PostgreSQL

PostgreSQL too many connections

warning

Overview

What does this alert mean?

Active connections exceed 80% of max_connections.

Contributing factors

PgBouncer not in use or misconfigured
Connection leak in application
Idle-in-transaction connections accumulating

Affected components

Application services opening new connections

Expected action

Identify and terminate idle or idle-in-transaction connections. Consider deploying PgBouncer.

Services

PostgreSQL
https://www.postgresql.org/docs/
Team: Fill in: owning team name

Metrics

Metric

sum(pg_stat_activity_count) / pg_settings_max_connections

Description & unit

Ratio of active connections to the configured maximum.

Unit: ratio (0–1), alert threshold at 0.8

Threshold rationale

At 80% there is still headroom to act before new connections are refused.

Normal behavior

Below 50% in healthy operation.

Screenshots

Dashboard when connection ratio exceeds 80%

Alert Behavior

Silencing

Silence during load tests.

Expected frequency

Occasional.

Severities

Severity guidance

Warning. Escalate if connections reach 95%+ or application errors appear.

Impacted users

Users of services opening new connections.

Things to check to determine severity

Are idle-in-transaction sessions accumulating?
Is PgBouncer deployed and healthy?

Verification

Prometheus query

sum(pg_stat_activity_count) / pg_settings_max_connections > 0.8

Dashboards

PostgreSQL Connections — Fill in: dashboard URL

Log queries

Application connection errors — Fill in: log query URL

Troubleshooting

Steps

1Count connections: SELECT count(*) FROM pg_stat_activity;
2Find idle-in-transaction: SELECT pid, now() - state_change AS duration, query FROM pg_stat_activity WHERE state = 'idle in transaction' ORDER BY duration DESC;
3Terminate long idle sessions: SELECT pg_terminate_backend(pid) FROM pg_stat_activity WHERE state = 'idle in transaction' AND now() - state_change > interval '10 minutes';
4Check max_connections: SHOW max_connections;

Useful commands

SELECT count(*) FROM pg_stat_activity;SHOW max_connections;

Possible Resolutions

Deployed PgBouncer in transaction pooling mode — sustained connection count dropped by 80%.

Dependencies

PgBouncer (if applicable)
Application connection pools

Escalation

Guidance

Escalate if connections exceed 95% or new connection errors appear in application logs.

Slack channels

#database-oncall — Fill in: channel URL

Definitions

Alert rule

Fill in: link to the alert rule in _data/rules.yml on GitHub

Tuning notes

The 80% threshold is self-normalizing against max_connections.