Re: Remote "Local Address" of netstat and SCAN listener and VIP on different hosts
- From: Yong Huang <yong321@xxxxxxxxx>
- To: oracle-l@xxxxxxxxxxxxx
- Date: Wed, 25 Apr 2012 07:58:38 -0700 (PDT)
I find that "Local Address" of netstat is not reliable and I can reproduce its
odd behavior, although I still can't reproduce the Oracle problem.
[root@dcprperschdb1b oracle]# export PS1='NodeB# ' <- make prompt shorter
NodeB# netstat -anp | grep 1234 <- port is not taken
NodeB# ifconfig | grep 10.111.108.167 <- this IP is on this box
inet addr:10.111.108.167 Bcast:10.111.108.255 Mask:255.255.255.128
NodeB# cat myserver.pl <- my dummy server/listener will use that IP
#!/usr/bin/perl
use Socket;
$server_port = 1234;
socket(Server, PF_INET, SOCK_STREAM, getprotobyname('tcp'));
setsockopt(Server, SOL_SOCKET, SO_REUSEADDR, 1);
#$my_addr = sockaddr_in($server_port, INADDR_ANY);
$my_addr = sockaddr_in($server_port, inet_aton("10.111.108.167"));
bind(Server, $my_addr) or die "Can't bind to port $server_port: $!\n";
listen(Server, SOMAXCONN) or die "Can't listen on port $server_port: $!\n";
while (accept(Client, Server))
{
}
client Server;
NodeB# ./myserver.pl & <- run dummy listener on that IP on port 1234
[1] 21092
NodeB# su - oracle
dcprperschdb1b ~ $ srvctl config scan -i 3 <- verify 10.111.108.167 is SCAN VIP
SCAN name: scan_erschp.mdanderson.edu, Network:
1/10.111.108.128/255.255.255.128/bond0
SCAN VIP name: scan3, IP: /scan_erschp.mdanderson.edu/10.111.108.167
dcprperschdb1b ~ $ srvctl status scan -i 3 <- it runs on node b
SCAN VIP scan3 is enabled
SCAN VIP scan3 is running on node dcprperschdb1b
dcprperschdb1b ~ $ srvctl status scan_listener -i 3 <- also on node b
SCAN Listener LISTENER_SCAN3 is enabled
SCAN listener LISTENER_SCAN3 is running on node dcprperschdb1b
dcprperschdb1b ~ $ srvctl relocate scan -i 3
dcprperschdb1b ~ $ srvctl status scan -i 3 <- changes to node a
SCAN VIP scan3 is enabled
SCAN VIP scan3 is running on node dcprperschdb1a
dcprperschdb1b ~ $ srvctl status scan_listener -i 3 <- also changes to node a
SCAN Listener LISTENER_SCAN3 is enabled
SCAN listener LISTENER_SCAN3 is running on node dcprperschdb1a
The above shows that both SCAN VIP and SCAN listener are relocated together
even if the IP is being used by a process (owned by root or oracle, which
makes no difference).
The following shows the non-existing "Local Address" of `netstat -an':
dcprperschdb1b ~ $ exit
logout
NodeB# ifconfig | grep 10.111.108.167 <- IP no longer on this box
NodeB# netstat -anp | grep 10.111.108.167 <- but netstat Local Address
still has it!
tcp 0 0 10.111.108.167:1234 0.0.0.0:*
LISTEN 21092/perl
tcp 0 0 10.111.108.160:20909 10.111.108.167:1521
ESTABLISHED 17743/ora_pmon_ersc
NodeB#
On node a, everything is normal:
dcprperschdb1a ~ $ sudo netstat -anp | grep 10.111.108.167 <- node a runs
SCAN_LISTENER3 now
[sudo] password for oracle:
tcp 0 0 10.111.108.167:1521 0.0.0.0:*
LISTEN 29943/tnslsnr
tcp 0 0 10.111.108.167:53 0.0.0.0:*
LISTEN 8328/named
tcp 0 0 10.111.108.159:60641 10.111.108.167:1521
ESTABLISHED 26129/ora_pmon_ersc
tcp 0 0 10.111.108.167:1521 10.111.108.159:60641
ESTABLISHED 29943/tnslsnr
tcp 0 0 10.111.108.167:1521 10.111.108.160:20909
ESTABLISHED 29943/tnslsnr
udp 0 0 10.111.108.167:53 0.0.0.0:*
8328/named
dcprperschdb1a ~ $ ps -fp 29943
UID PID PPID C STIME TTY TIME CMD
oracle 29943 1 0 09:29 ? 00:00:00
/u01/app/11.2.0/grid/bin/tnslsnr LISTENER_SCAN3 -inherit
As expected, from a 3rd box, I can no longer connect to my dummy server (was
able to before relocate):
$ telnet 10.111.108.167 1234
Trying 10.111.108.167...
telnet: connect to address 10.111.108.167: Connection refused
Yong Huang
------ Original message ------
2-node Oracle 11.2.0.1 RAC, RHEL 5.7 x86_64, kernel 2.6.18-274.7.1.el5
One of the 3 SCAN listeners listens on an IP which exists on the other
node of this 2-node RAC.
C:\>nslookup scancs4.<domainname>
...
Name: scancs4.<domainname>
Addresses: 10.111.76.85
10.111.76.84
10.111.76.86
dcsrpcora4a ~ $ ifconfig | egrep '10.111.76.84|10.111.76.85|10.111.76.86'
inet addr:10.111.76.85 Bcast:10.111.76.127 Mask:255.255.255.128
inet addr:10.111.76.84 Bcast:10.111.76.127 Mask:255.255.255.128
dcsrpcora4b ~ $ ifconfig | egrep '10.111.76.84|10.111.76.85|10.111.76.86'
inet addr:10.111.76.86 Bcast:10.111.76.127 Mask:255.255.255.128
The problem is that the 3 IP's, supposedly each backed by one Oracle
SCAN listener, do not all have SCAN listeners listening on them.
Specifically, 10.111.76.84 on node a has no listener, and on node b there
*is* a SCAN listener that claims to be listening on that IP. (Note that
the 4th field of `netstat -an' is "Local Address".)
dcsrpcora4b ~ $ netstat -anp 2>/dev/null | grep 10.111.76.84 <-- this IP exists
on node a
tcp 0 0 10.111.76.84:1521 0.0.0.0:*
LISTEN 15130/tnslsnr
tcp 0 0 10.111.76.70:55578 10.111.76.84:1521
ESTABLISHED 12061/ora_pmon_orac
dcsrpcora4b ~ $ ps -fp 15130
UID PID PPID C STIME TTY TIME CMD
oracle 15130 1 0 Jan27 ? 00:04:40
/u01/app/11.2.0/grid/bin/tnslsnr LISTENER_SCAN3 -inherit
How can a listener process running on its own server (node b) claim to be
listening on an IP which is physically located on a different server (node
a)? On node a, everything looks normal from the OS perspective, and there
actually is a process, named, listening on 10.111.76.84 using port 53.
(Not sure why named uses a virtual interface created by Oracle.)
[root@dcsrpcora4a ~]# netstat -anp | grep 10.111.76.84
tcp 0 0 10.111.76.84:53 0.0.0.0:*
LISTEN 5001/named
udp 0 0 10.111.76.84:53 0.0.0.0:*
5001/named
We know a SCAN VIP can "float" or relocate between the 2 nodes. But at any
give point in time, when netstat says a specific IP is local to a specific
host, that IP must be given by that host (as shown by ifconfig), not by a
different host, regardless what magic Oracle's SCAN listener software does.
Checking with srvctl:
dcsrpcora4a ~ $ srvctl status scan -i 3
SCAN VIP scan3 is enabled
SCAN VIP scan3 is running on node dcsrpcora4a
dcsrpcora4a ~ $ srvctl status scan_listener -i 3
SCAN Listener LISTENER_SCAN3 is enabled
SCAN listener LISTENER_SCAN3 is running on node dcsrpcora4b <-- not dcsrpcora4a!
On another RAC cluster, I tried 'srvctl relocate scan' and 'srvctl
relocate scan_listener'. In both cases, both the SCAN VIP and SCAN
listener are relocated *together* to a different node. It's not possible
to reproduce relocating one but not the other.
I believe to correct the problem we have now, we may just run srvctl
relocate either the VIP (...84) or the SCAN listener (LISTENER_SCAN3). But
I'd like to find out what caused this situation.
Yong Huang
--
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