CACHE.CONFIG(5) - Linux man page online | File formats

The cache.config file defines how Traffic Server caches web objects. You can add caching rules.

Feb 16, 2018
CACHE.CONFIG(5) Apache Traffic Server CACHE.CONFIG(5)


cache.config - 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 modifying cache.config, run traffic_ctl config reload to apply changes. When you apply the changes to one node in a cluster, Traffic Server automatically applies the changes to all other nodes in the cluster.


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 sec‐ ondary specifier. The following list shows the possible primary destinations with allowed values. Primary Destinations The primary destination field on each line is used to restrict the requests to which the caching rule will apply. dest_domain A requested domain name. Traffic Server matches the host name of the destination from the URL in the request. dest_host Alias for dest_domain. dest_ip A requested IP address. Traffic Server matches the IP address of the destination in the request. host_regex A regular expression to be tested against the destination host name in the request. url_regex A regular expression to be tested against the URL in the request. Secondary Specifiers The secondary specifiers are optional and may be used to further restrict which requests are impacted by the caching rule. Multiple secondary specifiers may be used within a sin‐ gle rule, though each type of specifier can appear at most one time. In other words, you may have both a port and scheme in the same rule, but you may not have two ports. port Request URL port. scheme Request URL protocol (http or https). prefix Prefix in the path part of a URL. suffix File suffix in the URL. method Request URL method (get, put, post, trace, etc.). time A time range, such as 08:00-14:00. Specified using a 24-hour clock in the timezone of the Traffic Server server. src_ip Client IP address. internal A boolean value, true or false, specifying if the rule should match (or not match) a transaction originating from an internal API. This is useful to differentiate transactions originating from a Traffic Server plugin. Actions The final component of a caching rule is the action, which determines what Traffic Server will do with all objects matching the primary destinations and secondary specifiers of the rule in question. action One of the following values: ┌───────────────────────┬─────────────────────────────────┐ │Value │ Effect │ ├───────────────────────┼─────────────────────────────────┤ │never-cache │ Never cache specified objects. │ ├───────────────────────┼─────────────────────────────────┤ │ignore-no-cache │ Ignore all Cache-Control: │ │ │ no-cache headers. │ ├───────────────────────┼─────────────────────────────────┤ │ignore-client-no-cache │ Ignore Cache-Control: no-cache │ │ │ headers from client requests. │ ├───────────────────────┼─────────────────────────────────┤ │ignore-server-no-cache │ Ignore Cache-Control: no-cache │ │ │ headers from origin server │ │ │ responses. │ ├───────────────────────┼─────────────────────────────────┤ │cluster-cache-local │ Allow for this content to be │ │ │ stored locally on every cluster │ │ │ node. │ └───────────────────────┴─────────────────────────────────┘ cache-responses-to-cookies Change the style of caching with regard to cookies. This effectively overrides the configuration parameter proxy.config.http.cache.cache_responses_to_cookies and uses the same values with the same semantics. The override happens only for requests that match. pin-in-cache Preserves objects in cache, preventing them from being overwritten. Does not affect objects that are determined not to be cacheable. This setting can have per‐ formance issues, and severely affect the cache. For instance, if the primary des‐ tination matches all objects, once the cache is full, no new objects could get written as nothing would be evicted. Similarly, for each cache-miss, each object would incur extra checks to determine if the object it would replace could be over‐ written. The value is 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 For objects that are in cache, overrides the the amount of time the object(s) are to be considered fresh. Use the same time formats as pin-in-cache. ttl-in-cache Forces object(s) to become cached, as if they had a Cache-Control: max-age:<time> header. Can be overruled by requests with cookies. The value is the amount of time object(s) are to be kept in the cache, regardless of Cache-Control response headers from the origin server. Use the same time formats as pin-in-cache.


When multiple rules are specified in cache.config, Traffic Server will check all of them in order for each request. Thus, two rules which match the same request but have conflict‐ ing actions will result in their actions being compounded. In other words, Traffic Server does not stop on the first match. In some cases, this may lead to confusing behavior. For example, consider the following two rules: prefix=foo suffix=js revalidate=7d suffix=js action=never-cache Reading that under the assumption that Traffic Server stops on the first match might lead one to assume that all Javascript files will be excluded from the Traffic Server cache, except for those whose paths begin with foo. This, however, is not correct. Instead, the first rule establishes that all Javascript files with the path prefix foo will be forced to revalidate every seven days, and then the second rule also sets an action on all Javascript files, regardless of their path prefix, to never be cached at all. Because none of the Javascript files will be cached at all, the first rule is effectively voided. A similar example, but at least one with a correct solution, might be an attempt to set differing values for the same action, as so: # Incorrect! prefix=foo suffix=js revalidate=7d suffix=js revalidate=1d # Correct! suffix=js revalidate=1d prefix=foo suffix=js revalidate=7d The latter accomplishes the implied goal of having a default, or global, timer for cache object revalidations on Javascript files, as well as a more targeted (and longer) revali‐ dation time on just those Javascript files with a particular prefix. The former fails at this goal, because the second rule will match all Javascript files and will override any previous revalidate values that may have been set by prior rules.


The following example configures Traffic Server to revalidate gif and jpeg objects in the domain every 6 hours, and all other objects in every hour. The rules are applied in the order listed. revalidate=1h suffix=gif revalidate=6h suffix=jpeg revalidate=6h Force a specific regex to be in cache between 7-11pm of the server's time for 26 hours.* time=19:00-23:00 ttl-in-cache=1d2h Prevent objects from being evicted from cache:* pin-in-cache=1h
7.1 Feb 16, 2018 CACHE.CONFIG(5)
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