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.mcma...@oracle.com <mailto:michael.x.mcma...@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
