Systemd Tricks We Use to Keep Services Boring
Concrete systemd unit patterns that reduced flakiness: restart policies, resource limits, and structured logs.
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Concrete systemd unit patterns that reduced flakiness: restart policies, resource limits, and structured logs.
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Systemd Tricks We Use to Keep Services Boring#
After a few painful outages caused by homemade init scripts, we moved everything to systemd and wrote down the patterns that worked.
Pattern: Restart with Backoff#
We had a service that occasionally failed to bind its port on boot.
```ini [Unit] Description=API service After=network-online.target Wants=network-online.target
[Service] ExecStart=/usr/local/bin/api Restart=on-failure RestartSec=5
[Install] WantedBy=multi-user.target ```
- Restart=on-failure + RestartSec gave the process room to recover without flapping.
Pattern: Non-Root with Limits#
We saw file descriptor exhaustion during load tests.
- Added User=api and LimitNOFILE=65536.
- Used Ansible to roll the unit file change across the fleet.
Pattern: Journald as a Timeline#
When something goes wrong, we start with:
- `journalctl -u api -b`
- `journalctl -u api --since "-15min"`
Systemd didn’t fix our code, but it made failures predictable and repeatable.
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