Run Lokad.CQRS code natively on Windows Azure

As it seems, the most common use of Lokad.CQRS Sample these days is for building CQRS-based applications for Intranet (and migrating legacy projects). I didn't see that coming, but glad that the latest "lean" version makes some sense to people (more about it).

However, one of the initial purposes of this Sample is to enable and demonstrate cross-cloud portability of projects developed using abstractions from Lokad.Cqrs.Portable. That's how we use it at Lokad.

So to highlight this (and to help folks from Microsoft CQRS Advisory Board that showed interest in trying Lokad.CQRS with Azure), I've added two new projects: Sample.Azure.Wires and Sample.Azure.Deploy. There is nothing really special, first project just wires SampleProject to run on Windows Azure in a Worker Role, without touching existing domain code. Second project is the actual deployment.

As expected, trace output is similar to the one we get from running sample in on-premises mode (via Sample.Engine console).

Obviously, this worker is wired to use native components of Windows Azure, instead of file system. These components (developed in Lokad and production-tested over the last few years in various scenarios) include:

• BlockBlobTapeStorage (used for append-only event streams on Azure)
• AzureAtomicStorage (used for storing documents, saga state and persistent read models)
• BlobStreamingStorage (used for streaming large BLOBs for Big DataProcessing)
• Azure Queues (for your message sending needs)

If you have latest Azure SDK installed, just open Lokad.CQRS.Sample.withAzure.sln to see these additional Azure projects and get a taste of event sourcing on the cloud (actually tastes exactly like any other ES, but feels cooler).

Maintenance Tip: By the way, you can download domain log file (sample-tapes/domain.tmd) from the Azure Storage to your disk and open it with Audit tool. This helps to visualize and investigate processes that happen in your CQRS system on the cloud (actually saved my day more than once, when production systems hit unexpected problems). Likewise you can also download and investigate event streams of any single aggregate.

Actually, this Audit tool was also designed to open event streams directly from Azure (and allow sending selected messages back or rebuilding all projections), however this functionality is not ported to open source yet. If somebody finds it useful, I'll try to find time and export it (there is nothing really fancy there, though - just using append-only nature of event streams for efficient data replication from remote cloud to local machine).

Maintenance Tip: Those, that plan to use this in a production, might want to plug the quarantine into the message handlers. For instance, here is a sample that records every handler failure and send a detailed report (with stack traces and message information) to email as soon as message is quarantined. The latter helps to deal with cloud problems really fast.

The next thing I want to include in this Sample Project is a lean Web UI, using ASP.NET MVC 3 Razor Views with jQuery and Bootstrap.css. Just to demonstrate how easy it is to add browser-friendly and fast Web UI to existing CQRS systems (and have it hosted on-premises or in the cloud, of course). What do you think?

Meanwhile, have fun, join the community of people abusing the project and be sure to fill in CQRS Survey put out by P&P Team