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This tag is part of the assert category of tags, which are assertions made by the project team themselves about their maturity.

The assert:supports-zero-impact-upgrade tag asserts that in addition to a project supporting zero-downtime, rolling upgrade capabilities, it does so without incurring any perceivable performance penalty.

Application to current projects


No projects are using assert:supports-zero-impact-upgrade, yet.


OpenStack projects represent code that is installed and deployed on many distributed systems in order to provide services to users. Operators need to know what projects support a seamless upgrade process that does not impact the performance of the cloud.


  • The project is already tagged as type:service.
  • The project has already successfully asserted the assert:supports-upgrade, assert:supports-rolling-upgrade, and assert:supports-zero-downtime-upgrade tags. All the requirements for those tags are requirements for this tag, and assertion of both those tags are requirements to assert this tag.
  • In addition to the plan required by the assert:supports-zero-downtime-upgrade tag which allows for performance degradation during the upgrade process, this tag requires services to completely eliminate any perceivable performance penalty during the upgrade process. In other words, operators should not expect any portion of the upgrade or migration process to place abnormally high load on any part of the cloud, or to cause delays in the handling of API requests, even intermittently.
  • In addition to the gate testing required by the assert:supports-zero-downtime-upgrade tag, services should be capable of receiving and handling requests throughout the rolling upgrade process within normal performance parameters. In order to assert this tag, services should prevent regression by implementing a zero-impact gate job wherein both a new version of the service and an old version of the service are run concurrently under load. A measurement of API response times must show that there are no statistically significant outliers during the upgrade process when compared to normal operations.