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Spree on Heroku for Development

By Steph Skardal
March 8, 2010

Yesterday, I worked through some issues to setup and run Spree on Heroku. One of End Point’s clients is using Spree for a multi-store solution. We are using the the recently released Spree 0.10.0.beta gem, which includes some significant Spree template and hook changes discussed here and here in addition to other substantial updates and fixes. Our client will be using Heroku for their production server, but our first goal was to work through deployment issues to use Heroku for development.

Since Heroku includes a free offering to be used for development, it’s a great option for a quick and dirty setup to run Spree non-locally. I experienced several problems and summarized them below.

Application Changes

1. After a failed attempt to setup the basic Heroku installation described here because of a RubyGems 1.3.6 requirement, I discovered the need for Heroku’s bamboo deployment stack, which requires you to declare the gems required for your application. I also found a Spree Heroku extension and reviewed the code, but I wanted to take a more simple approach initially since the extension offers several features that I didn’t need. After some testing, I created a .gems file in the main …

Riak Install on Debian Lenny

By Ethan Rowe
March 4, 2010

I’m doing some comparative analysis of various distributed non-relational databases and consequently wrestled with the installation of Riak on a server running Debian Lenny.

I relied upon the standard “erlang” debian package, which installs cleanly on a basically bare system without a hitch (as one would expect). However, the latest Riak’s “make” tasks fail to run; this is because the rebar script on which the make tasks rely chokes on various bad characters:

riak@nosql-01:~/riak$ make all rel
./rebar compile
./rebar:2: syntax error before: PK
./rebar:11: illegal atom
./rebar:30: illegal atom
./rebar:72: illegal atom
./rebar:76: syntax error before: ��n16
./rebar:79: syntax error before: ','
./rebar:91: illegal integer
./rebar:149: illegal atom
./rebar:160: syntax error before: Za��ze
./rebar:172: illegal atom
./rebar:176: illegal atom
escript: There were compilation errors.
make: *** [compile] Error 127

Delicious.

Ultimately, I came across this article describing issues getting Riak to install on Ubuntu 9.04, and ultimately determined that the Erlang version mentioned seemed to apply here. Following the article’s instructions for building Erlang from source worked out …

PostgreSQL EC2/EBS/RAID 0 snapshot backup

By Jon Jensen
February 23, 2010

One of our clients uses Amazon Web Services to host their production application and database servers on EC2 with EBS (Elastic Block Store) storage volumes. Their main database is PostgreSQL.

A big benefit of Amazon’s cloud services is that you can easily add and remove virtual server instances, storage space, etc. and pay as you go. One known problem with Amazon’s EBS storage is that it is much more I/O limited than, say, a nice SAN.

To partially mitigate the I/O limitations, they’re using 4 EBS volumes to back a Linux software RAID 0 block device. On top of that is the xfs filesystem. This gives roughly 4x the I/O throughput and has been effective so far.

They ship WAL files to a secondary server that serves as warm standby in case the primary server fails. That’s working fine.

They also do nightly backups using pg_dumpall on the master so that there’s a separate portable (SQL) backup not dependent on the server architecture. The problem that led to this article is that extra I/O caused by pg_dumpall pushes the system beyond its I/O limits. It adds both reads (from the PostgreSQL database) and writes (to the SQL output file).

There are several solutions we are considering so that …

More Code and SEO with the Google Analytics API

By Steph Skardal
February 22, 2010

My latest blog article inspiration came from an SEOmoz pro webinar on Actionable Analytics. This time around, I wrote the article and it was published on SEOmoz’s YOUmoz Blog and I thought I’d summarize and extend the article here with some technical details more appealing to our audience. The article is titled Visualizing Keyword Data with the Google Analytics API.

In the article, I discuss and show examples of how the number of unique keywords receiving search traffic has diversified or expanded over time and that our SEO efforts (including writing blog articles) are likely resulting in this diversification of keywords. Some snapshots from the articles:

[The unique keyword (keywords receiving at least one search visit) count per month (top) compared to the number of articles available on our blog at that time (bottom).]

I also briefly examined how unique keywords receiving at least one visit overlapped between each month and saw about 10-20% of overlapping keywords (likely the short-tail of SEO).

[The keyword overlap per month, where the keywords receiving at least one visit in consecutive months are shown in the overlap section.]

Now, on to things that End Point’s audience …

PostgreSQL tip: dump objects into a new schema

By David Christensen
February 16, 2010

Sometimes the need arises to export a PostgreSQL database and put its contents into its own schema; say you’ve been busy developing things in the public schema. Sometime people suggest manipulating the pg_dump output either manually or using a tool such as sed or perl to explicitly schema-qualify all table objects, etc, but this is error-prone depending on your table names, and can be more trouble than its worth.

One trick that may work for you if your current database is not in use by anyone else is to rename the default public schema to your desired schema name before dumping, and then optionally changing it back to public afterward. This has the benefit that all objects will be properly dumped in the new schema (sequences, etc) and not just tables, plus you don’t have to worry about trying to parse SQL with regexes to modify this explicitly.

$ psql -c "ALTER SCHEMA public RENAME new_name"
$ pg_dump --schema=new_name > new_name_dump.sql
$ psql -c "ALTER SCHEMA new_name RENAME public"
$ # load new_name_dump.sql elsewhere

Cheers!

GNU diff: changing the output filenames

By David Christensen
February 15, 2010

I was working on a script to monitor/compare remote versions of a file and compare against our local mirror; part of this work involved fetching the remote file to a temporary location and doing a diff -u against the local file to see if there were any changes. This worked fine, but the temporary filename was less-than descriptive.

The man page for diff was somewhat cryptic when it came to changing the displayed output filenames themselves, however based on some figuring-out, you can pass the -L (–label) flag to diff. You need to pass it twice; the first -L will replace the filename in the — output line and the second -L replaces the file in the +++ line.

$ wget -qO /tmp/grocerylist
$ diff -u /path/to/local/grocerylist -L /path/to/local/grocerylist /tmp/grocerylist -L http://mirrorsite.com/grocerylist

--- /path/to/local/grocerylist
+++ http://mirrorsite.com/grocerylist
@@ -11,7 +11,7 @@
potatoes
bread
eggs
-    milk
+    soda
oranges
apples
celery

Obvious shortcomings in this approach are the fact that you need to specify a redundant -L line to the first file; in my case, this was all handled programatically, so I just substituted the same parameter in both places. …

MRM: The power of ‘random’, program maintenance, weave and electricity

By Selena Deckelmann
February 14, 2010

Time for another installment of Monday Reading Material!

I’m in New Zealand (and across the dateline!) so this is appearing a day early for many of you :)

Reading material from last week:

• The power of ‘random’. Work done with routers to combine messages (improve efficiency of transport) and then forward them at random on to another hop. Turned out this was better overall than trying to selectively forward to “most likely” next hops.

• A Perl Programming maintenance checklist. Things you can do to make your code maintainable (in any language!)

• Mozilla Weave. Bookmark sync!

• How much energy How do I find out how much electricity something uses?. Great article on figuring this out. I have a kill a watt and need to investigate a few appliances I have at home.

Safari 4 Top Sites feature skews analytics

By Jon Jensen
February 13, 2010

Safari version 4 has a new “Top Sites” feature that shows thumbnail images of the sites the user most frequently visits (or, until enough history is collected, just generally popular sites).

Martin Sutherland describes this feature in details and shows how to detect these requests, which set the X-Purpose HTTP header to “preview”.

The reason this matters is that Safari uses its normal browsing engine to fetch not just the HTML, but all embedded JavaScript and images, and runs in-page client JavaScript code. And these preview thumbnails are refreshed fairly frequently—​possibly several times per day per user.

Thus every preview request looks just like a regular user visit, and this skews analytics which see a much higher than average number of views from Safari 4 users, with lower time-on-site averages and higher bounce rates since no subsequent visits are registered (at least as part of the preview function).

The solution is to simply not output any analytics code when the X-Purpose header is set to “preview”. In Interchange this is easily done if you have an include file for your analytics code, by wrapping the file with an [if] block such as this:

[tmp x_purpose][env …