Red Hat Summit6.2.2. Geo-replication requirements and constraints
To run geo-replication reliably in Red Hat Quay, you must meet strict requirements for shared object storage, networking, load balancing, and external health monitoring. Geo-replication does not provide automatic failover, database replication, or storage awareness, so you must design and manage these behaviors outside of Red Hat Quay.
The following are the requirements and constraints for geo-replication:
- In geo-replicated setups, Red Hat Quay requires that all regions are able to read and write to all other region’s object storage. Object storage must be geographically accessible by all other regions.
- In case of an object storage system failure of one geo-replicating site, that site’s Red Hat Quay deployment must be shut down so that clients are redirected to the remaining site with intact storage systems by a global load balancer. Otherwise, clients will experience pull and push failures.
- Red Hat Quay has no internal awareness of the health or availability of the connected object storage system. Users must configure a global load balancer (LB) to monitor the health of your distributed system and to route traffic to different sites based on their storage status.
-
To check the status of your geo-replication deployment, you must use the
/health/endtoendcheckpoint, which is used for global health monitoring. You must configure the redirect manually using the/health/endtoendendpoint. The/health/instanceend point only checks local instance health. - If the object storage system of one site becomes unavailable, there will be no automatic redirect to the remaining storage system, or systems, of the remaining site, or sites.
- Geo-replication is asynchronous. The permanent loss of a site incurs the loss of the data that has been saved in that sites' object storage system but has not yet been replicated to the remaining sites at the time of failure.
A single database, and therefore all metadata and Red Hat Quay configuration, is shared across all regions.
Geo-replication does not replicate the database. In the event of an outage, Red Hat Quay with geo-replication enabled will not failover to another database.
- A single Redis cache is shared across the entire Red Hat Quay setup and needs to be accessible by all Red Hat Quay pods.
-
The exact same configuration should be used across all regions, with exception of the storage backend, which can be configured explicitly using the
QUAY_DISTRIBUTED_STORAGE_PREFERENCEenvironment variable. - Geo-replication requires object storage in each region. It does not work with local storage.
- Each region must be able to access every storage engine in each region, which requires a network path.
- Alternatively, the storage proxy option can be used.
- The entire storage backend, for example, all blobs, is replicated. Repository mirroring, by contrast, can be limited to a repository, or an image.
- All Red Hat Quay instances must share the same entrypoint, typically through a load balancer.
- All Red Hat Quay instances must have the same set of superusers, as they are defined inside the common configuration file.
In geo-replication environments, your Clair configuration can be set to
unmanaged. An unmanaged Clair database allows the Red Hat Quay Operator to work in a geo-replicated environment where multiple instances of the Operator must communicate with the same database. For more information, see Advanced Clair configuration.If you keep your Clair configuration
managed, you must retrieve the configuration file for the deployed Clair instance that is deployed by the Operator. For more information, see Retrieving and decoding the Clair configuration secret for Clair deployments on OpenShift Container Platform.- Geo-Replication requires SSL/TLS certificates and keys. For more information, see * Geo-Replication requires SSL/TLS certificates and keys. For more information, see Proof of concept deployment using SSL/TLS certificates. .
If the above requirements cannot be met, you should instead use two or more distinct Red Hat Quay deployments and take advantage of repository mirroring functions.
'%20d='M201.5%20305.5c-13.8%200-24.9-11.1-24.9-24.6%200-13.8%2011.1-24.9%2024.9-24.9%2013.6%200%2024.6%2011.1%2024.6%2024.9%200%2013.6-11.1%2024.6-24.6%2024.6zM504%20256c0%20137-111%20248-248%20248S8%20393%208%20256%20119%208%20256%208s248%20111%20248%20248zm-132.3-41.2c-9.4%200-17.7%203.9-23.8%2010-22.4-15.5-52.6-25.5-86.1-26.6l17.4-78.3%2055.4%2012.5c0%2013.6%2011.1%2024.6%2024.6%2024.6%2013.8%200%2024.9-11.3%2024.9-24.9s-11.1-24.9-24.9-24.9c-9.7%200-18%205.8-22.1%2013.8l-61.2-13.6c-3-.8-6.1%201.4-6.9%204.4l-19.1%2086.4c-33.2%201.4-63.1%2011.3-85.5%2026.8-6.1-6.4-14.7-10.2-24.1-10.2-34.9%200-46.3%2046.9-14.4%2062.8-1.1%205-1.7%2010.2-1.7%2015.5%200%2052.6%2059.2%2095.2%20132%2095.2%2073.1%200%20132.3-42.6%20132.3-95.2%200-5.3-.6-10.8-1.9-15.8%2031.3-16%2019.8-62.5-14.9-62.5zM302.8%20331c-18.2%2018.2-76.1%2017.9-93.6%200-2.2-2.2-6.1-2.2-8.3%200-2.5%202.5-2.5%206.4%200%208.6%2022.8%2022.8%2087.3%2022.8%20110.2%200%202.5-2.2%202.5-6.1%200-8.6-2.2-2.2-6.1-2.2-8.3%200zm7.7-75c-13.6%200-24.6%2011.1-24.6%2024.9%200%2013.6%2011.1%2024.6%2024.6%2024.6%2013.8%200%2024.9-11.1%2024.9-24.6%200-13.8-11-24.9-24.9-24.9z'/%3e%3c/svg%3e){kind=small}