Centralized Rsyslog : Max Size of Message

In a centralized rsyslog setup, managing the maximum size of log messages is important to ensure that large messages do not cause issues with performance or storage. rsyslog has configuration options that allow you to control and manage message size.

Configuring Max Size of Messages in Rsyslog

1. Setting the Maximum Message Size

You can configure the maximum size of messages in rsyslog by setting the maxMessageSize parameter. This parameter specifies the maximum size of a message that rsyslog will accept.

Edit the Rsyslog Configuration File

1. Open the rsyslog configuration file for editing. You can edit the main configuration file or create a custom configuration file under /etc/rsyslog.d/.

    

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   sudo nano /etc/rsyslog.conf
   

   or

    

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   sudo nano /etc/rsyslog.d/99-custom.conf
   

2. Add or modify the following line to set the maximum message size. The value is specified in bytes:

    

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   $MaxMessageSize 1000000
   

   In this example, the maximum message size is set to 1,000,000 bytes (approximately 1 MB).

3. Save and exit the editor.

4. Restart rsyslog to apply the changes:

    

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   sudo systemctl restart rsyslog
   

2. Handling Large Messages

If you expect very large messages, consider configuring rsyslog to handle them properly:

• Log Splitting: Ensure that the logging application is configured to split large messages if needed. This is often handled by the application generating the logs.
• Message Truncation: Configure rsyslog to truncate messages that exceed the maximum size. By default, rsyslog will discard messages that exceed the configured size limit.

3. Monitoring and Troubleshooting

• Check Logs for Errors: Monitor rsyslog logs for any errors related to message sizes. These logs can help you identify if messages are being discarded or if there are any configuration issues.

   

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  sudo tail -f /var/log/syslog
  

• Adjust Size Limits as Needed: Depending on the volume and size of messages, you might need to adjust the MaxMessageSize parameter to balance performance and log management.

Example of Complete Configuration

Here's an example configuration snippet that sets a maximum message size and handles other basic settings:

# Set maximum message size to 1 MB
$MaxMessageSize 1000000

# Additional configuration settings
module(load="imudp") # For UDP input
input(type="imudp" port="514")

module(load="omfile") # For file output
action(type="omfile" file="/var/log/remote.log")

# Handle messages from a specific application
if $programname == 'myapp' then /var/log/myapp.log
& ~

In this example, messages are handled with a maximum size of 1 MB, and specific messages are routed to designated log files.

Additional Notes

• Performance Considerations: Be mindful of the impact of large messages on rsyslog performance. Very large messages can affect processing and storage efficiency.
• Documentation: For more details on configuring rsyslog and handling large messages, refer to the rsyslog documentation.

By configuring the maximum message size and handling large messages appropriately, you can ensure that your centralized rsyslog setup remains efficient and manageable.

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