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.
Feature | |
---|---|
Supported storage types | Sagas, Outbox, Subscriptions |
Transactions | Using TransactionalBatch, with caveats |
Concurrency control | Optimistic concurrency |
Scripted deployment | Not supported |
Installers | Supported. Subscription, the default table or saga tables derived by convention when no default table is set are created at runtime, when enabled. |
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.
.
var persistence = endpointConfiguration.UsePersistence<AzureTablePersistence>();
persistence.ConnectionString("DefaultEndpointsProtocol=https;AccountName=[ACCOUNT];AccountKey=[KEY];");
Transactions
The Azure Table persister supports using the Azure Table TableBatchOperation API. However, Azure Table only allows operations to be batched if all operations are performed within the same partition key. This is due to the distributed nature of the Azure Table service, which does not support distributed transactions.
The transactions documentation provides additional details on how to configure NServiceBus to resolve the incoming message to a specific partition key to take advantage of this Azure Table feature.
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:
Microsoft.WindowsAzure.Storage.StorageException: Element 0 in the batch returned an unexpected response code.
Request Information
RequestID:010c234e-3002-0145-06eb-72b85a000000
RequestDate:Tue, 24 Sep 2019 15:16:45 GMT
StatusMessage:The update condition specified in the request was not satisfied.
ErrorCode:
ErrorMessage:The update condition specified in the request was not satisfied.
RequestId:010c234e-3002-0145-06eb-72b85a000000
Time:2019-09-24T15:16:46.0746310Z
Supported saga properties' types
Azure Table Persistence supports same set of types as Azure Table Storage and additional types that can be serialized into JSON. 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.
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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