Upgrading¶
Ceilometer’s services support both full upgrades as well as partial (rolling) upgrades. The required steps for each process are described below.
Full upgrades¶
The following describes how to upgrade your entire Ceilometer environment in one pass.
Upgrade the database (if applicable)
Run ceilometer-upgrade to upgrade the storage backend if using one of Ceilometer’s databases (see Choosing a database backend). The database does not need to be taken offline. Ideally this should be done during a period of low activity. Best practices should still be followed (ie. back up your data). If not using a Ceilometer database, you should consult the documentation of that storage beforehand.
Upgrade the collector service(s)
Shutdown all collector services. The new collector, that knows how to interpret the new payload, can then be started. It will disregard any historical attributes and can continue to process older data from the agents. You may restart as many new collectors as required.
Upgrade the notification agent(s)
The notification agent can then be taken offline and upgraded with the same conditions as the collector service.
Upgrade the polling agent(s)
In this path, you’ll want to take down agents on all hosts before starting. After starting the first agent, you should verify that data is again being polled. Additional agents can be added to support coordination if enabled.
Note
The API service can be taken offline and upgraded at any point in the process (if applicable).
Partial upgrades¶
The following describes how to upgrade parts of your Ceilometer environment gradually. The ultimate goal is to have all services upgraded to the new version in time.
Upgrade the database (if applicable)
Upgrading the database here is the same as the full upgrade path.
Upgrade the collector service(s)
The new collector services can be started alongside the old collectors. Collectors old and new will disregard any new or historical attributes.
Upgrade the notification agent(s)
The new notification agent can be started alongside the old agent if no workload_partioning is enabled OR if it has the same pipeline configuration. If the pipeline configuration is changed, the old agents must be loaded with the same pipeline configuration first to ensure the notification agents all work against same pipeline sets.
Upgrade the polling agent(s)
The new polling agent can be started alongside the old agent only if no new pollsters were added. If not, new polling agents must start only in its own partitioning group and poll only the new pollsters. After all old agents are upgraded, the polling agents can be changed to poll both new pollsters AND the old ones.
Upgrade the API service(s)
API management is handled by WSGI so there is only ever one version of API service running
Note
Upgrade ordering does not matter in partial upgrade path. The only requirement is that the database be upgraded first. It is advisable to upgrade following the same ordering as currently described: database, collector, notification agent, polling agent, api.
Developer notes¶
When updating data models in the database or IPC, we need to adhere to a single mantra: ‘always add, never delete or modify.’