I have a scenario to check some validation before sending data to the db via my masstransit consumer. Here i have my controller which use Isendendpointprovider send method to send message. Before this send i need to call the db validation to check if same data is in the db. I have now published and event before calling Isendendpointprovider.send method ie using publishEndpoint.Publish( new ValidationMessage) . Is this the right way to implement . So in my controller publishEndpoint.Publish( new ValidationMessage) which gives a response of bool field(by checking a select query in db) and based on that variable value Isendendpointprovider.send is called. Is this the rihgt approach in case of masstransit implementation. I am using .net core
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I have a MassTransit routing slip configured and working. For reference, the routing slip takes in an ID of an item in a MongoDB database and then creates a "version" of that document in a SQL database using EF Core. The activities (as commands) are:
Migrate document to SQL
Update audit info in MongoDB document
Update MongoDB document status (i.e. to published)
All of the above are write commands.
I have added a new 1st step which runs a query to make sure the MongoDB document is valid (e.g. name and description fields are completed) before running the migration. If this step fails it throws a custom exception, which in turns fires a failed event which is then picked up and managed by my saga. Below is a snippet of my activity code followed by the routing slip builder code:
Activity code
var result = await _queryDispatcher.ExecuteAsync<SelectModuleValidationResultById, ModuleValidationResult>(query).ConfigureAwait(false);
if (!result.ModuleValidationMessages.Any())
{
return context.Completed();
}
return context.Faulted(new ModuleNotValidException
{
ModuleId = messageCommand.ModuleId,
ModuleValidationMessages = result.ModuleValidationMessages
});
Routing slip builder code
builder.AddActivity(
nameof(Step1ValidateModule),
context.GetDestinationAddress(ActivityHelper.BuildQueueName<Step1ValidateModule>(ActivityQueueType.Execute)),
new SelectModuleValidationResultById(
context.Message.ModuleId,
context.Message.UserId,
context.Message.LanguageId)
);
builder.AddSubscription(
context.SourceAddress,
RoutingSlipEvents.ActivityFaulted,
RoutingSlipEventContents.All,
nameof(Step1ValidateModule),
x => x.Send<IModuleValidationFailed>(new
{
context.Message.ModuleId,
context.Message.LanguageId,
context.Message.UserId,
context.Message.DeploymentId,
}));
Whilst all of this works and the event gets picked up by my saga I would ideally like to add the ModuleValidationMessages (i.e. any failed validation messages) to the event being returned but I can't figure out how or even if that's possible (or more fundamentally if it's right thing to do).
It's worth noting that this is a last resort check and that the validation is checked by the client before even trying the migration so worse case scenario I can just leave it has "Has validation issues" but ideally I would like to include the derail in the failed response.
Good use case, and yes, it's possible to add the details you need to the built-in routing slip events. Instead of throwing an exception, you can Terminate the routing slip, and include variables - such as an array of messages, which are added to the RoutingSlipTerminated event that will be published.
This way, it isn't a fault but more of a business decision to terminate the routing slip prematurely. It's a contextual difference, which is why it allows variables to be specified (versus Faulted, which is a full-tilt exception).
You can then pull the array from the variables and use those in your saga or consumer.
So this is maybe pretty simple for network programming dudes but I'm a little confused about this. Let me try to ask given an example of usage.
Say I were to create a chat server with clients being able to join with a username. No accounts or passwords. Just username.
I have a working Echo Server example running that uses async calls so all that is good. Now I need to define some message handling between the client and the server.
Lets say the client now connects and it wants to get the list of connected users. How would I go about doing that?
My thought is that I create a function called BeginGetConnectedUsers and that will send message to the server. The server will then reply with a list of users but because I'm using async calls I'll now have my accept code look at the message and figure out that it is a reply from a BeginGetConnectedUsers so it will send the data to a EndGetConnectedUsers.
But I have no idea if this is a good way to do something like this?
But also with this design I'll have to pair every BeginGet function with an EndGet function. This could be made more readable with the async await style but though but that may not be preferable either.
I have no experience with how to structure the following communication between client and server when they have to start exchanging all the interesting data stuff...
And advice? Places to look? All my google searches that include the work TCPLISTENER will all show me examples of Echo Servers and I already know how to do that.
There are many posible implementations here.
I woudl implement an strategy pattern or a controller pattern. Other options are state machines (deterministic automatas) or even a simple and big switch case.
So basically you have only one function to receive the messages from the wire.
All the messages implements the same interface may be
IMessage<T>
{
string Type {get;set;}
T Data {get;set;}
}
So when you get the message you use the Type property to route the T Data to the actual method you want.
In a simple implementation using a controller, you anotate the controller methods with an attribute indicating the message type you want to manage:
class Controller
{
[Messagetype("GetConnectedUsersResponse")]
Response GetConnectedUsers(IEnumerable<User> users)
{
//...
}
[Messagetype("AnothermessageType")]
Response OtherStuffToDo(....)
{
//...
}
}
When you receives the message, by using some simple reflection you dynamically call to the method wich has the attibute with the matching message type attribute.
If you dont like reflection another option (among a lot of docens else) is to use an strategy patter
So you can register some message Handlers by key in your IoC container for example.
All hadlers implement a function lets say
interface MessageHandler<T>
{
Response Handle(T Data);
}
When you receive the message you just resolve the handler using your favourite IoC container (resolving by name is lately considered as an atipattern, so take it with a pinch of salt)
var handler = container.resolve(message.Type);
var response = handler.handle(message.Data);
In both implementations you should define how you respond (if you do) and adjust the "Response" return type (May be you just dont have response so it is void)
I have a (c#) server and client with webhook implementation.
I have a custom authentication handler to authenticate client receivers when they subscribe for events.
This works ok.
Now, I want to trigger an event from inside the server's code on some condition. At that moment, I call method:
this.NotifyAsync()
located on source code:
namespace System.Web.Http
public static class ApiControllerExtensions
public static Task<int> NotifyAsync(this ApiController controller, string action, object data)
Problem is that this call to NotifyAsync() will check that there is an authenticated user, which is not the case because is the server itself triggering this action..
Did I need to generate an AuthenticationTicket() from inside servers code in order to trigger webhook notification or there is other way to do it ??
thanks
just calling NotifyAllAsync() !!! no authentication required here and it will send notification to all clients...
I have inside my hub a method that is used to send to specific clients that a ticket was updated. However I want it to send it to the server inside the controller and to specific users, you can see how I am doing it below:
I am using the following method to send to the specific clients:
public void NotifyUpdatedTicket(Ticket ticket, string note, params string[] aliases)
{
foreach (string a in aliases)
{
foreach (string connectionId in _allConnections.GetConnections(a))
{
Clients.Client(connectionId).notifyUpdatedTicket(ticket, note);
}
}
}
The _allConnections is the same as the class in http://www.asp.net/signalr/overview/guide-to-the-api/mapping-users-to-connections#inmemory
However instead of passing 1 user I passed a list of aliases and then get their connections and send to their connection ids.
However it does not seem to be sending properly it sends it to all clients. Here is the command I am using to call the method in my controller:
GlobalHost.ConnectionManager.GetHubContext<TicketHub>().Clients.All.notifyUpdatedTicket(viewModel.Current, viewModel.NewNote, viewModel.Current.OpenedBy, viewModel.Current.AssignedTo);
When I send the above command with the specific OpenedBy and AssignedTo, it sends it all users when it shouldn't.
Am I missing something from calling it in the controller that sends it only to specific users or something?
Even when I put in the persons alias directly into the hub method it still sends to everyone. I assume this has to do with the controller method.
This
Clients.All.notifyUpdatedTicket
will send a message to all clients. It won't call your method with this signature (I assume that's what you're trying to do):
public void NotifyUpdatedTicket(Ticket ticket, string note, params string[] aliases)
I assume this is a method you added to your hub class.
It's not a good idea to put methods in a hub class if their sole purpose is to be called from the server-side.
Anyway, if you do, you need to use GetHubContext<TicketHub>() from within that method even if it is part of the hub class, because the hub context is set up as part of the hub pipeline when a request to that hub arrives. Without that, the hub is just a regular class and you don't have access to dynamic members like Clients.
So, all in all, it seems like you're confused about some fundamentals. I'd suggest moving NotifyUpdatedTicket to a separate class that also caches the relevant hub context, then call that method when needed (e.g. from a MVC controller method if that is your intent).
According to the documentation I have read, in order to send a message to a client, I just need to call:
var hubContext = GlobalHost.ConnectionManager.GetHubContext<MyHub>();
hubContext.Clients.All.foo(msg);
So... does the Hub class need any methods? If not, then all I have is an empty class:
public class MyHub : Hub
{
}
which just seems like a pointless setup. Am I implementing this incorrectly? because it makes more sense to have methods in a hub class, and then call those methods to send a message to the client.
Also, in the hub itself, I can access Context.connectionId, so that I can get the requestor's connection Id and then stop the message from being fired to that client.... If a Hub shouldn't have methods, then is there a way to access the requestor's connection id?
Yes, you need an empty HUB class declaration, because - It is actually just a proxy between the JS client and the controller so it could be empty since all methods are called via the Clients dynamic variable.
I mean without this , you can work, but you have to write JS for that. This is explained briefly in following link.
For more info refer this link - http://www.asp.net/signalr/overview/signalr-20/hubs-api/hubs-api-guide-javascript-client#genproxy