Error
Error Code:
57P03
PostgreSQL Error 57P03: Database Connection Temporarily Unavailable
Description
Error 57P03, "cannot connect now," indicates that the PostgreSQL server is temporarily unable to accept new client connections. This typically occurs due to planned maintenance, high server load, or an administrator's intervention, preventing immediate access to the database.
Error Message
cannot connect now
Known Causes
4 known causesDatabase in Recovery/Maintenance
The PostgreSQL server might be undergoing maintenance, backup, or recovery operations, temporarily preventing new connections.
Maximum Connections Reached
The server has reached its configured limit for active connections (max_connections), temporarily refusing new client requests.
Server Startup/Shutdown
The PostgreSQL server process is currently starting up or shutting down, making it unavailable for new client connections.
Administrator Intervention
A database administrator might have explicitly configured the server to temporarily disallow new connections for specific tasks or security reasons.
Solutions
4 solutions available1. Check PostgreSQL Server Status easy
Verify that the PostgreSQL server process is running and accessible.
1
Connect to your PostgreSQL server's host machine.
2
Check the status of the PostgreSQL service. The command might vary slightly depending on your operating system.
sudo systemctl status postgresql3
If the service is not running, start it.
sudo systemctl start postgresql4
After starting, check the status again to confirm it's active.
sudo systemctl status postgresql2. Review PostgreSQL Logs for Specific Errors medium
Examine PostgreSQL logs to identify the root cause of connection issues.
1
Locate the PostgreSQL log files. The default location is typically within the PostgreSQL data directory.
2
Use a command like `find` to locate the logs if you're unsure of the exact path.
sudo find / -name 'postgresql-*.log' 2>/dev/null3
Open the most recent log file and search for error messages or warnings related to connections, resource exhaustion, or startup failures.
sudo tail -f /var/log/postgresql/postgresql-14-main.log4
Common log entries to look for include 'FATAL: remaining connection slots are reserved for non-replication superuser connections', 'out of memory', or specific errors during server startup.
3. Adjust Maximum Concurrent Connections medium
Increase the `max_connections` setting if the server has reached its connection limit.
1
Connect to your PostgreSQL server as a superuser (e.g., `postgres`).
psql -U postgres2
Check the current value of `max_connections`.
SHOW max_connections;3
If the current value is low and logs indicate connection limits are being hit, you can increase it. This requires editing the `postgresql.conf` file.
4
Locate your `postgresql.conf` file. You can often find its location by running `SHOW config_file;` in `psql`.
SHOW config_file;5
Edit the `postgresql.conf` file (e.g., using `nano` or `vim`). Find the `max_connections` line and increase the value. Be mindful of available system resources.
sudo nano /etc/postgresql/14/main/postgresql.conf6
Save the changes and restart the PostgreSQL service for the new setting to take effect.
sudo systemctl restart postgresql4. Investigate Resource Exhaustion (CPU, Memory, Disk) advanced
Determine if the server is overloaded and unable to accept new connections due to insufficient system resources.
1
Connect to your PostgreSQL server's host machine.
2
Use system monitoring tools to check CPU usage.
top3
Check memory usage.
free -h4
Verify disk space. Insufficient disk space can prevent PostgreSQL from operating correctly.
df -h5
If resources are consistently maxed out, consider optimizing queries, scaling up hardware, or distributing the workload.