Oct 1, 2021 by Thibault Debatty | 6284 views
Loki is a log database developed by Grafana Labs. It's similar to Elasticsearch, with some major conceptual differences:
This may seem quite simplistic, but the result is actually extremely effective: in a comparison based on 42GB of logs generated by Nginx, ELK consumed 107GB of disk space to store the data and index, while Loki consumed only 9GB!
A typical Loki stack consists of:
Next to promtail, some other tools can also be used to inject logs into Loki:
The easiest way to test Loki is using docker and docker-compose:
Download the docker-compose.yaml file:
wget https://raw.githubusercontent.com/grafana/loki/v2.3.0/production/docker-compose.yaml -O docker-compose.yaml
Or copy the following content to docker-compose.yaml:
version: "3" networks: loki: services: loki: image: grafana/loki:2.3.0 ports: - "3100:3100" command: -config.file=/etc/loki/local-config.yaml networks: - loki promtail: image: grafana/promtail:2.3.0 volumes: - /var/log:/var/log command: -config.file=/etc/promtail/config.yml networks: - loki grafana: image: grafana/grafana:latest ports: - "3000:3000" networks: - loki
As you can see, this docker-compose configuration uses
/var/log as a volume, such that promtail can scrape and index the logs from your host system.
You can start the containers with:
Once the containers are running, the Grafana web interface will be available at
The default credentials are:
Grafana is initially not connected to the Loki server. To establish the connection:
Configuration > Data sourcesin the left menu
Add a data sourceand select
Lokiin the list
http://loki:3100, then click on
Save & testat the bottom
To discover Loki and Grafana, and to inspect your logs, you can click on the
Explore button on the left (the compass).
The main field at the top allows to type a
LogQL query. You can try with the following query, that will show you the logs from
shift + enter;
You can also use the following query to count the number of log entries received per second, using an aggregation window of 5 minutes:
Now you can use Loki and Grafana to monitor Kubernetes containers
Loki and Grafana also have other features like dashboards and alerting. These will be covered in coming blog posts...