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HTCondor Networking Concepts

HTCondor Networking Concepts. Disclaimers. Not about configuration macros Not about host or daemon lookups Not about HTCondor internals. Asking the Right Questions. There will be a quiz at the end Start by reviewing fairy-tale networking … then add IPv6 … then add schedd firewalls

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HTCondor Networking Concepts

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  1. HTCondorNetworking Concepts

  2. Disclaimers • Not about configuration macros • Not about host or daemon lookups • Not about HTCondor internals

  3. Asking the Right Questions • There will be a quiz at the end • Start by reviewing fairy-tale networking • … then add IPv6 • … then add schedd firewalls • … then add startd firewalls • End by passing the quiz (open-manual)

  4. Fairy-tale Networking • Single network protocol • All addresses publically routable • No firewalls • Fewer than ~25k simultaneous running jobs

  5. Working in a Fairy Tale negotiator collector schedd startd shadow* starter* * One shadow, starter per running job

  6. IPv6 negotiator collector schedd startd shadow starter IPv4 IPv6

  7. IPv6 + IPv4 negotiator collector schedd startd shadow starter startd IPv4 starter IPv6

  8. Shared Port • Problem: Firewall • Admin willing to open only one port • Problem: only ~60k TCP ports • Need one per shadow • Shared Port Service • Listens on single port for incoming connections • Hands each connection to intended recipient

  9. Shared Port Internet Fire wall startd schedd shared_port starter

  10. Firewalled Submit Node negotiator collector schedd Wall startd shared port starter Fire shadow

  11. TCP Forwarding Host • Problem: Private network with NAT • Traverse firewall via port forwarding • Allocate a public IP address • Connections to public address forwarded by NAT to machine on private network • Common in the Cloud

  12. Condor Connection Broker • Problem: Private network with NAT • Or firewall with no opening for HTCondor • Traverse firewall by reversing connection • Client sends connection request via broker • Server initiates TCP connection to client • Only bypasses one firewall • Client and broker (CCB server) must have publically routable addresses

  13. CCB: Condor Connection Broker CCB Internet Outbound firewall schedd startd schedd

  14. NATd Execute Nodes negotiator collector/CCB schedd Wall NAT shared port startd Fire shadow starter

  15. Port Usage (Digression) • Shadow for each running job • In fairy-tale setup • Each shadow uses two ports • Limit of ~25k running jobs • With shared port and CCB • Shadow use no ports • No network limit on number of running jobs

  16. Quiz • Why do schedds and central managers need to be mixed-mode in a pool split between IPv4 and IPv6 nodes? • Why use CCB on execute nodes? • Why use both CCB and shared port? • If both the schedd and the execute nodes are NATd, what do you do?

  17. Question1 • Why do schedds and central managers need to be mixed-mode in a pool split between IPv4 and IPv6 nodes? • They need to be able to talk to all execute nodes

  18. Question2 • Why use CCB on execute nodes (and not submit nodes)? • Easier to make submit nodes publically accessible (fewer of them)

  19. Question3 • Why use both CCB and shared port? • Can’t use CCB for both schedd and startd • No ports used for shadow, so no limit on number of running jobs

  20. Question4 • If both the schedd and the execute nodes are NATd, what do you do? • If same NAT, no problem • TCP Forwarding Host for schedd

  21. Congratulations! HTCondor Administrator Networking

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