The cache.config file defines how Traffic Server caches web objects. You can add caching rules to specify the following: - Not to cache objects from specific IP addresses - How long to pin particular objects in the cache - How long to consider cached objects as fresh - Whether to ignore no-cache directives from the server

IMPORTANT: After you modify the cache.config file, navigate to the Traffic Server bin directory; then run the traffic_line -x command to apply changes. When you apply the changes to a node in a cluster, Traffic Server automatically applies the changes to all other nodes in the cluster.

Format

Each line in the cache.config file contains a caching rule. Traffic Server recognizes three space-delimited tags:

primary_destination=value secondary_specifier=value action=value

You can use more than one secondary specifier in a rule. However, you cannot repeat a secondary specifier. The following list shows the possible primary destinations with allowed values.

dest_domain

A requested domain name. Traffic Server matches the domain name of the destination from the URL in the request.

dest_host

A requested hostname. Traffic Server matches the hostname of the destination from the URL in the request.

dest_ip

A requested IP address. Traffic Server matches the IP address of the destination in the request.

url_regex

A regular expression (regex) to be found in a URL.

The secondary specifiers are optional in the cache.config file. The following list shows possible secondary specifiers with allowed values.

port

A requested URL port.

scheme

A request URL protocol: http or https.

prefix

A prefix in the path part of a URL.

suffix

A file suffix in the URL.

method

A request URL method: get, put, post, trace.

time

A time range, such as 08:00-14:00.

src_ip

A client IP address.

The following list shows possible actions and their allowed values.

action

One of the following values:

• never-cache configures Traffic Server to never cache specified objects.
• ignore-no-cache configures Traffic Server to ignore all Cache-Control: no-cache headers.
• ignore-client-no-cache configures Traffic Server to ignore Cache-Control: no-cache headers from client requests.
• ignore-server-no-cache configures Traffic Server to ignore Cache-Control: no-cache headers from origin server responses.

pin-in-cache

The amount of time you want to keep the object(s) in the cache. The following time formats are allowed:

• d for days; for example: 2d
• h for hours; for example: 10h
• m for minutes; for example: 5m
• s for seconds; for example: 20s
• mixed units; for example: 1h15m20s

revalidate

The amount of time object(s) are to be considered fresh. Use the same time formats as pin-in-cache.

ttl-in-cache

The amount of time object(s) are to be kept in the cache, regardless of Cache-Control response headers. Use the same time formats as pin-in-cache and revalidate .

Examples

The following example configures Traffic Server to revalidate gif and jpeg objects in the domain mydomain.com every 6 hours, and all other objects in mydomain.com every hour. The rules are applied in the order listed.

dest_domain=mydomain.com suffix=gif revalidate=6h
dest_domain=mydomain.com suffix=jpeg revalidate=6h
dest_domain=mydomain.com revalidate=1h