mydocker/promtail/README.md

Promtail - Log Shipper

Log collection agent that discovers Docker containers via the Docker socket and forwards stdout/stderr to Loki.

Access

Endpoint	Details
HTTP Port	9080 (health check, metrics)
Public access	None
Docker socket	unix:///var/run/docker.sock

Configuration

Config file: ./promtail/promtail-config.yaml

Key Parameters

Parameter	Value
HTTP Port	9080
Push target	http://loki:3100/loki/api/v1/push
Positions file	/tmp/positions.yaml (checkpointing)
Container refresh	Every 5s

Scrape Job: docker

• Discovers containers via docker_sd_configs
• Label container - container name (without leading /)
• Label stream - stdout or stderr
• Pipeline: docker parser for Docker log format

Data Collected

Collects logs from all running Docker containers on the host. Each log entry is enriched with:

Label	Description
container	Container name
stream	Stream type (stdout/stderr)
Docker metadata	Image, compose project, etc.

Dependencies

Service	Role
Docker socket	Log source (service discovery + streaming)
Loki	Push destination
Grafana	Indirect - Grafana queries Loki

Useful Commands

# Restart
docker compose restart promtail

# Follow logs
docker compose logs -f promtail

# Check status
curl http://localhost:9080/ready
curl http://localhost:9080/targets

# Upgrade
./upgrade-container-by-name.sh promtail