Concurrent Subscriptions

Concurrent workers are defined similarly to other workers, except their strategy is set to SubscriptionOpeningStrategy.Concurrent.

• To define a concurrent worker:

  • Create the worker using GetSubscriptionWorker.
  • Pass it a SubscriptionWorkerOptions instance.
  • Set the strategy to SubscriptionOpeningStrategy.Concurrent

• Usage:

  • Define two concurrent workers
    

    // Define concurrent subscription workers
    var worker1 = store.Subscriptions.GetSubscriptionWorker<Order>(
        // Set the worker to connect to the "Get all orders" subscription task
        new SubscriptionWorkerOptions("Get all orders")
        {
            // Set Concurrent strategy
            Strategy = SubscriptionOpeningStrategy.Concurrent,
            MaxDocsPerBatch = 20
        });
    
    var worker2 = store.Subscriptions.GetSubscriptionWorker<Order>(
        new SubscriptionWorkerOptions("Get all orders")
        {
            Strategy = SubscriptionOpeningStrategy.Concurrent,
            MaxDocsPerBatch = 20
        });

  • Run both workers
    

    // Start the concurrent worker.
    // Workers will connect concurrently to the "Get all rders" subscription task.
    var worker1Task = worker1.Run(batch =>
    {
        // Process batch
        foreach (var item in batch.Items)
        {
            // Process item
        }
    });
    
    var worker2Task = worker2.Run(batch =>
    {
        // Process batch
        foreach (var item in batch.Items)
        {
            // Process item
        }
    });

• Use Subscriptions.DropSubscriptionWorker to forcefully disconnect the specified worker from the subscription it is connected to.
  

  public void DropSubscriptionWorker<T>(SubscriptionWorker<T> worker, string database = null)

• Usage:
  

  // Drop a concurrent subscription worker
  store.Subscriptions.DropSubscriptionWorker(worker2);

• When a concurrent worker's connection ends unexpectedly, the server may reassign the documents this worker has been processing to any other concurrent worker that is available.
• A worker that reconnects after a connection failure will be assigned a new batch of documents.
  It is not guaranteed that the new batch will contain the same documents this worker was processing before the disconnection.
• As a result, documents may be processed more than once:
  • first by a worker that disconnected unexpectedly without acknowledging the completion of its assigned documents,
  • and later by other workers the documents are reassigned to.