Re: Name resolution limits
Re: Name resolution limits
- Subject: Re: Name resolution limits
- From: Stéphane Sudre <email@hidden>
- Date: Fri, 8 Feb 2002 19:40:31 +0100
On Friday, February 8, 2002, at 07:25 PM, Becky Willrich wrote:
I'm always surprised by the answers on this topic (and every time I'm
checking my code for the safety of my mind).
Name resolution with up to 10 Threads (pool of potential and reusable
Threads) using the Cocoa APIs is working fine.
No performance issue.
I don't want to be the bearer or bad news, but this is not true. The
Cocoa APIs go through gethostbyname, same as everyone else; this is the
API bottleneck for host resolution. It is possible that the Cocoa APIs
are sufficiently aggressive with caching that they can appear timely in
all but the most perverse cases; I don't know. It is also possible the
Cocoa APIs take care of the thread-safety issues by locking, but that
won't change the fact that host lookups are serialized, so the total
time is still going to be O(n), where n is the number of requests.
The misunderstanding on my side might be on the Serialized word.
Is this what is called Serialized lookups ? (I thought serialized meant
that you have to wait for the reply of the DNS query to send another
one).
17:10:38.118397 xxxxxxxxxxxxxxx.49162 > xxxxxxxxxxxxxxx.53:
22246+[|domain]
17:10:38.119140 xxxxxxxxxxxxxxx.49154 > xxxxxxxxxxxxxxx.53:
15566+[|domain]
17:10:38.120890 xxxxxxxxxxxxxxx.49174 > xxxxxxxxxxxxxxx.53:
18191+[|domain]
17:10:38.122429 xxxxxxxxxxxxxxx.49175 > xxxxxxxxxxxxxxx.53:
59167+[|domain]
17:10:38.123835 xxxxxxxxxxxxxxx.49176 > xxxxxxxxxxxxxxx.53:
29265+[|domain]
17:10:38.125067 xxxxxxxxxxxxxxx.49177 > xxxxxxxxxxxxxxx.53:
6009+[|domain]
17:10:38.125550 xxxxxxxxxxxxxxx.53 > xxxxxxxxxxxxxxx.49162: 22246
NXDomain[|domain] (DF)
17:10:38.125859 xxxxxxxxxxxxxxx.49162 > xxxxxxxxxxxxxxx.53:
14021+[|domain]
17:10:38.126862 xxxxxxxxxxxxxxx.49178 > xxxxxxxxxxxxxxx.53:
7164+[|domain]
17:10:38.128364 xxxxxxxxxxxxxxx.49179 > xxxxxxxxxxxxxxx.53:
49016+[|domain]
17:10:38.129976 xxxxxxxxxxxxxxx.49180 > xxxxxxxxxxxxxxx.53:
231+[|domain]
17:10:38.131320 xxxxxxxxxxxxxxx.49181 > xxxxxxxxxxxxxxx.53:
53155+[|domain]
17:10:38.132989 xxxxxxxxxxxxxxx.53 > xxxxxxxxxxxxxxx.49154: 15566
NXDomain[|domain] (DF)
17:10:38.133203 xxxxxxxxxxxxxxx.49154 > xxxxxxxxxxxxxxx.53:
52062+[|domain]
17:10:38.134530 xxxxxxxxxxxxxxx.53 > xxxxxxxxxxxxxxx.49174: 18191
NXDomain 0/0/0 (43) (DF)
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