# Comment Filter

## Overview

With the _comment_ filter it is possible to define comments that are
injected before the actual statements. These comments appear as sql
comments when they are received by the server.

```
[MyComment]
type=filter
module=comment
inject=Comment to be injected

[MyService]
type=service
router=readwritesplit
servers=server1
user=myuser
passwd=mypasswd
filters=MyComment
```


## Filter Parameters

The Comment filter requires one mandatory parameter to be defined.

### `inject`

A parameter that contains the comment injected before the statements.
There is also defined variable $IP that can be used to comment the
IP address of the client in the injected comment.
Variables must be written in all caps.


## Examples

### Example 1 - Inject IP address of the connected client into statements
as comment.

You want to see the IP addresses of the clients with the server so you
define filter to comment the into the statements they send.


```
[IPComment]
type=filter
module=comment
inject=IP=$IP

[MyService]
type=service
router=readwritesplit
servers=server1
user=myuser
passwd=mypasswd
filters=IPComment
```

In this example when MaxScale receives statement like:
```
 SELECT user FROM people;
```
It would look like
```
/* IP=::ffff:127.0.0.1 */SELECT user FROM people;
```
when received by server.