Prometheus as a Service for Tsuru

What is Prometheus as a Service?

It is a service created for Tsuru[1]. It creates a prometheus time series database in Tsuru to get all the app's metrics that can be exposed to the user using grafana

Diagram

Workflow

1- The client creates a prometheus instance:

tsuru service-instance-add prometheus my-instance

2- The prometheus instance is created and can be accessed by its url: prometheus-cloud.tsuru.com
3- The app should expose /metrics with the TSDB notation[2]:

api_http_requests_total{method="GET", handler="/path1"} 172
api_http_requests_total{method="GET", handler="/path2"} 774

4- Prometheus instance will gather these metrics exposed by the app by bindind prometheus instance to the app:

tsuru service-instance-bind prometheus my-instance -a my-app

The Project

• First, it was necessary to build a custom prometheus' docker image because we needed to change the custom target to the app by setting an environment var in Tsuru.
• It was built on the prometheus official repo[3]
• So we needed to build this image using 'make' and running 'docker build' with the Dockerfile the repo provides.
• We had to create a shell script(prometheus.sh) and override the default image entrypoint to get the tsuru's enviroment and set it to the default prometheus target
• We've created an api to handle all the calls from tsuru's api to create/remove/update/bind/unbind prometheus' service instances.
• We also had to create the service on tsuru using this doc[4]

Creating an app with metrics exposed

There's an example of app created for testing purposes[5]

Next Steps

1- First we need to use kubernetes to mount a tmpfs to write data into memory. Its writing these data to the disk and its bad. =(
1.1- To accomplish this we must use kubernetes to mount this filer. We use kubernetes through Tsuru or directly.
2- It should support large memory plans to retain more data
3- It should scrap(get) metrics from apps from all units. Today its scraping only the app's endpoint
4- We should finish implementing the status/remove routes for this service. Its only creating the instance and binding it to the app

Learning Tsuru

[1] Tsuru's documentation: https://tsuru.io/
[2] Open TSDB: http://opentsdb.net/
[3] Prometheus' docker image repo: https://github.com/prometheus/prometheus
[4] Creating Tsuru's services: https://docs.tsuru.io/stable/services/build.html
[5] Creating app with metrics: https://github.com/tsuru/prometheus-as-a-service/tree/master/app-demo