---
layout: default
navsection: userguide
-navmenu: Tutorials
title: "Debugging a Crunch script"
-
...
-h1. Debugging a Crunch script
-
To test changes to a script by running a job, the change must be pushed into @git@, the job queued asynchronously, and the actual execution may be run on any compute server. As a result, debugging a script can be difficult and time consuming. This tutorial demonstrates using @arv-crunch-job@ to run your job in your local VM. This avoids the job queue and allows you to execute the script from your uncomitted git tree.
*This tutorial assumes that you are "logged into an Arvados VM instance":{{site.baseurl}}/user/getting_started/ssh-access.html#login, and have a "working environment.":{{site.baseurl}}/user/getting_started/check-environment.html*
-This tutorial uses _you_ to denote your username. Replace _you_ with your user name in all the following examples.
+This tutorial uses *@you@* to denote your username. Replace *@you@* with your user name in all the following examples.
h2. Create a new script
-Change to your git directory and create a new script in "crunch_scripts/".
+Change to your git directory and create a new script in @crunch_scripts/@.
<notextile>
<pre><code>~$ <span class="userinput">cd <b>you</b>/crunch_scripts</span>
h2. Using arv-crunch-job to run the job in your VM
-Instead of a git commit hash, we provide the path to the directory in the "script_version" parameter. The script specified in "script" will actually be searched for in the "crunch_scripts/" subdirectory of the directory specified "script_version". Although we are running the script locally, the script still requires access to the Arvados API server and Keep storage service. The job will be recorded in the Arvados job history, and visible in Workbench.
+Instead of a git commit hash, we provide the path to the directory in the "script_version" parameter. The script specified in "script" will actually be searched for in the @crunch_scripts/@ subdirectory of the directory specified "script_version". Although we are running the script locally, the script still requires access to the Arvados API server and Keep storage service. The job will be recorded in the Arvados job history, and visible in Workbench.
<notextile>
<pre><code>~/<b>you</b>/crunch_scripts$ <span class="userinput">cat >~/the_job <<EOF
{
+ "repository":"",
"script":"hello-world.py",
- "script_version":"/home/you/you",
+ "script_version":"$HOME/$USER",
"script_parameters":{}
}
EOF</span>
-~/<b>you</b>/crunch_scripts</span>$ <span class="userinput">arv-crunch-job --job "$(cat ~/the_job)"</span>
+</code></pre>
+</notextile>
+
+Your shell should fill in values for @$HOME@ and @$USER@ so that the saved JSON points "script_version" at the directory with your checkout. Now you can run that job:
+
+<notextile>
+<pre><code>~/<b>you</b>/crunch_scripts</span>$ <span class="userinput">arv-crunch-job --job "$(cat ~/the_job)"</span>
2013-12-12_21:36:42 qr1hi-8i9sb-okzukfzkpbrnhst 29827 check slurm allocation
2013-12-12_21:36:42 qr1hi-8i9sb-okzukfzkpbrnhst 29827 node localhost - 1 slots
2013-12-12_21:36:42 qr1hi-8i9sb-okzukfzkpbrnhst 29827 start
2013-12-12_21:36:42 qr1hi-8i9sb-okzukfzkpbrnhst 29827 script hello-world.py
-2013-12-12_21:36:42 qr1hi-8i9sb-okzukfzkpbrnhst 29827 script_version /home/you/you
+2013-12-12_21:36:42 qr1hi-8i9sb-okzukfzkpbrnhst 29827 script_version /home/<b>you</b>/<b>you</b>
2013-12-12_21:36:42 qr1hi-8i9sb-okzukfzkpbrnhst 29827 script_parameters {}
2013-12-12_21:36:42 qr1hi-8i9sb-okzukfzkpbrnhst 29827 runtime_constraints {"max_tasks_per_node":0}
2013-12-12_21:36:42 qr1hi-8i9sb-okzukfzkpbrnhst 29827 start level 0
2013-12-12_21:36:42 qr1hi-8i9sb-okzukfzkpbrnhst 29827 0 stderr hello world
2013-12-12_21:36:43 qr1hi-8i9sb-okzukfzkpbrnhst 29827 0 child 29834 on localhost.1 exit 0 signal 0 success=
2013-12-12_21:36:43 qr1hi-8i9sb-okzukfzkpbrnhst 29827 0 failure (#1, permanent) after 0 seconds
-2013-12-12_21:36:43 qr1hi-8i9sb-okzukfzkpbrnhst 29827 0 output
+2013-12-12_21:36:43 qr1hi-8i9sb-okzukfzkpbrnhst 29827 0 output
2013-12-12_21:36:43 qr1hi-8i9sb-okzukfzkpbrnhst 29827 Every node has failed -- giving up on this round
2013-12-12_21:36:43 qr1hi-8i9sb-okzukfzkpbrnhst 29827 wait for last 0 children to finish
2013-12-12_21:36:43 qr1hi-8i9sb-okzukfzkpbrnhst 29827 status: 0 done, 0 running, 0 todo
The script's output is captured in the log, which is useful for print statement debugging. However, although this script returned a status code of 0 (success), the job failed. Why? For a job to complete successfully scripts must explicitly add their output to Keep, and then tell Arvados about it. Here is a second try:
<notextile>
-<pre><code>~/<b>you</b>/crunch_scripts$ <span class="userinput">cat >hello-world.py <<EOF
+<pre><code>~/<b>you</b>/crunch_scripts$ <span class="userinput">cat >hello-world-fixed.py <<EOF
#!/usr/bin/env python
import arvados
~/<b>you</b>/crunch_scripts$ <span class="userinput">chmod +x hello-world-fixed.py</span>
~/<b>you</b>/crunch_scripts$ <span class="userinput">cat >~/the_job <<EOF
{
+ "repository":"",
"script":"hello-world-fixed.py",
- "script_version":"/home/you/you",
+ "script_version":"$HOME/$USER",
"script_parameters":{}
}
EOF</span>
2013-12-12_21:56:59 qr1hi-8i9sb-79260ykfew5trzl 31578 check slurm allocation
2013-12-12_21:56:59 qr1hi-8i9sb-79260ykfew5trzl 31578 node localhost - 1 slots
2013-12-12_21:57:00 qr1hi-8i9sb-79260ykfew5trzl 31578 start
-2013-12-12_21:57:00 qr1hi-8i9sb-79260ykfew5trzl 31578 script hello-world.py
-2013-12-12_21:57:00 qr1hi-8i9sb-79260ykfew5trzl 31578 script_version /home/you/you
+2013-12-12_21:57:00 qr1hi-8i9sb-79260ykfew5trzl 31578 script hello-world-fixed.py
+2013-12-12_21:57:00 qr1hi-8i9sb-79260ykfew5trzl 31578 script_version /home/<b>you</b>/<b>you</b>
2013-12-12_21:57:00 qr1hi-8i9sb-79260ykfew5trzl 31578 script_parameters {}
2013-12-12_21:57:00 qr1hi-8i9sb-79260ykfew5trzl 31578 runtime_constraints {"max_tasks_per_node":0}
2013-12-12_21:57:00 qr1hi-8i9sb-79260ykfew5trzl 31578 start level 0
2013-12-12_21:57:02 qr1hi-8i9sb-79260ykfew5trzl 31578 Freeze not implemented
2013-12-12_21:57:02 qr1hi-8i9sb-79260ykfew5trzl 31578 collate
2013-12-12_21:57:02 qr1hi-8i9sb-79260ykfew5trzl 31578 output 576c44d762ba241b0a674aa43152b52a+53
+WARNING:root:API lookup failed for collection 576c44d762ba241b0a674aa43152b52a+53 (<class 'apiclient.errors.HttpError'>: <HttpError 404 when requesting https://qr1hi.arvadosapi.com/arvados/v1/collections/576c44d762ba241b0a674aa43152b52a%2B53?alt=json returned "Not Found">)
2013-12-12_21:57:03 qr1hi-8i9sb-79260ykfew5trzl 31578 finish
-2013-12-12_21:57:04 qr1hi-8i9sb-79260ykfew5trzl 31578 meta key is 9f937693334d0c9234ccc1f808ee7117+1761
</code></pre>
</notextile>
+(The WARNING issued near the end of the script may be safely ignored here; it is the Arvados SDK letting you know that it could not find a collection named @576c44d762ba241b0a674aa43152b52a+53@ and that it is going to try looking up a block by that name instead.)
+
The job succeeded, with output in Keep object @576c44d762ba241b0a674aa43152b52a+53@. Let's look at our output:
<notextile>
notextile. <pre><code>~$ <span class="userinput">export KEEP_LOCAL_STORE=/tmp</span></code></pre>
-Next, "parallel tasks.":tutorial-parallel.html
projects / arvados.git / blobdiff