Topper's blog about ruby on rails and javascript

Jun 10 10

Review: Byline app for iPhone

by Topper

The Byline reader for iPhone is awesome. It syncs your google reader account into an offline cache that is simply perfect for the subway. I am currently using the new free version which is ad supported. The ads are unobtrusive and the app just seems to work.

I did have one problem that after reading several articles I would keep getting a white screen. I have hundreds of feeds with thousands of articles and interrupted a sync – so maybe that was the cause.

The app is so good I missed two subway stops on the way to work. Woops! But I recommend anyone who has an iPhone and a Google Reader account to get this app.

I am in no way affiliated with the Byline team.

May 27 10

Zookeeper – Distributed cluster software

by Topper

I read this article about Apache Zookeeper at Igvita and was intrigued.

I started looking around for ruby libraries, but nothing was as mature as I would like. I forked a branch on github and chugged along on getting the jruby and c versions to work with the same api.

Zookeeper exposes a super simple API, but with that simple stuff you can build a lot of complex cluster logic.

PLAIN TEXT

RUBY:

zk = ZooKeeper.new("localhost:2181", :watcher => :default) #this will handle events using my built-in event handler
zk2 = ZooKeeper.new("localhost:2181", :watcher => false) #this one won't receive watch events
zk.watcher.register("/mypath") do |event, zookeeper_client|
$stderr.puts("got an event on: #{event.path}")
end
zk.exists?("/mypath", :watch => true) # returns nil, but sets up the app to watch for the existence of /mypath
zk2.create("/mypath", "my data up to 1mb", :mode => :ephemeral)
# create modes can be any of
# :persistent_sequential, :ephemeral_sequential, :persistent, :ephemeral
# now the registered watcher will fire (at least within a few 100 miliseconds)
# because we set that node to be :ephemeral - when zk2 closes its connection, the "/mypath" will go away
# but watches are one-time firing only - so we need to set it up again
zk.exists?("/mypath", :watch => true) #returns true
zk2.close! #or delete or whatever
# the watcher fires again and
zk.exists?("/mypath") #returns false

A limited api of create, delete, get, set, watch lets you do some really advanced things around a cluster.

Examples

I added some abstractions based on the Zookeeper recipes.

Locks

PLAIN TEXT

RUBY:

#these 2 clients could be on totally separate boxes, different processes, whatever
zk = ZooKeeper.new("localhost:2181", :watcher => :default)
zk2 = ZooKeeper.new("localhost:2181", :watcher => :default)
lock1 = zk.locker("/mypath")
lock1.lock #true
lock2 = zk2.locker("/mypath")
lock2.lock #false
lock1.unlock #true
lock2.lock #true
# locks are also released on a client close/crash
lock1.lock #false
zk2.close!
lock1.lock #true

Message Queues

I also implemented a simple message queue on top of zookeeper. However, because of the way the zookeeper "children" calls are made (returning all children), I wouldn't recommend using this for queues where pending messages will reach into the thousands.

PLAIN TEXT

RUBY:

client1 = ZooKeeper.new("localhost:2181", :watcher => :default)
client2 = ZooKeeper.new("localhost:2181", :watcher => :default)
publisher = client1.queue("myqueue")
receiver = client2.queue("myqueue")
receiver.subscribe do |title, data|
# data will be whatever was published, title will be the node name
# for the message
$stderr.puts "got a message with: #{data}"
# having a true state from the block will mark the message as 'answered'
# sending back a false will requeue
true
end

More...

There's a ton you can do with this thing (priority queues, meta data store, etc). I think it's a nice addition to the ruby toolset.

Apr 26 10

New Facebook Javascript API

by Topper

UPDATE:
http://developers.facebook.com/docs/reference/javascript/FB.login
Only allowed to prompt for permissions due to a user action. Which is shitty, but I should have seen is documented.

I love the *looks* of the new Facebook javascript API. It's got one major flaw though. It doesn't work in Safari or Chrome. I have an app setup to use http://localhost:7000/ as the connect url and everything works *great* in Firefox. Things even work mostly ok in safari or chrome... but as soon as you try to launch the permissions dialog box you get the browser cycling through "unsafe javascript attempt to access frame with URL."

Best part about this whole thing is: the facebook developer forums throw the *same* error.

Also, when I try to create an account on the forums (not using facebook connect) I get a "cannot connect to socket" error.

I guess I go back to their older clunkier API? Seems to be a number of complaints but no answers from Facebook.

Any ideas?

UPDATE:

That error just keeps growing and growing.

I'm initializing my facebook like:

PLAIN TEXT

JavaScript:

FB.init({
appId : '<myappid>',
status : true, // check login status
cookie : true, // enable cookies to allow the server to access the session
xfbml : true // parse XFBML
});

Minimal Repro:

If you put the following HTML at 127.0.0.1:7000 and hit the page you are UNABLE to do the following from the console:

PLAIN TEXT

JavaScript:

FB.login(function (resp) { console.dir(resp);}, {perms: 'publish_stream'})

PLAIN TEXT

HTML:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns:fb='http://www.facebook.com/2008/fbml' xmlns='http://www.w3.org/1999/xhtml'>
<head>
<title>
Test page
</title>
</head>
<body class='mbx'>
<div id='fb-root'></div>
<script src="http://connect.facebook.net/en_US/all.js" type="text/javascript"></script>
<script type='text/javascript'>
//<![CDATA[
FB.init({
appId : '10562765058',
status : true, // check login status
cookie : true, // enable cookies to allow the server to access the session
xfbml : true // parse XFBML
});
//]]>
</script>
</body>
</html>

Feb 28 10

_method in recent rails is brokenish

by Topper

I was trying to pass in _method: 'put' as part of a json body and for some reason rails kept not realizing that I wanted to put.

Then I came across this article: http://stackoverflow.com/questions/1249282/set-method-to-put-in-rails-xml-requests

So... if you're using prototype your "put" methods look something like this:

PLAIN TEXT

JavaScript:

new Ajax.Request(url, {
onSuccess: callback,
requestHeaders: {'X-Http-Method-Override': 'put'},
postBody: Object.toJSON(params),
contentType: "application/json"
});

Jan 27 10

Rails thread safety

by Topper

Calling Rails.configuration.threadsafe! at the end of your environment.rb does *not* turn on multi-threading. Adding config.threadsafe! to your individual environments (like production.rb) *does* turn on multi-threading.

You can also check that your multi-threading is active by seeing if ActionController::Base.allow_concurrency is true.

We add ::RAILS_DEFAULT_LOGGER.fatal { "Mulithreading is active? #{ActionController::Base.allow_concurrency}" }
to the end of our environment.rb to let us know that it worked.

Dec 2 09

Google Analytics Launches Asynchronous Support

by Topper

Google Code Blog: Google Analytics Launches Asynchronous Tracking

Google Analytics Launches Asynchronous Tracking
Tuesday, December 01, 2009

Today we're excited to announce our new Google Analytics Asynchronous Tracking Code snippet as an alternative way to track your websites! It provides the following benefits:

* Faster tracking code load times for your web pages due to improved browser execution
* Enhanced data collection & accuracy
* Elimination of tracking errors from dependencies when the JavaScript hasn't fully loaded

This is excellent news. I had implemented something similar on my own, but it always had its own problems. I'm glad to see it officially supported.

Topper’s Blog

Review: Byline app for iPhone

New Facebook Javascript API

_method in recent rails is brokenish

Rails thread safety

Google Analytics Launches Asynchronous Support

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