Deprecate Glance Registry¶
Glance registry has, historically, helped to scale Glance by allowing for centralizing the database access (glance-registry) while distributing the data access (glance-api). In addition, it’s helped as a safe-guard for the database access credentials as it shouldn’t be deployed as a public endpoint.
With the release and support of Glance’s V2, the Glance Registry service has become redundant, hence this proposal to deprecate it.
Glance Registry serves a very specific use case, which is to serve as a proxy for the database operations in a Glance deployment. This use case came as part of older Glance API versions and a certainly older architecture.
Unfortunately, it’s becoming more of a burden to maintain it - development, operations and documentation wise - than a benefit for the project itself.
From a development perspective, the team has to maintain the API updated for every change in the database API. From an operational perspective, there’s another set of API nodes that need to be deployed, monitored, and upgraded. From a documentation stand point, the team needs to make sure the service docs are up-to-date, the best practices are spelled out and configuration files updated.
The benefits of this service have been discussed in a recent thread  on both developers and operators, mailing lists. The output of this thread is not really conclusive, although it suggests there’s no real use case for this service anymore and that OPs would be better off by not having it.
Rolling upgrades was brought as a possible blocker for this deprecation. As it’s been explained in the thread , upgrading Glance (or even the planned work on rolling upgrades) should not depend on the presence of this service. Anything needed from Glance Registry should be possible to obtain from Glance API itself.
Glance Glare is not going to use Glance registry, which would also leave us with an inconsistent deployment and a bad user experience.
This spec proposes to deprecate the glance-registry service. Mark the service as deprecated and ready for removal in the Q release.
Keep maintaining the Glance Registry service.
Data model impact¶
REST API impact¶
The public facing API won’t be changed. The registry API will be deprecated and not required anymore.
Deployers will have to put the database credentials in the glance-api config files. This might be seen as a security issue for some deployments as this means an attacker that gains access to the glance-api server could potentially access glance’s database. However, this is not any different than what other services.
Other end user impact¶
This change should actually improve the overall performance as it’d get rid of an extra step glance-api needs to go through to access the image metadata.
Other deployer impact¶
Glance deployments will eventually have to move away from using the registry. This can’t be done for glance-api nodes using v1 but it can certainly be done for v2-only nodes.
Less code to maintain, happier developers.
- Primary assignee:
- Other contributors:
<launchpad-id or None>
- Core reviewer(s):
rosmaita jokke nikhil
- Other reviewer(s):
<launchpad-id or None> <launchpad-id or None>
Add a glance-api only job
Mark the registry service as deprecated
Test a registry-less deployment in the OpenStack CI.
Document the motivations behind this deprecation and a recommended upgrade path from Mitaka to Newton and on.