serrislew opened a new pull request #8473:
URL: https://github.com/apache/trafficserver/pull/8473
For hierarchical caching, when a child proxy needs to revalidate its stale
content with the parent proxy but the parent returns an invalid response or is
marked "unavailable", the child proxy should still return the stale content
with a warning header. This is the same behavior without hierarchical caching,
when the origin server is down and a server tries to revalidate its stale
content and when it fails to, it returns back a 200 OK response with a warning
header.
These changes still respect the `max_stale_age` configurations and do not
serve stale content pass the expiration date.
Changes made:
- when child receives invalid response from parent, it first checks if the
stale cache response is returnable. if not, then it calls `handle_parent_died`
to build the error response message
- when the parent is marked down or unavailable (without making a request),
it first checks if the stale cache response is returnable before building the
error response message
- the parent can be marked unavailable when the number of retries to the
parent exceeds `proxy.config.http.parent_proxy.fail_threshold` within
`proxy.config.http.parent_proxy.retry_time`
- the `is_server_negative_cached` is removed as the conditional checks
with configs only applicable to origin server. parent server status and
selection (whether its marking a parent down or deciding the next available
parent) are already decided in `ParentSelectionStrategy`
Autest checks the following using a PUSH workaround to mock parent going
down:
- Child returns stale content with warning header when object's age is less
than `max_stale_age` and parent fail count is below
`parent_proxy.fail_threshold`
- Child returns stale content with warning header when object's age is less
than `max_stale_age` and parent fail count is passed
`parent_proxy.fail_threshold` and parent is marked unavailable
- Child does not return stale content when object's age exceeds
`max_stale_age`
Note: this is an updated PR from #8248
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