services, so any validation of connection information (complete with diagnostic logging and reporting of any problems) should be performed in initialize().

Notes

Event and handler registration decorators such as @DBOS.scheduled, @KafkaConsume, @DBOS.getApi, and @DBOS.putApi cannot be applied to instance methods.