Should You Disable DNS Lookups for MySQL/MariaDB Connections? (skip-name-resolve Explained)

• Disables DNS lookups for connecting clients.
• MySQL/MariaDB will only use IP addresses for access control checks, bypassing hostname resolution.

Why you might use it:

• Performance improvement: If you have a slow DNS server and many connections, this can potentially speed up connection times by avoiding DNS queries.

Important considerations before using:

• Security implications: Grant privileges must be set up specifically for IP addresses instead of hostnames. This can make them less flexible and potentially introduce security risks if not managed carefully.
• Local connections: Using localhost won't work as expected with skip-name-resolve enabled. You'll need to use the specific IP address (e.g., 127.0.0.1 for IPv4 or ::1 for IPv6) for local connections.
• Limited impact: If your DNS is fast or you don't have many connections, the performance gain may be negligible.

How to enable:

1. Configuration file: Edit the MySQL/MariaDB configuration file (usually my.cnf or mariadb.cnf).
   • Add the line skip-name-resolve under the appropriate section.
2. Command-line startup: Start the MySQL/MariaDB server with the --skip-name-resolve option.

Restart the server after making the change for it to take effect.

Alternatives to skip-name-resolve:

• Increase host_cache_size: This can improve performance by caching successful DNS lookups, reducing the number of queries needed.

Example Configurations for skip-name-resolve

MySQL (my.cnf):

[mysqld]
# Other configuration options...
skip-name-resolve

MariaDB (mariadb.cnf):

[mysqld]
# Other configuration options...
skip-name-resolve

Note:

• The location of the configuration file (e.g., /etc/mysql/my.cnf or /etc/mariadb/mariadb.cnf) may vary depending on your system.
• Make sure to replace # Other configuration options... with any existing settings you might have in your configuration file.

Command-Line Startup (for both MySQL and MariaDB):

mysqld --skip-name-resolve

Remember to restart the MySQL/MariaDB server after making changes to the configuration file for them to take effect. You can typically do this using a command like:

sudo service mysql restart  # For Ubuntu/Debian-based systems

Important:

• Double-check the specific restart command for your operating system.
• Using skip-name-resolve requires careful consideration of its security implications and potential downsides.

Alternate Methods to skip-name-resolve in MySQL/MariaDB

Optimize DNS Resolution:

• Fast DNS Server: Use a reliable and fast DNS server for your system. This can significantly reduce the time spent on DNS lookups.
• Local DNS Caching: Configure your system for local DNS caching to store frequently accessed DNS records, minimizing external DNS queries.

Increase host_cache_size (MySQL/MariaDB):

• This built-in mechanism caches successful DNS lookups for a certain period. Increasing the cache size can reduce the number of redundant DNS queries for frequently connected hosts.
  • Configuration File:

    [mysqld]
    host_cache_size = 256  # Adjust the value as needed
    

  • Command Line:

    mysqld --host_cache_size=256
    

  • Note: Requires the SYSTEM_VARIABLES_ADMIN privilege to modify at runtime.

Use IP Addresses in Grant Statements:

• Instead of relying on hostnames, explicitly grant access to users based on their IP addresses. This can be more secure than relying solely on skip-name-resolve. However, it requires managing IP addresses for users, which can be less flexible compared to hostnames.

Analyze Connection Bottlenecks:

• Use profiling tools to identify potential connection bottlenecks. Issues like slow network connections or overloaded servers could be the root cause, not necessarily DNS lookups. Address these underlying issues for better performance gains.