see on GitHub

Data Subscriptions : Consumption API Overview



Subscription worker generation

Subscription worker generation is accessible through the DocumentStore's Subscriptions Property, of type DocumentSubscriptions:

SubscriptionWorker<dynamic> GetSubscriptionWorker(string subscriptionName, string database = null);
SubscriptionWorker<dynamic> GetSubscriptionWorker(SubscriptionWorkerOptions options, string database = null);
SubscriptionWorker<T> GetSubscriptionWorker<T>(string subscriptionName, string database = null) where T : class;
SubscriptionWorker<T> GetSubscriptionWorker<T>(SubscriptionWorkerOptions options, string database = null) where T : class;

Parameters
subscriptionName string The subscription's name. This parameter appears in more simple overloads allowing to start processing without creating a SubscriptionCreationOptions instance, relying on the default values
options SubscriptionWorkerOptions Contains subscription worker, affecting the interaction of the specific worker with the subscription, but does not affect the subscription's definition
database string Name of the database to look for the data subscription. If null, the default database configured in DocumentStore will be used.
Return value
SubscriptionWorker A created data subscription worker. When returned, the worker is Idle and it will start working only when the Run function is called.

SubscriptionWorkerOptions

Note

The only mandatory parameter for SubscriptionWorkerOptions creation is the subscription's name.

Member Type Description
SubscriptionName string Returns the subscription name passed to the constructor. This name will be used by the server side to identify the subscription in question.
TimeToWaitBeforeConnectionRetry TimeSpan Time to wait before reconnecting, in the case of non-aborting failure during the subscription processing. Default: 5 seconds.
IgnoreSubscriberErrors bool If true, will not abort subscription processing if client code, passed to the Run function, throws an unhandled exception. Default: false.
Strategy SubscriptionOpeningStrategy(enum) Sets the way the server will treat current and/or other clients when they will try to connect. See Workers interplay. Default: OpenIfFree.
MaxDocsPerBatch int Maximum amount of documents that the server will try sending in a batch. If the server will not find "enough" documents, it won't wait and send the amount it found. Default: 4096.
CloseWhenNoDocsLeft bool If true, it performs an "ad-hoc" operation that processes all possible documents, until the server can't find any new documents to send. At that moment, the task returned by the Run function will fail and throw a SubscriptionClosedException exception. Default: false.

Running subscription worker

After receiving a subscription worker, the subscription worker is still not processing any documents. SubscriptionWorker's Run function allows you to start processing worker operations.
The Run function receives the client-side code as a delegate that will process the received batches:

Task Run(Action<SubscriptionBatch<T>> processDocuments, CancellationToken ct = default(CancellationToken));
Task Run(Func<SubscriptionBatch<T>, Task> processDocuments, CancellationToken ct = default(CancellationToken));

Parameters
processDocuments Action<SubscriptionBatch<T>> Delegate for sync batches processing
processDocuments Func<SubscriptionBatch<T>, Task> Delegate for async batches processing
ct CancellationToken Cancellation token used in order to halt the worker operation
Return value
Task Task that is alive as long as the subscription worker is processing or tries processing. If the processing is aborted, the task exits with an exception

SubscriptionBatch<T>

Member Type Description
Items List<SubscriptionBatch&lt;T&gt;.Item> Batch's items list.
NumberOfItemsInBatch int Amount of items in the batch.
Method Signature Return value Description
OpenSession() IDocumentSession New document session, that tracks all items and included items of the current batch.
OpenAsyncSession() IDocumentSession New asynchronous document session, that tracks all items and included items of the current batch.

Subscription Session characteristics

Session will be created by the same document store that created the worker, therefore will receive the same configurations as any other session created by the store.
However, in order to maintain consistency, the session will address the same server that the batch was received from.
It won't try to fail over to another server. It might also fail if the subscription worker changes the node it communicates with.
Such event could happen if the subscription worker starts again to address its original node after a fallback occurrence.
If such failure occurs, the subscription processing will be stopped, and will have to be restarted, as shown here

SubscriptionBatch<T>.Item

Note

if T is BlittableJsonReaderObject, no deserialization will take place

Member Type Description
Result T Current batch item.
ExceptionMessage string Message of the exception thrown during current document processing in the server side.
Id string Current batch item's underlying document ID.
ChangeVector string Current batch item's underlying document change vector of the current document.
RawResult BlittableJsonReaderObject Current batch item before serialization to T.
RawMetadata BlittableJsonReaderObject Current batch item's underlying document metadata.
Metadata IMetadataDictionary Current batch item's underlying metadata values.

Warning

Usage of RawResult, RawMetadata, and Metadata values outside of the document processing delegate are not supported

SubscriptionWorker<T>

Methods

Method Signature Return Type Description
Dispose() void Aborts subscription worker operation ungracefully by waiting for the task returned by the Run function to finish running.
DisposeAsync() Task Async version of Dispose().
Dispose(bool waitForSubscriptionTask) void Aborts the subscription worker, but allows deciding whether to wait for the Run function task or not.
DisposeAsync(bool waitForSubscriptionTask) void Async version of DisposeAsync(bool waitForSubscriptionTask).
Run (multiple overloads) Task Starts the subscription worker work of processing batches, receiving the batch processing delegates (see above).

Events

Event Type\Return type Description
AfterAcknowledgment AfterAcknowledgmentAction (event) Event that is risen after each the server acknowledges batch processing progress.
OnSubscriptionConnectionRetry Action<Exception> (event) Event that is fired when the subscription worker tries to reconnect to the server after a failure. The event receives as a parameter the exception that interrupted the processing.
OnDisposed Action<SubscriptionWorker<T>> (event) Event that is fired after the subscription worker was disposed.

AfterAcknowledgmentAction

Parameters
batch SubscriptionBatch&lt;T&gt; The batch process which was acknowledged
Return value
Task Task for which the worker will wait for the event processing to be finished (for async functions etc.)

Properties

Member Type\Return type Description
CurrentNodeTag string Returns current processing RavenDB server's node tag.
SubscriptionName string Returns processed subscription's name.