Chapter 10. Tuning the WSGI processes

If you are seeing request failures due to long-running API processes, those API processes can benefit from tuning.

By default, IPA allocates 4 Web Server Gateway Interface (WSGI) processes for the API service on 64-bit systems. This default limitation to 4 processes is implemented for memory conservation purposes. Increasing the number of the WSGI processes allows more requests to be accepted at the expense of higher CPU use and memory consumption. By default, IPA uses approximately 100 to 110MB of resident memory for the API per WSGI process. With tuning this to 16 processes, which is the recommended limit, the amount is approximately 1.3GB.

Any of the longer-running API endpoints can benefit from tuning. This tuning decision is for the user to make.

For example, an OpenStack installation consists of several controllers containing multiple services. Each service requests a certificate so that all internal communication occurs over Transport Layer Security (TLS). When installing or refreshing a controller or compute node, these certificates can be requested or refreshed. In scenarios involving multiple controllers or compute nodes, the volume of certificate requests can become considerable. These requests are automated, so they happen at or nearly at the same time. Increasing the number of the WSGI threads allows the installation to complete.