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Description

Error 08006, 'connection failure', indicates that a client application was unable to establish a connection with the PostgreSQL database server. This typically occurs when the client cannot reach the server or the server refuses the connection attempt.

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Error Message

connection failure

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Known Causes

4 known causes

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PostgreSQL Server Unavailable

The PostgreSQL server process is not running or is not accessible from the client's network location.

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Invalid Connection Parameters

The hostname, port, username, or password provided by the client application is incorrect or misconfigured.

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Network Firewall Blocking

A firewall on either the client or server machine, or an intermediate network device, is preventing the connection.

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General Network Connectivity Issues

Underlying network problems, such as a disconnected cable or routing issues, are preventing communication.

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Solutions

5 solutions available

1. Check PostgreSQL is Running easy

Verify server is started and healthy

1

Check server status

sudo systemctl status postgresql

2

Start if stopped

sudo systemctl start postgresql

3

Check logs for errors

sudo tail -100 /var/log/postgresql/postgresql-14-main.log

2. Check Network Connectivity easy

Verify network path to server

1

Test connectivity

ping postgresql-server
telnet postgresql-server 5432

2

Check if port is listening

ss -tlnp | grep 5432

3

Check firewall

sudo ufw status
sudo iptables -L -n | grep 5432

3. Check listen_addresses medium

Ensure server accepts remote connections

1

Check current setting

SHOW listen_addresses;

2

Update in postgresql.conf

# Listen on all interfaces:
listen_addresses = '*'

# Or specific IP:
listen_addresses = '192.168.1.100'

3

Restart PostgreSQL

sudo systemctl restart postgresql

4. Implement Connection Retry medium

Handle temporary connection failures

1

Python retry logic

import psycopg2
import time

def get_connection(dsn, max_retries=5):
    for i in range(max_retries):
        try:
            return psycopg2.connect(dsn)
        except psycopg2.OperationalError as e:
            if 'connection' in str(e).lower():
                time.sleep(2 ** i)  # Exponential backoff
                continue
            raise
    raise Exception('Could not connect after retries')

5. Check SSL/TLS Configuration medium

Fix SSL connection issues

1

Try connecting without SSL

psql "host=server dbname=db sslmode=disable"

2

Check SSL settings

SHOW ssl;

3

Connection string with SSL

psql "host=server dbname=db sslmode=require"

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Related Errors

5 related errors

PostgreSQL Error 08006: Client Connection Failure