# Rsyslog Conditional Repeatedmsgreduction

`rsyslog`'s `repeatedmsgreduction` feature is designed to reduce the verbosity of logs by suppressing repeated messages that occur within a specified time interval. This is particularly useful for managing high-volume logs where the same message may be logged multiple times in quick succession.

Here's how you can configure `rsyslog` to conditionally apply repeated message reduction:

### 1. **Understand the `repeatedmsgreduction` Feature**

- **Purpose**: Reduces the frequency of repeated log messages to avoid log flooding.
- **How It Works**: When enabled, `rsyslog` will aggregate repeated messages and include only the first instance and a count of the repetitions.

### 2. **Basic Configuration**

To enable `repeatedmsgreduction`, you need to configure it in your `rsyslog` configuration file. This configuration can be applied globally or conditionally based on specific criteria.

### **2.1 Global Configuration**

1. **Open the `rsyslog` Configuration File**
    
    Open `/etc/rsyslog.conf` or a file in `/etc/rsyslog.d/`:
    
    ```bash
    sudo nano /etc/rsyslog.conf
    ```
    
2. **Add or Modify the Configuration**
    
    Add the following line to enable repeated message reduction globally:
    
    ```
    $RepeatedMsgReduction on
    ```
    
3. **Save and Exit**
    
    Save your changes and exit the editor.
    
4. **Restart `rsyslog`**
    
    Apply the changes by restarting `rsyslog`:
    
    ```bash
    sudo systemctl restart rsyslog
    ```
    

### **2.2 Conditional Configuration**

To apply `repeatedmsgreduction` conditionally, you can use `if` conditions in your configuration. For example, you might want to enable it only for specific log sources or facilities.

1. **Edit or Create a Custom Configuration File**
    
    You can create or edit a configuration file in `/etc/rsyslog.d/` for conditional settings:
    
    ```bash
    sudo nano /etc/rsyslog.d/10-reduced-repeated-messages.conf
    ```
    
2. **Add Conditional Configuration**
    
    Example configuration to apply repeated message reduction conditionally:
    
    ```
    if ($programname == 'myapp') then {
        $RepeatedMsgReduction on
        *.* /var/log/myapp.log
    }
    
    ```
    
    In this example:
    
    - `if ($programname == 'myapp')` applies the configuration only to logs from `myapp`.
    - `$RepeatedMsgReduction on` enables message reduction for these logs.
    - `.* /var/log/myapp.log` specifies that all messages from `myapp` should be logged to `/var/log/myapp.log`.
3. **Save and Exit**
    
    Save your changes and exit the editor.
    
4. **Restart `rsyslog`**
    
    Restart `rsyslog` to apply the conditional configuration:
    
    ```bash
    sudo systemctl restart rsyslog
    ```
    

### 3. **Additional Configuration Options**

- **Setting Time Intervals**: `rsyslog` uses a default time interval for message reduction. If needed, you can adjust the interval using additional configuration options.
- **Message Reduction Limits**: You may want to set limits on the number of messages or the time window for message reduction. However, `rsyslog` itself doesn’t directly support fine-grained time interval configuration for repeated message reduction beyond its default behavior.

### 4. **Verify Configuration**

After applying the configuration:

1. **Check Log Files**
    
    Verify that repeated messages are being reduced as expected. Look at your log files to ensure that repeated messages are aggregated correctly.
    
    ```bash
    tail -f /var/log/myapp.log
    ```
    
2. **Monitor `rsyslog` Logs**
    
    Check the `rsyslog` logs for any errors or warnings related to configuration:
    
    ```bash
    sudo tail -f /var/log/syslog
    ```
    

By configuring `repeatedmsgreduction`, you can manage high-volume logs more effectively and reduce the noise from repeated log messages.