Getting Started: Multiple node Condor pool with firewalls

Creating a Condor pool with no firewalls up is quite a simple task. Before the condor_shared_port daemon, doing the same with firewalls was a bit painful.

Condor uses dynamic ports for everything except the Collector. The Collector endpoint is the bootstrap. This means a Schedd might start up on a random ephemeral port, and each of its shadows might as well. This causes headaches for firewalls as large ranges of ports need to be opened for communication. There are ways to control the ephemeral range used. Unfortunately, doing so just reduced the port range some, did not guarantee Condor was on the ports, and could limit scale.

The condor_shared_port daemon allows Condor to use a single inbound port on a machine.

Again, using Fedora 15. I had no luck with firewalld and firewall-cmd. Instead I fell back to using straight iptables.

The first thing to do is pick a port for Condor to use on your machines. The simplest thing to do is pick 9618, the port typically known as the Collector’s port.

On all machines where Condor is going to run, you want to –

# lokkit --enabled

# service iptables start
Starting iptables (via systemctl):  [  OK  ]

# service iptables status
Table: filter
Chain INPUT (policy ACCEPT)
num  target     prot opt source               destination
1    ACCEPT     all  --  0.0.0.0/0            0.0.0.0/0           state RELATED,ESTABLISHED
2    ACCEPT     icmp --  0.0.0.0/0            0.0.0.0/0
3    ACCEPT     all  --  0.0.0.0/0            0.0.0.0/0
4    REJECT     all  --  0.0.0.0/0            0.0.0.0/0 reject-with icmp-host-prohibited

Chain FORWARD (policy ACCEPT)
num  target     prot opt source               destination
1    REJECT     all  --  0.0.0.0/0            0.0.0.0/0 reject-with icmp-host-prohibited

Chain OUTPUT (policy ACCEPT)
num  target     prot opt source               destination

If you want to ssh to the machine again, be sure to insert rules above the “REJECT ALL — …” –

# iptables -I INPUT 4 -p tcp -m tcp --dport 22 -j ACCEPT

And open a port, both TCP and UDP, for the shared port daemon –

# iptables -I INPUT 5 -p tcp -m tcp --dport condor -j ACCEPT
# iptables -I INPUT 6 -p udp -m udp --dport condor -j ACCEPT

Next you want to configure Condor to use the shared port daemon, with port 9618 –

# cat > /etc/condor/config.d/41shared_port.config
SHARED_PORT_ARGS = -p 9618
DAEMON_LIST = $(DAEMON_LIST), SHARED_PORT
COLLECTOR_HOST = $(CONDOR_HOST)?sock=collector
USE_SHARED_PORT = TRUE
^D

In order, SHARED_PORT_ARGS tells the shared port daemon to listen on port 9618, DAEMON_LIST tells the master to start the shared port daemon, COLLECTOR_HOST specifies that the collector will be on the sock named “collector”, and finally USE_SHARED_PORT tells all daemons to register and use the shared port daemon.

After you put that configuration on all your systems, run service condor restart, and go.

You will have the shared port daemon listening on 9618 (condor), and all communication between machines will around through it.

# lsof -i | grep $(pidof condor_shared_port)
condor_sh 31040  condor    8u  IPv4  74105      0t0  TCP *:condor (LISTEN)
condor_sh 31040  condor    9u  IPv4  74106      0t0  UDP *:condor

That’s right, you have a condor pool with firewalls and a single port opened for communication on each node.

Tags: Condor, Firewall, Security, Tutorial