Odoo PostgreSQL Zu viele Verbindungen nach dem Upgrade – Fix

After an Odoo upgrade or a worker count change, users start seeing this:

ERROR: connection to server failed: FATAL: sorry, too many clients already

Or the Python-side variant:

psycopg2.OperationalError: FATAL: remaining connection slots are reserved for non-replication superuser connections

PostgreSQL's connection limit is a hard wall. Odoo's worker pool, the longpolling worker, the cron threads, and any external tools all open connections from a fixed pool. When the math is wrong, you hit the wall. This guide tunes Odoo 17.0/18.0/19.0 to fit within a sensible PostgreSQL configuration.

Quick Fix

Compute the actual connection demand:

worker_connections = workers × (1 + max_cron_threads) × 2 + longpolling_workers × 2 + 10

For a typical Odoo 18.0 production with 8 workers and 2 cron threads:

8 × (1 + 2) × 2 + 1 × 2 + 10 = 60 connections from Odoo alone

Set PostgreSQL's max_connections to at least 100, restart, and monitor:

# postgresql.conf
max_connections = 200

sudo systemctl restart postgresql

If you cannot raise max_connections (RDS limits, RAM constraints), add PgBouncer as a connection pooler.

Why This Happens

Odoo's connection demand has many dimensions:

1. Per-worker connections. Each gunicorn worker holds at minimum one connection. Long-running requests can hold multiple (one for the main cursor, one for cron-like sub-flows).
2. Cron threads. --max-cron-threads=N adds N more long-lived connections per worker.
3. Longpolling worker. Holds one persistent connection per active longpoll, plus one shared.
4. Test runners and shells. A odoo-bin shell session adds one more connection.
5. External tools. pgbench, pg_dump, monitoring queries, replication, all consume connection slots.
6. Connection leaks. A module that opens raw connections without closing them quietly drains the pool.

After a major version upgrade, two common things change: worker count is often increased to handle new modules, and connection-keeping behaviour can shift slightly between PostgreSQL client library versions.

Step-by-Step Diagnosis

1. See exactly who is connected.

SELECT pid, usename, datname, application_name, state, query_start, state_change
FROM   pg_stat_activity
ORDER  BY query_start NULLS LAST;

Group by application_name to see how many connections each tool holds.

2. Count by category.

SELECT application_name, count(*) FROM pg_stat_activity
GROUP BY application_name ORDER BY 2 DESC;

If odoo shows more connections than your worker math predicts, you have a leak. If psql or pg_dump shows surprisingly many, an external tool is contributing.

3. Check Odoo's configured worker count.

grep -E "^(workers|max_cron_threads|longpolling)" /etc/odoo/odoo.conf

Compute expected demand. If it exceeds max_connections, you have a configuration mismatch.

4. Check PostgreSQL's limit.

SHOW max_connections;
SELECT count(*) FROM pg_stat_activity;

If the count is at or near the limit and growing, you are connection-limited.

5. Look for idle-in-transaction.

SELECT count(*) FROM pg_stat_activity WHERE state = 'idle in transaction';

Non-zero values for more than a few seconds indicate a transaction that hung mid-flight, holding a connection forever. These are the silent killers.

Permanent Fix

Step 1 — Right-size max_connections. PostgreSQL's max_connections is bounded by RAM (each connection costs roughly 10 MB of memory for catalog cache and work buffers). For a 16 GB server, 200 connections is comfortable; for a 64 GB server, 500 is reasonable. Do not blindly raise it to 1000 — the kernel and PostgreSQL itself become overhead-bound.

# postgresql.conf
max_connections = 200
work_mem = 16MB
shared_buffers = 4GB

Step 2 — Right-size Odoo workers. A common rule: 2 workers per CPU core, 2 cron threads per worker, 1 longpolling worker.

# odoo.conf — for a 4-core server
workers = 8
max_cron_threads = 2
longpolling_port = 8072

Avoid the temptation to set workers=20 on a 4-core box. Each worker is a Python process; oversubscription causes context-switch thrash, not throughput.

Step 3 — Add PgBouncer for shared installations. For multi-database installations or many workers, a connection pooler dramatically reduces connection count to PostgreSQL itself:

# pgbouncer.ini
[databases]
* = host=127.0.0.1 port=5432

[pgbouncer]
listen_port = 6432
pool_mode = transaction
max_client_conn = 500
default_pool_size = 25

Odoo connects to PgBouncer (port 6432) which pools to PostgreSQL (port 5432). Hundreds of Odoo workers share a few dozen real PostgreSQL connections.

PgBouncer in transaction mode requires care with prepared statements and session-level state. Test thoroughly; some Odoo flows assume session pooling. ECOSIRE's Odoo support team tunes PgBouncer for high-traffic Odoo deployments routinely.

Step 4 — Add idle-transaction reaping.

# postgresql.conf
idle_in_transaction_session_timeout = 300000   # 5 minutes
statement_timeout = 600000                      # 10 minutes

These caps prevent any single hung query from locking a connection forever.

Step 5 — Fix Odoo connection leaks. If any custom module opens raw psycopg2.connect() without closing, find and fix it:

grep -rn "psycopg2.connect\|psycopg2.pool" /opt/odoo/custom/

Use self.env.cr whenever possible. Raw connections are almost always wrong in Odoo modules.

How to Prevent It

• Capacity-plan before the upgrade. Compute expected connection demand for the new worker count. Verify max_connections accommodates it with headroom (at least 30 percent buffer). Do this before the deploy, not when users complain.
• Monitor pg_stat_activity continuously. Prometheus's postgres_exporter ships a pg_stat_activity_count metric. Alert at 80 percent of max_connections.
• Cap Odoo's connection use per process. db_maxconn in odoo.conf limits the per-worker connection count — set it to a sensible value like 20 to prevent runaway leaks from one bad request taking down the pool.
• Use PgBouncer from day one. Even small Odoo deployments benefit. The "I'll add it later" trap is real — adding PgBouncer to a stressed system mid-incident is the worst time to learn it.
• Test connection limits with a load test. k6 or Locust against your Odoo + ramped to peak QPS reveals connection saturation in staging. Far cheaper than debugging it in production.
• Respect statement_timeout. Long queries should die. A multi-hour query holding a connection is a bug, not a feature.

Related Errors

• Upgrade aborted, database corrupted — what happens when an upgrade saturates connections mid-flight.
• PostgreSQL deadlock during stock move — different DB-level pain, often shows up alongside this.
• Database locked during import — connection exhaustion via long writes.
• Slow list view on > 1M rows — list views can pile up connections quickly.

Frequently Asked Questions

Why does the connection count keep growing after a worker restart?

If your worker actually restarts, its old connections should be cleaned up by PostgreSQL within tcp_keepalives_idle seconds. If counts grow without bound, the workers are not actually restarting, or some external tool is opening connections and not closing them. Check pg_stat_activity.application_name and state_change to see who is holding stale connections.

Should I use connection pooling inside Odoo or in PgBouncer?

Both. Odoo has its own per-worker connection pool (db_maxconn). PgBouncer pools across workers. They complement each other — Odoo's pool prevents one request from spawning many DB connections, PgBouncer's pool prevents many workers from each opening a separate DB connection.

What is the difference between pool_mode = session and pool_mode = transaction?

session keeps a PostgreSQL connection bound to one client for the whole session — minimal pooling benefit, full session-state semantics. transaction releases the PG connection back to the pool at every commit — high pooling benefit, but advisory locks and prepared statements are scoped to a single transaction. Odoo works with transaction mode if you avoid cr.execute("PREPARE") patterns.

My RDS PostgreSQL has a hard max_connections cap I cannot raise. What now?

PgBouncer is essentially mandatory in that situation. Run it on the application host (or on a small EC2 instance shared by all app hosts), point Odoo at it, and your effective connection count to RDS drops to whatever PgBouncer's default_pool_size is. ECOSIRE has shipped this pattern for several customers running Odoo on RDS-Postgres.

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