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OpenLDAP N-way multi-master replication (docs/replication.md) required an operator to hand-set LDAP_SERVER_ID (unique per site) and LDAP_REPLICATION_HOSTS (every OTHER site's LDAP URL, kept in sync by hand across every node) -- real coordination work, and easy to get wrong or let drift as sites are added. Automates the coordination the master is already in a position to do: - SiteSpoke gets ldapServerId, auto-assigned (next free from 2 upward, 1 reserved for the master) at registration and reused across re-registrations -- same pattern as jump-host's mesh index. - ldapHost is derived from each site's already-known HTTP(S) endpoint (same hostname, port 636) rather than a separately-configured field that could drift from it. - New utils/ldap_replication.js (nextFreeLdapServerId, ldapHostFor), shared between the spoke-facing GET /api/site/ldap-peers (Bearer site join key, returns this caller's own ID + every peer) and the master-local GET /directory-admin/ldap-replication-config (computes its own config directly from SiteSpoke, no HTTP round-trip needed). Verified against real running containers (docker-compose.multisite-e2e.yml): after a real join, the master's computed config correctly includes the spoke as a peer with an assigned ID, and the spoke's own fetched config matches that ID and correctly excludes itself from its own peer list. Known limitation, documented in docs/replication.md: the master's own LDAP_REPLICATION_HOSTS only gets recomputed when ITS setup.sh is re-run (or an admin re-applies it directly) -- there's no live push to an already-running master when a new spoke joins. A spoke's own config is re-checked on every setup.sh run, which is the common/recurring event; the master side is a documented manual step for now rather than a live hot-reload (which would need OpenLDAP's dynamic cn=config backend -- a bigger change, deliberately out of scope here to avoid risking a live directory's LDAP replication on undertested config).
75 lines
4.1 KiB
Markdown
75 lines
4.1 KiB
Markdown
---
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layout: default
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title: Geo-Location Scaling (Replication)
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---
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# Geo-Location Scaling (Replication)
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SSO Manager is built to be a self-contained identity provider, but if you have multiple physical sites, you may want a local copy of the directory at each site to ensure low latency and high availability.
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## Why and when to use this?
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- **High Availability (HA)**: If your primary site goes completely offline, your other sites can still authenticate users locally without depending on a WAN link.
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- **Low Latency**: Applications at a remote site can bind directly to their local LDAP server (`localhost` or LAN IP) instead of traversing the internet to query the primary site, making logins blazing fast.
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- **Independent Failure Domains**: By replicating only the LDAP directory (the source of truth) and keeping session state (Redis) independent, you prevent complex "split-brain" scenarios in the web UI. A failure at Site A won't bring down Site B.
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By default, the `sso-manager` Docker container runs a single, independent OpenLDAP instance. However, you can enable **N-Way Multi-Master Replication** via environment variables.
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## How it works
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In an N-Way Multi-Master setup, every site runs a fully active OpenLDAP server (`slapd`).
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- **Reads and Writes anywhere**: A user can change their password or update their profile at Site A, Site B, or Site C.
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- **Conflict Resolution**: OpenLDAP's `syncrepl` engine uses Context Sequence Numbers (CSN) to track changes. If Site A goes offline and a user changes their password at Site B, Site A will automatically pull the newest changes the moment it rejoins the cluster.
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- **Independent Redis**: Session data, API Tokens, and OAuth Clients are stored in Redis. By design, Redis is NOT replicated in this geographic setup. This ensures that a failure at Site A never causes Site B's Redis to become read-only, which would break the web UI at Site B. OAuth clients must be configured per-site.
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## Configuration
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The container's entrypoint reads two environment variables to configure this
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-- `LDAP_SERVER_ID` (a unique integer for this node) and
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`LDAP_REPLICATION_HOSTS` (a space-separated list of every **other** node's
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LDAP URL) -- and, when both are set, automatically loads the `syncprov`
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module, enables `mirrormode`, and generates the necessary `syncrepl` blocks
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in `/etc/openldap/slapd.conf`.
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**If you're using `theta-suite`'s `setup.sh`, you don't set these by hand.**
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The master assigns each spoke a unique `LDAP_SERVER_ID` at join time (the
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same way it assigns a WireGuard mesh index), and `LDAP_REPLICATION_HOSTS` is
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derived automatically from every site's already-known HTTPS endpoint
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(`ldaps://<same-host>:636`) -- see `GET /api/site/ldap-peers` (spoke) and
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`GET /api/directory-admin/ldap-replication-config` (master), and
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`theta-suite`'s `bootstrap/site-ldap-register.js`, which re-checks on every
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`setup.sh` run since the peer list changes as new spokes join.
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Setting the two env vars directly still works (e.g. a non-`theta-suite`
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deployment) -- example using three manually-configured nodes:
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**Site 1**
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```env
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LDAP_SERVER_ID=1
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LDAP_REPLICATION_HOSTS="ldaps://sso.site2.com:636 ldaps://sso.site3.com:636"
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```
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**Site 2**
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```env
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LDAP_SERVER_ID=2
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LDAP_REPLICATION_HOSTS="ldaps://sso.site1.com:636 ldaps://sso.site3.com:636"
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```
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**Site 3**
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```env
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LDAP_SERVER_ID=3
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LDAP_REPLICATION_HOSTS="ldaps://sso.site1.com:636 ldaps://sso.site2.com:636"
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```
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**A known limitation of the automatic path**: the *master's* own
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`LDAP_REPLICATION_HOSTS` only gets recomputed when its `setup.sh` is
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re-run (or the operator re-applies it directly) -- there's no live push
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telling the master's already-running container about a spoke that joined
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five minutes ago. A spoke's own config, by contrast, is re-checked and
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applied on every `setup.sh` run there, which is the common/recurring event.
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Re-run `setup.sh` on the master after bringing up a new spoke to pick up the
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new peer and restart replication with it.
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## User Locations
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When creating or editing a user, you can specify their **Location (Site)**. This maps directly to the standard LDAP `l` (localityName) attribute, allowing you to track which physical site a user belongs to natively within the directory.
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