ServiceContext and Lifecycle

ServiceContext

In Unary service and StreamingHub method, and inside filters, you can access this.Context to get ServiceContext.

Property	Type	Description
Items	ConcurrentDictionary<string, object>	Object storage per request/connection.
ContextId	Guid	Unique ID per request(Service)/connection(StreamingHub).
Timestamp	DateTime	Timestamp that request/connection is started time.
ServiceType	Type	Invoked Class.
MethodInfo	MethodInfo	Invoked Method.
AttributeLookup	ILookup<Type, Attribute>	Cached Attributes that merged both service and method.
CallContext	ServerCallContext	Raw gRPC Context
MessageSerializer	IMagicOnionSerializer	Using serializer.
ServiceProvider	IServiceProvider	Get the service provider.

You can use Items to set values from authentication filters and retrieve them from service methods.

warning

DO NOT cache ServiceContext. ServiceContext is only valid during the request and MagicOnion may reuse instances. The state of objects referenced from the context after the request is also undefined.

warning

ServiceContext is a "per connection" context. You can access ServiceContext inside StreamingHub, but be aware that the same context is shared throughout the connection. For example, Timestamp is the time when the connection was established, and properties related to methods are always set by special methods such as Connect. The Items property is not cleared per Hub method invocation.

Inside StreamingHubFilter, use StreamingHubContext. StreamingHubContext is the context for each StreamingHub method invocation.

Global ServiceContext

In MagicOnion, you can get the current context globally like HttpContext.Current. You can get it with ServiceContext.Current, but MagicOnionOptions.EnableCurrentContext = true is required. The default is false.

For reasons of performance and code complexity, it is recommended to avoid using ServiceContext.Current.

Lifecycle

The lifecycle of a Unary service is as follows in pseudo code. A new service instance is created each time a request is received and processed.

async Task<Response> UnaryMethod(Request request)
{
    var service = new ServiceImpl();
    var context = new ServiceContext();
    context.Request = request;

    var response = await Filters.Invoke(context, (args) =>
    {
        service.ServiceContext = context;
        return await service.MethodInvoke(args);
    });

    return response;
}

The lifecycle of a StreamingHub service is as follows in pseudo code. While connected, the StreamingHub instance is maintained, so state can be maintained.

async Task StreamingHubMethod()
{
    var context = new ServiceContext();

    var hub = new StreamingHubImpl();
    hub.ServiceContext = context;

    await Filters.Invoke(context, () =>
    {
        var streamingHubContext = new StreamingHubContext(context);
        while (connecting)
        {
            var message = await ReadHubInvokeMessageFromStream();
            streamingHubContext.Intialize(context);

            await StreamingHubFilters.Invoke(streamingHubContext, () =>
            {
                return await hub.MethodInvoke();
            });
        }
    });
}