C[omp]ute

Welcome to my blog, which was once a mailing list of the same name and is still generated by mail. Please reply via the "comment" links.

Always interested in offers/projects/new ideas. Eclectic experience in fields like: numerical computing; Python web; Java enterprise; functional languages; GPGPU; SQL databases; etc. Based in Santiago, Chile; telecommute worldwide. CV; email.

Personal Projects

Lepl parser for Python.

Colorless Green.

Photography around Santiago.

SVG experiment.

Professional Portfolio

Calibration of seismometers.

Data access via web services.

Cache rewrite.

Extending OpenSSH.

Last 100 entries

Re: Python's sad, unimaginative Enum; Some explanation; Printing binary trees sideways; About "Python's sad, unimaginative Enum"; Atoms in python; Some good feedback here; Frustration Understood; I agree with you #nt; What would be imaginative?; Re: Enum; this is fucking useless; Enum; Python's sad, unimaginative Enum; Possible Fix; Work, Exhaustion, Vacation; VirtualBox with Centos 6.3 to 6.4, client; Matasano - Programming Lessons Learned; PDF to HTML; Alternate Substitution; Why RSA Works; Trigger; Dreaming of Death; Example: Tracing; Using Coroutines In Protocol Simulations; Python 3.3 Only; Pure Python SHA1 and MD4 Implementations; Ubuntu on VirtualBox; Starting TOR as a service on OpenSuse 12.3; 1001 Albums; Using fail2ban on OpenSuse 12.3; PPPoE on OpenSuse 12.3; Good Article on Unified Physics; It's Police (Carabineros); Linux Software for Listening to and Exploring Music; Android is Pretty Bad; Lucky Number; 3D Printing for Casting; Cover Art for MPDroid; Who'd a thought the French were so bigoted?; PS Input Signal; Small Problem with Roksan K2 Amp; Roksan K2 Amp + ATC SCM7 Speakers; Do What Makes Sense; Re: Arguing About Tests, Still; Arguing About Tests, Still; Images; Good Article on NY Drummers; Related Bug Report; Getting Python 3.3 and Virtualenv Working in OpenSuse 12.3; How I Am; Awesome video about digital audio; The Difference Between Dimensional and Normalized Databases; The rise of the new Chinese bogeyman; Updated Syntax; Very First Steps to C-ORM; The Ideal User Interface For Music Exploration; Can The Republicans Be Saved?; Rate Limiting Calls to EchoNest; Mods to Cache; Comparing UYKFG and UYKFD/E/F; Someone Else is Concerned; EchoNest-based Playlist Generator for MPD; Example Voting Results; A Heavyweight Python Cache; Identifying Artists with EchoNest; Notes on Pregalex / Pregabalina / Lyrica; The Neil Cowley Trio; Drake - Make for Data; A Reliable Python Web Service; Useful Python Date/Time Library?; Need to Sleep, But this is Good; Command Line Set Difference; Little Details...; Linux Command Line Tricks; AutoTools Tutorial; Hangman Tactics; A Tor Proxy Embedded In A Web Page; Tree (Nested Dicts) in Python; Sleeping at Parties; I Know Someone Who Hurts Other People; Light and Tea; Description of the LCS35 Time Capsule Crypto-Puzzle; Re: I can relate to that ...; I can relate to that ...; Re: It's 2012 Why Does My IDE Suck?; My Own Alternative Medicine; Nice explanation of SVM; Why and How Writing Crypto is Hard; Re: It's 2012 Why Does My IDE Suck?; Incremental Regular Expressions; BBC Map Confused at Pole; Social Media: Ground Zero in the Culture War; My Visit to the Psycho Doc; Learning Modern 3D Graphics Programming; Hope you got some crackers to go with the cheese; Re: But how easy would it be ...; But how easy would it be ...; Powerline Freq Fingerprinting of Audio; The Folly of Scientism; Cheese - Because You're Going to Die Anyway; Another GPU Success - PyCUDA, Cross-Correlations

Caching In Web Apps

From: andrew cooke <andrew@...>

Date: Tue, 2 Oct 2012 07:51:17 -0300

Making a note here as this is too long to read right now, but looks
interesting.

http://martin.kleppmann.com/2012/10/01/rethinking-caching-in-web-apps.html

Also http://news.ycombinator.com/item?id=4599685

Andrew

Dynamic vs static generation

From: Daniel Yokomizo <daniel.yokomizo@...>

Date: Tue, 2 Oct 2012 13:02:30 -0300

Hi Andrew,

IME working with mostly read scenarios (e.g. blogs) it's better to
serve everything from a static webserver and generate the html on
updates. So every time you edit a post, add a comment, etc., some
piece of code (perhaps asynchronously) regenerate the associated html
files. For some scenarios this technique adds too much overhead (e.g.
you can't precompute every possible search results page) but you may
do a mixed scenario (e.g. precompute the item elements in the results
page and do the search using lucene over them, just assembling the
pieces and writing the directly on the response stream). This avoids
the entire cache invalidation/expiration issue, but you need to write
some tricky code to atomically replace the files in the filesystem (or
assume some read inconsistencies), there are many interesting choices
in this, some add a little logic to Apache, but overall the system
becomes way faster.

Daniel Yokomizo.

Re: Dynamic vs static generation

From: andrew cooke <andrew@...>

Date: Wed, 3 Oct 2012 18:46:00 -0300

Yes, I agree; that's how this blog works (email comes in and is used to
generate HTML via some simple Python; that's then pushed out to the web
server).  It's very efficient, but a pig to edit - hence all the typos that
never get fixed :o)

But I think the post I linked to is aimed at more dynamic processes, where
that's simply not possible.

I'm actually working on a similar problem at the moment.  A client has a
service that is rather slow.  So they want a facade that does three things:

 - It works as a cache, so that distributed clients, requesting the same
   data, don't hit the service multiple times.

 - It provides snapshotting / versioning / generationed data so that a
   client, as it makes several requests in a "transaction", sees consistent
   data.

 - It coallesces multiple "thin" calls into a single "fat" call to the API.

To do this I am using memcache with generational keys and two new components.

One component is a client-side library that reads from memcache where
possible.  If the data are not in memcache then the library calls the
underlying service.  The other component is a "primer".  Each time the service
starts a new generation the primer pre-loads memcache, before signalling the
client libraries to switch to a new prefix.

In terms of that work, the post I linked to is making a "programmable primer".
Which is very cool, but outside the scope of my work (in my case I have the
luxury of being able to call the service for unpredicted requests; the primer
only has to cover the common cases).

[Reading the above I haven't explained how coallescing works - the primer
pushes "fat" data; the client libraries load "fat" data and contain teh logic
to serve "thin" requests from that.]

Andrew

Comment on this post