I would refer you back to the other article I linked to on setting up your host
name properly.
When I test using the default DNS resolving I can resolve both ‘iMac’ and
‘iMac.local’ in 2-3 milliseconds without any entry in my /etc/hosts file. If I
add the entry ‘iMac.local’ to my /etc/hosts file it still resolves fine.
When I use a invalid hostname, it is 5 seconds - always. It appears it is using
a CGo/Library path that bypasses the DNS cache.
Note that this differs from the Go DNS resolver (using GODEBUG=netdns=Go) where
it is only 5 seconds at most the first time, then it is cached for some period
of time across process restarts, so that subsequent ‘invalid’ queries only take
a few milliseconds.
> On Feb 23, 2021, at 11:51 AM, Peng Yu <pengyu...@gmail.com> wrote:
>
>>> I don’t understand why ping does not have the same problem. Ping is not
>>> based on C library?
>>>
>>
>> Looking at the source code, the ping command on macOS use gethostbyname2()
>> [1][2], while the Go on macOS use C library through getaddrinfo [3][4].
>
> If so, I'd consider it as a performance bug of net.Dial() on macOS.
> After all, the following command runs quickly to resolve an IP address
> from a name (suffixed with .local) in /etc/hosts much faster. So
> net.Dial() could (and probably should) just use this (or something
> along this line) on macOS to fix the performance problem.
>
> net.ResolveIPAddr("ip4", addr)
>
> --
> Regards,
> Peng
>
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