How to set up ‘hourly’ logging with pywws

Introduction

There are two quite different modes of operation with pywws. Traditionally pywws.hourly would be run at regular intervals (usually an hour) from cron. This is suitable for fairly static websites, but more frequent updates can be useful for sites such as Weather Underground (http://www.wunderground.com/). The newer pywws.livelog program runs continuously and can upload data every 48 seconds.

Note that although this document (and the program name) refers to ‘hourly’ logging, you can run pywws.hourly as often or as infrequently as you like, but don’t try to run it more often than double your logging interval. For example, if your logging interval is 10 minutes, don’t run pywws.hourly more often than every 20 minutes.

Getting started

First of all, you need to install pywws and make sure it can get data from your weather station. See How to get started with pywws for details.

Try running pywws.hourly from the command line, with a high level of verbosity so you can see what’s happening. Use the pywws-hourly command to run pywws.hourly:

pywws-hourly -vvv ~/weather/data

(As usual, replace ~/weather/data with your weather data directory.) Within five minutes (assuming you have set a 5 minute logging interval) you should see a ‘live_data new ptr’ message, followed by fetching any new data from the weather station and processing it.

Changed in version 14.04.dev1194: the pywws-hourly command replaced scripts/pywws-hourly.py.

Configuring file locations

Open your weather.ini file with a text editor. You should have a [paths] section similar to the following (where xxx is your user name):

[paths]
work = /tmp/pywws
templates = /home/xxx/weather/templates/
graph_templates = /home/xxx/weather/graph_templates/
local_files = /home/xxx/weather/results/

Edit these to suit your installation and preferences. work is a temporary directory used to store intermediate files, templates is the directory where you keep your text template files, graph_templates is the directory where you keep your graph template files, and local_files is a directory where template output that is not uploaded to your web site is put. Don’t use the pywws example directories for your templates, as they will get over-written when you upgrade pywws.

Copy your text and graph templates to the appropriate directories. You may find some of the examples provided with pywws useful to get started. The pywws-version -v command should show you where the examples are on your computer.

New in version 14.04.dev1194: the pywws-version command.

Configuring periodic tasks

In weather.ini you should have [live], [logged], [hourly], [12 hourly], and [daily] sections similar to the following:

[logged]
services = []
text = []
plot = []

[hourly]
...

These specify what pywws.hourly should do when it is run. Tasks in the [live] and [logged] sections are done when there is new logged data, tasks in the [hourly] section are done every hour, tasks in the [12 hourly] section are done twice daily and tasks in the [daily] section are done once per day.

The services entry is a list of online weather services to upload data to. The plot and text entries are lists of template files for plots and text files to be processed and, optionally, uploaded to your web site. Add the names of your template files and weather services to the appropriate entries, for example:

[logged]
services = ['underground', 'metoffice']
plot = []
text = []

[hourly]
services = []
plot = ['7days.png.xml', '24hrs.png.xml', 'rose_24hrs.png.xml']
text = [('tweet.txt', 'T'), '24hrs.txt', '6hrs.txt', '7days.txt']

[12 hourly]
services = []
plot = []
text = []

[daily]
services = []
plot = ['28days.png.xml']
text = [('forecast.txt', 'T'), 'allmonths.txt']

Note the use of the 'T' flag – this tells pywws to send the template result to Twitter instead of uploading it to your ftp site.

It’s probably best not to add all of these at once. You could start by uploading one file to your web site, then when that’s working add the remaining web site files. You can add Twitter and other services later on. You can test that things are working by removing the [last update] section from status.ini, then running pywws.hourly again:

pywws-hourly -v ~/weather/data

New in version 14.05.dev1211: [cron name] sections. If you need more flexibility in when tasks are done you can use [cron name] sections. See weather.ini - configuration file format for more detail.

Changed in version 13.06_r1015: added the 'T' flag. Previously Twitter templates were listed separately in twitter entries in the [hourly] and other sections.

Changed in version 13.05_r1009: the last update information was previously stored in weather.ini, with last update entries in several sections.

Run as a cron job

Most UNIX/Linux systems have a ‘cron’ daemon that can run programs at certain times, even if you are not logged in to the computer. You edit a ‘crontab’ file to specify what to run and when to run it. For example, to run pywws.hourly every hour, at zero minutes past the hour:

0 * * * *       pywws-hourly /home/xxx/weather/data

This might work, but if it didn’t you probably won’t get any error messages to tell you what went wrong. It’s much better to run a script that runs pywws.hourly and then emails you any output it produces. Here’s the script I use:

#!/bin/sh
#
# weather station logger calling script

export PATH=$PATH:/usr/local/bin

if [ ! -d ~/weather/data/ ]; then
  exit
  fi

log=/var/log/log-weather

pywws-hourly -v ~/weather/data >$log 2>&1

# mail the log file
/home/jim/scripts/email-log.sh $log "weather log"

You’ll need to edit this quite a lot to suit your file locations and so on, but it gives some idea of what to do.


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