I have a WCF service, hosted in a win form application, that receive the requests from the clients. One of this requests, is update the stock of the items.
Well, my idea is to use a client to send to the WCF service the new amount of items, then the service use Entity Framework 4.1 to update the database with the new stock.
How the service is duplex, when the services has finished the update, it sends a message to the client to notify that the operations is successful. That's if there is no problems.
However, I have a question. It's possible that the client send the command to the service to update the stock. The service receive the command correctly, but before the operation is finished, the client lost the connection with the service, so the services can't send to the client the status of the operation, so the user does not know if it's all ok or not.
My second question has the same logic, but with the WCF service. It's possible that the WCF service is installed in other computer different to the computer in which is installed the database. So it's possible that the WCF services send correctly the command to the database, but before the database notify that the operation is successful, the WCF service lost the connection, so it never receive a response from the database but the operation is successful. How can the user know if the operation is ok or not?
So my question is, in WCF, how can I be sure that critical operations are successful or not?
Thanks.
Daimroc.
Related
in my scenario, I want to have some services to be fixed (as in not needing to be updated) and as time goes by adding other services. (I'm using one DB instance, but it shouldn't matter in service broker)
I want to set up the fixed ones in a way to be able to send back a message to the initiator of any message in its queue without me changing its logic and procedures every time I add another service.
is it even possible or do I have to add more logic as new services are created?
If I'm understanding your question correctly, this is how Service Broker works by default. Which is to say that a conversation is between two parties (initiator and target). Once that conversation is established, either party can send messages on it and they will go to the other party. So, if you want to send a message back to the initiator, just send a message on the same conversation handle as the message was received on and you should be good to go.
I'm creating a wcf project with a wpf client using mvvm design pattern,
Where do I need to implement the ICallback interface so I will be able to update the
window.
The callback contract should be implemented on the client-side. Likewise, the service contract should be implemented on the server-side, with which the server can send data to the client-side by the callback contract.
Please refer to my example of the previous post.
TimeOut exception in WCF while implementing duplex
the client sends a parameter to the server by using the service interface, subsequently, the server sends the handled result to the client with the callback contract so that the client application gets the updated.
Feel free to let me know if there is anything I can help with.
We are making a web application in Go with a MySQL database. Our users are allowed to only have one active client at a time. Much like Spotify allows you to only listen to music on one device at a time. To do this I made a map with as key the user ids and a reference to their active websocket connection as a value. Based on the websocket id that the client has to send in the header of the request we can identify weather the request comes from their active session.
My question is if it's a good practice to store data (in this case the map with the user ids and websockets) in a global space or is it better to store it in the database.
We don't expect to reach over 10000 simultaneously active clients. Average is probably gonna be around 1000.
If you only run one instance of the websocket server storing it in memory should be sufficient. Because if it for some reason goes down/restarts then all the connections will be lost and all the clients will have to create them again (and hence the list of connection will once again be populated by all the clients who want to use the service).
However, if you plan on scaling it horizontally so you have multiple websocket services behind a load balancer, then the connections may need to be stored in a database of some sort. And not because it necessarily needs to be more persistant but because you need to be able to check the request against all the services connections.
It is also possible to have a separate service which handles the incoming request and asks all the websocket services if any of them have the connection specified in the request. This could be done if you add a pub/sub queue and every websocket service subscribes to channels for all its websocket ids and the service that receives the request then publishes the websocket id, and the websocket services can then send back replies on a separate channel if they have that connection. You must decide how to handle if no one is responding (no websocket service has the websocket id). Either the channel does not exist, or you expect the answer within a specific time. Or you could publish the question on a general topic and expect all the websocket services to reply (yes or no).
And regarding whether you need to scale it I guess depends mostly on the underlying server you're running the service on. If I understand it correctly the websocket service will basically not do anything except from keeping track of its connections (you should add some ping pong to discover if connections are lost). Then your limitation should mainly be on how many file descriptors your system can handle at once. If that limit is much larger than your expected maximum number of users, then running only one server and storing everything in memory might be an OK solution!
Finally, if you're in the business of having a websocket open for all users, why not do all the "other" communication over that websocket connection instead of having them send HTTP requests with their websocket id? Perhaps HTTP fits better for your use case but could be something to think about :)
I am using WPF and WCF for client server application. but i got a problem.
How to notify any update of client to other client.
Server(WCF)
Client1(WPF)
Client2(WPF)
if client1 enter any new record,immediatly notification send to client2 .
please suggest me best way to this complete task.
Thanks..
We have achieved such a requirement by using WCF Duplex Services. You can find enough information by googling about implementing a duplex service.
Basically;
clients send a client identifier (uniquely generated for each client) while registering to duplex service.
when WCF service updates data, pushes an update notification (including the notification source's client identifier) to all the registered clients
clients check for the originator's identifier when they got a notification. Discarding notifications caused by itself.
A few notes:
You can include everything about the updated data inside pushed notification payload to understand the change type or entity type.
Different bindings supported by duplex services. Usage of nettcpbinding is suggested if clients and service are in the same network and .net dependency is not a problem. You can find more information about support binding types from here or here.
I have a WCF service which I host inside a WFP application, which acts as one of the clients of service as well. There is one more WPF app which acts as another client for service. After a timeout occurs and clients get disconnected, What is the proper way to clean up resources and connect the clients again. I am trying to create new proxies but I am not able to use them for communication. I know I can increase the recieve timeout on service but I need my clients to be able to communicate always not just for long enough. I have also tried continously sending a message to service at interval but that's something I don't want to go for. What approach is best for continous communication between clients and service? My service might need to be connected to clients for months or may be years.
Any help will be of great value.
Thanks in advance.
You can catch the CommunicationException or something like that and then restore the channel.