Small improvements to reverse resolver #451
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tomwilkie
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…negative responses.
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| if _, err := r.cache.Get(request); err == nil { | ||
| continue | ||
| } | ||
| <-r.Throttle // rate limit our DNS resolutions |
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LGTM. |
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Sep 7, 2015
Small improvements to reverse resolver
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Don't rate limit requests that have already been resolved, and cache negative responses.
We do this as we generate so many reverse-ip lookups that we quickly overwhelm the the channel and start dropping them. At a rate of 10 lookups per second, we never get through the queue.
By not rate limiting requests that are in the cache we don't actually do any more requests, it just allows us to burn through the queue quicker. And by caching negative responses, we prevent the queue for growing massive to begin with.
I tested this by doing a
telnet google.com 80and then checking we got the right hostname in the applications view. Before this fix it would never show any hostname, after the fix it shows something.