John Rushford created TS-4287:
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Summary: Add a simple and dead 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
Parent Selection nows 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', 'dead_server_retry_responses', 'max_simple_retries', and
'max_dead_server_retries'.
'parent_retry' - May be set to the value: 'simple_retry', 'dead_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 'dead_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_dead_server_retries' configuration parameter.
'dead_server_retry_responses' is an optional comma separated list of response
codes that may be configured to trigger a dead_server_retry when 'parent_retry'
is set to 'dead_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 dead_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_dead_server_retries' is set to 1 by default but may be increased within
the range 1 to 5.
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