IDM 7.2.0

Gzip compression for HTTP responses

IDM uses the Jetty Gzip handler to compress HTTP responses. The default Gzip handler configuration, in conf/jetty.xml, is as follows:

...
<Call name="insertHandler">
    <Arg>
        <!-- https://www.eclipse.org/jetty/documentation/9.4.x/gzip-filter.html -->
        <New id="GzipHandler" class="org.eclipse.jetty.server.handler.gzip.GzipHandler">
            <Set name="minGzipSize"><Property name="jetty.gzip.minGzipSize" default="2048"/></Set>
            <Set name="compressionLevel"><Property name="jetty.gzip.compressionLevel" default="-1"/></Set>
            <Set name="inflateBufferSize"><Property name="jetty.gzip.inflateBufferSize" default="0"/></Set>
            <Set name="syncFlush"><Property name="jetty.gzip.syncFlush" default="false" /></Set>
            <Set name="excludedAgentPatterns">
                <Array type="String">
                    <!-- IE 6 has known bugs related to GZIP compression -->
                    <Item><Property name="jetty.gzip.excludedUserAgent" default=".*MSIE.6\.0.*"/></Item>
                </Array>
            </Set>
            <Set name="includedMethodList"><Property name="jetty.gzip.includedMethodList" default="GET" /></Set>
            <Set name="excludedMethodList"><Property name="jetty.gzip.excludedMethodList" default="" /></Set>
        </New>
    </Arg>
</Call>
...

Adjust this configuration if the default does not suit your deployment. Configuration properties are as follows:

minGzipSize

Content is compressed only if the content length is unknown or is greater than the minGzipSize. By default, content is compressed only if the response is greater than 2048MB.

compressionLevel

The compression level (1-9, with 1 being the fastest compression speed but a lower compression ratio, and 9 being the highest compression ratio but lowest compression speed. The default configuration sets the compression level to -1, which indicates that the application should use the default. The default Gzip handler uses level 6, favoring higher compression over speed.

inflateBufferSize

Number of bytes in the request decompression buffer. The default setting is -1, which disables this feature. Use this feature only if you want to compress large POST/PUT request payloads. Be aware that this setting exposes a potential Zip bomb risk.

syncFlush

By default, this setting is false, which lets the deflater determine how much data to accumulate, before it produces output. This achieves the best compression. When true, this setting forces flushing of the buffer of data to compress. This can result in poor compression.

excludedAgentPatterns

A list of regex patterns for User-Agent names. Requests from these names should not be compressed.

includedMethodList

A list of HTTP methods to compress. By default, only GET requests are compressed.

excludedMethodList

A list of HTTP methods that should not be compressed.

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