dns-discovery-netty: Add support for DNS hedging requests #2918
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We need a budget and a way of tracking percentiles
bryce-anderson
changed the title
| boolean withdraw(); | ||
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| // TODO: both these implementations are un-synchronized and rely on netty using only a single event loop. |
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We always use only a single event loop and this is ensured by inEventLoop checks across DefaultDnsClient
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Motivation:
DNS often sends requests over UDP and UDP transport is
not durable, meaning that it needs to be expected that
packets will get lost. This will translate into DNS timeouts.
This is unfortunate because timeouts can be very long, on
the order of seconds, while DNS resolutions can be much
faster than this.
Modifications:
Add support for hedging. After a period of time we can
send a second request that can race with the first to hedge
against lost packets. To make sure we don't end up with
a flood we use a token bucket to limit how often we can
send hedging requests.