Farming with Condor Douglas Thain [email protected] INFN Bologna, December 2001.
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Transcript of Farming with Condor Douglas Thain [email protected] INFN Bologna, December 2001.
Outline• Introduction
– What is Condor? Why Condor on the Farm?
• Components– Daemons, pools, flocks, ClassAds
• Short Example– Executing 1000 jobs.
• Complications– Firewalls, security, etc…
The Condor Project (Est. 1985)
Distributed systems CS research performed by a team that faces
– software engineering challenges in a UNIX/Linux/NT environment,
– active interaction with users and collaborators,– daily maintenance and support challenges of a distributed
production environment,– and educating and training students.
Funding -
NSF, NASA,DoE, DoD, IBM, INTEL,
Microsoft and the UW Graduate School
A Bird of Opportunity
CentralManager
Job
Job
Job
Job
Job
Busy
Busy
Idle
IdleJob
Job
“I have work.”
“I am idle.”
“I am idle.”
Over the course of a week, 80% of a desktop machine’s time is wasted.
The Condor Principle:
The Condor Corollary:
The owner isabsolutelyin charge!
The visitor must beprepared for the
unexpected!
Tricky Details• What if the user returns?
– Checkpoint the job periodically.
– Restart the job elsewhere from a checkpoint.
• What if the machine does not have your files?– Perform I/O via Remote System Calls
• These two features require that you link with the Condor C library.
• Can’t relink? You may still use Condor, but with some loss in opportunities.
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226 Condor Pools5576 Condor Hosts
Top 10 Condor Pools:
Back to the Farm
• The cluster is the new engine of scientific computing.
• Inexpensive to:– procure– expand– repair
The Ideal Cluster
• The ideal cluster has every node identical, in every way:– CPU– Memory– File system– User accounts– Software installation
• Users expect to be able to execute on any node.
• Some models (MPI) require perfectly matched nodes.
The Bad News• Keeping the entire cluster available for use is very
difficult, when users expect complete symmetry!• Software failures:
– Full disk, wild process, etc...
• Hardware failures:– Replace with exact match? (not best buy)– Replace with better hardware? (goes unused)
• Much better to query rather than assume state of the cluster.
Why Condor on the Farm?• Condor is expert at managing very heterogeneous
resources for high-throughput computing.• Large clusters, despite our best efforts, will always be
slightly heterogeneous.– (It may not be in your financial interests to keep them
perfectly homogeneous.)
• Condor assists users in making progress, despite the imperfections of the cluster.– Few users *require* the whole identical cluster.
– The pursuit of cluster perfection is then an in issue of small throughput improvement, rather than 0 or max.
Basic HTC Mechanisms• Matchmaking - enables requests for services and offers to
provide services find each other (ClassAds).• Persistence - records are kept in stable storage -- any component
may crash and reboot.• Asynchronous API - enables management of dynamic
(opportunistic) resources.• Checkpointing - enables preemptive resume scheduling (go ahead
and use it as long as it is available!).
• Remote I/O - enables remote (from execution site) access to local (at submission site) data.
City Bird, Country Farm
• The lessons learned and techniques used in stealing cycles from workstations are just as important when trying to maximize the throughput of a homogeneous luster.
Outline• Introduction
– What is Condor? Why Condor on the Farm?
• Components– Daemons, pools, flocks, ClassAds
• Short Example– Executing 1000 jobs.
• Complications– Firewalls, security, etc…
Components• Condor can be quite complicated:
– Many daemons, many connections, many logs...
• The complexity is necessary and desirable:– Each process represents an independent interest:
• Machine requirements (startd)
• User requirements (schedd)
• System requirements (central manager)
• Explain the structure by working from the bottom up.
A Single Machine
condorstartd
Localpolicy
filediskRAMcpu
condormaster
keyboard
CentralManager
Size?Speed?Load?
User present?
Size?Avail?
Machine state and
policy.“Only run jobs submitted from Bologna or Milan.
Prefer jobs owned by thain.
Evict jobs that don’t fit in memory. “
administratoremail
“Some-thing is wrong!”
A Single Pool
condorstartd
diskRAMcpu
CentralManager
condorstartd
diskRAMcpu
condorstartd
diskRAMcpu
condorstartd
diskRAMcpu
condorstartd
diskRAMcpu
condorstartd
diskRAMcpu
Local Policy:
“I prefer thain” Local Policy:
“I don’t care.”
Local Policy:
“I prefer mazzanti”
Machine state and
policy.
Machine state and
policy.Global Policy:
“All things being equal, Bologna gets 2x as many machines as Milan.”
A Typical Pool
CentralManager
condorstartd
RAMcpu
Uniform Local Policy:
“All machines except #3 prefer mazzanti”
NFS / AFSServer
diskRAMcpu
condorstartd
RAMcpu
condorstartd
RAMcpu
condorstartd
RAMcpu
condorstartd
RAMcpu
condorstartd
RAMcpuGlobal Policy:
“All things being equal, Bologna gets 2x as many machines as Milan.”
Schedulers
CentralManager
condorstartd
RAMcpu
condorstartd
RAMcpu
condorstartd
RAMcpu
condorstartd
RAMcpu
condorstartd
RAMcpu
condorschedd
Job
Job
Job
Job
Job
condorstartd
RAMcpu
condorschedd
Job
Job
Job
Job
Job
I havework.
I havework.
I amidle.
I amidle.
I amidle. Job Job
Job
JobJob
Job
Multiple Pools
INFN CentralManager
condorschedd
Job
Job
Job
Job
Job
condorstartd
RAMcpu
condorstartd
RAMcpu
condorstartd
RAMcpu
condorstartd
RAMcpu
condorstartd
RAMcpu
condorstartd
RAMcpu
Job Job
Job
JobJob
Job
condorstartd
RAMcpu
condorstartd
RAMcpu
condorstartd
RAMcpu
condorstartd
RAMcpu
condorstartd
RAMcpu
condorstartd
RAMcpu
Job Job
Job
JobJob
Job
condorstartd
RAMcpu
condorstartd
RAMcpu
condorstartd
RAMcpu
condorstartd
RAMcpu
condorstartd
RAMcpu
condorstartd
RAMcpu
Job Job
Job
JobJob
Job
UWCS CentralManager
Matchmaking• Each Central Manager is an introduction service
that matches compatible machines and jobs.• A simple language (ClassAds) is used to represent
everyone’s needs and desires.• The match is not binding contract -- each side is
responsible for enforcing its own needs.• If a central manager crashes, jobs will continue to
run, but no further introductions are made.
ClassAd Example
Job Ad:
Type = “Job”
Cmd = “cmsim.exe”
Owner = “thain”
Requirements =
(OpSys==LINUX) &&
(Memory>128)
Machine Ad:
Type = “Machine”
Name = “vulture”
OpSys = “LINUX”
Memory = 256
Requirements =
(Owner==“thain”)
Matchmaking with ClassAds
StartdStartdScheddSchedd
matc
h
Central Manager
Claim and execute
Match notification
JobAd
JobAd
I have work.
MachineAd
MachineAd
I am idle.
Execute again.…and again!
Placement vs. Scheduling• A Condor Central Manager suggests the
placement of jobs on machines, with the understanding that all jobs are ready to run.
• A Condor scheduler is responsible for executing a list of jobs with various requirements. It may order jobs according to the users requests.
• Neither component plans ahead to make a schedule or a reservation for execution -- it is assumed change is so frequent that schedules are not useful.
Can we Schedule?• Of course, schedule is important for users that
have strict time contraints.• Scheduling is more important to High-
Performance Computing (HPC) than High-Throughput Computing (HTC.)
• Scheduling requirements may be worked into Condor in one of two ways:– 1 - Users may share a single submission point.
– 2 - The administrator may periodically reconfigure policy according to a schedule established elsewhere.
Scheduling
CentralManager
condorstartd
RAMcpu
condorstartd
RAMcpu
condorstartd
RAMcpu
condorstartd
RAMcpu
condorstartd
RAMcpu
condorschedd
Job
Job
Job
Job
Job condorstartd
RAMcpu
Job
Job
Job
Job
Job
I amidle.
I amidle.
I amidle. Job Job
Job
JobJob
JobMethod 1: All users share a schedd.
Method 2: Modify global policy when necessary.
8:00: All nodes prefer thain.
10:00: All nodes prefer mazzanti.
Outline• Introduction
– What is Condor? Why Condor on the Farm?
• Components– Daemons, pools, flocks, ClassAds
• Short Example– Executing 1000 jobs.
• Complications– Firewalls, security, etc…
How Many Machines?
% condor_statusName OpSys Arch State Activity LoadAv Mem
lxpc1.na.infn LINUX-GLIBC INTEL Unclaimed Idle 0.000 30axpd21.pd.inf OSF1 ALPHA Owner Idle 0.266 96vlsi11.pd.inf SOLARIS26 SUN4u Claimed Busy 0.000 256
. . . Machines Owner Claimed Unclaimed Matched Preempting
ALPHA/OSF1 115 67 46 1 0 1 INTEL/LINUX 53 18 0 35 0 0 INTEL/LINUX-GLIBC 16 7 0 9 0 0 SUN4u/SOLARIS251 1 1 0 0 0 0 SUN4u/SOLARIS26 6 2 0 4 0 0 SUN4u/SOLARIS27 1 1 0 0 0 0 SUN4x/SOLARIS26 2 1 0 1 0 0
Total 194 97 46 50 0 1
Submit the Job
• Create a submit file:• vi sim.submit
• Submit the job:• condor_submit sim.submit
Executable = sim
Input = sim.in
Output = sim.out
Log = sim.log
queue
Watch the Progress
% condor_q
-- Submitter: axpbo8.bo.infn.it : <131.154.10.29:1038> :
ID OWNER SUBMITTED RUN_TIME ST PRI SIZE CMD
5.0 thain 6/21 12:40 0+00:00:15 R 0 2.5 sim.exe
Each job gets a unique number.
Status: Unexpanded, Running or Idle
Size of program image (MB)
Receive E-mail When DoneThis is an automated email from the Condor systemon machine "axpbo8.bo.infn.it". Do not reply.
Your condor job /tmp_mnt/usr/users/ccl/thain/test/sim 40exited with status 0.
Submitted at: Wed Jun 21 14:24:42 2000Completed at: Wed Jun 21 14:36:36 2000
Real Time: 0 00:11:54Run Time: 0 00:06:52Committed Time: 0 00:01:37. . .
Running Many Processes• The real benefit of Condor comes from
managing 1000s of jobs.
• First, get organized. Write a script to make 1000 input files.
• Now, simply adjust your submit file:
Executable = sim.exe
Input = sim.in.$(PROCESS)
Output = sim.out.$(PROCESS)
Log = sim.log
Queue 1000
What can go wrong?
• If an execution site crashes:– Your job will restart elsewhere.
• If the central manager crashes:– Jobs will continue to run, no new matches will be
made.
• If the submit machine crashes:– Jobs will stop, but be re-started when it reboots.
• The only way to lose a job is to throw away the disk on the submit machine!
Outline• Introduction
– What is Condor? Why Condor on the Farm?
• Components– Daemons, pools, flocks, ClassAds
• Short Example– Executing 1000 jobs.
• Complications– Firewalls, security, etc…
Firewalls• Why a firewall?
– Prevent all outside contact.– Prevent non-approved contact.– Carefully securing every node is too much work.
• What’s the problem?– A variety of processes comprise Condor.– A variety of ports must be used at once.– Submit and execute machines must communicate
directly, not through the CM.
The Firewall Problem
CentralManager
condorstartd
RAMcpu
condorstartd
RAMcpu
condorstartd
RAMcpu
condorstartd
RAMcpu
condorstartd
RAMcpu
condorschedd
condorstartd
RAMcpu
Firewall
PrivateNetwork
PublicNetwork
Firewall Solution #1
CentralManager
condorstartd
RAMcpu
condorstartd
RAMcpu
condorstartd
RAMcpu
condorstartd
RAMcpu
condorstartd
RAMcpu
condorschedd
condorstartd
RAMcpu
Firewall
PrivateNetwork
PublicNetwork
Allow ports 1000-1010.
Use only ports 1000-1010.
Firewall Solution #1• Pros:
– Easy to configure Condor.– Easy to configure firewall.– Machine remain a part of the pool.
• Cons:– Number of ports limits number of simultaneous
interactions with the node. (running jobs + queue ops + negotiations, etc.)
– More ports = more connections, less security
Firewall Solution #2
CentralManager
condorstartd
RAMcpu
condorstartd
RAMcpu
condorstartd
RAMcpu
condorstartd
RAMcpu
condorstartd
RAMcpu
condorstartd
RAMcpu
Firewall
PrivateNetwork
PublicNetwork
condorschedd
ssh
Firewall Solution #2
• Pros:– Only port through router is ssh.
• Cons:– Pool is partitioned!– Users must manually submit to every pool that
is behind a firewall. (I.e. they won’t.)– No global policy possible.– No global management/status possible.
Network Address Translation
• Both solutions only work as long as the firewall simply drops packets it doesn’t like.
• If the firewall is a Network Address Translator (masquerade,) then only solution #2 works.
• Research in Progress: A Condor NAT that runs on the firewall and exports the pool to the outside world.
Security
• Current Condor security:– Authenticate via DNS.– Authorize classes of hosts for certain tasks.
• New Condor (6.3.X?) security:– Authenticate with encrypted credentials.– Authorize on a per-user basis.– Forward credentials to necessary sites.
Condor 6.2 Security• Authentication: DNS is queried for each incoming
connection in order to determine the name.• Authorization: Each participant permits a class of
hosts to perform certain tasks. At UW-CS:– HOSTALLOW_READ = *.wisc.edu, *.infn.it
• Hosts that may query the machine state.
– HOSTALLOW_WRITE = *.cs.wisc.edu, *.infn.it
• Hosts that may execute jobs, send updates, etc...
– HOSTALLOW_OWNER= $(FULL_HOSTNAME)
• Hosts that may cause this machine to vacate.
– HOSTALLOW_ADMINISTRATOR= condor.cs.wisc.edu
• Hosts that may change priorities, turn Condor on/off
Condor 6.3.X? Security• Principle: No single security mechanism is
appropriate for all sites. Condor must have many tools. – United States Air Force:
• Kerberos authentication, all connections encrypted
– Cluster behind a firewall:• Host authentication, no encryption
– Grid Computing:• GSI credentials from certain authorities, encryption is up to
the user.
Condor 6.3.X Security
CentralManager
Datastorage
condorstartd
RAMcpu
condorschedd
RAMcpu
Disk
Execute
I/OKR
B 5 ?
NO GS
I ?
YE
S!
Submit
GSI ?
YES!
FORWARD CERT GSI
Getting Condor
• Condor Home Page– http://www.cs.wisc.edu
• Binaries are freely available.
• Versions:– 6.2.x - Stable releases, bug fixes only– 6.3.x - Development releases
For More Info
• Condor Home Page– http://www.cs.wisc.edu/condor
• These slides:– http://www.cs.wisc.edu/~thain
• Douglas Thain– [email protected]
• Questions Now?