Refactoring Tornado Coroutines
[Source] Sometimes writing callback-style asynchronous code with Tornado is a pain. But the real hurt comes when you want to refactor your async code into reusable subroutines. Tornado's coroutines make refactoring easy. I'll explain the rules. (This article updates my old "Refactoring Tornado Code With gen.engine". The updated code here demonstrates the current syntax for Tornado 3 and Motor 0.3.
Analyzing Python C Extensions With CPyChecker
Writing C extension modules for Python is tricky: the programmer must manually manage reference counts and the exception state, in addition to the usual dangers of coding in C. CPyChecker is a new static checker being developed by David Malcom to rescue us from our mistakes. I was introduced to it at PyCon when Malcolm gave his Death By A Thousand Leaks talk. The tool is work in progress, buggy an
Introducing Motor, an asynchronous MongoDB driver for Python and Tornado
Tornado is a popular asynchronous Python web server, and MongoDB a widely used non-relational database. Alas, to connect to MongoDB from a Tornado app requires a tradeoff: You can either use PyMongo and give up the advantages of an async web server, or use AsyncMongo, which is non-blocking but lacks key features. I decided to fill the gap by writing a new async driver called Motor (for "MOngo + TO
An Event synchronization primitive for Ruby
I helped some Ruby friends implement a rendezvous (aka a barrier). I'm accustomed to using an Event to implement a rendezvous in Python but Ruby doesn't have Events, only Mutexes and ConditionVariables. That's fine, Python's Event is implemented in terms of a mutex and a condition, so it's easy to make an Event in Ruby: class Event def initialize @lock = Mutex.new @cond = ConditionVariable.new @fl
MongoDB Full Text Search
Wikimedia commons Yesterday we released the latest unstable version of MongoDB; the headline feature is basic full-text search. You can read all about MongoDB's full text search in the release notes. This blog had been using a really terrible method for search, involving regular expressions, a full collection scan for every search, and no ranking of results by relevance. I wanted to replace all th
Python's += Is Weird, Part II
I wrote the other day about two things I think are weird about Python's += operator. In the comments, famed Twisted hacker Jean-Paul Calderone showed me something far, far weirder. This post is a record of me playing around and trying to understand it. To begin let's review what we know. Tuples are immutable in Python, so you can't increment a member of a tuple: >>> x = (0,) >>> x (0,) >>> x[0] +=
Toro: synchronization primitives for Tornado coroutines
I took a break from Motor to make a new package "Toro": queues, semaphores, locks, and so on for Tornado coroutines. (The name "Toro" is from "Tornado" and "Coro".) Why would you need something like this, especially since Tornado apps are usually single-threaded? Well, with Tornado's gen module you can turn Python generators into full-featured coroutines, but coordination among these coroutines is
Optimizing MongoDB Compound Indexes
Courtesy The Beinecke Library How do you create the best index for a complex MongoDB query? I'll present a method specifically for queries that combine equality tests, sorts, and range filters, and demonstrate the best order for fields in a compound index. We'll look at the explain() output to see exactly how well it performs, and we'll see how the MongoDB query-optimizer selects an index. Content
Python's Thread Locals Are Weird
The Weirdness What do you think this script prints?: import thread, threading, sys class Weeper(object): def del(self): sys.stdout.write('oh cruel world %s\n' % thread.get_ident()) local = threading.local() def target(): local.weeper = Weeper() t = threading.Thread(target=target) t.start() t.join() sys.stdout.write('done %s\n' % thread.get_ident()) getattr(local, 'whatever', None)
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Paper review: Paxos vs Raft
Current and Future Tools for Interactive TLA+
Efficiently Paging Geospatial Data With MongoDB
Real-time Profiling a MongoDB Sharded Cluster
Wasp's Nest: The Read-Copy-Update Pattern In Python
A Curious Concurrency Case
Knowing When A Python Thread Has Died
Python's += Is Weird