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maintain-samplerr-data

This project aim at making the most fine-grained data stored by samplerr available easily without being annoyed with coarse data.

Illustration of an uptime metric before and after using maintain-samplerr-aliases

Running maintain-samplerr-data

Basics

The maintain-samplerr-data command needs 3 arguemnts:

  1. The number of daily indices to maintain;
  2. The number of monthly indices to maintain;
  3. The number of yearly indices to maintain.

These values should match the TTL configured in sampler's archives for purging and rotation. For example, if sampler's archives is configured as

(def archives     [{:tf "YYYY.MM.dd" :step (t/seconds 20) :ttl   (t/days 3) :cfunc cfunc}
                   {:tf "YYYY.MM"    :step (t/minutes 10) :ttl (t/months 2) :cfunc cfunc}
		   {:tf "YYYY"       :step    (t/hours 1) :ttl (t/years 10) :cfunc cfunc}])

the equivalent maintain-samplerr-data call-sequence is:

maintain-samplerr-data 3 2 10

Because maintain-samplerr-data will remove outdated indices and update aliases, the configuration of samplerr's purge ((purge), (periodically-purge)) and rotation (rotate, periodically-rotate) can be removed from your configuration.

Icing

The rotation should happen on day change in Coordinated Universal Time (UTC). Using cron(1) may not be suited because the system time zone may be changed and daylight saving might happen. Relying on systemd's timers is an elegant way of circumventing this issue:

[Unit]
Description=Manage samplerr data

[Timer]
OnCalendar=*-*-* 00:00:20 UTC

[Install]
WantedBy=timers.target

Beware that the current day index must exist for maintain-samplerr-data to work correctly, hense the OnCalendar schedules running the script 20 seconds after the day change to be sure that samplerr has already created the index.