Can not resolve localhost

[IvanUkhov]

Hi!

I'm trying to run phat. I start memcached, but in the log file I see the following error:

MemCacheError (No connection to server (localhost:11211 DEAD (SocketError: Hostname not known: localhost), will retry at 2010-04-05 14:09:22 +0400)): No connection to server (localhost:11211 DEAD (SocketError: Hostname not known: localhost), will retry at 2010-04-05 14:09:22 +0400)

Without em-resolv-replace it works fine.

Ivan.

[mperham]

Works fine for me. Can you give me more detail? OS? Contents of /etc/hosts?

[IvanUkhov]

Mac OS X 10.6.3, /etc/hosts:

127.0.0.1 localhost uvsoft.localhost uvsoft
255.255.255.255 broadcasthost
::1 localhost fe80::1%lo0 localhost

even if I specify memcached IP (my local IP address like 192.168.x.x) in the config, I get the same error, but s/localhost/192.168.x.x

[IvanUkhov]

with config.cache_store = :mem_cache_store, '127.0.0.1:11211', the same:

MemCacheError (No connection to server (127.0.0.1:11211 DEAD (SocketError: Hostname not known: 127.0.0.1), will retry at 2010-04-05 17:19:27 +0400)): No connection to server (127.0.0.1:11211 DEAD (SocketError: Hostname not known: 127.0.0.1), will retry at 2010-04-05 17:19:27 +0400)

It looks like it is trying to resolve IP address of IP address)

[IvanUkhov]

Mb it is because of ruby? You suggest 1.9.1, but mine version is 1.9.2....

ruby:
  interpreter:  "ruby"
  version:      "1.9.2dev"
  date:         "2010-04-05"
  platform:     "x86_64-darwin10.3.0"
  patchlevel:   "2010-04-05 trunk 27222"
  full_version: "ruby 1.9.2dev (2010-04-05 trunk 27222) [x86_64-darwin10.3.0]"

[mperham]

Does this work for you?

~> rvm 1.9.1
~> irb
>> require 'em-resolv-replace'
=> true
>> Resolv.getaddress('localhost')
=> "::1"

Note it's returning an IPv6 address. Make sure that memcached is listening on the IPv6 interface:

~> netstat -a | grep 11211
tcp4       0      0  *.11211                *.*                    LISTEN
tcp6       0      0  *.11211                *.*                    LISTEN

[IvanUkhov]

soft@iUVSoft ~/work/sites/phat $ rvm ruby-head
soft@iUVSoft ~/work/sites/phat $ irb
ruby-head > require 'em-resolv-replace'
 => true 
ruby-head > Resolv.getaddress('ya.ru')
 => "77.88.21.8" 
ruby-head > Resolv.getaddress('localhost')
 => "fe80::1%lo0" 
ruby-head > 

[IvanUkhov]

soft@iUVSoft ~/work/sites/phat $ netstat -a | grep 11211
tcp4       0      0  *.11211                *.*                    LISTEN
tcp6       0      0  *.11211                *.*                    LISTEN
udp4       0      0  *.11211                *.*                    
udp6       0      0  *.11211                *.*    

[mperham]

Sorry, I wasn't starting the reactor and so em-resolv-replace wasn't using its own code for the resolution. Try this in irb:

require 'em-resolv-replace'
EM.run {
  Fiber.new do
    p Resolv.getaddresses('localhost')
    p Resolv.getaddress('localhost')
    EM.stop
  end.resume
}

[mperham]

I get:

["127.0.0.1"]
"127.0.0.1"

[IvanUkhov]

soft@iUVSoft ~/work/sites/phat $ irb
ruby-1.9.2-p-1 > require 'em-resolv-replace'
 => true 
ruby-1.9.2-p-1 > EM.run {
ruby-1.9.2-p-1 >       Fiber.new do
ruby-1.9.2-p-1 >           p Resolv.getaddresses('localhost')
ruby-1.9.2-p-1 ?>        p Resolv.getaddress('localhost')
ruby-1.9.2-p-1 ?>        EM.stop
ruby-1.9.2-p-1 ?>      end.resume
ruby-1.9.2-p-1 ?>  }
Resolv::ResolvError: ["rcode=3"]
    from /Users/soft/.rvm/gems/ruby-head/gems/em-resolv-replace-1.0.0/lib/em-resolv-replace.rb:37:in `em_getaddress'
    from /Users/soft/.rvm/gems/ruby-head/gems/em-resolv-replace-1.0.0/lib/em-resolv-replace.rb:21:in `getaddresses'
    from /Users/soft/.rvm/rubies/ruby-head/lib/ruby/1.9.1/resolv.rb:50:in `getaddresses'
    from (irb):4:in `block (2 levels) in irb_binding'
ruby-1.9.2-p-1 > 

[IvanUkhov]

Here is an example with remote host:

ruby-1.9.2-p-1 > require 'em-resolv-replace'
 => false 
ruby-1.9.2-p-1 > EM.run {
ruby-1.9.2-p-1 >       Fiber.new do
ruby-1.9.2-p-1 >           p Resolv.getaddresses('ya.ru')
ruby-1.9.2-p-1 ?>        p Resolv.getaddress('ya.ru')
ruby-1.9.2-p-1 ?>        EM.stop
ruby-1.9.2-p-1 ?>      end.resume
ruby-1.9.2-p-1 ?>  }
["93.158.134.8", "213.180.204.8", "77.88.21.8"]
"77.88.21.8"
 => nil 

[mperham]

I suspect the issue is that em-resolv-replace may not support /etc/hosts. It is depending on your DNS server to return 127.0.0.1 for localhost. Yours is instead returning an error code. Do you get the same error if you use an IP address?

[mperham]

Just pushed support for /etc/hosts. Let me know if this fixes your issue.

[IvanUkhov]

So, if I leave this line in environment.rb unchanged "config.cache_store = :mem_cache_store", now everything works fine, it can connect to memcached. But the strage thing is that when I specify the IP address like "config.cache_store = :mem_cache_store, '127.0.0.1:11211'", it is trying to resolve IP address of '127.0.0.1' like it is a doman name (not already an IP address)... and eventually can do this, so in this case connection to memcached fails.

[IvanUkhov]

According to the code in em-dns-resolver.rb, it does not try to figure out whether @hostname already contains an IP address or not... It always fires request to the DNS server, doesn't it?

[mperham]

Exactly. I'm accepting patches if you have some time. :-)