init logs

content/posts/07-build-your-own-docker-swarm-cluster-part-6/index.md

@@ -12,11 +12,99 @@ Build your own cheap while powerful self-hosted complete CI/CD solution by follo
 
 This is the **Part VI** of more global topic tutorial. [Back to first part]({{< ref "/posts/02-build-your-own-docker-swarm-cluster" >}}) to start from beginning.
 
+## Why centralized logs ?
+
+A real production cluster should have centralized logs. Of course, we have some basic service logs viewer on Portainer, which shows the containers STDOUT, but :
+
+* With more and more containers, it can be unmanageable
+* Logs of containers will not persist after each container restart
+* Not very powerful to navigate, can be tedious with huge logs
+
+Moreover, it'll be nice if logs of `data-01` services (MySQL, PostgreSQL, etc.) can be centralized too.
+
+### Why Loki ?
+
+The common way to deal with this is to use *ELK*, but I'll show you a better option which is far less resource demanding. *Loki* is a perfect viable option and perfectly integrated to Grafana. It works exactly like Prometheus in terms of architecture, but for logs :
+
+* Loki as itself is a powerful database index search service like Elasticsearch, but optimized for logs
+* Completely integrated to Grafana thanks to LogQL language, similar to PromQL for Prometheus
+* Like Prometheus, we need to install many type of exporters in order to feed the Loki database.
+
+The mains exporters are :
+
+* Promtail which fetch logs local file based on some patterns perfect for our `data-01` managed server
+* Docker driver plugin which redirect all STDOUT to Loki.
+
 ## Logs with Loki 📄
 
+First, let's install the main Loki service :
+
+```sh
+curl -O -L "https://github.com/grafana/loki/releases/download/v2.4.2/loki-linux-amd64.zip"
+sudo apt install -y unzip
+unzip "loki-linux-amd64.zip"
+chmod a+x "loki-linux-amd64"
+sudo mv loki-linux-amd64 /usr/local/bin/loki
+```
+
+Prepare the config file :
+
+```sh
+wget https://raw.githubusercontent.com/grafana/loki/master/cmd/loki/loki-local-config.yaml
+sudo mkdir /etc/loki
+sudo mv loki-local-config.yaml /etc/loki/
+sudo mkdir /var/lib/loki
+sudo chown swarm:swarm /var/lib/loki
+```
+
+> Change default /tmp/loki to /var/lib/loki
+
+Then prepare the service `/etc/systemd/system/loki.service`
+
+```conf
+[Unit]
+Description=Loki
+After=network.target
+
+[Service]
+Type=simple
+User=swarm
+ExecStart=/usr/local/bin/loki -config.file=/etc/loki/loki-local-config.yaml
+
+[Install]
+WantedBy=multi-user.target
+```
+
+Finally, start the service
+
+```sh
+sudo service loki start
+sudo service loki status
+sudo systemctl enable loki.service
+sudo systemctl status loki.service
+```
+
+### Data logs with Promtail
+
 ### Docker hosts
 
-### Data logs with Promtail
+<https://grafana.com/docs/loki/latest/clients/docker-driver/>
+
+```sh
+docker plugin install grafana/loki-docker-driver:latest --alias loki --grant-all-permissions
+```
+
+`/etc/docker/daemon.json`
+
+```json
+{
+  "log-driver": "loki",
+  "log-opts": {
+    "loki-url": "http://data-01:3100/loki/api/v1/push",
+    "loki-batch-size": "400"
+  }
+}
+```
 
 ### Grafana explore and dashboard