Provided by: trafficserver_8.0.5+ds-1_amd64 bug

NAME

       parent.config - Traffic Server parent cache configuration file

       The  parent.config file identifies the parent proxies used in an cache hierarchy. Use this
       file to perform the following configuration:

       · Set up parent cache hierarchies, with multiple parents and parent failover

       · Configure selected URL requests to bypass parent proxies

       Traffic Server uses the parent.config file only when the parent caching option is  enabled
       (refer to configuring-traffic-server-to-use-a-parent-cache).

       After  you  modify  the  parent.config  file, run the traffic_ctl config reload command to
       apply your changes.

FORMAT

       Each line in the parent.config file must contain a parent  caching  rule.  Traffic  Server
       recognizes three space-delimited tags:

          primary_destination=value secondary_specifier=value  action=value

       The following list shows the possible primary destinations and their allowed values.

       dest_domain
              A requested domain name, and its subdomains.

       dest_host
              A requested hostname.

       dest_ip
              A requested IP address or range of IP addresses separated by a dash (-).

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

       The  secondary specifiers are optional in the parent.config file. The following list shows
       the  possible  secondary  specifiers  and  their  allowed  values.  Every  line   in   the
       parent.config file must contain either a parent= or go_direct= directive.

       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. It can be one of the following:

              · get

              · post

              · put

              · trace

       time   A  time  range, such as 08:00-14:00, during which the parent cache is used to serve
              requests.

       src_ip A 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
              transaction originating from an ATS plugin.

       The following list shows the possible actions and their allowed values.

       parent (hostname or IP address):port[|weight][,another host]
              An ordered list of parent servers,  separated  by  commas  or  semicolons.  If  the
              request  cannot  be  handled by the last parent server in the list, then it will be
              routed to the origin server.  You can specify either a hostname or an  IP  address,
              but,  you  must  specify  the  port  number.  If  there  are  multiple IP addresses
              associated with the hostname, Traffic Server will treat them  as  a  single  entity
              when tracking health. Example:

                 parent="p1.x.com:8080, 192.168.0.3:80, 192.168.0.4:80"

              An  optional  weight can be specified after a pipe (|). This example has one parent
              take 20% (2/(2+3+5)) of the requests, another 30% (3/(2+3+5)),  and  the  last  50%
              (5/(2+3+5)):

                 parent="p1.x.com:8080|2.0, 192.168.0.3:80|3.0, 192.168.0.4:80|5.0"

       secondary_parent
              An  optional ordered list of secondary parent servers in the same format as parent.
              This optional list may only be used when round_robin is set to consistent_hash.  If
              the  request  cannot  be  handled by the first parent server chosen from the parent
              list, then the request will be re-tried from a server found in this  list  using  a
              consistent  hash  of  the  url.  The  parent servers in this list will be exhausted
              before the selection function will revert to  trying  alternative  parents  in  the
              parent list.

       secondary_mode
              One of the following values:

              · 1 This is the default. The parent selection will first attempt to choose a parent
                from the parent list. If the chosen parent is not available or marked  down  then
                another  parent  will  be  chosen from the secondary_parent list.  Choices in the
                secondary_parent list will be  exhausted  before  attempting  to  choose  another
                parent from the parent list.

              · 2  The  parent  selection  will  first attempt to choose a parent from the parent
                list. If the chosen parent is not available or marked down  then  another  parent
                will  be  chosen  from  the  parent  list.   Choices  in  the parent list will be
                exhausted before attempting to choose another parent  from  the  secondary_parent
                list.

              · 3  The  parent  selection  will  first attempt to choose a parent from the parent
                list.

                · If the chosen parent is marked down then another parent will be chosen from the
                  secondary_parent  list.  The  secondary_parent  list  will  be exhausted before
                  attempting to choose another parent in the parent list.

                · If the chosen parent is unavailable but not marked  down  then  another  parent
                  will  be  chosen from the parent list. The parent list will be exhausted before
                  attempting to choose another parent in the secondary_parent list.

       parent_is_proxy
              One of the following values:

              · true - This is the default.  The list of parents and secondary parents are  proxy
                cache servers.

              · false  -  The  list  of  parents  and  secondary  parents  are the origin servers
                go_direct  flag  is  ignored  and  origins  are  selected  using  the   specified
                round_robin algorithm.  The FQDN is removed from the http request line.

       parent_retry

              · simple_retry  - If the parent origin server returns a 404 response on a request a
                new parent is selected and the request is retried.   The  number  of  retries  is
                controlled by max_simple_retries which is set to 1 by default.

              · unavailable_server_retry  -  If  the  parent  returns  a  503  response or if the
                response   matches   a    list    of    http    5xx    responses    defined    in
                unavailable_server_retry_responses,  the currently selected parent is marked down
                and a new parent is selected to retry the request.   The  number  of  retries  is
                controlled by max_unavailable_server_retries which is set to 1 by default.

              · both  -  This enables both simple_retry and unavailable_server_retry as described
                above.

       unavailable_server_retry_responses
              If parent_retry is set to either unavailable_server_retry or both,  this  parameter
              is  a  comma  separated  list  of  http  5xx  response  codes  that will invoke the
              unavailable_server_retry  described  in  the  parent_retry  section.   By  default,
              unavailable_server_retry_responses is set to 503.

       max_simple_retries
              By  default  the  value for max_simple_retries is 1.  It may be set to any value in
              the range 1 to 5.  If parent_retry is set to simple_retry or both  a  404  response
              from a parent origin server will cause the request to be retried using a new parent
              at most 1 to 5 times as configured by max_simple_retries.

       max_unavailable_server_retries
              By default the value for max_unavailable_server_retries is 1.  It may be set to any
              value in the range 1 to 5.  If parent_retry is set to unavailable_server_retries or
              both a 503 response by default  or  any  http  5xx  response  listed  in  the  list
              unavailable_server_retry_responses  from  a  parent  origin  server  will cause the
              request to be retried using a new parent after first  marking  the  current  parent
              down.   The  request  will  be  retried  at  most  1  to  5  times as configured by
              max_unavailable_server_retries.

       round_robin
              One of the following values:

              · true - Traffic Server determines the parent based on client IP address.

              · strict - Traffic Server machines serve requests strictly in  turn.  For  example:
                machine proxy1 serves the first request, proxy2 serves the second request, and so
                on.

              · false - Round robin selection does not occur.

              · consistent_hash - consistent hash of the url so that one parent is chosen  for  a
                given  url.  If a parent is down, the traffic that would go to the down parent is
                rehashed amongst the remaining parents.  The other traffic  is  unaffected.  Once
                the  downed  parent  becomes  available,  the traffic distribution returns to the
                pre-down state.

              · latched - The first parent in the list is marked as primary and is always  chosen
                until  connection  errors  cause it to be marked down.  When this occurs the next
                parent in the list then becomes primary.  The primary will wrap back to the first
                parent  in the list when it is the last parent in the list and is marked down due
                to a connection error.  Newly chosen primary parents marked as  unavailable  will
                then  be restored if the failure retry time has elapsed and the transaction using
                the primary succeeds.

       go_direct
              One of the following values:

              · true - requests bypass parent hierarchies and go directly to the origin server.

              · false - requests do not bypass parent hierarchies.

       qstring
              One of the following values:

              · consider - Use the query string when finding a parent.

              · ignore - Do not consider  the  query  string  when  finding  a  parent.  This  is
                especially useful when using the consistent_hash selection strategy, and a random
                query string would prevent a consistent parent selection.

EXAMPLES

       The following rule configures a parent cache hierarchy consisting of Traffic Server (which
       is the child) and two parents, p1.x.com and p2.x.com. Traffic Server forwards the requests
       it cannot serve to the parent servers p1.x.com and p2.x.com in a round-robin fashion:

          dest_domain=. method=get parent="p1.x.com:8080; p2.y.com:8080" round_robin=true

       The following rule configures Traffic Server to route all requests containing the  regular
       expression  politics  and the path /viewpoint directly to the origin server (bypassing any
       parent hierarchies):

          url_regex=politics prefix=/viewpoint go_direct=true

       The following configures Traffic Server to route http requests  for  example.com  (neither
       https  nor www.example.com would match) through parent servers. Each url will be hashed to
       a specific parent. If the chosen parent has been marked down, a parent from the  secondary
       ring will be chosen for the retry.:

          dest_host=example.com scheme=http parent="p1.x.com:80,p2.x.com:80" secondary_parent="p3.x.com:80,p4.x.com:80" round_robin=consistent_hash go_direct=false

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