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https://issues.apache.org/jira/browse/TS-4287?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15234343#comment-15234343
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ASF GitHub Bot commented on TS-4287:
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Github user zwoop commented on the pull request:
https://github.com/apache/trafficserver/pull/530#issuecomment-208091454
I'll review this tomorrow (Monday).
> Add a simple and unavailable server retry feature to Parent Selection.
> ----------------------------------------------------------------------
>
> Key: TS-4287
> URL: https://issues.apache.org/jira/browse/TS-4287
> Project: Traffic Server
> Issue Type: New Feature
> Components: Parent Proxy
> Reporter: John Rushford
> Assignee: John Rushford
> Fix For: 6.2.0
>
>
> Parent Selection now supports the use of origin servers in the parent list.
> It would be useful to add a simple retry feature that would try another
> parent when a 404 response is received for content that may not be available
> on one origin but may be available on another parent origin in the parent
> list. This can happen when packagers are pushing live video chunks to
> multiple origins and a request comes into an origin that may not yet have
> received the requested file.
> It would also be useful to mark a parent origin down and retry a request
> using another parent origin if a 503 unavailable response is received or if
> some other other application 5xx response were received.
> A pull request will follow this ticket that adds the following configuration
> parameters to parent.config and that implements the retry functionality.
> The following new configuration parameters are available in parent.config
> when parent_is_proxy is false (parent origin):
> 'parent_retry', 'unavailable_server_retry_responses',
> 'max_simple_retries', and 'max_unavailable_server_retries'.
> 'parent_retry' - May be set to the value: 'simple_retry',
> 'unavailable_server_retry', or 'both'. parent_retry is disabled by default
> and may only be enabled with one of these values when 'parent_is_proxy' is
> false (parent origin).
> if 'parent_retry' is set to 'simple_retry' another parent will be retried
> when a 404 response is received from the parent origin. By default only one
> retry will be attempted for a 404 response but this may be increased from 1
> to 5 with 'max_simple_retries' parameter.
> if 'parent_retry' is set to 'unavailable_server_retry' and a response is
> received that is contained in a configurable list of response codes (503 by
> default), the parent that returned the code is marked down and another parent
> is retried. By default only one retry will be attempted but his may be
> increased from 1 to 5 using the 'max_unavailable_server_retries'
> configuration parameter.
> 'unavailable_server_retry_responses' is an optional comma separated list of
> response codes that may be configured to trigger a unavailable_server_retry
> when 'parent_retry' is set to 'unavailable_server_retry'. If not specified
> in the parent.config, the default response code is 503.
> If 'parent_retry' is set to 'both' then both simple_retry and
> unavailable_server_retry are enabled for this list of parents.
> 'max_simple_retries' is set to 1 by default but may be increased within the
> range 1 to 5.
> 'max_unavailable_server_retries' is set to 1 by default but may be increased
> within the range 1 to 5.
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