Announcing the RSS connector for MS-CRM 3.0
We've finally released the RSS connector for MS-CRM. I've mentioned this tool a few times. This has been a long release mired in a few documentation, legal, and technical issues. But, that's not your concern, you probably just want to download this thing, install it, and make things happen. Well, here's the backgrounder on what's making the connector tick. The MSDN article which comes with the connector download covers some basic information. Look for a longer whitepaper from our UE team in the next few weeks.
We want to hear how you've used, modified, or extended the connector. If you use it, let me know. This is the last bit of code that I built for the CRM team (well, it's the last bit that I released, I was still working on the add-entity framework and address book right up to RTM) and I'd like to see what happens with it (and no, this isn't typical of the code quality that I usually write, this was a prototype first and a public release second; if we were going to release this is would be very different). We're releasing this under a different model (see the EULA) and we're very interested in its life once it leaves here.
Basics of the connector
The RSS connector for CRM is built on top of the advanced find and web service Fetch functionality. For the most part it directly executes the requested query and returns the results as RSS-formatted XML. However, there are a few changes that are made to the base query (if you're wondering, all queries are stored as serialized <fetch> requests, which means the connector gets to mess with XML).
First thing that happens is that the connector loads the actual <fetch> definition for the requested user or system query. Next, it creates an array of the columns specified in the query's grid. These are used for specifying the simple list extension attributes for IE7 sorting and grouping. The one change from the grid columns is that the connector adds the modifiedon attribute if it's part of the underlying entity's definition.
Once the connector has cached away the display attributes it modifies the in-memory copy of the query so that all attributes are available. The query definition has all of its selection criteria removed as well so that the feed data is as broad as possible given the caller's security attributes.
User queries vs. system queries
Under the covers system queries and user queries are structurally the same. They are stored in different tables in the database (don't ask, it was a decision that couldn't be undone by the time it was noticed), they have the same columns, and they have the same semantics. The primary difference is that the security model changes: system queries are effectively public and user queries are effectively private. A secondary difference is that they had different APIs during the TAP and alpha releases because they just happen to be written in two different languages (again, don't ask).
This does have the nice side-effect that the RSS connector simply reads the query definition through the proper entity. It's really just a <fetch> that changes entity names and some minor decorations.
When the RSS connector displays the nice HTML-based list of available feeds it does so in two sections. The top contains user-specific feeds and the bottom contains all accessible system feeds. The connector also generates HTML <link> elements for each user query. This tells RSS-aware browsers and readers that there are feeds published on the page. The connector only does this for user queries otherwise the list would be unreasonable long.
How the connector selects attributes for display
Because the connector modifies the query definition to force all attribute selection (this isn't just done for display, it's also done to support instance delivery, but more on that in a minute) it's able to present a rich view of the instance data to the RSS aggregator. In WriteItemData the connector loops over the entity's attribute list in a semi-intelligent order. It writes the primary field, any audit attributes, any state or status attributes, ownership data, any "description" attributes, and then all the rest. Nearly all attributes retrieved from the platform are displayed: there are a few attributes that have no public view and no reasonable display label, so those are skipped.
Riding on coattails - using the list extensions
The connector uses the query's grid column to select the set of attributes used in the list extensions elements. Technically, this is a de-selection, because the connector rewrites the query to remove the attribute list and adds an <all-attributes> clause to the <fetch>. In the foreach loop in WriteCrmAttributes there's a check to see if the "current" attribute is in the cell list and if it's not it's skipped. The data is written in a manner that makes list extension display useful to the user and executable to the extension processor. That is, all "codes" and other internal details are tossed away and nice display values are used instead.
The lightweight metadata cache and the service proxy
Two things that held up earlier release of the connector were technologies that I used to make the connector happen but which aren't supported outside of the CRM team. These are use of the 1.2 COM proxy (which is finally gone in the upcoming CRM release - I hated that thing because I had to code it over my wife's birthday a few years back and that got me in a lot of trouble) and the internal metadata cache assemblies.
I didn't want to freak out our development team so I had to use the same metadata interfaces that everyone else uses. The problem is that the MD web service delivers too much data too slowly for me (speaking of slow, one optimization I'd like to see in the connector is to read the queries in one batch instead of on a per-entity type basis). To get around the metadata problem I rolled a very lightweight and purpose-built cache that uses the web service to read the metadata and keep it around in a static. There are a ton of problems with this approach: there's another copy of the cache floating around and CRM is already memory-hungry, and this cache isn't aware of customization changes (i.e. Publish) so it can get out of sync. I didn't consider either of these show-stoppers for this add-on, but the PM in charge of programmability does and he's doing something about it for V.next.
One thing that I did that might be a little surprising was that I asked for the WSDL and then hand-edited down to its absolute basic bits for this solution. I didn't want a 650Kb proxy loaded into the connector and I didn't want the connector to pay the late compilation and reflection hit when W3WP loaded the proxy. The connector only uses the Fetch method and the SOAP header. That means I was able to strip all the types and method definitions out (sorry Kevin and Arash). And no, I'm not using this as an apology for the web service shape in V3, it's a good thing. I didn't have to do the same thing with the metadata proxy because it's fairly small and the connector needs a lot of the definitions from it.
If you've gotten this far make sure you read my entry on using the offline client hosting process otherwise known as Cassini. I used the connector to verify that I could make the offline client web services work.
Optional non-IE7 "list extension" behavior
When the RSS feeds are displayed to the user there are two RSS icons and a text-based hyperlink. The two icons represent the "simple" RSS feed and the RSS feed with the complete instance data. The text link will show a down-level IE representation of the IE7 RSS viewer. This bit of code is a very early prototype put together by the IE and RSS team to show what the IE7 experience might look like. I lifted the code from those teams for the PDC demo and just never got around to removing it. Someone better versed in cross-browser AJAX stuff might be able to make this work better in other browsers. For now, this link can be ignored (and I would recommend replacing the link with the "real" RSS link and let the browser figure it out).
Delivering a complete CRM instance in the <item> data
The RSS connector has the capability to deliver, as part of the item data, the XML serialized representation of a complete entity instance. It does this to enable a set of scenarios supported by really simple sharing and by some hub and spoke delivery models that we're looking at. When this option is enabled the <channel> element contains the underlying entity's XSD (this is a different XSD generation process than the WSDL uses). When a smart RSS aggregator loads a feed with the CRM namespace it knows that the entity definition and entire entity instances are available to it. This means you can tunnel select CRM instance data over RSS without exposing the CRM web services. RSS provides the pipe through which this data moves. We've come up with dozens of applications for this delivery mechanism and will start building some software based on this model over the summer. (This is the project that I've left the CRM team to work on and I couldn't be more excited about it.)
Wrapping things up
The rest of the code is just infrastructure used to make CRM data into RSS. It's missing support for HTTP 304 and ETags. I'm hoping that someone will add that and drop me an update so I can reverse-integrate it into the code. I'm assuming that the connector will fall under the "unsupported sample code" umbrella which means that there isn't a formal support infrastructure in place for it. However, if you post a comment to this entry I'll see that they get to someone in the CRM team.
Building and installing the connector is easy. I'm assuming that the MSDN document talks about this, but if it doesn't here's the short and sweet. With the connector code is a small CMD script that if executed from a VS2003 command window will compile and copy the assembly to the bin directory. My demo installation uses the ISV extensions to add a "Web feeds" item to the menu which points at the RSS feed display and a convenient OPML page. There's a 16x16 PNG file that fits nicely in the menu and just happens to match the IE7 and Firefox RSS icons.
More things to read
RSS and CRM - a little history
Where is the RSS connector for CRM 3.0
“Democratizing” Business Logic and Data
Simple List Extensions
Really Simple Sharing
Using the CRM SDK offline
Microsoft Dynamics CRM RSS Connector
