Foreach functions return aggregate values from the history of multiple items. Foreach functions are used in aggregate calculations.
The following foreach functions are supported:
|avg_foreach||Returns average values|
|bucket_rate_foreach||Returns pairs (bucket upper bound, rate value) suitable for use in the histogram_quantile() function, where "bucket upper bound" is the value of item key parameter defined by the <parameter number> parameter.|
|count_foreach||Returns the number of values|
|exists_foreach||Returns the number of currently enabled items|
|last_foreach||Returns last values|
|max_foreach||Returns maximum values|
|min_foreach||Returns minimum values|
|sum_foreach||Returns the sum of values|
Foreach functions return an array of values - one for each item. Items are selected by using filters in the first parameter.
See aggregate calculations for more details on using foreach functions.
Foreach functions support two common parameters - item filter and time period:
Some functions support additional parameters.
The first parameter allows to filter the items we are interested in. A complex filter may be used, referencing the item key, host group and tags, as illustrated by the examples:
|/host/key[abc,*]||Matches similar items on this host.|
|/*/key||Matches the same item of any host.|
|/*/key?[group="ABC" and tag="tagname:value"]||Matches the same item of any host from the ABC group having 'tagname:value' tags.|
|/*/key[a,*,c]?[(group="ABC" and tag="Tag1") or (group="DEF" and (tag="Tag2" or tag="Tag3:value"))]||Matches similar items of any host from the ABC or DEF group with the respective tags.|
All referenced items must exist and collect data. Only enabled items on enabled hosts are included in the calculations.
If the item key of a referenced item is changed, the filter must be updated manually.
Specifying a parent host group includes the parent group and all nested host groups with their items.
The second parameter allows to specify the time period for aggregation. The time period can only be expressed as time, the amount of values (prefixed with #) is not supported.
Supported unit symbols can be used in this parameter for convenience, for example '5m' (five minutes) instead of '300s' (300 seconds) or '1d' (one day) instead of '86400' (86400 seconds).
Time period is ignored by the server if passed with the last_foreach function and can thus be omitted:
Time period is not supported with the exists_foreach function.
A third optional parameter is supported by the bucket_rate_foreach function:
where <parameter number> is the position of the "bucket" value in the item key. For example, if the "bucket" value in myItem[aaa,0.2] is '0.2', then its position is 2.
The default value of <parameter number> is '1'.