ClickHouse/docs/en/table_engines/graphitemergetree.md

GraphiteMergeTree

This engine is designed for rollup (thinning and aggregating/averaging) Graphite data. It may be helpful to developers who want to use ClickHouse as a data store for Graphite.

Graphite stores full data in ClickHouse, and data can be retrieved in the following ways:

• Without thinning.

  Uses the MergeTree engine.

• With thinning.

  Using the GraphiteMergeTree engine.

The engine inherits properties from MergeTree. The settings for thinning data are defined by the graphite_rollup parameter in the server configuration.

Using the engine

The Graphite data table must contain the following fields at minimum:

• Path – The metric name (Graphite sensor).
• Time – The time for measuring the metric.
• Value – The value of the metric at the time set in Time.
• Version – Determines which value of the metric with the same Path and Time will remain in the database.

Rollup pattern:

pattern
    regexp
    function
    age -> precision
    ...
pattern
    ...
default
    function
       age -> precision
    ...

When processing a record, ClickHouse will check the rules in the patternclause. If the metric name matches the regexp, the rules from pattern are applied; otherwise, the rules from default are used.

Fields in the pattern.

• age – The minimum age of the data in seconds.
• function – The name of the aggregating function to apply to data whose age falls within the range [age, age + precision].
• precision– How precisely to define the age of the data in seconds.
• regexp– A pattern for the metric name.

Example of settings:

<graphite_rollup>
    <pattern>
        <regexp>click_cost</regexp>
        <function>any</function>
        <retention>
            <age>0</age>
            <precision>5</precision>
        </retention>
        <retention>
            <age>86400</age>
            <precision>60</precision>
        </retention>
    </pattern>
    <default>
        <function>max</function>
        <retention>
            <age>0</age>
            <precision>60</precision>
        </retention>
        <retention>
            <age>3600</age>
            <precision>300</precision>
        </retention>
        <retention>
            <age>86400</age>
            <precision>3600</precision>
        </retention>
    </default>
</graphite_rollup>