Configuration

Configuring Project References

Grain Interfaces

As before, interfaces depend only on the Microsoft.Orleans.Core package, because the grain interface is independent of the implementation.

Grain Implementations

JournaledGrains need to derive from JournaledGrain<S,E> or JournaledGrain<S>, which is defined in the Microsoft.Orleans.EventSourcing package.

Log-Consistency Providers

We currently include three log-consistency providers (for state storage, log storage, and custom storage). All three are contained in the Microsoft.Orleans.EventSourcing package as well. Therefore, all Journaled Grains already have access to those. For a description of what these providers do and how they differ, see Included Log-Consistency Providers.

Cluster Configuration

Log-consistency providers are configured just like any other Orleans providers. For example, to include all three providers (of course, you probably won't need all three), add this to the <Globals> element of the configuration file:

<LogConsistencyProviders>
  <Provider Type="Orleans.EventSourcing.StateStorage.LogConsistencyProvider" Name="StateStorage" />
  <Provider Type="Orleans.EventSourcing.LogStorage.LogConsistencyProvider" Name="LogStorage" />
  <Provider Type="Orleans.EventSourcing.CustomStorage.LogConsistencyProvider" Name="CustomStorage" />
</LogConsistencyProviders>

The same can be achieved programmatically. Moving forward to 2.0.0 stable, ClientConfiguration and ClusterConfiguration no longer exist! It has now been replaced by a ClientBuilder and a SiloBuilder (notice there is no cluster builder).

builder.AddLogStorageBasedLogConsistencyProvider("LogStorage")

Grain Class Attributes

Each journaled grain class must have a LogConsistencyProvider attribute to specify the log-consistency provider. Some providers additionally require a StorageProvider attribute. Eg:

[StorageProvider(ProviderName = "OrleansLocalStorage")]
[LogConsistencyProvider(ProviderName = "LogStorage")]
public class EventSourcedBankAccountGrain : JournaledGrain<BankAccountState>, IEventSourcedBankAccountGrain
{ ... }

So here "OrleansLocalStorage" is being used for storing the grain state, where was "LogStorage" is the in-memory storage provider for EventSourcing events.

LogConsistencyProvider Attributes

To specify the log-consistency provider, add a [LogConsistencyProvider(ProviderName=...)] attribute to the grain class, and give the name of the provider as configured by the Cluster Configuration. For example:

[LogConsistencyProvider(ProviderName = "CustomStorage")]
public class ChatGrain : JournaledGrain<XDocument, IChatEvent>, IChatGrain, ICustomStorage { ... }

StorageProvider Attributes

Some log-consistency providers (including LogStorage and StateStorage) use a standard StorageProvider to communicate with storage. This provider is specified using a separate StorageProvider attribute, as follows:

[LogConsistencyProvider(ProviderName = "LogStorage")]
[StorageProvider(ProviderName = "AzureBlobStorage")]
public class ChatGrain : JournaledGrain<XDocument, IChatEvent>, IChatGrain { ... }

Default Providers

It is possible to omit the LogConsistencyProvider and/or the StorageProvider attributes, if a default is specified in the configuration. This is done by using the special name Default for the respective provider. For example:

<LogConsistencyProviders>
  <Provider Type="Orleans.EventSourcing.LogStorage.LogConsistencyProvider" Name="Default" />
</LogConsistencyProviders>
<StorageProviders>
  <Provider Type="Orleans.Storage.MemoryStorage" Name="Default" />
</StorageProviders>