Added an example of using external arbiter to the multi-cluster setup#342
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Added an example of using external arbiter to the multi-cluster setup#342nastena1606 wants to merge 15 commits into
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Pull request overview
Adds documentation for a multi-cluster cross-site replication topology that uses a shared external arbiter, and links it into the existing replication deployment guides and reference docs.
Changes:
- Adds a new “external arbiter” deployment guide and supporting diagram.
- Expands replication planning docs with “voting topology” guidance and cross-links between approaches.
- Updates navigation and reference docs to surface the new topology and the
replsets.externalNodes.arbiterOnlyfield.
Reviewed changes
Copilot reviewed 9 out of 10 changed files in this pull request and generated 16 comments.
Show a summary per file
| File | Description |
|---|---|
| mkdocs-base.yml | Adds nav entries for the new external-arbiter guide and a new release notes link. |
| docs/replication.md | Adds a section introducing voting-topology options and links to the new guide. |
| docs/replication-replica.md | Minor formatting change. |
| docs/replication-plan-deployment.md | Adds “Choose a voting topology” section and updates next-step links. |
| docs/replication-main.md | Updates namespace example used in the setup steps. |
| docs/replication-interconnect.md | Clarifies interconnect steps and updates YAML examples (including exposure configuration). |
| docs/replication-external-arbiter.md | New end-to-end guide for an external-arbiter topology (setup, interconnect, failover). |
| docs/operator.md | Documents replsets.externalNodes.arbiterOnly. |
| docs/assets/images/replication-pods-external-arbiter.svg | Adds a new architecture diagram for the external arbiter topology. |
| docs/arbiter.md | Fixes arbiter wording and links to the new voting-topology section. |
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Updated Split a rs across data centers to focus on PSA architecture Added references to this setup in cross-site replication docs
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nastena1606
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eleo007
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| You get two data-bearing clusters and a third site that hosts only the arbiter. When you interconnect sites, you add the Replica member and the arbiter as voting `externalNodes` on the Main site. The arbiter breaks election ties so the replica set keeps an odd number of voters. | ||
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| TLS certificates generated by the Operator are not suitable and it’s required to [generate certificates manually](tls-manual.md) on the _Main_ site before creating a database cluster, with all names from `replsetOverrides` and `externalNodes`. | ||
| This topology uses `replsets.externalNodes.arbiterOnly` and requires Percona Operator for MongoDB 1.23.0 or later. Do not enable `replsets.arbiter.enabled` on the Main or Replica data-bearing sites when the arbiter runs as an external node. |
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Do not enable
replsets.arbiter.enabledon the Main or Replica data-bearing sites when the arbiter runs as an external node.
Do not understand this , why?
eleo007
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Jul 16, 2026
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| ??? admonition "Deploying the arbiter outside Kubernetes" | ||
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| 1. Install `mongod` on a host in a third location that can reach both data-bearing sites. | ||
| 2. Use the same user credentials and TLS certificates as the Main and Replica sites. | ||
| 3. Ensure the arbiter hostname resolves from every site and appears on the TLS certificates. | ||
| 4. Do not initiate a replica set on the arbiter host. The Main site Operator adds it when you configure `externalNodes`. |
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I would not mention this - it was not tested
eleo007
reviewed
Jul 16, 2026
| arbiterOnly: true | ||
| ``` | ||
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| Apply the Main site Custom Resource. Do not run `rs.addArb()` manually — the Operator overwrites manual replica set changes on reconciliation. Do not enable `replsets.arbiter.enabled` on the Main or Replica data-bearing sites. |
Restructured the doc to show clear paths for the setup steps
egegunes
previously approved these changes
Jul 17, 2026
… link to multi-dc setup.
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