Configuring Rules for HTTP Responses Compression 

Use

The J2EE Engine is capable of applying the IANA (The Internet Assigned Numbers Authority) gzip message transfer encoding mechanism to HTTP responses. The purpose is to reduce the length of the response message body to be transmitted to the client, and hence, to achieve better communication performance.

This function is managed entirely by the HTTP Provider Service. Considering this procedure, you can define rules that determine the behavior of the service when applying the gzip transfer encoding to both static HTTP responses and dynamic ones (that is, dynamic servlet or JSP responses). The only exception is that you can use a function of the Web Container Service to configure two HTTP headers that prevent or force, respectively, servlet or JSP responses from being compressed as described in Configuring the Headers That Affect Dynamic Responses Compression.

Procedure

Use the Visual Administrator tool to define the gzip compression related settings:

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       1.      Open the Properties tab of the HTTP Provider Service running on the server process.

       2.      Edit any of the following properties on the Properties screen:

                            a.      Specify the minimum required length of the response message to which gzip transfer encoding can be applied using the MinimumGZipLength property. The value of the property is specified in bytes. By default, it is 8192 bytes.

Response messages that are shorter than the value of the MinimumGZipLength property are sent as-is. The reason for this is that for fast local area networks, data compression and decompression is usually slower than when the data is transmitted uncompressed. Therefore, you can use this property to utilize your network capacity and achieve the best communication performance.

                            b.      Define a comma-separated list of file extensions or MIME types that must always be compressed with gzip encoding as a value of the AlwaysCompressed property. However, response messages that appear in this list and are shorter than the value of the MinimumGZipLength property are not compressed.

When you add a file extension to the list, it must start with an asterisk, such as *.html. All other strings are considered to be MIME types.

There is a special value for this property: this is the string [unknown]. It refers to dynamic response messages that do not have the Content-Type header set.

                            c.      Define a comma-separated list of file extensions or MIME types that must never be compressed with gzip encoding as a value of the NeverCompressed property.

When you add a file extension to the list, it must start with an asterisk, such as *.html. All other strings are considered to be MIME types.

There is a special value for this property: this is the string [unknown]. It refers to dynamic response messages that do not have the Content-Type header set.

                            d.      Determine whether or not the response messages types that do not appear in the AlwayCompressed and NeverCompressed lists are compressed with gzip encoding using the CompressedOthers property. If you set it to true, the HTTP Provider Service compresses all other response messages that are longer than the value of the MinimumGZipLength property.

                            e.      Specify the request URL size above which the generated response for that request is not compressed (even if it should be according to the rules defined by the above properties) using the MaximumCompressedURLLength property. The URL size is specified in bytes. Using this property, you can overcome known problems with caching compressed responses that are generated for long URLs on some browsers.

By default, the MaximumCompressedURLLength property has a value of -1, which means the request URL size does not affect the rules for compressing the response.