The remap.config file contains mapping rules that Traffic Server uses to perform the following actions:

• Map URL requests for a specific origin server to the appropriate location on Traffic Server when Traffic Server acts as a reverse proxy for that particular origin server
• Reverse-map server location headers so that when origin servers respond to a request with a location header that redirects the client to another location, the clients do not bypass Traffic Server
• Redirect HTTP requests permanently or temporarily without Traffic Server having to contact any origin servers

Refer to Reverse Proxy and HTTP Redirects, for information about redirecting HTTP requests and using reverse proxy.

IMPORTANT: After you modify the remap.config run the traffic_line -x command to apply the 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.

Format

Each line in the remap.config file must contain a mapping rule. Traffic Server recognizes three space-delimited fields: type, target, and replacement. The following list describes the format of each field.

type

Enter one of the following:

• map --translates an incoming request URL to the appropriate origin server URL.

• reverse_map --translates the URL in origin server redirect responses to point to the Traffic Server.

• redirect --redirects HTTP requests permanently without having to contact the origin server. Permanent redirects notify the browser of the URL change (by returning an HTTP status code 301) so that the browser can update bookmarks.

• redirect_temporary --redirects HTTP requests temporarily without having to contact the origin server. Temporary redirects notify the browser of the URL change for the current request only (by returning an HTTP status code 307).

Note: use the regex_ prefix to indicate that the line has a regular expression (regex).

target

Enter the origin ("from") URL. You can enter up to four components:

scheme://host:port/path_prefix

where scheme is http.

replacement

Enter the origin ("from") URL. You can enter up to four components:

scheme://host:port/path_prefix

where scheme can be http or https.

Precedence

Remap rules are not processed top-down, but based on an internal priority

1. map and reverse_map
2. redirect and redirect_temparary
3. regex_remap
4. regex_redirect and regex_redirect_temporary

Examples

The following section shows example mapping rules in the remap.config file.

Reverse Proxy Mapping Rules

The following example shows a map rule that does not specify a path prefix in the target or replacement:

map http://www.x.com/ http://server.hoster.com/
reverse_map http://server.hoster.com/ http://www.x.com/

This rule results in the following translations:

The following example shows a map rule with path prefixes specified in the target:

map http://www.intranet.y.com/marketing/ http://marketing.y.com/
reverse_map http://marketing.y.com/ http://www.intranet.y.com/marketing/
map http://intranet.y.com/sales/ http://sales.y.com/
reverse_map http://sales.y.com/ http://intranet.y.com/sales/
map http://intranet.y.com/engineering/ http://engineering.y.com/
reverse_map http://engineering.y.com/ http://intranet.y.com/engineering/
map http://intranet.y.com/ http://info.y.com/
reverse_map http://info.y.com/ http://intranet.y.com/

These rules result in the following translations:

The following example shows that the order of the rules matters:

map http://www.g.com/ http://external.g.com/
reverse_map http://external.g.com/ http://www.g.com/
map http://www.g.com/stuff/ http://stuff.g.com/
reverse_map http://stuff.g.com/ http://www.g.com/stuff/

These rules result in the following translation.

In the above examples, the second rule is never applied because all URLs that match the second rule also match the first rule. The first rule takes precedence because it appears earlier in the remap.config file.

The following example shows a mapping with a path prefix specified in the target and replacement:

map http://www.h.com/a/b/ http://server.h.com/customers/x/y
reverse_map http://server.h.com/customers/x/y/ http://www.h.com/a/b/

This rule results in the following translation.

The following example shows reverse-map rules:

map http://www.x.com/ http://server.hoster.com/x/
reverse_map http://server.hoster.com/x/ http://www.x.com/

These rules result in the following translations.

When acting as a reverse proxy for multiple servers, Traffic Server is unable to route to URLs from older browsers that do not send the Host: header. As a solution, set the variable proxy.config.header.parse.no_host_url_redirect in the records.config file to the URL to which Traffic Server will redirect requests without host headers.

Redirect Mapping Rules

The following rule permanently redirects all HTTP requests for www.company.com to www.company2.com:

redirect http://www.company.com/ http://www.company2.com/

The following rule temporarily redirects all HTTP requests for www.company1.com to www.company2.com:

redirect_temporary http://www.company1.com/ http://www.company2.com/

Regular Expression (regex) Remap Support

Regular expressions can be specified in remapping rules, with the limitations below:

• Only the host field can contain a regex; the scheme, port, and other fields cannot. For path manipulation via regexes, use the regex_remap plugin.
• The number of capturing subpatterns is limited to 9. This means that $0 thru $9 can be used as subtraction placeholders ($0 will be the entire input string).
• The number of substitutions in the expansion string is limited to 10.
• There is no regex_ equivalent to reverse_remap, so when using regex_remap you should make sure the reverse path is clear by setting (proxy.config.url_remap.pristine_host_hdr)

Examples

regex_map http://x([0-9]+).z.com/ http://real-x$1.z.com/
regex_redirect http://old.(.*).z.com http://new.$1.z.com

Plugin Chaining

Plugins can be configured to be evaluated in a specific order, passing the results from one in to the next (unless a plugin returns 0, then the "chain" is broken).

Examples

map http://url/path http://url/path @plugin=/etc/traffic_server/config/plugins/plugin1.so @pparam=1 @pparam=2 @plugin=/etc/traffic_server/config/plugins/plugin2.so @pparam=3

will pass "1" and "2" to plugin1.so and "3" to plugin2.so.

This will pass "1" and "2" to plugin1.so and "3" to plugin2.so