Nix implementation of https://github.com/miku/lpug-luigi, re-using the scripts from there.

It needs a working install of Nix (not necessarily NixOS).

The task is to generate various top-lists from some artificial data. As luigi is coming from spotify, the demo is creating a data-file that contains the played audio titles of a month. From this the played titles of one day should be extracted. And then a list containing the five most played artists for a day should be found. And the most played artists for a range of days.

All these steps can be implemented as small jobs with interdependencies and show-case a build-system or job-scheduler. So here I will show how to divide and schedule these jobs with nix.

rawplays.nix and scripts/makesample.py create the data file plays.ldj. The nix-expression is rather simple, just scripts/ as the source and a build- and an install-phase. The arguments for this nix-expression are just the stdenv for the build environment and the pkgs to depend on python 3.4.

To extract the played titles for one day, dailyplays.nix is running scripts/dailyplays.py. The nix expressions has an additional parameter, the date (as full 'YYYY-MM-DD'-string) is used on the name of the derivation and passed to the python scripts to extract the data.

This expression has an additional build-input: it depends both on python 3.4 and on the rawplays.nix.

With the date as parameter, this expression produces different output depending on the input and shows that the dependency tracking of nix works.

tbd.

tbd.

tbd.

Inside this folder run nix-build. This will start with generating the data, evaluate all the dependencies and in the end produce a link result/:

$> ls result -la
lrwxrwxrwx 1 arnold arnold 57 Nov 21 17:30 result -> /nix/store/xgb1wz44wjrm273vka8w3wfxw0c4psai-nixtopartists

which points to the concrete 'package' produced by these expressions. It contains:

$> ls result/ -la
total 316
dr-xr-xr-x   2 arnold arnold   4096 Jan  1  1970 .
drwxrwxr-t 534 arnold nixbld 303104 Nov 21 17:30 ..
-r--r--r--   1 arnold arnold     86 Jan  1  1970 topartists_firsthalf.ldj
-r--r--r--   1 arnold arnold     84 Jan  1  1970 topartists_firstweek.ldj
-r--r--r--   1 arnold arnold     84 Jan  1  1970 topartists_lastweek.ldj