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https://issues.apache.org/jira/browse/TS-4115?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15171277#comment-15171277
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ASF GitHub Bot commented on TS-4115:
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Github user jrushf1239k closed the pull request at:
https://github.com/apache/trafficserver/pull/407
> Add a multi origin hierarchy to parent selection.
> -------------------------------------------------
>
> Key: TS-4115
> URL: https://issues.apache.org/jira/browse/TS-4115
> Project: Traffic Server
> Issue Type: New Feature
> Components: Core
> Reporter: John Rushford
> Assignee: John Rushford
> Fix For: 6.2.0
>
>
> Parent Selection is currently used to create a hierarchy of cache server
> groups. It would be useful to create an origin server hierarchy through
> parent selection so that say mid tier caches could round robin requests to
> multiple origin servers possibly at different sites using round robin load
> balancing and possibly consistent hashing algorithms.
> FEATURE DESCRIPTION:
> A pull request accompanies this ticket that adds this feature to parent
> selection. A new configuration parameter "parent_is_proxy" is available in
> parent config. parent_is_proxy=true is the default and indicates that a list
> of parents and secondary_parents are the usual parent caches but, when set to
> false, it indicates that the list of parents are origin servers.
> When marked as origin servers, the server FQDN is removed from the http GET
> request so that only the relative path is in the request. Note that if
> connectivity fails to all the origins listed or all are marked down, there is
> no go direct behavior as these are the origins.
> When marked as origin servers, the following features are also available:
> 1) simple retry - the response from the origin server is checked and if
> simple retry is enabled and a response of 404 is received, the transaction is
> retried using another parent origin. This feature is enabled in
> records.config using:
> CONFIG proxy.config.http.parent_origin.simple_retry_enabled INT 1
> The response code may be changed or added to from the default 404 by using a
> comma separated list in records.config with:
> CONFIG proxy.config.http.parent_origin.simple_retry_response_codes STRING
> 404,4xx,...
> Both parameters are reloadable and overridable.
> 2) dead server retry - Same as simple retry except that the parent is marked
> down before the next parent is tried when a 503 response is received when
> dead server retry is enabled. The following record.config parameters control
> this feature and both are reloadable and overridable:
> CONFIG proxy.config.http.parent_origin.dead_server_retry_enabled INT 0
> CONFIG proxy.config.http.parent_origin.dead_server_retry_response_codes
> STRING 503
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