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How to get IE to accept third party cookies

Third party cookies are most often used by ad serving companies, because they are set by an image or other resource that can be pulled from a different domain, they are one way of tracking behavior across websites.

A short example: If I visit site A (www.foo.com) and site B (www.bar.com) and they both pull an image from site C (www.baz.com), it can set cookies for the site C domain (.baz.com), with a value of siteA or siteB.  Then when I visit site C, it ‘knows’ that I’ve been to sites A and B.

This can be sinister (see the wikipedia link above for privacy concerns).  However, if you have multiple web properties, then you may want to tie user behavior together across properties.  Third party tools like Google Analytics offer one way to do this, but if you want custom application behavior, then third party cookies are probably the way to go.

Firefox (at least my version of firefox, without any add ons or options changes) treats third party cookies much the same as first party cookies; that is, they just work.  However, IE requires a bit more hoop jumping, as they check the p3p compact policy.  A compact policy is basically a header you set which looks like this: P3P: CP="CAO PSA CONi OTR OUR DEM ONL".  I looked around for an easy explanation of what the various values are and how to set them in a coherent manner, but didn’t run into anything very useful.  However, I finally stumbled on this tutorial, which points you to this IBM software, which you can use to create a compact policy.  The tutorial also walks you how to use that software, which is not entirely intuitive.

As far as I can tell, IE doesn’t actually check for the existence of the corresponding policy file, nor does it care if the site does what the p3p header says it does, but it does require a valid compact policy.

After you’ve added that header, IE (versions 6-8) will accept your third party cookies.

[tags]third party cookies, compact policy, howto[/tags]

Tips Web Applications | moore |

GWT widgets and code splitting, a match made in heaven

If you are writing a typical GWT application, which is monolithic and controls the entire viewport of the browser, you probably don’t want to read this post.  Go on, read something else interesting–you probably have emails or tweets or something better to do with your time.

OK, now we just have the people left who are using GWT to build widgets; that is small encapsulated pieces of functionality that integrate into an existing web based application (case #2 outlined here).  If you’re doing this, and you use the “span to enable” gwt mini pattern, you want to upgrade to GWT 2.0 simply to get the new code splitting functionality.  If you don’t want to read that previous link, the synopsis is that code splitting lets you define a number of pieces of distinct code, using GWT.runAsync.  Then, that code won’t be downloaded until it is reached.

Previous to this feature, if you had a number of widgets, you ended up with a large chunk of code to download on every page (this is an issue with GWT that the monolithic applications simply don’t have to deal with).  Some of that code will be run.  Some will not, but you’re still paying for download and parsing of that code.  You had some unsavory options to deal with this–let all the code be downloaded, or manually split up code into separate modules that you managed (either by hand or with deferred binding).  The second solution led to smaller downloads, but meant a lot more management–if you wanted to add a widget to a page, you not only had to add the enabling span, you had to recompile the entire GWT module–and much longer compilation when you deployed your entire web application.  However, if your widgets were static, this path might have been an option.

My client used the former solution (entire code download on every page), and was very excited about the code splitting, since that essentially automates the second choice above.  In the space of about one half hour, I was able to reduce the initial download size of the GWT javascript by 10%, and there’s scope for much more, since the code is pretty naturally split up into separate chunks for each widget.

It’s not perfect, however. The two concerns I’ve had so far:

  1. The XS linker is not supported.  This means that if any of your widgets need to be cross domain, you need to create an additional module specifically for that.  For example, if I have one module, A, which is used to start up all the widgets on the site, and inherits from both module B, which has some GWT code split calls, and module C, which needs to be cross domain, the compiler will error out when compiling module A.  I need to create a second module XSModuleC which inherits from module C and is compiled by the XS linker, and then use that module for all cross domain purposes.
  2. If you call GWT.runAsync from an event handler, like onClick, you will not have a valid event on the first call (when the module is loaded) but will on all subsequent calls.  This is easy to fix, but was a bit mystifying to me.  Basically, if you have code like this:

onClick(ClickEvent event) {
if (event.getSource() instanceof Image) {
// do something with image
}
}

you need to replace it with:

onClick(ClickEvent event) {
if (event.getSource() instanceof Image) {
// save event.getSource into an instance variable
GWT.runAsync(new RunAsyncCallback() {
// do something with image in instance variable
}
}
}

I'm sure there are other complications I'll find once I do more code splitting.  (Here's an interesting post about code splitting in large applications, and simplifying the API of code that is split (plus, you get to see the word cromulent in context).)  But, for now, code splitting and GWT widget development seem like a match made in heaven.
[tags]gwt,code splitting[/tags]

GWT Tips | moore |

Whitespace and tables in IE

I was using the excellent displaytag library recently, and had written a table decorator to append some information about each row for a GWT widget to read and use.  The table ended up looking like this:

<table>
<tr>
<td>data</td>
…
</tr>
<script type=”text/javascript”>var …</script><span id=’uniqid’ style=’display:none’>gwt config data</span>
<tr>
<td>data</td>
…
</tr>
<script type=”text/javascript”>var …</script><span id=’uniqid’ style=’display:none’>gwt config data</span>
…
</table>

This worked fine in Firefox and Safari, but IE (versions 6, 7 and 8 ) were displaying whitespace above the table.  I couldn’t figure out why, until I commented out the table and the whitespace went away.  Then I re-enabled the table, and commented out the finishRow method; the whitespace was still gone.

The answer, of course, is that IE doesn’t like stuff outside of the <tr> tags.  Once I wrapped the span tag in <tr><td> tags, the whitespace went away for all browsers:

<table>
<tr>
<td>data</td>
…
</tr>
<tr><td><script type=”text/javascript”>var …</script><span id=’uniqid’ style=’display:none’>gwt config data</span></td></tr>
<tr>
<td>data</td>
…
</tr>
<tr><td><script type=”text/javascript”>var …</script><span id=’uniqid’ style=’display:none’>gwt config data</span></td></tr>
…
</table>

[tags]ie html quirks[/tags]

Tips Web Applications | moore |

What to do when you get 504 and 500 errors from your Google Mini

I have a client who uses a Google Mini (a search appliance created by Google) as a key part of their business.  The appliance worked fine, gave great search results, and was happily humming along until very recently.  At some point over the last couple of months, the number of 504 errors visible to the users using the mini increased drastically.

At one point, no matter what term you searched on, you would see this error message:

Error: Unknown XML result type.

View page source to see the offending XML.

504

When I took a look at this to try to troubleshoot, the results were very arbitrary--some search terms would show this message, some would not.  However, when a search term did show the error message, it would do so consistently, at least for 5-10 minutes.  Perhaps that had to do with caching?

The benefit of the mini is that you get great google like search results.  The detriment is that it is a black box--you don't even get a login to the box, etc.  And when your support contract runs out, you're left with very few options.

So, we troubleshot with one hand tied behind our back.  We:

  • tried rebooting the box a couple of times (via the web interface)
  • considered rolling back the index, but we only had about 36 hours of index history
  • generated and analyzed the search logs
  • searched the Google Groups for mini support.  All that turned up was this post which was not exactly helpful, since we no longer had support

Finally, the client suggested resetting the index, as it was conceivable that the mini index had been somehow corrupted.  This was an option for the client because their documents are re-crawled every day.  If that wasn't the case, it would have been a harder decision.

Resetting the index solved the problem.  Some numbers:

  • a few months ago, 0.5% of search requests were returning either 500 or 504 errors.
  • just before the index was reset, 40.2% of the requests were either 500 or 504 errors.
  • now, 0% of requests are either 500 or 504 errors.

FYI, this post is applicable to the Google Mini version 4.6.4--I'm not sure how more current versions of software work/break.

[tags]google mini,black box troubleshooting,504 error[/tags]

Technology Tips Useful Tools | moore |

List of Front Range Software Networking Events and Conferences

Updated March 21: crossed out ‘conferences’ because I don’t do a good job of listing those.
Boulder, Colorado, has a great tech scene, that I’ve been a peripheral member of for a while now.  I thought I’d share a few of the places I go to network.  And by “network”, I mean learn about cool new technologies, get a feel for the state of the scene (are companies hiring?  Firing?  What technologies are in high demand?) and chat with interesting people.  All of the events below focus on software, except where noted.

NB: I have not found work through any of these events.  But if I needed work, these communities are the second place I’d look.  (The first place would be my personal network.)

Boulder Denver New Tech Meetup

  • 5 minute presentions.  Two times a month.  Audience varies wildly from hard core developers to marketing folks to graphic designers to upper level execs.  Focus is on new technologies and companies.  Arrive early, because once the presentations start, it’s hard to talk to people.
  • Good for: energy, free food, broad overviews, regular meetings, reminding you of the glory days in 1999.
  • Bad for: diving deep into a subject, expanding your technical knowledge

User groups: Boulder Java Users Group, Boulder Linux Users Group, Rocky Mountain Adobe Users Group, Denver/Boulder Drupal Users Group, Denver Java Users Group others updated 11/12 8:51: added Denver JUG

  • Typically one or two presentations each meeting, for an hour or two.  Tend to focus on a specific technology, as indicated by the names.  Sometimes food is provided.
  • Good for: diving deep into a technology, networking amongst fellow nerds, regular meetings
  • Bad for: anyone not interested in what they’re presenting that night, non technical folks

Meetups (of which BDNT, covered above, is one)

  • There’s a meetup for everything under the sun.  Well, almost.  If you’re looking to focus on a particular subject, consider starting one (not free) or joining one–typically free.
  • Good for: breadth of possibility–you want to talk about Google?  How about SecondLife?
  • Bad for: many are kind of small

Startup Drinks

  • Get together in a bar and mingle. Talk about your startups dreams or realities.
  • Good: have a beer, talk tech–what’s not to like?, takes place after working hours, casual
  • Bad: hard to target who to talk to, intermittent, takes place after working hours.

BarCamp

  • Originally started, I believe, in response to FooCamp, this is an unconference. On Friday attendees get together and assemble an interim conference schedule.  On Saturday, they present, in about an hour or so.  Some slots are group activities (“let’s talk about technology X”) rather than presentations.  Very free form.
  • Good: for meeting people interested in technologies, can be relatively deep introduction to a technology
  • Bad: if you need lots of structure, if you want a goodie bag from a conference, presentations can be uneven in quality, hasn’t been one in a while around here (that I know of)

Ignite

  • Presentations on a variety of topics, some geeky, some not.  Presentations determined by vote.  Presentations are 20 slide and 5 minutes total.  Costs something (~$10).
  • Good: happens in several cities (Denver, Boulder, Fort Collins) so gives you chance to meet folks in your community, presentations tend to be funny, wide range of audience
  • Bad: skim surface of topic, presentation quality can vary significantly, not a lot of time to talk to people as you’re mostly watching presentations

CU Computer Science colloquia

  • Run by the CU CS department, these are technical presentations.  Usually given by a visiting PhD.
  • Good: Good to see what is coming down the pike, deep exposure to topics you might never think about (“Effective and Ubiquitous Access for Blind People”, “Optimal-Rate Routing in Adversarial Networks”)
  • Bad: The ones I’ve been to had no professionals there that I could see, happen during the middle of the work day, deep exposure to topics you might not care about

Jelly

  • Cooperative work environments, hosted at a coffee shop or location.
  • Good: informal, could be plenty of time to talk to peers
  • Bad: not sure I’ve ever heard of one happening on the front range, not that different from going to your local coffee shop

Boulder Open Coffee Club

  • From the website: it “encourage entrepreneurs, developers and investors to organize real-world informal meetups”.  I don’t have enough data to give you good/bad points.

Startup Weekend

  • BarCamp with a focus–build a startup company.  With whoever shows up.
  • Good: focus, interesting people, you know they’re entrepeneurial to give a up a weekend to attend, broad cross section of skills
  • Bad: you give up a weekend to attend

Refresh Denver

  • Another group that leverages meetup.com, these folks are in Denver.  Focus on web developers and designers.  Again, I don’t have enough to give good/bad points.

Except for Ignite, everything above is free or donation-based.  The paid conferences around Colorado that I know about, I’ll cover in a future post.

What am I missing?  I know the list is skewed towards Boulder–I haven’t really been to conferences more than an hours drive from Boulder.

Do you use these events as a chance to network?  Catch up with friends?  Learn about new technologies, processes and companies?

BarCamp BJUG Conferences CU Colloquia Drupal Java New Tech Meetup Presentations RIA Tips | moore |

Setting variables across tasks in capistrano

I am learning to love capistrano–it’s a fantastic deployment system for remote server management.  I’m even learning enough ruby to be dangerous.

One of the issues I ran into was I wanted to set a variable in one task and use it in another (or, more likely, in more than one other task).  I couldn’t find any examples of how to do this online, so here’s how I did it:

task :set_var
self[:myvar]= localvar
end

task :read_var
puts self[:myvar]
end

Note that myvar and localvar need to be different identifiers–“local variables take precedence”.  Also, the variable can be anything, I think.  I use this method to create an array in one task, then iterate over it in another.

[tags]capistrano, remote deployment, ruby newbie[/tags]

Cloud Computing Tips Web Applications | moore |

Flex textareas, newlines and posting to a unix server

I was working on a flex app and wanted to post the contents of a flex textarea to a php script on a unix server, among other fields.  This is easy to do with the URLRequest.  The php script on the server then parsed the form fields.  In particular, it split the textarea’s contents on the newline.

When I first tried this, the php script only found one record, no matter how big the textarea content.  After haivng the php script write the content to a file, it was clear why.  The flex app was sending the textarea with Windows line endings.  I’ve never experienced this particular issue before.  I tested a plain old HTML form, and somewhere the newlines are converted from Windows to unix (for more than you ever wanted to know about the humble newline, consider wikipedia.)

Regardless, the answer was to make sure that wordwrap was set to false, and run a regular expression on the content of the textarea before sending it.  From the comments on this blog post:

loremTEXT2 = loremTEXT.replace(/[\r\n]+/g, “\n”);

[tags]the humble newline, flex, textarea[/tags]

RIA Tips | moore |

How to turn off red/green/blue lines in Sketchup drawings

This frustrated me to no end, so I’m posting it here.

If you’re using Google Sketchup to sketch a model, and you want to export it to a two dimensional file (e.g, a PNG), without the green, red and blue axis lines, you can do so by following these steps.

  • open your model
  • choose the window menu option
  • choose the styles menu
  • choose edit
  • change the ‘color’ drop down (at the bottom of the popup) from ‘by axis’ to ‘all same’.

This works for Google Sketchup 6.4.112.
[tags]google sketchup, basics[/tags]

Tips | moore |