Tuesday February 05, 2008 Meena Vyas
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Tuesday February 05, 2008 Using HTTP compression to speed up content delivery in Sun Java System Web Server 7.0 update 2
Using HTTP compression to speed up content delivery in Sun Java System Web Server 7.0 update 2
If you are looking for faster web page downloads, you can use HTTP compression feature which compresses your content to speed it up. It is especially beneficial for low bandwidth connections. This also reduces the number of bytes transferred and improves the overall server performance.
How it Works
Browsers that support compressed content send an Accept-encoding header with value gzip, deflate. Our Web Server sees the header and chooses to provide compressed content, and sends Content-encoding: gzip response header. The browser on seeing this header tries to decompress the content and renders it.Now the question is how to enable HTTP compression feature can be configured in obj.conf. Let me explain that in detail in this blog.
HTTP Compression of Static Files
For dynamic compression of static files in Sun Java System Web Server 7.0 Update 2, we need to use compress-file SAF with find-compressed SAF.The compress-file function creates the compressed file in the subdirectory specified if the file size is in between min-size and max-size the first time a request is sent on the URI. If Web Server needs to compress that static file for every static request then it may not really improve performance. It will reduce the network traffic but will cause more CPU usage. So content compression will only happen once or until the uncompressed original file is modified. If check-age is set to true, it recreates the compressed file if the compressed version is not as recent as the non-compressed version. The find-compressed function checks if a compressed version of the requested file is available. If the following conditions are met, find-compressed changes the path to point to the compressed file:
- A compressed version is available.
- The compressed version is as recent as the non-compressed version.
- The client supports compression.
- If the HTTP method is GET or HEAD.
Example
This is an example of how server compresses html files and places them in .compressed directory (relative to the original file location). Modify the default object of obj.conf as shown below<Object
name="default">
NameTrans fn="assign-name" from="*.html" name="find-compressed"
...
Service method=(GET|HEAD|POST) type=*~magnus-internal/* fn=compress-file subdir=".compressed-files"
Service method=(GET|HEAD|POST) type=*~magnus-internal/* fn=send-file
...
</Object>
<Object name="find-compressed">
PathCheck fn="find-compressed"
</Object>
NameTrans fn="assign-name" from="*.html" name="find-compressed"
...
Service method=(GET|HEAD|POST) type=*~magnus-internal/* fn=compress-file subdir=".compressed-files"
Service method=(GET|HEAD|POST) type=*~magnus-internal/* fn=send-file
...
</Object>
<Object name="find-compressed">
PathCheck fn="find-compressed"
</Object>
However, if you plan to put precompressed content in the location where the original file is present yourself, you can just use find-compressed SAF . A compressed version of a file must have the same file name as the non-compressed version but with a .gz suffix. For example, the compressed version of a file named /httpd/docs/index.html would be named /httpd/docs/index.html.gz. To compress files, you can use the freely available gzip program.
<Object name="default">
NameTrans fn="assign-name" from="*.html" name="find-compressed"
...
</Object>
<Object name="find-compressed">
PathCheck fn="find-compressed"
</Object>
The http-compression
filter compresses
outgoing dynamic content such as the output from SHTML
pages, CGI programs, or pages created with JavaServer PagesTM
(JSPTM) technology that
need to be interpreted by the server.
Example
Output fn="insert-filter" type="text/*" filter="http-compression" vary="on" compression-level="9"
In this example, type="text/*" restricts compression to documents that have a MIME type of text/* (for example, text/ascii, text/css, text/html, and so on).
Suppose you want to compress only JSPs. Modify the default object of obj.conf as shown below<Object
name="default">
NameTrans fn="assign-name" from="*.jsp" name="compress-on-demand"
...
</Object>
<Object name="compress-on-demand">
Output fn="insert-filter" filter="http-compression"
</Object>
NameTrans fn="assign-name" from="*.jsp" name="compress-on-demand"
...
</Object>
<Object name="compress-on-demand">
Output fn="insert-filter" filter="http-compression"
</Object>
Parameters
Here is a list of parameters you can use if you want to tune these functionsParameters for compress-file
- subdir
- (Optional) This should be a directory name only relative to the
directory
in which the original non-compressed file is located.
- To overwrite a pre-compressed compressed file lying in
docroot set the subdir to ".".
- The default value is "." will overwrite any precompressed gz files if any.
- check-age (Optional) The values can be true or false. The default value is true.
- vary (Optional) The values can be true or false. The default value is true.
- compression-level (Optional) The values can be 1 to 9. The default value is 6.
- min-size
(Optional) The values can be 0
to INT_MAX.
The default value is 256.
- max-size (Optional) The values can be min-size to INT_MAX. The default value is 1048576.
Parameters for find-compressed
- check-age
- (Optional) Specifies whether to check if the compressed version is older than the non-compressed version.
- The values can be yes or no. By default, the value is set to yes.
- If set to yes, the compressed version will not be selected if it is older than the non-compressed version.
- If set to no, the compressed version is always selected, even if it is older than the non-compressed version.
- vary
- (Optional) Specifies whether to insert a Vary:
Accept-Encoding header.
- The values can be yes or no. By default, the value is set to yes.
- If set to yes, a Vary: Accept-Encoding header is always inserted when a compressed version of a file is selected.
- If set to no, a Vary: Accept-Encoding header is never inserted.
Parameters for http-compression
- vary
- Controls whether the filter inserts a Vary:
Accept-encoding header.
- If vary is absent, the default value is yes. yes tells the filter to insert a Vary: Accept-encoding header when it compresses content.
- no tells the filter to never insert a Vary: Accept-encoding header.
- fragment-size
- Size in bytes of the memory fragment used
by the compression library
to control how much to compress at a time.
- The default value is 8096.
- compression-level
- Controls the compression level used
by the compression library.
- Valid
values are from 1 to 9. A
value of 1 results in the best speed.
- A value
of 9 results in the best
compression.
- The default value is 6.
- window-size
- Controls an internal parameter of the
compression library.
- Valid values
are from 9 to 15.
- Higher values result in better compression at the
expense
of memory usage.
- The default value is 15.
- memory-level
- Controls how much memory is used by the
compression library.
- Valid values
are from 1 to 9.
- A value of 1 uses the minimum amount of memory but is
slow.
- A value of 9 uses the maximum amount of memory for optimal
speed.
- The default value is 8.
Using wadm (Administration CLI) to configure these HTTP compression features
You can use the following wadm commands to configure these.
For compression of static content i.e. find-compressed and compress-file functions use
wadm>
enable-precompressed-content
Usage: enable-precompressed-content --help|-?
or enable-precompressed-content [--echo] [--no-prompt] [--verbose] [--uri-pattern=pattern] [--no-vary-header] [--no-age-check] [--compress-file] [--sub-dir=sub-directory] [--compression-level=1-9] [--min-size=size-in-bytes] [--max-size=size-in-bytes] --config=config-name --vs=vs-name
CLI014 vs is a required option.
wadm>
For compression of dynamic content i.e. http-compression function use
Usage: enable-precompressed-content --help|-?
or enable-precompressed-content [--echo] [--no-prompt] [--verbose] [--uri-pattern=pattern] [--no-vary-header] [--no-age-check] [--compress-file] [--sub-dir=sub-directory] [--compression-level=1-9] [--min-size=size-in-bytes] [--max-size=size-in-bytes] --config=config-name --vs=vs-name
CLI014 vs is a required option.
wadm>
wadm>
enable-on-demand-compression
Usage: enable-on-demand-compression --help|-?
or enable-on-demand-compression [--echo] [--no-prompt] [--verbose] [--uri-pattern=pattern] [--no-vary-header] [--fragment-size=size] [--compression-level=1-9] --config=config-name --vs=vs-name
CLI014 vs is a required option.
You can also try experimenting with other related CLIs
Usage: enable-on-demand-compression --help|-?
or enable-on-demand-compression [--echo] [--no-prompt] [--verbose] [--uri-pattern=pattern] [--no-vary-header] [--fragment-size=size] [--compression-level=1-9] --config=config-name --vs=vs-name
CLI014 vs is a required option.
- get-precompressed-content-prop
- get-on-demand-compression-prop
- disable-precompressed-content
- disable-on-demand-compression
How do I test if my configuration is working or not
You can use telnet to submit HTTP requests, impersonating a web browser. The stuff in bold is the stuff I typed. Here's an example on a Solaris machine testserver, where I have a Web Server instance running on port 2600:
$ telnet testserver 2600
Trying 1.2.3.4...
Connected to testserver.
Escape character is '^]'.
GET / HTTP/1.0 [press enter twice]
HTTP/1.1 200 OK
Server: Sun-Java-System-Web-Server/7.0
Date: Wed, 06 Feb 2008 12:09:45 GMT
Content-type: text/html
Last-modified: Fri, 25 Jan 2008 00:12:38 GMT
Content-length: 355
Connection: close
<html>...</html>
Connection to testserver closed by foreign host.
$
I'll try that same HTTP request again, but this time indicate that I
want a compressed response:
Trying 1.2.3.4...
Connected to testserver.
Escape character is '^]'.
GET / HTTP/1.0 [press enter twice]
HTTP/1.1 200 OK
Server: Sun-Java-System-Web-Server/7.0
Date: Wed, 06 Feb 2008 12:09:45 GMT
Content-type: text/html
Last-modified: Fri, 25 Jan 2008 00:12:38 GMT
Content-length: 355
Connection: close
<html>...</html>
Connection to testserver closed by foreign host.
$
$telnet testserver 2600
Trying 1.2.3.4...
Connected to testserver.
Escape character is '^]'.
GET / HTTP/1.0 [press enter]
Accept-encoding: gzip [press enter twice]
HTTP/1.1 200 OK
Server: Sun-Java-System-Web-Server/7.0
Date: Wed, 06 Feb 2008 12:09:45 GMT
Content-type: text/html
Last-modified: Fri, 25 Jan 2008 00:12:38 GMT
Content-encoding: gzip
Vary: accept-encoding
Connection: close
MPËNÄ0...ó²õã\å
Connection to testserver closed by foreign host.
$
When I ask for a compressed response, the server responds with a
Content-encoding: gzip
header and returns compressed response instead of the html.Trying 1.2.3.4...
Connected to testserver.
Escape character is '^]'.
GET / HTTP/1.0 [press enter]
Accept-encoding: gzip [press enter twice]
HTTP/1.1 200 OK
Server: Sun-Java-System-Web-Server/7.0
Date: Wed, 06 Feb 2008 12:09:45 GMT
Content-type: text/html
Last-modified: Fri, 25 Jan 2008 00:12:38 GMT
Content-encoding: gzip
Vary: accept-encoding
Connection: close
MPËNÄ0...ó²õã\å
Connection to testserver closed by foreign host.
$
**Note that compress-file SAF is not available in Web Server 6.1, in that case you have to put pre compressed content into document root for find-compressed to work.
References
- Web Server software forum questions
- Compressing Web Content with mod_gzip and mod_deflate
- Best Practices for Speeding Up Your Web Site
- HTTP Compression
- Web Server 7.0 update 2 documentation about find-compressed function
- Web Server 7.0 update 2 documentation about http-compression function
- my previous blog Dynamic Compression Of Static Files
Posted by meena ( Feb 05 2008, 02:24:29 PM IST ) Permalink Comments [3]
Trackback URL: http://blogs.sun.com/meena/entry/about_http_compression_in_sun
Post a Comment:
Thanks! Since much of the web content these days is based on javascript, and they tend to get large pretty soon, we could also compress the javascript that is sent back to the client.
Posted by Venky on February 05, 2008 at 04:21 PM IST #
Hmm, that sounds vaguely familiar: http://forum.java.sun.com/thread.jspa?threadID=5050775&messageID=9186726
Posted by Chris Elving on February 12, 2008 at 11:08 PM IST #
doesnt seem to work on https. I tried dynamic compression , printed encoding type in access log. It shows as blank. Any thoughts?
Posted by Abhay Dabholkar on April 08, 2008 at 12:10 AM IST #