Appendix A. Capsule Server Scalability Considerations
The maximum number of Capsule Servers that the Satellite Server can support has no fixed limit. The tested limit is 17 Capsule Servers with 2 vCPUs on a Satellite Server with Red Hat Enterprise Linux 7. However, scalability is highly variable, especially when managing Puppet clients.
Capsule Server scalability when managing Puppet clients depends on the number of CPUs, the run-interval distribution, and the number of Puppet managed resources. The Capsule Server has a limitation of 100 concurrent Puppet agents running at any single point in time. Running more than 100 concurrent Puppet agents results in a 503 HTTP error.
For example, assuming that Puppet agent runs are evenly distributed with less than 100 concurrent Puppet agents running at any single point during a run-interval, a Capsule Server with 4 CPUs has a maximum of 1250-1600 Puppet clients with a moderate workload of 10 Puppet classes assigned to each Puppet client. Depending on the number of Puppet clients required, the Satellite installation can scale out the number of Capsule Servers to support them.
If you want to scale your Capsule Server when managing Puppet clients, the following assumptions are made:
- There are no external Puppet clients reporting directly to the Satellite 6 integrated Capsule.
- All other Puppet clients report directly to an external Capsule.
- There is an evenly distributed run-interval of all Puppet agents.
Deviating from the even distribution increases the risk of filling the passenger request queue. The limit of 100 concurrent requests applies.
The following table describes the scalability limits using the recommended 4 CPUs.
| Puppet Managed Resources per Host | Run-Interval Distribution |
|---|---|
| 1 | 3000-2500 |
| 10 | 2400-2000 |
| 20 | 1700-1400 |
The following table describes the scalability limits using the minimum 2 CPUs.
| Puppet Managed Resources per Host | Run-Interval Distribution |
|---|---|
| 1 | 1700-1450 |
| 10 | 1500-1250 |
| 20 | 850-700 |
