simple-node-exporter

Simple Node Exporter

A simple node exporter for prometheus metrics. It provides a subset of https://github.com/prometheus/node_exporter but smaller and without the necessity to mount the whole filesystem into the container.

General facts

Why I start this project?

If you found this repo you will properly familiar with prometheus and the node exporter which is an official tool to grab a lot of metrics from a server/node. My problem was that the original node exporter needs access to the whole file system and I want to have a tool with minimized dependencies, which can run on any linux server with installed docker and no requirement to mount any files from the host system into the docker container.

What was the goal of the project?

Create a simple tool which can be used at every of my linux servers with ease. I use prometheus and grafana to monitor them so a /metrics-endpoint for prometheus is the only thing I need.

What exactly does the tool?

This tool uses gopsutil and the prometheus golang client to fetch basic information about cpu, memory and disk and provide them as prometheus metrics.

Features

Webserver

The simple-node-exporter only has one endpoint /metrics and provides the following metrics:

You can also add any other metric. Have a look at the following example to get an idea how the configuration should look like. The json or yaml must be placed inside the directory additional/

Example-file:

{
    "name": "node_apt_update_count",
    "type": "gauge",
    "help": "number of updates of apt",
    "labels": ["type"],
    "metrics": [
        {
            "labelValues": ["normal"],
            "value": 5
        },
        {
            "labelValues": ["security"],
            "value": 0
        }
    ]
}

name: node_apt_update_count
type: gauge
help: number of updates of apt
labels: [ type ]
metrics:
    -   labelValues: [ normal ]
        value: 5
    -   labelValues: [ security ]
        value: 0

This json/yaml will create the following metrics:

# HELP node_node_apt_update_count number of updates of apt
# TYPE node_node_apt_update_count gauge
node_apt_update_count{hostname="myhost",type="normal"} 5
node_apt_update_count{hostname="myhost",type="security"} 0

Please also have a look at the examples for generating metric-files via script.

Single Execution

If you don't like or don't need a webserver to run on your server you can use the flag -print-only.

./simple-node-exporter -print-only

This will print out the data which is normally provided via /metrics endpoint to stdout. You can pipe the output into any file to e.g. use the data in other scripts or provide the data by a webserver which is already running on your server. This can be useful on managed servers/webhosters where you are not able to install software or block additional ports.

If you do not want any error to be printed you can use the flag -suppress-errors when starting the program.

Example

Let's assume you have a managed server at hetzner (a german server and cloud provider). Since the server is managed by hetzner you cannot install software by yourself or block additional ports. Nevertheless, an apache webserver is already running on the system. Since we don't want outdated data we use the system cron and add the following line:

* * * * * /path/to/simple-node-exporter -print-only > /path/to/web/root/metrics

You should also setup a protection via htaccess to prevent exposing sensitive data to public.

Important: there might be constraints which prevent this example to work in your special case.

Usage

You can simply use the following docker-compose.yml to test and use the simple-node-exporter

version: "3"

services:
    simple-node-exporter:
        image: bosix/simple-node-exporter
        ports:
            - "3322:3322"
        environment:
            - "HOSTNAME=myhost"
        volumes:
            - ./additional:/app/additional

docker-compose up -d

After starting the container you can call the metrics with curl http://localhost:3322/metrics. The environment-variable hostname can be used to identify the server. It will be added as a label to all metrics.

If you don't trust me, the docker-image or the binary I put into the image, you can of course compile and build everything by yourself:

# build the standalone binary (requires go1.16+)
go build .

# build the docker image (requires docker or any other image creating tool) 
docker build -t simple-node-exporter .

Configuration

Config can be set via env:

The hostname can also be set by mounting a file named hostname next to the executable. Inside the provided docker image it would be /app/hostname.

Limitations

Please take notice that in some cases some metrics might not work. A known issue is e.g. that on windows load1/5/15 is always 0.

Used 3rd Party Libraries

This app uses several 3rd party libraries. Their licenses can be viewed here (gitlab pages).