---
layout: default
navsection: installguide
title: Install the Crunch dispatcher

...

The dispatcher normally runs on the same host/VM as the API server.

h2. Perl SDK dependencies

Install the Perl SDK on the controller.

* See "Perl SDK":{{site.baseurl}}/sdk/perl/index.html page for details.

h2. Python SDK dependencies

Install the Python SDK and CLI tools on controller and all compute nodes.

* See "Python SDK":{{site.baseurl}}/sdk/python/sdk-python.html page for details.

h2(#slurm). Set up SLURM

On the API server, install SLURM and munge, and generate a munge key.

On Debian-based systems:

<notextile>
<pre><code>~$ <span class="userinput">sudo /usr/bin/apt-get install slurm-llnl munge</span>
~$ <span class="userinput">sudo /usr/sbin/create-munge-key</span>
</code></pre>
</notextile>

On Red Hat-based systems, "install SLURM and munge from source following their installation guide":https://computing.llnl.gov/linux/slurm/quickstart_admin.html.

Now we need to give SLURM a configuration file in @/etc/slurm-llnl/slurm.conf@. Here's an example:

<notextile>
<pre>
ControlMachine=uuid_prefix.your.domain
SlurmctldPort=6817
SlurmdPort=6818
AuthType=auth/munge
StateSaveLocation=/tmp
SlurmdSpoolDir=/tmp/slurmd
SwitchType=switch/none
MpiDefault=none
SlurmctldPidFile=/var/run/slurmctld.pid
SlurmdPidFile=/var/run/slurmd.pid
ProctrackType=proctrack/pgid
CacheGroups=0
ReturnToService=2
TaskPlugin=task/affinity
#
# TIMERS
SlurmctldTimeout=300
SlurmdTimeout=300
InactiveLimit=0
MinJobAge=300
KillWait=30
Waittime=0
#
# SCHEDULING
SchedulerType=sched/backfill
SchedulerPort=7321
SelectType=select/cons_res
SelectTypeParameters=CR_CPU_Memory
FastSchedule=1
#
# LOGGING
SlurmctldDebug=3
#SlurmctldLogFile=
SlurmdDebug=3
#SlurmdLogFile=
JobCompType=jobcomp/none
#JobCompLoc=
JobAcctGatherType=jobacct_gather/none
#
# COMPUTE NODES
NodeName=DEFAULT
PartitionName=DEFAULT MaxTime=INFINITE State=UP
PartitionName=compute Default=YES Shared=yes

NodeName=compute[0-255]

PartitionName=compute Nodes=compute[0-255]
</pre>
</notextile>

Please make sure to update the value of the @ControlMachine@ parameter to the hostname of your dispatcher (API server).

h2. Enable SLURM job dispatch

In your API server's @application.yml@ configuration file, add the line @crunch_job_wrapper: :slurm_immediate@ under the appropriate section.  (The second colon is not a typo.  It denotes a Ruby symbol.)

h2. Crunch user account

Run @sudo adduser crunch@.  The crunch user should have the same UID, GID, and home directory on all compute nodes and on the dispatcher (API server).

h2. Git Repositories

Crunch scripts must be in Git repositories in the directory configured as @git_repositories_dir@/*.git (see the "API server installation":install-api-server.html#git_repositories_dir).

Once you have a repository with commits -- and you have read access to the repository -- you should be able to create a new job:

<pre>
read -rd $'\000' newjob <<EOF; arv job create --job "$newjob"
{"script_parameters":{"input":"f815ec01d5d2f11cb12874ab2ed50daa"},
 "script_version":"master",
 "script":"hash",
 "repository":"arvados"}
EOF
</pre>

Without getting this error:

<pre>
ArgumentError: Specified script_version does not resolve to a commit
</pre>

h2. Running jobs

* @services/api/script/crunch-dispatch.rb@ must be running.
* @crunch-dispatch.rb@ needs @services/crunch/crunch-job@ in its @PATH@.
* @crunch-job@ needs the installation path of the Perl SDK in its @PERLLIB@.
* @crunch-job@ needs the @ARVADOS_API_HOST@ (and, if necessary in a development environment, @ARVADOS_API_HOST_INSECURE@) environment variable set.

Example @/var/service/arvados_crunch_dispatch/run@ script:

<pre>
#!/bin/sh
set -e

rvmexec=""
## uncomment this line if you use rvm:
#rvmexec="/usr/local/rvm/bin/rvm-exec 2.1.1"

export PATH="$PATH":/path/to/arvados/services/crunch
export ARVADOS_API_HOST={{ site.arvados_api_host }}
export CRUNCH_DISPATCH_LOCKFILE=/var/lock/crunch-dispatch

# This is the path to docker on your compute nodes. You might need to
# change it to "docker", "/opt/bin/docker", etc.
export CRUNCH_JOB_DOCKER_BIN=docker.io

fuser -TERM -k $CRUNCH_DISPATCH_LOCKFILE || true

## Only if your SSL cert is unverifiable:
# export ARVADOS_API_HOST_INSECURE=yes

cd /path/to/arvados/services/api
export RAILS_ENV=production
exec $rvmexec bundle exec ./script/crunch-dispatch.rb 2>&1
</pre>