Empty values and commented lines will result in the default value, if any, being selected. If a setting is set, but not used by a given filtertype, it may generate an error.

This filtertype will iterate over the actionable list and match indices based on their age. They will remain in, or be removed from the actionable list based on the value of exclude.

Age calculationedit

units are calculated as follows:

Unit Seconds Note



One second



Calculated as 60 seconds



Calculated as 60 minutes (60*60)



Calculated as 24 hours (24*60*60)



Calculated as 7 days (7*24*60*60)



Calculated as 30 days (30*24*60*60)



Calculated as 365 days (365*24*60*60)

All calculations are in epoch time, which is the number of seconds elapsed since 1 Jan 1970. If no epoch is specified in the filter, then the current epoch time-which is always UTC-is used as the basis for comparison.

As epoch time is always increasing, lower numbers indicate dates and times in the past.

When age is calculated, unit is multiplied by unit_count to obtain a total number of seconds to use as a differential.

For example, if the time at execution were 2017-04-07T15:00:00Z (UTC), then the epoch timestamp would be 1491577200. If I had an age filter defined like this:

 - filtertype: age
   source: creation_date
   direction: older
   unit: days
   unit_count: 3

The time differential would be 3*24*60*60 seconds, which is 259200 seconds. Subtracting this value from 1491577200 gives us 1491318000, which is 2017-04-04T15:00:00Z (UTC), exactly 3 days in the past. The creation_date of indices or snapshots is compared to this timestamp. If it is older, it stays in the actionable list, otherwise it is removed from the actionable list.

age filter vs. period filter

The time differential means of calculation can lead to frustration.

Setting unit to months, and unit_count to 3 will actually calculate the age as 3*30*24*60*60, which is 7776000 seconds. This may be a big deal. If the date is 2017-01-01T02:30:00Z, or 1483237800 in epoch time. Subtracting 7776000 seconds makes 1475461800, which is 2016-10-03T02:30:00Z. If you were to try to match monthly indices, index-2016.12, index-2016.11, 2016.10, 2016.09, etc., then both index-2016.09 and index-2016.10 will be older than the cutoff date. This may result in unintended behavior.

Another way this can cause issues is with weeks. Weekly indices may start on Sunday or Monday. The age filter’s calculation doesn’t take this into consideration, and merely tests the difference between execution time and the timestamp on the index (from any source).

Another means of selecting indices and snapshots is the period filter, which is perhaps a better choice for selecting weeks and months as it compensates for these differences.

name-based agesedit

Using name as the source tells Curator to look for a timestring within the index or snapshot name, and convert that into an epoch timestamp (epoch implies UTC).

 - filtertype: age
   source: name
   direction: older
   timestring: '%Y.%m.%d'
   unit: days
   unit_count: 3

A word about regular expression matching with timestrings

Timestrings are parsed from strftime patterns, like %Y.%m.%d, into regular expressions. For example, %Y is 4 digits, so the regular expression for that looks like \d{4}, and %m is 2 digits, so the regular expression is \d{2}.

What this means is that a simple timestring to match year and month, %Y.%m will result in a regular expression like this: ^.*\d{4}\.\d{2}.*$. This pattern will match any 4 digits, followed by a period ., followed by 2 digits, occurring anywhere in the index name. This means it will match monthly indices, like index-2016.12, as well as daily indices, like index-2017.04.01, which may not be the intended behavior.

To compensate for this, when selecting indices matching a subset of another pattern, use a second filter with exclude set to True

- filtertype: pattern
 kind: timestring
 value: '%Y.%m'
- filtertype: pattern
 kind: timestring
 value: '%Y.%m.%d'
 exclude: True

This will prevent the %Y.%m pattern from matching the %Y.%m part of the daily indices.

This applies whether using timestring as a mere pattern match, or as part of date calculations.

creation_date-based agesedit

creation_date extracts the epoch time of index or snapshot creation.

 - filtertype: age
   source: creation_date
   direction: older
   unit: days
   unit_count: 3

field_stats-based agesedit

source can only be field_stats when filtering indices.

field_stats uses the Field Stats API to calculate either the min_value or the max_value of the field as the stats_result, and then use that value for age comparisons.

field must be of type date in Elasticsearch.

 - filtertype: age
   source: field_stats
   direction: older
   unit: days
   unit_count: 3
   field: '@timestamp'
   stats_result: min_value

Required settingsedit

Dependent settingsedit

  • timestring (required if source is name)
  • field (required if source is field_stats) [Indices only]
  • stats_result (only used if source is field_stats) [Indices only]

Optional settingsedit