TopK Processor Plugin
The TopK processor plugin is a filter designed to get the top series over a
period of time. It can be tweaked to calculate the top metrics via different
aggregation functions.
This processor goes through these steps when processing a batch of metrics:
- Groups measurements in buckets based on their tags and name
- Every N seconds, for each bucket, for each selected field: aggregate all the measurements using a given aggregation function (min, sum, mean, etc) and the field.
- For each computed aggregation: order the buckets by the aggregation, then returns all measurements in the top
K
buckets
Notes:
- The deduplicates metrics
- The name of the measurement is always used when grouping it
- Depending on the amount of metrics on each bucket, more than
K
series may be returned
- If a measurement does not have one of the selected fields, it is dropped from the aggregation
Configuration
# Print all metrics that pass through this filter.
[[processors.topk]]
## How many seconds between aggregations
# period = 10
## How many top buckets to return per field
## Every field specified to aggregate over will return k number of results.
## For example, 1 field with k of 10 will return 10 buckets. While 2 fields
## with k of 3 will return 6 buckets.
# k = 10
## Over which tags should the aggregation be done. Globs can be specified, in
## which case any tag matching the glob will aggregated over. If set to an
## empty list is no aggregation over tags is done
# group_by = ['*']
## The field(s) to aggregate
## Each field defined is used to create an independent aggregation. Each
## aggregation will return k buckets. If a metric does not have a defined
## field the metric will be dropped from the aggregation. Considering using
## the defaults processor plugin to ensure fields are set if required.
# fields = ["value"]
## What aggregation function to use. Options: sum, mean, min, max
# aggregation = "mean"
## Instead of the top k largest metrics, return the bottom k lowest metrics
# bottomk = false
## The plugin assigns each metric a GroupBy tag generated from its name and
## tags. If this setting is different than "" the plugin will add a
## tag (which name will be the value of this setting) to each metric with
## the value of the calculated GroupBy tag. Useful for debugging
# add_groupby_tag = ""
## These settings provide a way to know the position of each metric in
## the top k. The 'add_rank_field' setting allows to specify for which
## fields the position is required. If the list is non empty, then a field
## will be added to each and every metric for each string present in this
## setting. This field will contain the ranking of the group that
## the metric belonged to when aggregated over that field.
## The name of the field will be set to the name of the aggregation field,
## suffixed with the string '_topk_rank'
# add_rank_fields = []
## These settings provide a way to know what values the plugin is generating
## when aggregating metrics. The 'add_aggregate_field' setting allows to
## specify for which fields the final aggregation value is required. If the
## list is non empty, then a field will be added to each every metric for
## each field present in this setting. This field will contain
## the computed aggregation for the group that the metric belonged to when
## aggregated over that field.
## The name of the field will be set to the name of the aggregation field,
## suffixed with the string '_topk_aggregate'
# add_aggregate_fields = []
This processor does not add tags by default. But the setting add_groupby_tag
will add a tag if set to anything other than ""
Fields
This processor does not add fields by default. But the settings
add_rank_fields
and add_aggregation_fields
will add one or several fields if
set to anything other than ""
Example
Below is an example configuration:
[[processors.topk]]
period = 20
k = 3
group_by = ["pid"]
fields = ["cpu_usage"]
Output difference with topk:
< procstat,pid=2088,process_name=Xorg cpu_usage=7.296576662282613 1546473820000000000
< procstat,pid=2780,process_name=ibus-engine-simple cpu_usage=0 1546473820000000000
< procstat,pid=2554,process_name=gsd-sound cpu_usage=0 1546473820000000000
< procstat,pid=3484,process_name=chrome cpu_usage=4.274300361942799 1546473820000000000
< procstat,pid=2467,process_name=gnome-shell-calendar-server cpu_usage=0 1546473820000000000
< procstat,pid=2525,process_name=gvfs-goa-volume-monitor cpu_usage=0 1546473820000000000
< procstat,pid=2888,process_name=gnome-terminal-server cpu_usage=1.0224991500287577 1546473820000000000
< procstat,pid=2454,process_name=ibus-x11 cpu_usage=0 1546473820000000000
< procstat,pid=2564,process_name=gsd-xsettings cpu_usage=0 1546473820000000000
< procstat,pid=12184,process_name=docker cpu_usage=0 1546473820000000000
< procstat,pid=2432,process_name=pulseaudio cpu_usage=9.892858669796528 1546473820000000000
---
> procstat,pid=2432,process_name=pulseaudio cpu_usage=11.486933087507786 1546474120000000000
> procstat,pid=2432,process_name=pulseaudio cpu_usage=10.056503212060552 1546474130000000000
> procstat,pid=23620,process_name=chrome cpu_usage=2.098690278123081 1546474120000000000
> procstat,pid=23620,process_name=chrome cpu_usage=17.52514619948493 1546474130000000000
> procstat,pid=2088,process_name=Xorg cpu_usage=1.6016732172309973 1546474120000000000
> procstat,pid=2088,process_name=Xorg cpu_usage=8.481040931533833 1546474130000000000