Pondering RSS Syncing

  • Nov 23, 2011

I was listening to the latest episode of Build and Analyze on the way home from work yesterday and, as I am wont to do, I started yelling at my iPhone when they started talking about Google Reader and the difficulty of syncing. Admittedly, at the end, they got to the fact that, even if you could do it technically, it'd be tough to make money off of providing an RSS sync server. That part is fair enough, but I still can't let the technical difficulties stand, and I've been thinking more about how it would be done in Domino.

In the basic form, the problem in question is pretty much exactly what NSF and the Notes/Domino relationship is designed to do: seamless replication, deletion stubs, unread marks, and so forth. In fact, RSS syncing is a better fit for the model than mail, since mail required adding all kinds of extra (but useful) functionality, while RSS syncing would just be data and an agent to fetch the feeds periodically.

The way I figure it, there would only be a couple technical hurdles, both related to scaling: storing large volumes of data and fetching new feed content periodically.

Storing large volumes of data might not be too bad. There are a couple ways you could do it. One would be to store the user's list of subscribed feeds and "read" stubs in one database per user, and then store the feeds and feed content in another database (or databases), and do all data access via agents or web services that would pull the data from each distinct location. Another way could be to store the feeds and entries in each user's database, keeping the feed content as attached HTML documents and letting DAOS handle efficient storage. The latter route would let you take advantage of the Domino Data Service and read marks (which DAS conveniently supports).

Updating the feeds would be rough for a single server, but the job could be farmed out to many clusters in a server. You could write agents that would determine the server they're on and, based on, say, its name, pick a slice of the feeds to check, so if you have 10 servers, each would update 10% of the feeds.

I'm sure there'd be other roadblocks during actual implementation (it IS Domino, after all), but I think that'd be basically all you'd need on the server side. The client would be a little tougher, since you couldn't just use NSF and selective replication, but that wouldn't be terribly difficult to handle.

It's too bad it's likely not profitable, between licensing, hosting, and bandwidth costs - it'd be a fun project to try out.

That Counts as Progress

  • Nov 22, 2011

A while back, I described the problem I'm having in my guild-forums XPages app, which is that it very easily gets its environment out of whack, to the point where changing any design or data note from outside the XPages environment caused an "X is incompatible with X" ClastCastException. This improved gradually over time. At some point in 8.5.2, I started being able to modify data documents again without the problem. When 8.5.3 came out, it improved again: I can now replicate over changes from my development server to the production one without having to bounce HTTP on the production one. At that point, it became much less of a hassle - sure, I still had to re-save a Java class file every time I modified an XPage, but that was only in development, so I could deal.

However, I think I've found the proper solution. In 8.5.3 (I think), IBM added a custom editor for the xsp.properties file (which you can reach using the "Package Explorer" Eclipse view, in whatever.nsf/WebContent/WEB-INF). Many of the options are duplicates of what you see in the normal "Application Properties" editor (since they edit the same properties), but there are some nifty additional goodies. I won't go into them all, but I urge you to take a look. The important one here is in the "Timeouts" section of the "General" tab: "Refresh entire application when design changes" . That sounded perfect and, lo and behold, it seems to do what I want: once I turned that on, re-saving an XPage stopped causing the ClassCastException. I haven't given it a proper testing, so it might not be everything I'm looking for, but I'm thrilled at the initial results. Having to re-save a Java file for each change wasn't a HUGE problem, but it was a niggling one, and not having to jump through the hoop helps make the whole environment seem less rickety.

That's Weird

  • Nov 9, 2011

Yesterday, I started working on a small sidebar widget app using an XPage, after finding out that XPages can now (as of 8.5.3) be used in the Notes sidebar in the same way that Forms could before. It's quite a simple page, very Twitter-like: one text input field and then a list of posts. However, even though it's very simple, I ran into two annoying bugs quickly.

The first of them is a Schrödinbug. I set up some code in the "onClientLoad" event to start a setInterval to do a partialRefreshGet on the list of posts, so it would keep itself up to date:

<xp:eventHandler event="onClientLoad" submit="false"> <xp:this.script><![CDATA[ setInterval(function() { XSP.partialRefreshGet("#{id:messagesPanel}") }, 2000) ]]></xp:this.script> </xp:eventHandler>

Simple, right? But I started getting errors in the status bar, along the lines of somethingorother not being defined. That's... odd. So I swapped over to Safari, figuring it'd be some XPiNC-specific thing, but I started getting similar (albeit more specific) errors there, along the lines of:

TypeError: 'undefined' is not an object (evaluating '_166.formId')

Huh. So I tracked it down and the problem was in the code called by partialRefreshGet, where "_166" is the name given to the second (optional) parameter. It makes sense when seeing it - though the code is supposed to fail over when it doesn't work, I can see why the browser would throw up its hands when you try to get a property of an un-provided parameter. But this has worked before! Just looking around on the web, you run into plenty of examples that leave out the second parameter. But sure enough, when I changed the line to XSP.partialRefreshGet("#{id:messagesPanel}", {}), it started working great. I can only think that this is either some 8.5.3-specific bug or some weird thing I managed to do in my code... but there's not even really enough code to mess up.

The second bug is still annoying, and it's somewhere in between a bug and a security feature of Firefox/Gecko. Basically, while you can call the .click() method on a button in client-side JavaScript in Gecko, it doesn't behave exactly like clicking on the button. Specifically, I have a CSS-hidden button that executes the actual action of creating the message document from the text you type in, and I want it to happen when you hit enter. The button itself works great - if I have it show up, I can type, click, and it executes the action and partial-refreshes the list of posts. However, if I hit enter, which uses the .click() method, I get an error about not being able to refresh that part of the page, but then it forces a full-page refresh and still works. So it's KIND OF clicking it, but not quite.

I'm not sure what to do about this one. I looked up a couple things online about trying to emulate the actual click event, but with no better results. I could do a REST service on the page, but I don't want to have to roll out the Extension Library to everyone in the company. Maybe I'll look into sending along the data in a XSP.partialRefreshPost call and eliminate the button entirely. We shall see.

Trying To Escape From Designer

  • Nov 8, 2011

Though I've grown to more or less enjoy writing Domino applications, I always feel like this is in spite of the tools, namely Designer. In a lot of ways, Designer has improved significantly over the last couple versions: as long as you ignore the speed, the Eclipse-ified Java and LotusScript editors are miles ahead of the antiquated previous ones, and it's handy to be able to switch to the Java perspective. However, so much else makes it a drag:

  • It's a Windows app. I use a Mac, so there's simply a big hurdle to using Designer. Parallels has smoothed the process greatly - running Notes in Coherence mode means I can use my preferred OS while still getting work done. However, it means that it's a big to-do whenever I want to make any tiny change in the code. For day-to-day work stuff, I can get a lot done in the Mac Notes client, since I put in a lot of work to make managing client web sites doable without going to the design side, and the Mac client still lets you edit views and agents. However, there's no XPages editor, so I can't use that for serious work.
  • It has a mind of its own. For some reason, a new clean install of Designer I made the other day got it into its head that opening any database should involve recompiling every XPage and Java class. Sometimes, it turns off "Build Automatically" for no reason, and then turning that back on also requires a full recompilation. Sometimes, it just holds up all user actions while it does... something for five minutes. What's it doing? Beats me.
  • How many times have I seen this window? A billion?
    Removing a database from the project list has about a 30% chance of causing a crash and quitting Designer has about a 50% chance. Sometimes, saving a form will do it. Sometimes, walking away from the computer to get a drink is enough. And every time it crashes, I have to dismiss the dialogs and check the task manager to get rid of any residual processes, such as an instance of nsd pegging a processor, then relaunch Notes and get back to the environment I had, which is not a speedy process.
  • I'm not that crazy about Eclipse. DDE is better than previous Designers, yes, but Eclipse is still a giant beast with the same sense of style and simplicity as the monstrous Java language that spawned it. On the plus side, the blue look that IBM came up with is actually rather attractive compared to the standard Eclipse UI, but little quality-of-life things are a drag. For example, how do you specify how many spaces a tab should take up visually? It's in a couple places in the preferences and you have to set them all, including buried inside a weird sub-preferences dialog for messing with your Java formatter. And how about changing your code syntax coloring? You have to go to a dozen places, one for each syntax type. Compare to a text editor like TextMate, where you can swap between packaged color schemes with a drop-down.

That's enough for the rant. So what is there to do about it? I give this problem a thought from time to time, and I don't think there's really a great option, but there are some places to start. The real key to any alternative scheme is DXL - using that, you can (more or less) view and modify design elements freely. I've toyed with this notion before - maybe a web UI that lets me pick the DB and design element I want so I can tweak the DXL manually for when I want to make a quick change but don't already have Windows or Designer open. It would mostly work, but it would take a lot of work to make it practical.

There's a big sticking point, too: XPages. If you export an XPage to DXL, you can see that the exporter basically punts on it - it's exported as a generic "note" type with Base64-encoded binary fields. I haven't run the field data through a decoder, so maybe one of them is the XML "source" of the page, and maybe it could be made to work, but that just raises more questions. Would that require updating the other binary fields in some way? Would importing it with a DXL importer cause it to generate and compile the Java representations? What about generic Java classes? Would those work with DXL and would they be compiled?

I'm starting to get an idea of what would be ideal and almost practical, though. One could write a WebDAV server (possibly with a complex servlet, a small web server to the side, or other trickery) that represents the design elements as editable files in a folder structure similar to the Java perspective view of the database. Traditional files and image resources could be edited as-is (which I think the built-in WebDAV server does), but design elements could be represented just as DXL and then re-imported when modified. Even if it doesn't support XPages, such a scheme might have a lot of promise and wouldn't be reliant on Designer or any other IDE.

If I ever get brave enough to delve into WebDAV or frustrated enough with Designer, I might just look into it myself.