Add docs about upgrading primary mesh gateways

Care must be taken when replacing mesh gateways in the primary
datacenter, because if the old addresses become unreachable before the
secondary datacenters receive the new addresses then the primary
datacenter overall will become unreachable.

This commit adds docs related to this class of upgrades.
This commit is contained in:
freddygv 2022-10-18 10:08:43 -06:00
parent 0cca4c088d
commit b8ef47f6d6
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@ -184,3 +184,17 @@ expected result:
- Ensure any API request that activates datacenter request forwarding. such as
[`/v1/catalog/services?dc=<OTHER_DATACENTER_NAME>`](/api-docs/catalog#dc-1)
succeeds.
### Upgrading the primary gateways
Once federation has been established, updates for the addresses of new primary
gateways are propagated through the gateways in the primary themselves. If the primary
gateways are upgraded, and their previous instances are decommissioned before
the updates are propagated, then the primary datacenter will become unreachable.
To safely upgrade primary gateways it is preferable to do one of the following:
- Avoid decommissioning primary gateway IP addresses, since the [primary_gateways](/docs/agent/config/config-files#primary_gateways) addresses configured on the secondary
servers acts as a fallback mechanism to re-establish connectivity to the primary.
- Verify that addresses of the new mesh gateways in the primary were propagated
to the secondary datacenters before decommissioning the old mesh gateways in the primary.