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
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