Uyuni read-only replica
a project by cbosdonnat
Updated about 1 month ago. 8 hacker ♥️. 4 followers.

Description

For now, there is no possible HA setup for Uyuni. The idea is to explore setting up a read-only shadow instance of an Uyuni and make it as useful as possible.

Possible things to look at:

  • live sync of the database, probably using the WAL. Some of the tables may have to be skipped or some features disabled on the RO instance (taskomatic, PXT sessions…)
  • Can we use a load balancer that routes read-only queries to either instance and the other to the RW one? For example, packages or PXE data can be served by both, the API GET requests too. The rest would be RW.

Goals

  • Prepare a document explaining how to do it.
  • PR with the needed code changes to support it

Join this project

Looking for hackers with the skills:

uyuni ha database postgresql

This project is part of:

Hack Week 25

Activity

  • about 1 month ago: j_renner liked this project.
  • about 1 month ago: e_bischoff liked this project.
  • about 1 month ago: deneb_alpha liked this project.
  • about 1 month ago: epenchev liked this project.
  • about 1 month ago: juliogonzalezgil liked this project.
  • about 1 month ago: ygutierrez liked this project.
  • about 1 month ago: oholecek liked this project.
  • about 1 month ago: oholecek joined this project.
  • about 1 month ago: oscar-barrios liked this project.
  • about 1 month ago: cbosdonnat added keyword "database" to this project.
  • about 1 month ago: cbosdonnat added keyword "postgresql" to this project.
  • about 1 month ago: cbosdonnat added keyword "ha" to this project.
  • about 1 month ago: cbosdonnat added keyword "uyuni" to this project.
  • about 1 month ago: cbosdonnat started this project.
  • about 1 month ago: cbosdonnat originated this project.


    • Comments

    • epenchev
      about 1 month ago by epenchev | Reply

      Hi, I think there are a few solutions that might help.

      Since I'm dealing a lot with HA and databases, would like to share my thoughts.

      One possible solution would be to go with pgpool-II - Scaling PostgreSQL Master-Replica Load Balancing and Automatic Failover.

      Such approach is described very much in details -> https://medium.com/@deysouvik700/scaling-postgresql-with-pgpool-ii-master-replica-load-balancing-and-automatic-failover-091983d4dd9a. In the example architecture the PgPool proxy itself is a single point of failure. The example setup could be extended by adding an additional proxy instance. Both proxy instances could be managed by keepalived + VirtualIP config. Of course there are other resources you can refer to as well.

      Another possible solution which is kind of more automated would be to go with cnpg. This would require however to have a K8s cluster for your statefull PostgreSQL workload. So ideally you would need at least 3 Nodes HA K8s cluster. This is the minimal setup and all 3 nodes should be (control plane + worker roles) otherwise the standard setup will go up to 5 nodes (control planes and additional worker nodes.) With cnpg you can create multiple services (rw, ro, r) within you cluster and point clients to them https://cloudnative-pg.io/documentation/1.27/service_management/ and https://cloudnative-pg.io/documentation/1.27/architecture/.

      Something more experimental that I'm working on recently and hoping to be way easier in operational perspective is https://github.com/kqlite/kqlite. It's a SQLite over the PostgreSQL wire protocol, with support for replication and clustering. However this limits the scope of database functionality down to SQLite only. Unfortunately using any PostgreSQL specific features and data types will not work with kqlite .

      P.S. Also there is plenty of documentation on going with the standard approach patroni + HAProxy + etcd.

      • cbosdonnat
        about 1 month ago by cbosdonnat | Reply

        The first issue will be the replication of the DB itself. Since we have sequences and those are not logically replicated, we will have to check the possible options there.

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