Exporters

Gathering metrics in Prometheus involves pulling data from providers via agents called ‘exporters’. There are a wide range of pre-built exporters and a range of templates for writing custom exporters which will collect data from your infrastructure and send it to Prometheus.

Pre-built exporter examples include;

  • Node Exporter: Which exposes a wide variety of hardware- and kernel-related metrics like disk usage, CPU performance, memory state, etcetera for Linix systems.
  • SNMP Exporter: Which exposes information gathered from SNMP. Its most common use is to get the metrics from network devices like firewalls, switches and the devices which just supports SNMP only.
  • Database Exporters: These are a range of exporters that can retrieve performance data from databases such as MySQL, MSSQL, PostgreSQL, MongoDB and more.
  • Hardware Exporters: A number of hardware platforms have exporters supported including Dell, IBM, Netgear and Ubiquiti.
  • Storage Platforms: Such as Ceph, Gluster and Hadoop

Custom exporter examples include libraries for Go, Python, Java and Javascript.

Node Exporter

As node_exporter is an official exporter available from the Prometheus site, and as the binary is able to be installed standalone the installation process is fairly similar. We’ll download it, decompress it and run it as a service.

In the case of the installation below the node_exporter will be installed onto another Raspberry Pi operating on the local network at the IP address 10.1.1.109. It will pull our server metrics which will be things like RAM/disk/CPU utilization, network, io etc.

First then we will browse to the download page here - https://github.com/prometheus/node_exporter/releases/. Remembering that it’s important that we select the correct architecture for our Raspberry Pi.

As the Pi that I’m going to monitor in this case with node_exporter uses a CPU based on the ARMv7 architecture, use the drop-down box to show armv7 options.

Note the name or copy the URL for the node_exporter file that is presented. The full URL in this case is something like - https://github.com/prometheus/node_exporter/releases/download/v1.3.1/node_exporter-1.3.1.linux-armv7.tar.gz;

Using a terminal, ssh into the node to be monitored. In our case, this swill be as the pi user again on 10.1.1.109.

Once safely logged in and at the pi users’s home directory we can start the download (remember, the command below will break across lines, don’t just copy - paste it);

The file that is downloaded is compressed so once the download is finished we will want to expand our file. For this we use the tar command;

Housekeeping time again. Remove the original compressed file with the rm (remove) command;

We now have a directory called node_exporter-1.3.1.linux-armv7. Again, for the purposes of simplicity it will be easier to deal with a directory with a simpler name. We will therefore use the mv (move) command to rename the directory to just ‘node_exporter’ thusly;

Again, now we need to make sure that node_exporter starts up simply at boot. We will do this by setting it up as a service so that it can be easily managed and started.

The first step in this process is to create a service file which we will call node_exporter.service. We will have this in the /etc/systemd/system/ directory.

Paste the following text into the file and save and exit.

[Unit]
Description=Node Exporter
Wants=network-online.target
After=network-online.target

[Service]
User=pi
ExecStart=/home/pi/node_exporter/node_exporter

[Install]
WantedBy=default.target

The service file can contain a wide range of configuration information and in our case there are only a few details. The most interesting being the ‘ExecStart’ details which describe where to find the node_exporter executable.

Before starting our new service we will need to reload the systemd manager configuration again.

Now we can start the node_exporter service.

You shouldn’t see any indication at the terminal that things have gone well, so it’s a good idea to check node_exporter’s status as follows;

We should see a report back that indicates (amongst other things) that node_exporter is active and running.

Now we will enable it to start on boot.

The exporter is now working and listening on the port:9100

To test the proper functioning of this service, use a browser with the url: http://10.1.1.109:9100/metrics

This should return a lot lot statistics. They will look a little like this

# HELP go_gc_duration_seconds A summary of the GC invocation durations.
# TYPE go_gc_duration_seconds summary
go_gc_duration_seconds{quantile="0"} 0
go_gc_duration_seconds{quantile="0.25"} 0
go_gc_duration_seconds{quantile="0.5"} 0
go_gc_duration_seconds{quantile="0.75"} 0
go_gc_duration_seconds{quantile="1"} 0
go_gc_duration_seconds_sum 0
go_gc_duration_seconds_count 0
# HELP go_goroutines Number of goroutines that currently exist.
# TYPE go_goroutines gauge
go_goroutines 6
# HELP go_info Information about the Go environment.
# TYPE go_info gauge
go_info{version="go1.12.5"} 1

Now that we have a computer exporting metrics, we will want it to be gathered by Prometheus

Up next

Prometheus Collector Configuration