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. |
SendBufferSizeInBytes | int |
The size in bytes of the TCP socket buffer used for sending data. Default: 32,768 (32 KiB) |
ReceiveBufferSizeInBytes | int |
The size in bytes of the TCP socket buffer used for receiving data. Default: 32,768 (32 KiB) |
Running subscription worker
After generating 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<T>.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 Worker Connectivity
As long as there is no exception, the worker will continue addressing the same
server that the first batch was received from.
If the worker fails to reach that node, it will try to
failover to another node
from the session's topology list.
The node that the worker succeeded connecting to, will inform the worker which
node is currently responsible for data subscriptions.
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 time 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<T> |
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. |