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DevelopmentWhy CouchDB?Why should developers use CouchDB? It all comes down to replication, says Benjamin Young. Data is "lonely," trapped in proprietary formats and cloud silos, or remote applications that require dependable Internet connections. When the power goes out, when you want to work on the plane, or when you just want control over your data — Young says you want CouchDB. Young was speaking at the Strange Loop 2011 conference on Tuesday, September 20 in St. Louis. The mission? To convince some of the 900-plus developers at the conference to consider CouchDB as database to power their applications. It wouldn't be very convincing if Young wasn't a fan himself, of course. Young's history with CouchDB goes back to work with BlueInk, a content management system for building simple sites for small companies. BlueInk used CouchDB, which caught the attention of CouchOne (now Couchbase, following a merger of CouchOne and Membase). BlueInk was released as open source a year ago when Young joined CouchOne. What is CouchDB?After giving a bit of his history, Young moved on to talking about CouchDB and what it actually is. CouchDB is a document storage database written in Erlang. It is open source, and part of the Apache project — though several different implementations are offered by a handful of companies like Couchbase. It's one of the current crop of NoSQL, or coSQL if you prefer, databases. Documents in CouchDB are stored in JavaScript Object Notation (JSON)
format, plus attachments if you have binary data (photos, for example) to
put into the database. Queries are written using JavaScript. It's a
Young described a scenario of deploying an application using CouchDB in rural Africa. The users might only have Internet a couple of hours per day in rural Africa. If they were using a cloud-based application that depends on a constant connection "they'd be completely screwed." Using CouchDB, the data can be easily synced during the window of connectivity without any hassle. The database doesn't have to keep a constant state, CouchDB operates on the principle that it will be "eventually consistent." As the scenario Young described implies, CouchDB is not limited to running on a server. It will run on a desktop, server, or even on a mobile device. Any device running CouchDB can communicate and send data to another instance of CouchDB, so replication can be peer-based or follow a server-client model. Replication can also be filtered, so that an instance only receives some of the information relevant to its local application. For instance, Young mentioned you might use CouchDB for distributing shipping information — the primary instance of CouchDB getting all of the order information, and filtering the appropriate orders to the users who are filling some of the orders. Another argument for CouchDB? Young says "you already know the API," because it's basically HTTP. CouchDB provides a RESTful API with GET, PUT, POST, DELETE, as well as a non-standard extension to HTTP, COPY. The COPY API does what one would expect: it duplicates the contents and attachments of a document to a new document using a new name, and without requiring it to be retrieved first. Web 2.5: Work Locally, Sync GloballyThe big reason for choosing CouchDB according to Young? Replication. Like many in the open source community, Young doesn't express a lot of love for cloud services — which he describes as "managed and terms-of-serviced and fascist." That's not to say Young doesn't want to collaborate with his friends and co-workers. Far from it, but Young argues for a return to a "decentralized and very organic" Web. He calls it "Web 2.5" (because "Web 3.0 is already taken"). Web 2.0 gave us "cloud powers" but took away ownership of data. "For cloud powers we traded ownership, privacy, security, safety, stability... we need to get all those things back, to get that we need replication. Not only to move data, but applications." Web 2.5, says Young, is a situation where you have the browser and server "and then the .5 lives in the cloud, and that's a service that watches for changes in your CouchDB." Data a user chooses to share can still be synced up to cloud services, but it lives on the users' machine as well. "I as a person shouldn't have to keep everything that is me in a little package in the cloud... I can work locally on my laptop and then if I need to share I can go somewhere people are." Get StartedYoung suggests that developers interested in CouchDB start at Iris Couch as the fastest way to get started. He also suggested checking out the Apache project, and its mailing lists. For more immediate questions and feedback, Young noted that there was a decent community of CouchDB developers on Freenode on the #couchdb channel as well as in the #couchbase channel.
Brief items Quotes of the week
Making software flexible, safe, and correct is hard work. Wish I
still had my magic wand from kindergarten.
-- Greg Ward
(function(){var k=[];return function j(){k.push(i);j();}})()();
Jim
Sangwine
On every call, the function j attempts to add the contents of variable i out of the global scope to the enclosed array k. The eagle eyed will notice that I have not included a safety check here so that if i is undefined, the code will error out and the recursion of j will fail. This is intentional. The variable i represents input from other people, and I want to remember that I should always seek the advice and opinions of those around me. I know that I cannot grow in isolation, hence the catastrophic consequences of failing to garner the contributions of others. As I mentioned above, the k array represents knowledge or experience, and this part of the code also reminds me that I should always learn from the input I elicit.
Not spending as much time sitting in meetings and fighting with
other vendors is one of the competitive advantages PostgreSQL
development has vs. the "big guys". There needs to be a pretty
serious problem with your process before adding bureaucracy to it
is anything but a backwards move. And standardization tends to
attract lots of paperwork. Last thing you want to be competing
with a big company on is doing that sort of big company work.
-- Greg Smith
GNU Health 1.3.3 releasedGNU Health is a hospital information system with modules for electronic medical record, hospital information systems, and health information systems. The 1.3.3 release is out; beyond a name change (from GNU Medical) and improved installation scripts, it includes: "major improvements in the Laboratory module. Now we have automatic visual alerts, possibility to exclude analytes from the analysis, qualitative and quantitative testing."
Greedy register allocation in LLVM 3.0Readers interested in the grungy details of compilers may enjoy this LLVM project blog entry on their new register allocation algorithm. "The new basic allocator does away with linear scan's dependence on visiting live ranges in linear order. Instead, it uses a priority queue to visit live range in order of decreasing spill weight. The active list used for interference checks is replaced with a set of live interval unions. Implemented as a B+ tree per physical register, they are an efficient way of checking for interference with already assigned live ranges. Unlike the active list, live interval unions work with any priority queue order."
Openshot 1.4Version 1.4 of the OpenShot video editor has been announced. Changes include timeline improvements, a "more stable" effects engine, new color correction tools, more animations and transitions, and more. (LWN reviewed OpenShot in February).
Newsletters and articles Development newsletters from the last week
Bray: Preparing for [Android] Handsets
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![[Benjamin Young]](/images/2011/Benjamin-Young-sm.jpg)