Use Prometheus

Last updated 23th August, 2019

Objective

Prometheus is another open-source monitoring system that takes its root as a clone of Borgmon from Google. In this guide, you will learn how to use Prometheus protocol with Metrics.

Requirements

• a valid OVH Metrics account.

Instructions

Compatibility

How to Push data

Prometheus is using the pull-based approach to gather metrics. We developed an open-source tool called Beamium in order to scrape metrics in Prometheus format. Please see the dedicated guide to use Beamium.

In case you need to push, we also support the PushGateway with the following URL:

https://metrics:[WRITE_TOKEN]@prometheus.[region].metrics.ovh.net

How to query data with PromQL

PromQL is a Query Language for Prometheus. It offers basic query capabilities, like OpenTSDB, plus a way to use operators between two series. All query documentation is available here

For example to retrieve your data, you can simply execute the following HTTP request using cURL.

$ curl 'https://u:READ_TOKEN@prometheus.REGION.metrics.ovh.net/api/v1/query_range?query=SERIES_NAME\{LABEL0_KEY="LABEL0_VALUE",LABEL1_KEY="LABEL1_VALUE"\}&start=1533127072.115&end=1533127472.115&step=2m'

where:

• READ_TOKEN is your read token available on your OVH Metrics account
• SERIES_NAME is the series name to retrieve. It can be for example os.cpu
• LABEL0_KEY and LABEL1_KEY are specific labels that the series must have with
• LABEL0_KEY values is LABEL0_VALUE and LABEL1_KEY value is LABEL1_VALUE.

PromQL valid operators

Binary operators

A few binary arithmetic operators exists in PromQL and can be used on the Metrics platform:

Modulo (%) and exponentiation (^) are not yet supported accross several metrics. They both can still be applied between metrics and scalar value.

For all operators, the same precedance applies than in promQL.

Vector matching

PromQL has it's own method to manage how to match left and right entry of an operator. The valid vector matching on the Metrics platform are:

Only one keyword between on and ignoring can be applied to an operator. The same applies to group_left or group_right

Aggregation operators

The valid aggregation operators on the Metrics platform are:

The aggregation operator count_values expects a label string key for each new metrics created (per different values).

Aggregation operators clauses

PromQL has it's own method to manage how to match left and right entry of an operator. The valid vector matching on the Metrics platform are:

Only one keyword between without and by can be applied to an aggregation operator.

Supported PromQL functions

The valid promQL functions on the Metrics platform are:

PromQL examples queries

Here, you will find two valid queries examples.

For example this request will add 2 os.cpu series from host 1 and host 2 (we just replace the + character per it's URL encoded value %2B).

$ curl 'https://u:READ_TOKEN@prometheus.REGION.metrics.ovh.net/api/v1/query_range?query=os.cpu\{host="1",cpu="1"\}%2Bos.cpu\{host="2",cpu="2"\}&start=1533127072.115&end=1533127472.115&step=2m'

Our second example here will compute the rate of the os.cpu metric for the host 1 and all cpu.

$ curl 'https://u:READ_TOKEN@prometheus.REGION.metrics.ovh.net/api/v1/query_range?query=sum(rate(os.cpu\{host="1"\}\[1m\]))&start=1533127072.115&end=1533127472.115&step=2m'

To select a Time-series stored in Metrics with unvalid Prometheus character as "-" you can also use the PromQL {__name__="http-requests-total"} syntax as Time series matcher expression. Matchers other than = (!=, =~, !~) may also be used.

Go further

• Documentation: Guides
• Vizualize your data: https://grafana.metrics.ovh.net/login
• Community hub: https://community.ovh.com
• Create an account: Try it free!

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