A relative period will be reckoned relative to execution time, unless an epoch timestamp is provided. Reckoning is truncated to the most recent whole unit, where a unit can be one of seconds, minutes, hours, days, weeks, months, or years. For example, if I selected hours as my unit, and I began execution at 02:35, then the point of reckoning would be 02:00. This is relatively easy with days, months, and years, but slightly more complicated with weeks. Some users may wish to reckon weeks by the ISO standard, which starts weeks on Monday. Others may wish to use Sunday as the first day of the week. Both are acceptable options with the period filter. The default behavior for weeks is to have Sunday be the start of the week. This can be overridden with week_starts_on as follows:

 - filtertype: period
   period_type: relative
   source: name
   range_from: -1
   range_to: -1
   timestring: '%Y.%m.%d'
   unit: weeks
   week_starts_on: monday

range_from and range_to are counters of whole units. A negative number indicates a whole unit in the past, while a positive number indicates a whole unit in the future. A 0 indicates the present unit. With such a timeline mentality, it is relatively easy to create a date range that will meet your needs.

If the time of execution time is 2017-04-03T13:45:23.831, this table will help you figure out what the previous whole unit, current unit, and next whole unit will be, in ISO8601 format.

Ranges must be from older dates to newer dates, or smaller numbers (including negative numbers) to larger numbers or Curator will return an exception.

An example period filter demonstrating how to select all daily indices by timestring found in the index name from last month might look like this:

 - filtertype: period
   period_type: relative
   source: name
   range_from: -1
   range_to: -1
   timestring: '%Y.%m.%d'
   unit: months

Having range_from and range_to both be the same value will mean that only that whole unit will be selected, in this case, a month.

 - filtertype: period
   period_type: absolute
   source: name
   timestring: '%Y.%m.%d'
   unit: months
   date_from: 2017.01
   date_from_format: '%Y.%m'
   date_to: 2017.01
   date_to_format: '%Y.%m'

In addition to relative periods, you can define absolute periods. These are defined as the period between the date_from and the date_to. For example, if date_from and date_to are both 2017.01, and unit is months, all indices with a name, creation_date, or stats_result (depending on the value of source) within the month of January 2017 will match.

The date_from is used to establish the beginning of the time period, regardless of whether date_from_format is in hours, and the indices you are trying to filter are in weeks or months. The format and date of date_from will simply set the beginning of the time period.

The date_to, date_to_format, and unit work in conjunction to select the end date. For example, if my date_to were 2017.04, and date_to_format is %Y.%m to properly parse that date, it would follow that unit would be months.

Specific date ranges can be captured with up to whole second resolution:

 - filtertype: period
   period_type: absolute
   source: name
   timestring: '%Y.%m.%d.%H'
   unit: seconds
   date_from: 2017-01-01T00:00:00
   date_from_format: '%Y-%m-%dT%H:%M:%S'
   date_to: 2017-01-01T12:34:56
   date_to_format: '%Y-%m-%dT%H:%M:%S'

This example will capture indices with an hourly timestamp in their name that fit between the date_from and date_to timestamps.

The identifiers that Curator currently recognizes include: