Error

Error Code: 08000

PostgreSQL Error 08000: Failed Database Connection

📦 PostgreSQL

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Description

This error indicates that the client application was unable to establish a connection with the PostgreSQL database server. It typically occurs when there are issues preventing the client from reaching the server, such as network problems, incorrect connection details, or the server being offline.

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Error Message

connection exception

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Known Causes

4 known causes

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PostgreSQL Server Not Running

The PostgreSQL database server process is not active or has unexpectedly terminated, making it unreachable for client connections.

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Incorrect Connection Details

The client application is attempting to connect using an invalid hostname, port number, database name, username, or password.

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Network or Firewall Blockage

A network issue, such as an active firewall, routing problem, or general network outage, is preventing communication between the client and the server.

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Server Max Connections Exceeded

The PostgreSQL server has reached its configured limit for concurrent connections, rejecting any new connection attempts.

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Solutions

3 solutions available

1. Verify Network Connectivity and Firewall Rules easy

Ensure the client can reach the PostgreSQL server over the network and that firewalls allow traffic.

From the client machine experiencing the error, try to ping the PostgreSQL server's IP address or hostname.

ping <postgresql_server_ip_or_hostname>

If ping fails, check for network issues between the client and server. This might involve checking routers, switches, or network configurations.

Verify that the PostgreSQL port (default is 5432) is open on the server's firewall and any intermediate firewalls between the client and server. You can use `telnet` or `nc` (netcat) from the client to test.

telnet <postgresql_server_ip_or_hostname> 5432
# Or
nc -vz <postgresql_server_ip_or_hostname> 5432

If the port is blocked, configure the firewall to allow inbound connections on port 5432 from the client's IP address or subnet. The command to do this varies depending on the firewall software (e.g., `ufw`, `firewalld`, `iptables` on Linux, or Windows Firewall).

# Example for ufw:
sudo ufw allow from <client_ip_address> to any port 5432
# Example for firewalld:
sudo firewall-cmd --zone=public --add-rich-rule='rule family="ipv4" source address="<client_ip_address>" port protocol="tcp" port="5432" accept'
--permanent
sudo firewall-cmd --reload

2. Check PostgreSQL Server Status and Configuration medium

Ensure the PostgreSQL server process is running and configured to accept connections from the client.

On the PostgreSQL server, check if the PostgreSQL service is running. The command depends on your operating system and PostgreSQL installation method.

# For systems using systemd:
systemctl status postgresql
# For systems using init.d:
service postgresql status
# Or, to find the process directly:
ps aux | grep postgres

If the PostgreSQL service is not running, start it.

# For systems using systemd:
sudo systemctl start postgresql
# For systems using init.d:
sudo service postgresql start

Verify the `postgresql.conf` file (usually located in `/etc/postgresql/<version>/main/` or similar) for the `listen_addresses` setting. It should be set to `'*'` to listen on all network interfaces, or a specific IP address of the server. If it's commented out or set to `localhost`, it won't accept remote connections.

# Example in postgresql.conf:
listen_addresses = '*'

After modifying `postgresql.conf`, you need to reload or restart the PostgreSQL service for the changes to take effect.

# To reload configuration:
pg_ctl reload -D /path/to/your/data/directory
# Or, restart the service:
sudo systemctl restart postgresql

Check the `pg_hba.conf` file (usually in the same directory as `postgresql.conf`) to ensure there's an entry that allows connections from the client's IP address or network range for the specific database and user. The format is `host <database> <user> <address> <method>`.

# Example in pg_hba.conf allowing connections from any IP for user 'myuser' with password authentication:
host    all             myuser          0.0.0.0/0               md5

If you modify `pg_hba.conf`, you must reload the PostgreSQL configuration.

# To reload configuration:
pg_ctl reload -D /path/to/your/data/directory
# Or, restart the service:
sudo systemctl restart postgresql

3. Review Client Connection Parameters easy

Double-check the connection string or parameters used by the client application.

Carefully examine the connection string or parameters used by your application or tool to connect to PostgreSQL. Ensure the hostname/IP address, port, database name, username, and password are all correct.

# Example connection string (e.g., for psql):
psql "host=your_server_ip port=5432 dbname=your_db user=your_user password=your_password"

If you are using a hostname, try connecting using the server's IP address directly to rule out DNS resolution issues.

psql "host=<server_ip_address> port=5432 dbname=your_db user=your_user password=your_password"

If the error persists, try connecting with a known-working client (like `psql` on the server itself or another machine) using the same credentials and parameters to isolate the issue to the specific client application or its environment.

# On the PostgreSQL server:
psql -U your_user -d your_db -h localhost -p 5432

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Related Errors

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