grafana-zabbix/docs/sources/reference/direct-db-connection.md

Direct DB Connection

Since version 4.3 Grafana has MySQL data source, Grafana-Zabbix plugin can use it for querying data directly from Zabbix database.

One of the most hard queries for Zabbix API is history queries. For long time intervals history.get returns huge amount of data. In order to display it, plugin should adjust time series resolution by using consolidateBy function. Ultimately, Grafana displays this reduced time series, but that data should be loaded and processed on the client side first. Direct DB Connection solves this two problems by moving consolidation to the server side. Thus, client get ready-to-use dataset which has much smaller size. Data loads faster and client doesn't spend time for data processing.

Also, many users point better performance of direct database queries versus API calls. This caused by several reasons, such as additional PHP layer and additional SQL queries (user permissions checks).

Data Flow

This chart illustrates how plugin uses both Zabbix API and MySQL data source for querying different types of data from Zabbix. MySQL data source is used only for pulling history and trend data instead of history.get and trend.get API calls.

Query structure

Grafana-Zabbix uses queries like this for getting history:

SELECT itemid AS metric, clock AS time_sec, {aggFunc}(value) as value
  FROM {historyTable}
  WHERE itemid IN ({itemids})
    AND clock > {timeFrom} AND clock < {timeTill}
  GROUP BY time_sec DIV {intervalSec}, metric

where {aggFunc} is one of [AVG, MIN, MAX, SUM, COUNT] aggregation function, {historyTable} is a history table, {intervalSec} - consolidation interval in seconds.

When getting trends, plugin additionally queries particular value column (value_avg, value_min or value_max) depends on consolidateBy function value:

SELECT itemid AS metric, clock AS time_sec, {aggFunc}({valueColumn}) as value
  FROM {trendsTable}
  WHERE itemid IN ({itemids})
    AND clock > {timeFrom} AND clock < {timeTill}
  GROUP BY time_sec DIV {intervalSec}, metric

As you can see, plugin uses aggregation by given time interval. This interval is provided by Grafana and depends on the panel with in pixels. Thus, Grafana always gets data in necessary resolution.

Functions usage with Direct DB Connection

There's only one function affecting the backend. This function is consolidateBy. It changes what data comes from the backend. Other functions still work on the client side and transform data that comes from the backend. So you should clearly understand that this is pre-aggregated data (by AVG, MAX, MIN, etc).

For example, say you want to group values by 1 hour interval and max function. If you just apply groupBy(10m, max) function, your result will be wrong, because you would transform data aggregated by default AVG function. You should use consolidateBy(max) coupled with groupBy(10m, max) in order to get a precise result.