1 Foreach functions
- Overview
- Parameters

1 Foreach functions

Overview

Foreach functions return aggregate values from the history of multiple items. Foreach functions are used in aggregate calculations.

The following foreach functions are supported:

Function	Description
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.

Parameters

Foreach functions support two common parameters - item filter and time period:

foreach_function(item filter,time period)

for example:

avg_foreach(/*/mysql.qps?[group="MySQL Servers"],5m)

Some functions support additional parameters.

Item filter

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:

Syntax example	Description
/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.

Time period

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:

last_foreach(/*/key?[group="host group"])

Time period is not supported with the exists_foreach function.

Additional parameters

A third optional parameter is supported by the bucket_rate_foreach function:

bucket_rate_foreach(item filter,time period,<parameter number>)

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’.