JDK-8170910: Avoid 5 second localhost lookup behavior on OSX

Fri Apr 5 16:12:51 UTC 2019

I've spent some time trying to reproduce this on 10.13 but have not been 
able.
I have disabled all the services as suggested (including some additional)
such that the dns-sd command produces no output "records" and also by
disabling unicast DNS access.

I wonder if there has been a change in 10.13 to workaround this problem
as I don't see any delay or external MDNS lookups happening.
.
Could you send me the output of "scutil --dns" of your laptop?
At the same time, I will ask some colleagues here who might be running 10.12
to try it out.

Thanks,
Michael

On 04/04/2019, 18:38, Nora Howard wrote:
> Here's the diff http://cr.openjdk.java.net/~tonyp/8170910/webrev.0/ 
> <http://cr.openjdk.java.net/%7Etonyp/8170910/webrev.0/>
>
> To setup an env to reproduce the issue, on a OSX machine with >= 
> 10.12, turn off services that register with mDNS. For my laptop, I had 
> to turn off iTunes and General System Preferences, disable "Allow 
> Handoff between this Mac and your iCloud services". You might have to 
> restart. The reporter on the ticket said to run `dns-sd -lo -B 
> _services._dns-sd._udp local` to see whether you have any running.
>
> The file I used for exercising the behavior looks like this
>
> import java.net.InetAddress;
> public class Test {
>   public static void main(String[] args) throws Exception {
>       for (int i=0;i<4;i++){
>           long start = System.currentTimeMillis();
>           InetAddress localHost = InetAddress.getLocalHost();
>           System.out.println(localHost);
>           System.out.println(System.currentTimeMillis() - start);
> }}}
>
> The output I get on my laptop when I've set things up this way looks 
> like this on JDK 13 EA. The first call takes the full 5 seconds and 
> subsequent ones hit a cache.
>
> nhoward.local/10.0.0.3 <http://10.0.0.3>
> 5044
> nhoward.local/10.0.0.3 <http://10.0.0.3>
> 0
> nhoward.local/10.0.0.3 <http://10.0.0.3>
> 0
> nhoward.local/10.0.0.3 <http://10.0.0.3>
> 0
>
> On JDK 8, each request takes 5 seconds. JDK 8's address lookup cache 
> works differently. It's localhost name cache expiry is 5 seconds.
>
>
>
> On Thu, Apr 4, 2019 at 2:41 AM Michael McMahon 
> <michael.x.mcmahon at oracle.com <mailto:michael.x.mcmahon at oracle.com>> 
> wrote:
>
>     Hi Nora,
>
>     At first sight, the approach sounds reasonable to me. I'd like to
>     see the patch
>     and also do you have detailed instructions on how to reproduce the
>     issue (the 5 second delay)?
>
>     Thanks,
>     Michael.
>
>     On 03/04/2019, 17:46, Nora Howard wrote:
>>     I'd initially sent this to jdk-dev, but I was asked to move it to
>>     net-dev.
>>
>>     On OSX 10.12 or later, when no mDNS services are registered,
>>     getaddrinfo fails on looking up localhost addresses[1]. The jdk’s
>>     current implementation falls back to getifaddrs after getaddrinfo
>>     fails[2]. When getaddrinfo fails in this way, it takes 5 seconds
>>     to fail [3]. This means that calls to InetAddress.getLocalHost()
>>     may take up to 5 seconds to run.
>>
>>     I’d like to change the jdk’s behavior in this instance so that
>>     instead of falling back to calling getifaddrs after getaddrinfo
>>     fails, it instead calls getifaddrs first if we’re on OSX and the
>>     hostname is localhost’s.
>>
>>     Doing this will eliminate the 5 second delay looking up localhost
>>     on machines with this network setup. When looking up
>>     non-localhost addresses, it’ll add a call to os:gethostname and a
>>     comparison.
>>
>>     I’d like to get some feedback about whether this approach sounds
>>     reasonable, and some guidance about next steps. I’ve read the
>>     “how to contribute” page[4], and the “code review” guide[5].
>>
>>     I’ve put together a patch that I’ve tested locally by turning off
>>     mDNS services on my local OSX machine and exercising the
>>     behavior. I’d like to submit patches that target dev trunk as
>>     well as the jdk 8 and 11 branches.
>>
>>     References
>>
>>     1.
>>
>>         On a Macintosh running 10.12 or later, if there are no apps
>>         that have a mDNS services registered (for instance, iTunes)
>>         and there are no services selected in the Sharing System
>>         Preferences, then the getaddrinfo will fail.
>>
>>     (https://bugs.openjdk.java.net/browse/JDK-8170910)
>>
>>     2.
>>     http://hg.openjdk.java.net/jdk/jdk/file/cd3b7ad53265/src/java.base/unix/native/libnet/Inet6AddressImpl.c#l252
>>     http://hg.openjdk.java.net/jdk/jdk/file/cd3b7ad53265/src/java.base/unix/native/libnet/Inet4AddressImpl.c#l132
>>     (The lookupIfLocalhost function checks the passed hostname
>>     against os::get_host_name, and if they match, looks up via
>>     getifaddrs.)
>>
>>     3. This comment describes how to reproduce the issue. I’ve
>>     reproduced it locally on jdk 8, 11 and 13 ea.
>>     https://bugs.openjdk.java.net/browse/JDK-8170910?focusedCommentId=14038262&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#comment-14038262
>>     <https://bugs.openjdk.java.net/browse/JDK-8170910?focusedCommentId=14038262&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#comment-14038262>
>>
>>     4. https://openjdk.java.net/contribute/
>>
>>     5. https://openjdk.java.net/guide/codeReview.html
>>
>>     Thanks,
>>     -- 
>>     Nora
>
>
>
> -- 
> Nora
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