Connection string environment variable is required even if the connection string is provided another way

[mikeminutillo]

This package loads a connection string from an environment variable which by default is named AzureWebJobsServiceBus (but this can be overridden in the constructor for ServiceBusTriggeredEndpointConfiguration).

This is not the only way to set the transport connection. It can also be set like this:

var endpointConfiguration = new ServiceBusTriggeredEndpointConfiguration("MyEndpoint");
endpointConfiguration.Transport.ConnectionString(myConnectionString);

Unfortunately this fails as the endpoint still attempts to load the connection string from an environment variable, even if there is one. This code attempts to set the connection string to null which results in an exception:

NServiceBus.Core: Value cannot be null. (Parameter 'connectionString').

Workaround

To workaround this problem, a connection string must be available in the Azure Function environment variables and the ServiceBusTriggeredEndpointConfiguration should be configured to use this environment variable. Note that the connection string does not need to be for a valid ServiceBus account as it will not be used.

Expected Behavior

It should be possible to set the connection string on the transport without setting an environment variable.

[SeanFeldman]

It should be possible to set the connection string on the transport without setting an environment variable.

Does that mean the expected behaviour is not to have the environment variable AzureWebJobsServiceBus and solely use endpointConfiguration.Transport.ConnectionString(myConnectionString); to provide the connection string for NServiceBus endpoint?

[hardik-desai-kcl]

I think a second constructor with delegate as input parameter that allows configuring the EndpointConfiguration would be most appropriate solution

At the moment the License and service bus connection string can only be supplied through convention and for both the assumption is that they are always going to be available in the environment variable

But it is perfectly valid and possible that they may not be present in environment variables and it could be stored elsewhere i.e. in azure secure tables, keyvault, in local.settings.json during development or even some other secure storage and later retrieved through IConfiguration

I think the simplest solution would be to have a new construct for ServiceBusTriggeredEndpointConfiguration that takes a delegate as parameter and allows consumers to do all their custom configuration for EndpointConfiguration before constructor method is executed

Something like bellow,

please note through there are few issues with bellow example
the UseNServiceBus Method currently do not expose IServiceProvider so it would be ideal to have that available
ServiceBusTriggeredEndpointConfiguration uses internal implementation for Transport using ServerlessTransport class which is locked to internal only that would also need updating

builder.UseNServiceBus((ServiceProvider) =>
{
    IConfiguration configuration = ServiceProvider.GetService<IConfiguration>();
    var servicebusConfig = new ServiceBusTriggeredEndpointConfiguration1(() =>
    {
        var endpointConfiguration = new EndpointConfiguration("EndpointName  from external source");
        endpointConfiguration.License("License FROM external source");
        var transportExtensions = endpointConfiguration.UseTransport<AzureServiceBusTransport>();
        transportExtensions.ConnectionString("Connection string from external source");
        return endpointConfiguration;
    });

    return servicebusConfig;
});

[SeanFeldman]

@hardik-desai-kcl could you please elaborate on the use case? Specifically, could you provide an answer to the question here? I'd like to understand what drives this request prior to discussing how to solution it. Thank you.

[hardik-desai-kcl]

so the issue we are having is that the NServicebus License and azure service bus connection string are not available through Environment variable in our azure function

when I use ServiceBusTriggeredEndpointConfiguration to setup endpoint the only way to get the endpoint running is setting Environment variable AzureWebJobsServiceBus and NSERVICEBUS_LICENSE otherwise the ServiceBusTriggeredEndpointConfiguration constructor throws an exception

the expected behaviour is allow setting servicebus connection string and NSERVICEBUS_LICENSE at minimum, ideally allow configuring EndpointConfiguration fully

[SeanFeldman]

Thank you @hardik-desai-kcl.
The environment variable AzureWebJobsServiceBus is not NServiceBus environment variable but Azure Functions. The trigger will not work if it's not there unless you're planning to override it and specify the connection string name to the trigger function. Is that your intent?

[hardik-desai-kcl]

@SeanFeldman the AzureWebJobsServiceBus or a service connection string Name is only required if the Azure function had a service bus trigger function, even in the example here https://docs.particular.net/samples/azure-functions/service-bus/ there isn't any service bus trigger function and that is what our use case is, we want to build Azure function that has HTTP trigger and at the same time it hosts NSB endpoint and let NSB handle messages.

[SeanFeldman]

we want to build Azure function that has HTTP trigger and at the same time it hosts NSB endpoint and let NSB handle messages.

Thank you. That's all I needed to hear to understand the use case.