Cloud Monitoring metrics as Managed Service for Prometheus
Prometheus is an open-source systems monitoring and alerting toolkit. Prometheus collects and stores its metrics as time series data, such as metrics information is stored with the timestamp at which it was record, alongside optional key-value pairs. Prometheus provides a functional query language called PromQL (Prometheus Query Language) which lets the user select and aggregate time series data in real time.
According to a recent CNCF survey, 86% of the cloud-native community reports that, they use Prometheus for observability. As Prometheus becomes more of a standard, an increasing number of developers are becoming fluent in PromQL. PromQL is a powerful, flexible, and expressive query language but its only able to query Prometheus time series data. Other sources of telemetry, such as metrics generated from logs, remain isolated in separate products and might require developers to learn new query tools to access them.
Prometheus metrics alone aren’t enough to get a single pane of glass view of your Cloud footprint. Cloud Monitoring provides over 1,000 free metrics that let you monitor and alert on your usage of Google Cloud services, also all your metrics are stored together and are queryable together. Metrics in Cloud Monitoring are automatically generated when you use Google Cloud services at no additional cost to you.
This blog from the Google Cloud SRE & DevOps blogs explain a step-by-step guide on how to write PromQL for Google Cloud metrics and how you can query Cloud Monitoring metrics with PromQL by using the interactive query page in Cloud Console.
Read more at 
Google Cloud Blog
