[DPE-2953] Cross-region async replication #452
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Signed-off-by: Marcelo Henrique Neppel <marcelo.neppel@canonical.com>
Signed-off-by: Marcelo Henrique Neppel <marcelo.neppel@canonical.com>
Signed-off-by: Marcelo Henrique Neppel <marcelo.neppel@canonical.com>
Signed-off-by: Marcelo Henrique Neppel <marcelo.neppel@canonical.com>
Signed-off-by: Marcelo Henrique Neppel <marcelo.neppel@canonical.com>
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…ation Signed-off-by: Marcelo Henrique Neppel <marcelo.neppel@canonical.com>
Signed-off-by: Marcelo Henrique Neppel <marcelo.neppel@canonical.com>
…ation Signed-off-by: Marcelo Henrique Neppel <marcelo.neppel@canonical.com>
Signed-off-by: Marcelo Henrique Neppel <marcelo.neppel@canonical.com>
dragomirp
approved these changes
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Signed-off-by: Marcelo Henrique Neppel <marcelo.neppel@canonical.com>
Signed-off-by: Marcelo Henrique Neppel <marcelo.neppel@canonical.com>
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Issue
It's not possible to replicate data between regions.
Solution
Implement cross-region async replication. This PR is a rebranded and more stable version of #317.
With this PR, it's no longer necessary to remove the relation and relate again when a switchover is needed.
Also, the names of the relations can easily be changed to others, like
cluster-oneandcluster-two, for example, to avoid confusing users.This is mostly a copy and paste from canonical/postgresql-k8s-operator#447.
Important changes:
src/relations/async_replication.pycontains the logic to make one cluster the primary and the other the standby. To make the standby cluster follow the primary cluster, the candidate for the standby cluster needs to be restarted.The most important part of the logic is handled by the
_on_async_relation_changed, which takes care of restarting the standby cluster units databases in order to make them replicate data from the primary cluster.Additionally to everything implemented on [DPE-2897] Cross-region async replication postgresql-k8s-operator#447, this PR adds the coordination of which RAFT members should be part of the Patroni internal RAFT cluster while starting the units in the standby cluster. It's done through the return value from the
get_partner_addressesmethod.Passwords update will be implemented in another PR, as this one is already huge.
If the standby cluster has its relation removed, it goes to a
read-only modeand can be promoted later to a normal cluster through thepromote-clusteraction.How to deploy: https://discourse.charmhub.io/t/charmed-postgresql-deploy-async-replication/13991
How to trigger a switchover: https://discourse.charmhub.io/t/charmed-postgresql-async-switchover/13993
Additional instructions:
Integration tests: #453