Data Subscriptions: Consumption API Overview

A subscription worker can be created using the following getSubscriptionWorker methods available through the subscriptions property of the documentStore.

Note: Simply creating the worker is insufficient;
after creating the worker, you need to run the subscription worker to initiate document processing.

await documentStore.subscriptions.getSubscriptionWorker(subscriptionName);
await documentStore.subscriptions.getSubscriptionWorker(subscriptionName, database);

await documentStore.subscriptions.getSubscriptionWorker(options);
await documentStore.subscriptions.getSubscriptionWorker(options, database);

// The SubscriptionWorkerOptions object:
// =====================================
{
    subscriptionName;
    documentType;
    ignoreSubscriberErrors;
    closeWhenNoDocsLeft;
    maxDocsPerBatch;
    timeToWaitBeforeConnectionRetry;
    maxErroneousPeriod;            
    strategy;
}

When creating a worker with subscription worker options, the only mandatory property is subscriptionName.
All other parameters are optional and will default to their respective default values if not specified.

After creating a subscription worker, the subscription worker is still not processing any documents.
To initiate processing, you need to define an event handler and attach it to the worker's batch event listener.

This handler contains your client-side code responsible for processing the document batches received from the server. Whenever a new batch of documents is ready, the provided handler will be triggered.

subscriptionWorker.on("batch", (batch, callback) => {
    // Process incoming items:
    // =======================
    
    // 'batch': 
    // Contains the documents to be processed.
    
    // callback(): 
    // Needs to be called after processing the batch 
    // to notify the worker that you're done processing.
});

The subscription batch class contains the following public properties & methods:

This class represents a single item in a subscription batch result.

class Item
{
    result;
    exceptionMessage;
    id;
    changeVector;
    projection;
    revision;
    rawResult;
    rawMetadata;
    metadata;
}