singularity

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用户问题

i am running postgres in docker for local, i also have a postgres in a k8s pod for staging which i connect to using a port-forward. when the docker instance is running it takes up the port 5432 and the port forward cannot run as the port is busy, can i run both at the same time on different port? if yes, i also need to sync the two dbs so that local has all the data in staging. i never want to write anything to staging for this only to local. whats the best way todo this

ChatGPT

Yes – you can absolutely have two Postgres instances on your machine by mapping them to distinct host ports, and then pull data one‑way from staging into your local copy. Here’s the quick recipe:

1. Expose both ports

• Option A: leave your Docker Postgres on 5432 and port‑forward staging on another, e.g. 5434:

# keep docker’s -p 5432:5432 as-is
kubectl port-forward svc/postgres-staging 5434:5432 --namespace=staging

Now local Docker = 5432; staging = 5434.

• Option B: remap your Docker instance to 5433 and leave port‑forward at 5432:

docker run … -p 5433:5432 postgres:latest
# connect to Docker via host:5433; staging via host:5432

2. One‑way sync via pg_dump/pg_restore Dump staging and restore into local. This never writes back upstream.

# dump staging (read‑only)
pg_dump \
  --host=localhost --port=5434 --username=staging_user \
  --format=custom --file=staging.dump staging_db

# restore into your local Docker
pg_restore \
  --host=localhost --port=5432 --username=local_user \
  --clean --no-owner \
  --dbname=local_db staging.dump

Or pipe it in one shot:

pg_dump -h localhost -p 5434 -U staging_user -Fc staging_db \
| pg_restore -h localhost -p 5432 -U local_user -d local_db --clean

3. Automate or slice

• Cron/Makefile: wrap the above in a script or Make target.
• Selective data: if staging is huge, narrow with --schema= or --table= flags, or add WHERE clauses via pg_dump --column-inserts --table=….
• Incremental: for near‑real‑time, look at Postgres logical replication (publication/subscription) or postgres_fdw to pull only new rows.

4. Lock it down

• Use a read‑only role on staging.
• Keep credentials and connection URLs in environment variables or a .env.
• Double‑check your restore flags (--clean will drop & recreate objects).

That’s it – two running side‑by‑side, full control over which port points where, and a pull‑only dump/restore so staging stays pristine. You got this.