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https://issues.apache.org/jira/browse/TS-3750?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14624949#comment-14624949
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Adam W. Dace commented on TS-3750:
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Well, I've found a workaround for this problem. I simply disabled IPv6 DNS
lookups,
and now everything is running smoothly. My OpenDNS lookups are about 1/10th of
what they used to be and HostDB seems to be working properly.
I think the problem in terms of logic is happening like this:
1) ATS attempts IPv6 DNS lookup. DNS lookup fails(IPv4 host).
2) ATS HostDB invalidates the entry for the given host(the problem?).
3) ATS attempts IPv4 DNS lookup. DNS lookup succeeds.
4) Browsing in general is unaffected, but HostDB isn't doing its job, and
latency for some HTTP requests has doubled. Ouch.
Basically, I believe lookups and DNS caching for IPv6 hosts works fine but at
the expense of IPv4 hosts.
I'll try to keep plugging away at this, and see what I can come up with.
> HostDB: Setting DNS TTL to "ignore" still creates many DNS lookups
> -------------------------------------------------------------------
>
> Key: TS-3750
> URL: https://issues.apache.org/jira/browse/TS-3750
> Project: Traffic Server
> Issue Type: Bug
> Components: DNS, HostDB
> Affects Versions: 6.0.0
> Reporter: Adam W. Dace
> Priority: Minor
> Fix For: 6.1.0
>
>
> In an effort to further speed my forward-only proxy cache, I've been
> experimenting with using a 1-4 hour internal TTL in HostDB(as opposed to the
> default). Many websites set their DNS TTL extremely low(i.e. 60 seconds),
> and I'd like to bypass that behavior.
> Unfortunately, according to OpenDNS my proxy is still generating roughly 1
> DNS lookup per HTTP request. I don't know why.
> I've taken a look at the codebase, but frankly it's all state machines in
> there and I don't possess the skills to identify and fix this problem. I
> have turned on debugging and can say there does appear to be a lot of DNS
> activity going on.
> If someone could take a look, I'd greatly appreciate it. I'll be happy to
> help test, also. Thanks!
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