Chapter 11 Advanced Policies: Sending HTTP Service Callouts to Applications 187
• Parameters that the NetScaler uses to create an HTTP request or a single
parameter that contains a fully-formed HTTP request.
• Parameters for extracting data of interest from the HTTP response.
Note on the Format of an HTTP Request
You can specify a literal HTTP request in an HTTP callout policy. Even though
this is not required, it is useful to have a general idea of the format of an HTTP
request before configuring an HTTP callout.
An HTTP request contains a series of lines that each end with a carriage return
and a line feed, represented as either <CR><LF> or \r\n.
The first line of a request contains the HTTP method and target. For example, a
message line for a GET request contains the keyword GET and a string that
represents the object that is to be fetched, as in the following example:
GET /mysite/mydirectory/index.html HTTP/1.1\r\n
The rest of the request contains HTTP headers, including a required Host header
and, if applicable, a message body.
The request ends with a bank line (an extra <CR><LF> or \r\n).
Following is an example of a request:
Get /mysite/index.html HTTP/1.1\r\n
Host: 10.101.101.10\r\n
Accept: */*\r\n
\r\n
Note on the Format of an HTTP Response
Because the callout policy extracts data from an HTTP response, it is useful to
have a general idea of the format of an HTTP response before configuring an
HTTP callout policy.
An HTTP response contains a status message, response HTTP headers, and the
requested object, or, if the requested object cannot be served, an error message.
Following is an example of a response:
HTTP/1.1 200 OK\r\n
Content-Length: 55\r\n
Content-Type: text/html\r\n
Last-Modified: Wed, 12 Aug 1998 15:03:50 GMT\r\n
Accept-Ranges: bytes\r\n
ETag: “04f97692cbd1:377”\r\n
Date: Thu, 19 Jun 2008 19:29:07 GMT\r\n
\r\n
<55-character response>