mongodb-query-exporter

Export data from MongoDB as prometheus metrics.

This is still in development and a proof of concept for now. It has never been tested on a real application database, just test datasets.

How does it work?

You write an aggregation pipeline, that returns data in the form of

{
    "labels": {
        "labelKey": "labelValue",
        "anotherKey": "anotherValue"
    },
    "value": 1234
}

MongoDB Query Exporter takes these results and exports every result of the pipeline as a prometheus metric.

The pipeline needs to be placed in a JSON file with the following properties.

Property	Data type	Description
type	string	The prometheus metric type to export. Only gauge is supported currently. Support for more types, e.g. histograms are planned.
name	string	The name of the exported prometheus metric
help	string	The description text in the prometheus exposition format. This explains what the metric is supposed to represent.
labels	string[]	A string array of label names. These need to match exactly the labels returned from the aggregation pipeline.
database	string	The MongoDB database to run this aggregation pipeline in.
collection	string	The MongoDB collection in the database to run this aggregation pipeline on.
pipeline	Array of pipeline stages	This is the actual aggregation pipeline. It is executed every scrape. MongoDB Extended JSON is supported. See MongoDB docs for more information on how to write his.

Why would I want that?

You can generate nice dashboards in Grafana, based on your data in Prometheus. Also alerting on stuff happening in the database, but I think this is better handled by the application. It is however an option with this exporter.

Roadmap

• Pipeline validation
• Testing this with real application databases
• Support for other metric types than gauges