[rabbitmq-discuss] Plz give me help about EPMD: Non-local peer connected

Tim Watson tim at rabbitmq.com
Mon Jul 9 10:12:36 BST 2012


I also wonder how the hostname is getting resolved. Rabbit actually 
passes the hostname to erl, so you get something more like `erl -sname 
[email protected]<hostname>` which is calculated something like this:

SCRIPT_DIR=`dirname $SCRIPT_PATH`
RABBITMQ_HOME="${SCRIPT_DIR}/.."
[ "x" = "x$HOSTNAME" ] && HOSTNAME=`env hostname`
[email protected]${HOSTNAME%%.*}

So what does `env hostname` return on your machine, and can you start an 
Erlang node with this using erl -sname [email protected]`env hostname` or some 
such construct?

On 07/09/2012 10:00 AM, Tim Watson wrote:
> What OS and rabbit version are you running? I've not seen this happen 
> before but I'll investigate.
>
> On 9 Jul 2012, at 07:32, ?? <hebin7611 at hotmail.com 
> <mailto:hebin7611 at hotmail.com>> wrote:
>
>>
>> Hi Tim,
>>
>> Thanks for your reply.
>>
>> I tried "erl -sname rabbit", it's OK.
>>
>> my /etc/hosts looks like following:
>> 127.0.0.1    game-01 ZSWY76 localhost.localdomain localhost
>> ::1        localhost6.localdomain6 localhost6
>>
>> EPMD can be started successfully, but always reports "Non-local peer 
>> connected" then force disconnecting rabbit-server.
>>
>> Did I forget any necessory configration for RabbitMQ to use loopback 
>> interface to connect epmd?
>>
>> Thanks a lot.
>>
>> He Bin
>>
>>
>> > Date: Fri, 6 Jul 2012 18:34:07 +0100
>> > From: tim at rabbitmq.com <mailto:tim at rabbitmq.com>
>> > To: rabbitmq-discuss at lists.rabbitmq.com 
>> <mailto:rabbitmq-discuss at lists.rabbitmq.com>
>> > CC: hebin7611 at hotmail.com <mailto:hebin7611 at hotmail.com>
>> > Subject: Re: [rabbitmq-discuss] Plz give me help about EPMD: 
>> Non-local peer connected
>> >
>> > Hi there,
>> >
>> > On 06/07/2012 06:53, ?? wrote:
>> > > Hi all,
>> > >
>> > > I installed RabbotMQ & tried to start it.
>> > >
>> > > But I always got error as following:
>> > >
>> >
>> > Ok so first of all, let's see if we can get you to start a stand alone
>> > distributed Erlang node successfully. Normally stack traces like that
>> > occur when the host environment isn't set up quite right (from 
>> Erlang's
>> > perspective).
>> >
>> > We need to be able to run `erl -sname rabbit` on the command line and
>> > see the Erlang emulator start successfully. It should look something
>> > like this:
>> >
>> > ##############
>> >
>> > t4 at malachi:systest $ erl -sname rabbit
>> > Erlang R15B01 (erts-5.9.1) [source] [64-bit] [smp:2:2] 
>> [async-threads:0]
>> > [hipe] [kernel-poll:false]
>> >
>> > Eshell V5.9.1 (abort with ^G)
>> > (rabbit at malachi)1>
>> >
>> > ##############
>> >
>> > Can you start Erlang like that successfully? I'm assuming not, but
>> > please let us k now.
>> >
>> > I'm also interested in understanding what your hosts configuration
>> > (e.g., /etc/hosts) looks like. On some Operating Systems (such as 
>> CentOS
>> > for example), failing to set an explicit host name prevents you from
>> > starting a distributed Erlang node.
>> >
>> > > {error_logger,{{2012,7,6},{13,32,21}},"Protocol: ~p: register error:
>> > > 
>> ~p~n",["inet_tcp",{{badmatch,{error,epmd_close}},[{inet_tcp_dist,listen,1,[{file,"inet_tcp_dist.erl"},{line,70}]},{net_kernel,start_protos,4,[{file,"net_kernel.erl"},{line,1314}]},{net_kernel,start_protos,3,[{file,"net_kernel.erl"},{line,1307}]},{net_kernel,init_node,2,[{file,"net_kernel.erl"},{line,1197}]},{net_kernel,init,1,[{file,"net_kernel.erl"},{line,357}]},{gen_server,init_it,6,[{file,"gen_server.erl"},{line,304}]},{proc_lib,init_p_do_apply,3,[{file,"proc_lib.erl"},{line,227}]}]}]}
>> > > 
>> {error_logger,{{2012,7,6},{13,32,21}},crash_report,[[{initial_call,{net_kernel,init, 
>> ['Argument__1']}},{pid,<0.20.0>},{registered_name,[]},{error_info,{exit,{error,badarg},[{gen_server,init_it,6,[{file,"gen_server.erl"},{line,320}]},{proc_lib,init_p_do_apply,3,[{file,"proc_lib.erl"},{line,227}]}]}},{ancest
>> > > 
>> ors,[net_sup,kernel_sup,<0.9.0>]},{messages,[]},{links,[#Port<0.90>,<0.17.0>]},{dictionary,[{longnames,false}]},{trap_exit,true},{status,running},{heap_size,987},{stack_size,24},{reductions,551}],[]]}
>> > > 
>> {error_logger,{{2012,7,6},{13,32,21}},supervisor_report,[{supervisor,{local,net_sup}},{errorContext,start_error},{reason,{'EXIT',nodistribution}},{offender,[{pid,undefined},{name,net_kernel},{mfargs,{net_kernel,start_link,[[rabbitmqprelaunch1077,shortnames]]}},{restart_type,permanent},{shutdown,2000},{child_type,worker}]}]}
>> > > 
>> {error_logger,{{2012,7,6},{13,32,21}},supervisor_report,[{supervisor,{local,kernel_sup}},{errorContext,start_error},{reason,shutdown},{offender,[{pid,undefined},{name,net_sup}, 
>> {mfargs,{erl_distribution,start_link,[]}},{restart_type,permanent},{shutdown,infinity},{child_type,supervisor}]}]}
>> > > 
>> {error_logger,{{2012,7,6},{13,32,21}},std_info,[{application,kernel},{exited,{shutdown,{kernel,start,[normal,[]]}}},{type,permanent}]}
>> > > {"Kern el pid
>> > > 
>> terminated",application_controller,"{application_start_failure,kernel,{shutdown,{kernel,start,[normal,[]]}}}"}
>> > >
>> > > Crash dump was written to: erl_crash.dump
>> > > Kernel pid terminated (application_controller)
>> > > 
>> ({application_start_failure,kernel,{shutdown,{kernel,start,[normal,[]]}}})
>> > >
>> > >
>> > > I ran it on a server with public IP 183.*.*.* .
>> > >
>> > > In Erlang src, I found that epmd checks connection src.
>> > >
>> > > /* Determine if connection is from localhost */
>> > > if (getpeername(s->fd,(struct sockaddr*) &si,&st) ||
>> > > s t < sizeof(si)) {
>> > > /* Failure to get peername is regarded as non local host */
>> > > s->local_peer = EPMD_FALSE;
>> > > } else {
>> > > /* Only 127.x.x.x and connections from the host's IP address
>> > > allowed, no false positives */
>> > > s->local_peer =
>> > > (((((unsigned) ntohl(si.sin_addr.s_addr)) & 0xFF000000U) ==
>> > > 0x7F000000U) ||
>> > > (getsockname(s->fd,(struct sockaddr*) &di,&st) ?
>> > > EPMD_FALSE : si.sin_addr.s_addr == di.s in_addr.s_addr));
>> > > }
>> > > dbg_tty_printf(g,2,(s->local_peer) ? "Local peer connected" :
>> > > "Non-local peer connected");
>> > >
>> > >
>> > > But unfortunately, si.sin_addr.s_addr was 183.*.*.*, while
>> > > di.sin_addr.s_addr was 127.0.0.1
>> > >
>> & gt; > My log:Checking peer address, getsockname ret: 0, 
>> si_addr=0xb7??????,
>> > > di_addr=0x7f000001
>> > >
>> > >
>> >
>> > I could be wrong, but I suspect this is a red herring. You can restart
>> > epmd with -d to get debugging information as well, but I suspect this
>> > isn't relevant.
>> >
>> > Is there any way to force RabbitMQ server connect epmd via a specified
>> > > address?
>> > >
>> >
>> > I'm not really sure what you mean by this, but I'm fairly confident 
>> that
>> > it is not necessary to even attempt to do something like that. Erlang
>> > should be able to start up nodes with `-sname <name>` or `-name
>> > <name>@<host>` and if either doesn't work, a little tweaking of the 
>> host
>> > configuration should solve it.
>> >
>> > Based on your original comment (starting rabbitmq but always 
>> getting an
>> > error) my understanding is that you're trying to start rabbit on this
>> > machine and it fails. AFAIK when a distributed Erlang node connects to
>> > EPMD on the localhost it should be treated as such. The 
>> rabbitmq-server
>> > script starts rabbit up with `-sname rabbit` which implies that the 
>> node
>> > name will be [email protected]<hostname> so you should make sure that `erl 
>> -sname
>> > rabbit` works first of all.
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>
>
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