Bug #496 [ruby-core:18381]
DRb.start_service(nil) is very slow
| Status : | Open | Start : | 08/25/2008 | |
| Priority : | Normal | Due date : | ||
| Assigned to : | Masatoshi Seki | % Done : | 0% |
|
| Category : | lib | |||
| Target version : | - | |||
| ruby -v : | - |
Description
On some systems - such as mine - DRB.start_service(nil) is very slow. This is caused by the fact that DRb.open_server calls TCPServer.open(nil, 0).addr[1]. On my system, this takes about 3 seconds, and during those 3 seconds there is 0% CPU usage.
I suspect it has got something to do with the fact that retrieving the port of a server socket that's bound to 0.0.0.0 is for some unknown reason very slow.
The problem can be fixed by replacing the following line in drb.rb
uri = 'druby://:0' unless uri
with:
uri = 'druby://localhost:0' unless uri
This does not violate DRb.start_service's contract, because a nil indicates that it will bind to the default local host name.
The following monkeypatch works around the issue:
module DRb
class << self
alias orig_start_service start_service
end
def self.start_service(uri = nil, front = nil, config = nil)
if uri.nil?
orig_start_service("druby://localhost:0", front, config)
else
orig_start_service(uri, front, config)
end
end
end
Related issues
| related to Feature #1811 | Default BasicSocket.do_not_reverse_lookup to true | Closed | 07/23/2009 |
History
08/27/2008 09:56 PM - Brian Candler
I suspect a DNS/hostname resolution problem on your system.
Looking at 1.8.6p114, notice that DRbTCPSocket.getservername first calls Socket.gethostname to get the hostname, then calls Socket.gethostbyname which does both forward and reverse name resolution, presumably to map to a "canonical" name. Then DRbTCPSocket.open_server_inaddr_any also calls Socket.getaddrinfo, although it discards the results apart from using them to decide whether to bind to IPv4, IPv6, or both.
Try the following in irb - how long does each step take?
{{{
require 'socket'
h1 = Socket.gethostname
h2 = Socket.gethostbyname(h1)[0]
Socket.getaddrinfo(h2, nil, Socket::AF_UNSPEC, Socket::SOCK_STREAM, 0, Socket::AI_PASSIVE)
}}}
If one of these steps is slow, you may be able to solve the problem by adding an entry in /etc/resolv.conf to map your hostname to your primary interface IP.
09/04/2008 08:47 PM - Brian Candler
OK, how about this:
require 'socket'
t = TCPServer.new("", nil)
t.addr
t.addr
Socket.do_not_reverse_lookup=true
t.addr
On my machine, the first 't.addr' invocations take about 5 seconds. The last one is instant. I believe this is because of the delay looking up 0.0.0.0 in the DNS.
01/01/2009 03:04 AM - Roger Pack
Sounds like the problem is that
require 'socket'
t = TCPServer.new("", nil)
t.addr
is slow, is that the root of the problem?
-=r