Prometheus Exporter

Implementing a Prometheus exporter with Python. Prometheus follows an HTTP pull model, It scrapes Prometheus metrics from endpoints routinely. Typically the abstraction layer between the application and Prometheus is an exporter, which takes application-formatted metrics and converts them to Prometheus metrics for consumption.

Why exporter?

You might need to write your own exporter if:

• You are using 3rd party software that does not have an existing exporter already
• You want to generate Prometheus metrics from software that you have written

Schema

Example

Let's create a simple http service by the following command:

cd app
uvicorn main:app --reload

Now we have a http server that returns the following stats on localhost:8000/status:

{
    "current_requests": 10,
    "pending_requests": 2,
    "total_uptime": 25.99274135,
    "health": "healthy"
}

Now run the exporter by python exporter/exporter.py and you can see the response on localhost:9877.

ENV

Name	Description	Default
POLLING_INTERVAL_SECONDS	Interval time of polling metrics in exporter	5
EXPORTER_PORT	HTTP port of exporter	9877
TARGET_HOST	Address of target	localhost
TARGET_PORT	HTTP port of target	8000
TARGET_METRICS	Path of metrics	status

Response

Exporter provides the following output, which are prometheus metrics.

# HELP python_gc_objects_collected_total Objects collected during gc
# TYPE python_gc_objects_collected_total counter
python_gc_objects_collected_total{generation="0"} 626.0
python_gc_objects_collected_total{generation="1"} 33.0
python_gc_objects_collected_total{generation="2"} 0.0
# HELP python_gc_objects_uncollectable_total Uncollectable object found during GC
# TYPE python_gc_objects_uncollectable_total counter
python_gc_objects_uncollectable_total{generation="0"} 0.0
python_gc_objects_uncollectable_total{generation="1"} 0.0
python_gc_objects_uncollectable_total{generation="2"} 0.0
# HELP python_gc_collections_total Number of times this generation was collected
# TYPE python_gc_collections_total counter
python_gc_collections_total{generation="0"} 54.0
python_gc_collections_total{generation="1"} 4.0
python_gc_collections_total{generation="2"} 0.0
# HELP python_info Python platform information
# TYPE python_info gauge
python_info{implementation="CPython",major="3",minor="10",patchlevel="0",version="3.10.0"} 1.0
# HELP app_requests_current Current requests
# TYPE app_requests_current gauge
app_requests_current 4.0
# HELP app_requests_pending Pending requests
# TYPE app_requests_pending gauge
app_requests_pending 0.0
# HELP app_uptime Uptime
# TYPE app_uptime gauge
app_uptime 104.914734
# HELP app_health Health
# TYPE app_health gauge
app_health{app_health="healthy"} 1.0
app_health{app_health="unhealthy"} 0.0

Docker

Use the following command to execute the project in Docker:

docker compose up -d

Now go to localhost:9090 to get the app metrics.

Resources

• trstringer.com
• prometheus.io