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feat(request_forwarder): Add config option to set DNS cache TTL - #312
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ketiltrout
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September 28, 2026 23:40
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Adds an optional config parameter "dns_cache_ttl" to allow changing the AIOHTTP DNS caching time. The default TTL in coco is 10 seconds, which is also AIOHTTP's default value for this parameter. There's a bigger change here, though: * previoiusly coco would create a new connector (which is the object containing the DNS cache) for each endpoint forward. This connector would last until the end of a single endpoint forward at which point it would be closed and the cache deleted. Theoretically, the DNS cache could have been used if an endpoint had multiple forwards to the same host but, in practice, that's not how our endpoints usually work. (Typically a given endpoint forwards only once to a particular host.) The upshot is, in old coco, the DNS cache was essentially unused. * To fix this, the connector is now cached in the RequestForwarder itself and reused over-and-over again. I think this should be fine, but it will need some field testing to see if there's unintended consequences. If "dns_cache_ttl" is set to zero, DNS caching will be explicitly disabled in the request forwarder, which (due to the above) is effectively the legacy behaviour.
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Adds an optional config parameter "dns_cache_ttl" to allow changing the AIOHTTP DNS caching time. The default TTL in coco is 10 seconds, which is also AIOHTTP's default value for this parameter.
There's a bigger change here, though:
If "dns_cache_ttl" is set to zero, DNS caching will be explicitly disabled in the request forwarder, which (due to the above) is effectively the legacy behaviour.
Also, merged the
RequestForwarder.set_session_limitfunction intoRequestForwarder.__init__since it was only ever called immediately after creating the request forwarder. If there was a reason to have these separate in the past, that's no longer the case.A re-implementation of #243 now that the test-suite works again.