GZip Plugin

This plugin adds compression and decompression options to both origin and cache responses.

Purpose

Not all clients can handle compressed content. Not all origin servers are configured to respond with compressed content when a client says it can accept it. And it’s not always necessary to make two separate requests to an origin, and track two separate cache objects, for the same content - once for a compressed version and another time for an uncompressed version.

This plugin tidies up these problems by transparently compressing or deflating origin responses, as necessary, so that both variants of a response are stored as alternates and the appropriate version is used for client responses, depending on the client’s indication (via an Accept request header) of what it can support.

Additionally, this plugin adds configurability for what types of origin responses will receive this treatment, which will be proxied and cached with default behavior, and which may be explicitly disallowed to cache both compressed and deflated versions (because, for example, the cost of compression is known ahead of time to outweigh the space and bandwidth savings and you wish to avoid Traffic Server even testing for the possibility).

Installation

This plugin is considered stable and is included with Traffic Server by default. There are no special steps necessary for its installation.

Configuration

This plugin can be used as either global plugin or remap plugin. It can be enabled globally for Traffic Server by adding the following to your plugin.config:

gzip.so

With no further options, this will enable the following default behavior:

  • Enable caching of both compressed and uncompressed versions of origin responses as alternates.
  • Compress objects with text/* content types for every origin.
  • Don’t hide Accept encoding headers from origin servers (for an offloading reverse proxy).
  • No URLs are disallowed from compression.
  • Disable flush (flush gzipped content to client).

Alternatively, a configuration may be specified (shown here using the sample configuration provided with the plugin’s source):

gzip.so <path-to-plugin>/sample.gzip.config

This can be used as remap plugin by pointing to config file in remap rule remap.config:

@plugin=gzip.so @pparam=<path-to-plugin>/sample.gzip.config

The following sections detail the options you may specify in the plugin’s configuration file. Options may be used globally, or may be specified on a per-site basis by preceding them with a [<site>] line, where <site> is the client-facing domain for which the options should apply.

Per site configuration for remap plugin should be ignored.

cache

When set to true, causes Traffic Server to cache both the compressed and uncompressed versions of the content as alternates. When set to false, Traffic Server will cache only the compressed or decompressed variant returned by the origin. Enabled by default.

compressible-content-type

Provides a wildcard to match against content types, determining which are to be considered compressible. This defaults to text/*. Takes one Content-Type per line.

disallow

Provides a wildcard pattern which will be applied to request URLs. Any which match the pattern will be considered incompressible, and only deflated versions of the objects will be cached and returned to clients. This may be useful for objects which already have their own compression built-in, to avoid the expense of multiple rounds of compression for trivial gains.

allow

Provides a wildcard pattern which will be applied to request URLs. Any which match the pattern will be considered compressible, and only deflated versions of the objects will be cached and returned to clients. This may be useful for objects which already have their own compression built-in, to avoid the expense of multiple rounds of compression for trivial gains.

enabled

When set to true (the default) permits objects to be compressed, and when false effectively disables the plugin in the current context.

flush

Enables (true) or disables (false) flushing of compressed objects to clients.

remove-accept-encoding

When set to true this option causes the plugin to strip the request’s Accept encoding header when contacting the origin server. Setting this option to false will leave the header intact if the client provided it.

  • To ease the load on the origins.
  • For when the proxy parses responses, and the resulting compression and decompression is wasteful.

supported-algorithms

Provides the compression algorithms that are supported. This will allow the proxy to selectively support certain compressions. The default is gzip. Multiple algorthims can be selected using ‘,’ delimiter

– To selectively support only certain compression algorithms.

Examples

To establish global defaults for all site requests passing through Traffic Server, while overriding just a handful for requests to content at www.example.com, you might create a configuration with the following options:

# Set some global options first
cache true
remove-accept-encoding false
compressible-content-type text/*
compressible-content-type application/json
flush false

# Now set a configuration for www.example.com
[www.example.com]
cache false
remove-accept-encoding true
disallow /notthis/*.js
allow /this/*.js
flush true

# Allows brotli encoded response from origin but is not capable of brotli compression
[brotli.allowed.com]
enabled true
compressible-content-type text/*
compressible-content-type application/json
flush true
supported-algorithms gzip,deflate

# Supports brotli compression
[brotli.compress.com]
enabled true
compressible-content-type text/*
compressible-content-type application/json
flush true
supported-algorithms br, gzip

# This origin does it all
[bar.example.com]
enabled false

Assuming the above options are in a file at /etc/trafficserver/gzip.config the plugin would be enabled for Traffic Server in plugin.config as:

gzip.so /etc/trafficserver/gzip.config