In-flight deb packages of Go

Since relatively early in the public life of the Go language, I’ve been involved in pushing forward packages that might be used in Ubuntu, including making the compiler suite itself happier in such packaged environments. In due time, these packages were moved over to an automatic build system, so that people wouldn’t have to rely on my good will to have up-to-date packages, nor would I have to be regularly spending time maintaining those packages. Or so was the theory.

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Efficient XPath for Go

This week I found some time to work on another small spin-off from the juju project at Canonical, and I’m happy to make it openly available today: the xmlpath package, which implements an efficient and strict subset of the XPath specification for the Go language.

This new package will be used in an upcoming (and long due) revision of the goamz package API, which is currently limited by the fact that once the XML result returned by Amazon is unmarshalled into a static structure, any other data that the package wasn’t prepared to deal with becomes hard to access by clients. This problem is being solved by parsing the tree into an intermediary form which can then have XPath expressions conveniently and efficiently applied to it.

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Gopher-powered backups

10gen, the company behind the MongoDB database, recently announced the availability of the MongoDB Backup Service. This is not a traditional backup service, though. Rather than simply sending scheduled snapshots of the data over to a remote system, the backup service has an agent sitting next to the database that monitors its operation log, and streams the individual operations over to the remote backup servers. This model enables the service to offer some non-conventional features, such as restoring the state of the database at any point in the last 24h, in addition to more traditional snapshots over longer periods.

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jsonpeer puts the P in JSONP

Today ubuntufinder.com was updated with the latest image data for Ubuntu 13.04 and all the previous releases as well. Rather than simply hardcoding the values again, though, the JavaScript code was changed so that it imports the new JSON-based feeds that Canonical has been publishing for the official Ubuntu images that are available in EC2, thanks to recent work by Scott Moser. This means the site is always up-to-date, with no manual actions.

Although the new feeds made that quite straightforward, there was a small detail to sort out: the Ubuntu Finder is visually dynamic, but it is actually a fully static web site served from S3, and the JSON feeds are served from the Canonical servers. This means the same-origin policy won’t allow that kind of cross-domain import to be easily done without further action.

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Porting 6700 lines of C to Go

A few years ago, when I started pondering about the possibility of porting juju to the Go language, one of the first pieces of the puzzle that were put in place was goyaml: a Go package to parse and serialize a yaml document. This was just an experiment and, as a sane route to get started, a Go layer that does all the language-specific handling was written on top of the libyaml C scanner, parser, and serializer library.

This was a good initial plan, but for a number of reasons the end goal was always to have a pure Go implementation. Having a C layer in a Go program slows down builds significantly due to the time taken to build the C code, makes compiling in other platforms and cross-compiling harder, has certain runtime penalties, and also forces the application to drop the memory safety guarantees offered by Go.

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Exceptional crashes

Last week I was part of a rant with a couple of coworkers around the fact Go handles errors for expected scenarios by returning an error value instead of using exceptions or a similar mechanism. This is a rather controversial topic because people have grown used to having errors out of their way via exceptions, and Go brings back an improved version of a well known pattern previously adopted by a number of languages — including C — where errors are communicated via return values. This means that errors are in the programmer’s face and have to be dealt with all the time. In addition, the controversy extends towards the fact that, in languages with exceptions, every unadorned error comes with a full traceback of what happened and where, which in some cases is convenient.

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Synchronicity: threads vs. events

There are a number of common misconceptions in software development surrounding the idea of concurrency. This has been coming for decades, and some of the issues have just been reinforced one more time in an otherwise interesting post in LinkedIn’s engineering blog that recommends their development framework.

Such issues may be observed throughout the post, but can be elucidated via this short paragraph: Continue reading

12 years ago

These ancient entries were taken from my old Advogato diary, written in my early twenties, a year after I joined the development team of Conectiva Linux. I’m copying them for historic purposes, with the content untouched. It’s curious to look back and have such details of what was going on at the time, things that feel good, and things that feel awkward such as the “Dear Diary, …” style of writing, and the amount of exclamations!!

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