Alertmanager vs Oncall
A side-by-side comparison of two self-hosted monitoring & status options — licensing, setup difficulty, resource needs, and what each one replaces.
| Feature | Alertmanager | Oncall |
|---|---|---|
| Deploy effort | Under-an-hour setup | Under-an-hour setup |
| Health score | 92 · Excellent | 28 · At risk |
| Category | Monitoring & Status | Monitoring & Status |
| License | Apache-2.0 | BSD-2-Clause |
| Language | Go | Python |
| Setup difficulty | Medium | Medium |
| Min. RAM | 64 MB | 256 MB |
| Deployment | docker, kubernetes, binary | docker, bare-metal |
| GitHub stars | ★ 8,627 | ★ 1,258 |
| First released | 2015 | 2017 |
| Replaces | PagerDuty, Opsgenie | PagerDuty |
What are Alertmanager and Oncall?
Alertmanager
Alertmanager handles alerts sent by Prometheus and other clients, taking care of deduplication, grouping, and routing to receivers such as email, Slack, or PagerDuty. It also supports silences and inhibition rules.
- Alert deduplication and grouping
- Flexible routing trees
- Silences and inhibition
- Many notification integrations
Oncall
Oncall is a calendar tool for managing on-call schedules and rotations across teams. Developed at LinkedIn, it integrates with paging systems to ensure the right engineer is reachable at any time.
- Calendar-based rotations
- Team and event management
- Paging system integration
- REST API
Alertmanager vs Oncall: key differences
Alertmanager is written in Go, while Oncall is built with Python. Licensing differs — Apache-2.0 for Alertmanager versus BSD-2-Clause for Oncall. Alertmanager is the lighter option, starting around 64 MB of RAM against 256 MB for Oncall. Alertmanager is the more established project (first released 2015), while Oncall arrived in 2017. Alertmanager has the considerably larger community, at 8,627 GitHub stars versus 1,258.
Why pick each one
Choose Alertmanager if…
- Powerful routing logic
- Standard in the Prometheus stack
Watch out for
- YAML config can get complex
- Tied to Prometheus ecosystem
Choose Oncall if…
- Simple scheduling model
- Battle-tested at LinkedIn
Watch out for
- Needs Iris for actual paging
- UI is utilitarian
Frequently asked questions
Is Alertmanager or Oncall better?
Neither is universally better. Alertmanager has the larger community; both share a medium setup difficulty, so the decision comes down to features and licensing.
Are Alertmanager and Oncall free and open-source?
Yes. Alertmanager is licensed under Apache-2.0 and Oncall under BSD-2-Clause. Both can be self-hosted at no software cost.
Can I run Alertmanager and Oncall with Docker?
Alertmanager: yes. Oncall: yes.
Which is lighter on resources, Alertmanager or Oncall?
Alertmanager has the smaller minimum footprint at 64 MB of RAM, compared to about 256 MB for Oncall. Real-world usage depends on library size, user count, and enabled features.