NServiceBus: overview

We have seen how to setup NServiceBus but we have not told anything about what NServiceBus in the end is.

The phone call analogy

Bring up the phone; Compose a number; …no answer…; The phone call failed;

Bring up the phone; Compose a number; Start speaking with the called person; …our really powerful mobile phone infrastructure fails and the call is dropped in the middle; The phone call failed;

in both cases we have something really similar to what a typical “client to server” communication is:

• communication is initiated by the client;
• relies on a live and continuous connection;
• retries, handling of failures, are responsibility of the client;
• communication must be synchronous;

The express courier analogy

You order something at your favorite ecommerce web site; The ordered item gets delivered via UPS; The UPS delivery guy comes to your delivery address and tries to deliver the item; The delivery fails because no one is available to receive the package; The UPS system schedules a new delivery and tries for a fixed number of times; if in the end the delivery fails the item is returned to the deliverer with, attached, the full delivery report;

In this case we have introduced a third actor, the courier, in order to:

• Have a reliable delivery;
• Let someone specialized in the delivery process handle the delivery process;
• avoid putting in our hand all the details of the retry mechanism;
• communicate asynchronously;

The service bus

In the end NServiceBus perfectly impersonate the delivery process that an express courier does. Simple, reliable, asynchronous.

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