Connecting AlloyDB for PostgreSQL in RevOS

This guide walks you through every step of connecting an AlloyDB for PostgreSQL instance to RevOS so that Change Data Capture (CDC) runs reliably from day one.

What you need before you start

Hostname of the AlloyDB instance (see Instances → Connection info in the Google Cloud console)

Port — typically 5432

Database name

Username and password that can read data and replicate

Access to run SQL on the database (to create a replication slot and publication)

Why replication is required

Step 1. Enable logical replication in AlloyDB

AlloyDB must be started with wal_level = logical.

Console (UI)

Open your cluster → Instance → Flags → Add flag → wal_level = logical → Save & restart.

gcloud CLI (same result, handy for automation):

gcloud alloydb instances update INSTANCE_ID \
  --cluster=CLUSTER_ID \
  --database-flags wal_level=logical

After the instance restarts, verify the setting:

SHOW wal_level;         -- should output "logical"

Step 2. Create a replication slot and publication

Connect to the database with psql, DBeaver, or any SQL client.

-- 1. replication slot
SELECT pg_create_logical_replication_slot('RevOS_slot', 'pgoutput');

-- 2. publication (all tables by default)
CREATE PUBLICATION RevOS_pub FOR ALL TABLES;

Use different names if you prefer – just remember them for Step 3.

Grant replication permissions if the user does not already have them:

ALTER ROLE RevOS_user WITH REPLICATION;   -- requires admin privileges

Step 3. Fill out the connection form in RevOS

Add a new source → AlloyDB for PostgreSQL and populate the fields as follows.

Section	Field	What to enter
Basic	Name	Any label (e.g. `AlloyDB‑Prod`)
	Host	AlloyDB host
	Port	`5432` unless you changed it
	Database Name	Target database
	Username / Password	Account with read + replication rights
Optional	Schemas	`public` (default) or another schema
	JDBC URL Parameters	Leave blank unless you need custom driver options
Security	SSL Mode	`require` (minimum) or `verify-full`AlloyDB always uses TLS; `disable` will fail unless you connect to a local test server.
CDC	Update Method	Read Changes using Write‑Ahead Log (CDC) (recommended) Choose Detect Changes with Xmin only for very small/ephemeral databases; User Defined Cursor is for custom SQL polling.
	Plugin	`pgoutput` (mandatory for AlloyDB)
	Replication Slot	A plugin logical replication slot
	Publication	A Postgres publication used for consuming changes
	Initial Waiting Time	`300` s (increase if your first sync is huge)
	Queue Size	`10000` (raise for sustained high‑volume streams)

Step 4. (Optional) Set up an SSH tunnel

If the database is not reachable from the RevOS network (e.g. private VPC, no public IP):

SSH Key Authentication or SSH Password Authentication

Provide SSH host, port (usually 22), and tunnel user credentials.

Checklist before falling back to SSH

Public or private IP/firewall rules allow inbound traffic on 5432

RevOS workers share a VPC or have a VPC‑peering route

AlloyDB authorized networks include the RevOS egress range

Only enable SSH if direct TLS connectivity is impossible.

Step 5. Test and connect

Click Connect.

RevOS will validate credentials, network reachability, replication slot, and publication.

If the test succeeds, the source becomes active and RevOS starts the initial sync.

Common issues and fixes

Symptom	Likely cause	Fix
`connection refused`	Wrong host/port or firewall	Double‑check host, open port 5432, or configure SSH.
`FATAL: password authentication failed`	Wrong user or password	Re‑enter credentials; test them with `psql`.
`ERROR: logical decoding requires wal_level >= logical`	Flag not set	Repeat Step 1, then restart instance.
`ERROR: replication slot "RevOS_slot" does not exist`	Slot name mismatch	Verify name (`pg_replication_slots`) or recreate slot.
TLS handshake errors	SSL mode mismatch	Use `require` or `verify-full`; ensure CA certificates are trusted.

Useful queries while debugging:

-- List replication slots
SELECT slot_name, active FROM pg_replication_slots;

-- Drop a stale slot
SELECT pg_drop_replication_slot('RevOS_slot');

Final notes

RevOS does not create replication slots or publications automatically; they must exist prior to connecting.

The PostgreSQL user must have:

Access to the relevant schemas/tables

The REPLICATION attribute (or equivalent IAM role)

AlloyDB does not expose superuser accounts; the built‑in alloydb_admin role is usually sufficient.

Follow the steps above and your connector should be ready in a few minutes.

If you encounter problems not covered here, contact RevOS support — we’re happy to help.

AlloyDB for PostgeSQL

Connecting AlloyDB for PostgreSQL in RevOS

What you need before you start

Step 1. Enable logical replication in AlloyDB

Step 2. Create a replication slot and publication

Step 3. Fill out the connection form in RevOS

Step 4. (Optional) Set up an SSH tunnel