Azure Table Persistence

Certain features of NServiceBus require persistence to permanently store data. Among them are subscription storage, sagas, and outbox. Various storage options are available including Azure Table and Azure Cosmos DB Table API.

Azure Table Persistence stores NServiceBus data in Azure Table storage or Azure Cosmos DB using the Table API.

Persistence at a glance

For a description of each feature, see the persistence at a glance legend.

Enable Azure Table Persistence

First add a reference to the assembly that contains the Azure Table persistence, which is done by adding a NuGet package reference to NServiceBus.Persistence.AzureTable.

var persistence = endpointConfiguration.UsePersistence<AzureTablePersistence>();
persistence.ConnectionString("DefaultEndpointsProtocol=https;AccountName=[ACCOUNT];AccountKey=[KEY];");

Provisioned throughput rate-limiting with Azure Cosmos DB

When using the provisioned throughput feature, it is possible for the CosmosDB service to rate-limit usage, resulting in "request rate too large" RequestFailedExceptions indicated by a 429 status code.

The Azure.Data.Tables SDK handles these exceptions by automatically retrying the failed request based on headers included in the response. The retry policy can be adjusted through TableClientOptions when initializing the TableServiceClient.

Saga concurrency

When simultaneously handling messages, conflicts may occur. See below for examples of the exceptions which are thrown. Saga concurrency explains how these conflicts are handled, and contains guidance for high-load scenarios.

Starting, updating or deleting saga data

Azure Table Persistence uses optimistic concurrency control when updating or deleting saga data.

Example exception:

Azure.Data.Tables.TableTransactionFailedException: The update condition specified in the request was not satisfied.
RequestId:f0742973-2002-0060-09d3-f9afb2000000
Time:2022-11-16T15:53:36.0074148Z
Status: 412 (Precondition Failed)
ErrorCode: UpdateConditionNotSatisfied

Supported saga properties' types

Azure Table Persistence supports the same set of types as Azure Table Storage and additional types that can be serialized into JSON using Json.NET. When a saga containing a property of an unsupported type is persisted, an exception containing the following information is thrown: The property type 'the_property_name' is not supported on Azure Table Storage and it cannot be serialized with JSON.NET.

Customization

Saga data serialization can be configured by providing a custom JsonSerializerSettings instance:

var persistence = endpointConfiguration.UsePersistence<AzureTablePersistence, StorageType.Sagas>();

persistence.JsonSettings(new JsonSerializerSettings
{
    Converters =
        {
            new IsoDateTimeConverter
            {
                DateTimeStyles = DateTimeStyles.RoundtripKind
            }
        }
});

or with a custom JsonReader instance:

var persistence = endpointConfiguration.UsePersistence<AzureTablePersistence, StorageType.Sagas>();

persistence.ReaderCreator(
    readerCreator: textReader =>
    {
        return new JsonTextReader(textReader);
    });

or with a custom JsonWriter instance:

var persistence = endpointConfiguration.UsePersistence<AzureTablePersistence, StorageType.Sagas>();

persistence.WriterCreator(
    writerCreator: writer =>
    {
        return new JsonTextWriter(writer)
        {
            Formatting = Formatting.None
        };
    });

Saga Correlation property restrictions

Saga correlation property values are subject to the underlying Azure Storage table PartitionKey and RowKey restrictions:

• Up to 1KB in size
• Cannot contain invalid characters