# Prometheus sample app

This Prometheus sample app generates all 4 Prometheus metric types (counter, gauge, histogram, summary) and exposes them at the `/metrics` endpoint

At the same time, the generated metrics are also exposed at the `/expected_metrics` endpoint in the Prometheus remote write format

A health check endpoint also exists at `/`

The following is a list of optional environment variables for configuration:
* `LISTEN_ADDRESS`: (default = `0.0.0.0:8080`)this defines the address and port that the sample app is exposed to. This is primarily to conform with the test framework requirements.
* `INSTANCE_ID`: a unique identifier for a batch of metrics from 1 instance of a sample app. Every metric name from a sample app instance will be prefixed by `testINSTANCE_ID_` if specified, else the prefix would be `test_`
* `METRICS_LOAD`: (default=1) the amount of each type of metric to generate. The same amount of metrics is always generated per metric type.

Steps for running locally:
```bash
docker build . -t prometheus-sample-app
docker run -it -e INSTANCE_ID=test1234 \
-e LISTEN_ADDRESS=0.0.0.0:8080 \
-p 8080:8080 prometheus-sample-app
curl localhost:8080/metrics
```

Note that the port in LISTEN_ADDRESS must match the the second port specified in the port-forward

More functioning examples:

```bash
docker build . -t prometheus-sample-app
docker run -it -e INSTANCE_ID=test1234 \
-e LISTEN_ADDRESS=0.0.0.0:8080 \
-p 9001:8080 prometheus-sample-app
curl localhost:9001/metrics
```

```bash
docker build . -t prometheus-sample-app
docker run -it -e LISTEN_ADDRESS=0.0.0.0:8080 \
-e METRICS_LOAD=10 \
-p 9001:8080 prometheus-sample-app
curl localhost:9001/metrics
```