How to save/restore SignalR hub and connection state on app startup/shutdown?

browncat947

how do you save/restore signalr hub, connections, state on app shutdown/startup? We are using signalr in our web application. We have a requirement where in we need to save the signalr hub, connections, state when the user navigates away from the page and restore it when he comes back. We are using owin middleware for signalr. Is there a way to achieve this using owin middleware?

Johnny828

Saving and restoring a SignalR Hub, connections, and state on an app shutdown/startup is an important consideration when designing an application.

Fortunately, SignalR provides an out-of-the-box solution for persisting the connection and state data when an application restarts. This is possible through the use of the IUserIdProvider interface. Here are the steps to follow to save/restore SignalR Hub, connections, and state on an app shutdown/startup:

Implement the IUserIdProvider interface: This interface enables the application to provide user IDs to the SignalR Hub. The user IDs should be unique and consistent across a restart.
Add the service reference to the Hub’s configuration file: The service reference <IUserIdProvider> should be added to the configuration file for the Hub.
Persist connection and state data using the Service Bus: SignalR contains a backplane to persist the connection and state data when an application restarts by using an external service such as Azure Service Bus or Redis.
Initialize the hub on startup: When the application starts, the SignalR Hub should be initialized with the stored connection and state data.

For more information, please refer to the following Microsoft article:
https://docs.microsoft.com/en-us/aspnet/signalr/overview/guide-to-the-api/handling-connection-lifetime-events

steven_simmmons

When app shutdowns or startups, you can save the signalr hub, connections, and state by using the PersistentConnection.Extensions assembly which contains the OnDisconnected and OnConnected methods. Essentially, the OnDisconnected method stores the state in persistant storage (like a file or database) on shutdown and then retrieves that state via the OnConnected method when the app starts up.

You can also use the IUserIdProvider interface to identify which hub connections and state need to be saved and restored. In addition, you can use the HubPipeline to pipe delegation events, like a Disconnect, to save and restore the state.

Overall, saving and restoring signalr hub, connections, and state on app shutdown/startup can be a tricky process but it can be done reliably with the help of the PersistentConnection.Extensions and IUserIdProvider interfaces, as well as the HubPipeline.