Issue getting fault message from message context in Masstransit - masstransit

Question

I have an application that needs to intercept the current message consume context and extract a value that is defined in a base interface. That value is a tenant code that is eventually used in an EF database context.
I have a provider that takes a MassTransit ConsumerContext, and then using context.TryGetMessage(), extracts the tenant code, which is ultimately used to switch database contexts to a specific tenant database.
The issue lies in the MessageContextTenantProvider below. If a non-fault message is consumed then ConsumeContext<IBaseEvent> works fine. However if it is a fault, ConsumeContext<Fault<IBaseEvent>> doesn't work as expected.
Durring debugging I can see that the message context for a fault is ConsumeContext<Fault<IVerifyEvent>>, but why doesn't it work with a base interface as per the standard message? Of course, ConsumeContext<Fault<IVerifiedEvent>> works fine, but I have a lot of message types, and I don't want to have to define them all in that tenant provider.
Any ideas?
public interface ITenantProvider
{
string GetTenantCode();
}
public class MessageContextTenantProvider : ITenantProvider
{
private readonly ConsumeContext _consumeContext;
public MessageContextTenantProvider(ConsumeContext consumeContext)
{
_consumeContext = consumeContext;
}
public string GetTenantCode()
{
// get tenant from message context
if (_consumeContext.TryGetMessage(out ConsumeContext<IBaseEvent> baseEvent))
{
return baseEvent.Message.TenantCode; // <-- works for the non fault consumers
}
// get tenant from fault message context
if (_consumeContext.TryGetMessage<Fault<IBaseEvent>>(out var gebericFaultEvent))
{
return gebericFaultEvent.Message.Message.TenantCode; // <- doesn't work generically
}
// get tenant from fault message context (same as above)
if (_consumeContext.TryGetMessage(out ConsumeContext<Fault<IBaseEvent>> faultEvent))
{
return faultEvent.Message.Message.TenantCode; // <= generically doesn't work when using the base interface?
}
// get tenant from specific concrete fault class
if (_consumeContext.TryGetMessage(out ConsumeContext<Fault<IVerifiedEvent>> verifiedFaultEvent))
{
return verifiedFaultEvent.Message.Message.TenantCode; // <-- this works
}
// not able to extract tenant
return null;
}
}
public partial class VerificationDbContext
{
string connectionString;
public string ConnectionString
{
get
{
if (connectionString == null)
{
string tenantCode = _tenantProvider.GetTenantCode();
connectionString = _tenantConnectionManager.GetConnectionString(orgId);
}
return connectionString;
}
}
private readonly ITenantProvider _tenantProvider;
private readonly ITenantConnectionManager _tenantConnectionManager;
public VerificationDbContext(ITenantProvider tenantProvider, ITenantConnectionManager tenantConnectionManager)
{
_tenantProvider = tenantProvider;
_tenantConnectionManager = tenantConnectionManager;
}
protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
{
if (string.IsNullOrEmpty(this.ConnectionString))
{
optionsBuilder.UseSqlServer(#"Data Source=.\SQLEXPRESS;Initial Catalog=VerificationDb;Integrated Security=True")
.ConfigureWarnings((warningBuilder) => warningBuilder.Ignore(RelationalEventId.AmbientTransactionWarning));
}
else
{
optionsBuilder.UseSqlServer(this.ConnectionString)
.ConfigureWarnings((warningBuilder) => warningBuilder.Ignore(RelationalEventId.AmbientTransactionWarning));
}
}
}
public interface ITenantConnectionManager
{
string GetConnectionString(string tenantCode);
}
public class TenantConnectionManager : ITenantConnectionManager
{
private ITenantRepository _tenantRepository;
public TenantConnectionManager(ITenantRepository tenantRepository)
{
_tenantRepository = tenantRepository;
}
public string GetConnectionString(string tenantCode)
{
return _tenantRepository.GetByTenantCode(tenantCode).ConnectionString;
}
}
public interface IBaseEvent
{
string TenantCode { get; }
}
public interface IVerifiedEvent : IBaseEvent
{
string JobReference { get; }
}
public class VerifiedEventConsumer : IConsumer<IVerifiedEvent>
{
private readonly IVerifyCommand _verifyCommand;
private readonly ITenantProvider _tenantProvider;
public VerifiedEventConsumer(ITenantProvider tenantProvider, IVerifyCommand verifyCommand)
{
_verifyCommand = verifyCommand;
_tenantProvider = tenantProvider;
}
public async Task Consume(ConsumeContext<IVerifiedEvent> context)
{
await _verifyCommand.Execute(new VerifyRequest
{
JobReference = context.Message.JobReference,
TenantCode = context.Message.TenantCode
});
}
}
public class VerifiedEventFaultConsumer : IConsumer<Fault<IVerifiedEvent>>
{
private readonly IVerifyFaultCommand _verifyFaultCommand;
private readonly ITenantProvider _tenantProvider;
public CaseVerifiedEventFaultConsumer(ITenantProvider tenantProvider, IVerifyFaultCommand verifyFaultCommand)
{
_verifyFaultCommand = verifyFaultCommand;
_tenantProvider = tenantProvider;
}
public async Task Consume(ConsumeContext<Fault<ICaseVerifiedEvent>> context)
{
await _verifyFaultCommand.Execute(new VerifiedFaultRequest
{
JobReference = context.Message.Message.JobReference,
Exceptions = context.Message.Exceptions
});
}
}

Answer 1

I've solved the issue by using the GreenPipes TryGetPayload extension method:
public class MessageContextTenantProvider : ITenantProvider
{
private readonly ConsumeContext _consumeContext;
public MessageContextTenantProvider(ConsumeContext consumeContext)
{
_consumeContext = consumeContext;
}
public string GetTenantCode()
{
// get tenant from message context
if (_consumeContext.TryGetMessage(out ConsumeContext<IBaseEvent> baseEvent))
{
return baseEvent.Message.TenantCode;
}
// get account code from fault message context using Greenpipes
if (_consumeContext.TryGetPayload(out ConsumeContext<Fault<IBaseEvent>> payloadFaultEvent))
{
return payloadFaultEvent.Message.Message.TenantCode;
}
// not able to extract tenant
return null;
}
}