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TODO.md

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TODO

  • timing of SQL queries should be chosen to keep the load on the SQL server as low as possible

    • retain and re-use already downloaded data locally (in memory or in file)
    • execute queries on a semi-random cycle to reduce chance of simultaneous queries from different hosts
    • keep queries small; only query for the required period.

  • graphing

    1. GNUplot is faster; matplotlib is more challenging
    2. matplotlib is slow and resource hungry
    3. GNUplot is not re-iterable. matplotlib is?

Timing of graphs

  • Hourly graph from now() to now() - 70 minutes; resolution: 1 minute (60s)
  • Daily graph from now() - 70 minutes to now() - 30 hours(*); resolution: 30 minutes (1800s)
  • Weekly graph from now() - 24 hours to now() - 8 days(**); resolution: 4 hours (14400s)
  • Yearly graph from now() - 8 days to now() - 370 days(***) resolution: 1 day (or 1 week depending on resulting load on the server)

(*) = rounded to MOD :30 minutes
(**) = rounded to MOD 4 hours
(***) = rounded to start of day (00:00)

As a result of the chosen resolution, the queries can be timed appropriately:

  • Data for the hourly graph every 1 minute
  • Data for the daily graph every 30 minutes
  • Data for the weekly graph every 4 hours
  • Data for the yearly graph once every day

Also, all queries need to be performed at start-up. And it may be considered to have the daemons add the new data to the local store, thus reducing/eliminating the need for queries. That would also mean the need to construct a local data store. This could be achieved using rrdtool (which would add an addtional option for graphing) or a local database (SQL) or a local flat-textfile (CSV) The use of rrdtool on Raspberry Pi is less appropriate as it may reduce the SD-card's lifetime. However, if the RRD database is stored on tmpfss this should not be an issue.

GNUplot: http://gnuplot.sourceforge.net/demo/fillbetween.html