nServiceBus : How do I make a non-transactional call to a database from within the context of a transactional operation

1
votes

Quick overview of our topology:

Web sites sending commands to an nServiceBus server, which accepts the commands and then publishes the correct pub/sub events. This service also has message handlers that can do some process against the DB in response to the command, for instance:

1 user registers on web site 2 web site sends nServicebus command to nServicebus service on another server. 3 nServicebus server has a handler for that specific type of command, which logs something to the database and sends a welcome email

Since instituting this architecture we started to get deadlocks on the DB. I have traced it down to MSDTC on the database server. If I turn that service OFF on the database server nServicebus starts throwing up errors, which to me shows that nServiceBus has been enlisting the DB update in the transaction.

I don't wish this to happen, I want to handle the DB failing myself, I only want the transaction to ensure the message is delivered to my nServicebus proxy service. I don't want a transaction from the web all the way through 2 servers to the DB and back.

Any suggestions?

EDIT: this post provides some clues, however I'm not entirely sure it's the proper way to proceed.. NServiceBus - Problem with using TransactionScopeOption.Suppress in message handler

EDIT2: The reason that we want the DB work outside the scope of the transaction is that the intent is to 'asynchronously' process these commands on another server so as not to slow down the web site and/or cause users to wait for these long running aggregation commands. If the DB is within the scope of the transaction, is that blocking execution on the website at the point where the original command is fired to the distributor? Is there a better nServicebus architecture for this scenario? We want the command to fire quickly and return control to the web site so the user can quickly proceed and not have to wait for our longish running DB command, which is updating aggregate counts and sending emails etc.

1
nservicebusnservicebus-distributor

1 Answers

2
votes

I wouldn't recommend having the DB work outside the context of the NServiceBus transaction. Instead, try reducing the isolation level of the transactions. This can be done by calling:

.IsolationLevel(System.Transactions.IsolationLevel.ReadCommited)

in the fluent configuration. You'll have to put this after .MsmqTransport() in v2.6. In v3.0 you can put this call almost anywhere.

RESPONSE TO EDIT2:

Just using NServiceBus will achieve your objective of not slowing down the website, regardless of the level of the transactions run on the other server. The use of transactions is to provide a guarantee that messages won't be lost in case of failure and also that you won't have to write your own deduplication logic.