The Response Body Injection (RBI) module provides a filter that allows you to manipulate an HTML document received in an HTTP response from a backend server.
It can insert content into any of the following HTML elements:
Install the RBI module
Install the RBI module as follows, depending on your platform:
$ sudo apt install hapee-1.7r2-lb-htmldom
$ sudo yum install hapee-1.7r2-lb-htmldom
globalsection of your HAProxy configuration file, add the following line:
global module-load hapee-lb-htmldom.so
Configure the RBI module
filter htmldomdirective to a
backendsection to begin injecting content.
The following example replaces HTTP with HTTPS.
It injects the following markup into the
headof the HTML document, which replaces http:// with https:// in links:
When RBI automatically opts out
The RBI filter automatically deactivates under certain conditions. These are conditions when:
The request method is
Both request and response are HTTP/1.1, but the
Transfer-Encodingheader value is not
The response contains compressed content (i.e. the
Content-Encodingheader is present)
The response contains the
no-transformvalue in the
Cache-Controlheader (no transformations or conversions can happen)
Content-Typeheader value is other than
How RBI modifies responses
The filter also modifies the response in the following ways:
To ensure that the response does not get compressed, the filter removes all occurrences of the
Accept-Encodingheader from the incoming request.
In order to modify the response, the filter removes all occurrences of the
Content-Lengthheader. If the message is HTTP/1.1 or above, it sets the
Transfer-Encodingheader is set to
When you insert a large amount of content into a response, it is important to set
tune.bufsize to the appropriate size.
filter htmldom directive instructs HAProxy to inject content into an HTML document. You can declare it only once for each proxy section. Its syntax is:
# Used in the a frontend, listen, or backend section filter htmldom [mode <mode>] <action> <content>
| || |
Sets the HTML parser in either of these modes:
| || |
Identifies the HTML element in which to inject new content. It applies to the first matching element. Valid actions are:
| || |
The HTML content to inject into the response from a server. It is a
Precautions and troubleshooting
You can only use one
htmldomfilter per listener/frontend/backend.
Due to the current limitation of the filter's implementation, we do not recommended that you use this filter in combination with other filters that modify the response on the same listener/frontend/backend. Using them can cause undefined behavior (such as compression filter).
If you encounter problems with the response body manipulation, check HAProxy logs. The RBI filter logs problems related to the buffer operations, such as initialization and manipulation.