Whitespace Control with Jinja Templating in Ansible <= 2.2

The Situation

Using Ansible 2.2 or older, I need to create a bash script using the template module[1] that will modify a CentOS image. Specifically, I need to conditionally create a new user on the image before injecting ssh keys if we will not be using the root user on that image. This condition will be determined by the value associated with a supplemental_user variable.

In the following examples, assume that supplemental_user is stack.

Template One

virt-customize -a ~{{ supplemental_user }}/ipa.qcow2 \
    --root-password password:test1234 \
    --install openssh-server \
    --run-command "xfs_growfs /" \
    --run-command "echo 'GRUB_CMDLINE_LINUX=\"console=tty0 crashkernel=auto no_timer_check net.ifnames=0 console=ttyS0,115200n8\"' >> /etc/default/grub" \
    --run-command "grubby --update-kernel=ALL --args=net.ifnames=0" \
    --run-command "systemctl enable sshd" \
    {% if supplemental_user != 'root' %}--run-command "useradd {{ supplemental_user }} -m -p ''" \{% endif %}  # <-- Simple, right?
    --mkdir /root/.ssh \
    --copy-in ifcfg-eth0:/etc/sysconfig/network-scripts/ \
    --copy-in ifcfg-eth1:/etc/sysconfig/network-scripts/ \
    --ssh-inject {{ supplemental_user }}:file:$VMSSHKEY \

Output From Template One:

virt-customize -a ~stack/ipa.qcow2 \
    --root-password password:test1234 \
    --install openssh-server \
    --run-command "xfs_growfs /" \
    --run-command "echo 'GRUB_CMDLINE_LINUX=\"console=tty0 crashkernel=auto no_timer_check net.ifnames=0 console=ttyS0,115200n8\"' >> /etc/default/grub" \
    --run-command "grubby --update-kernel=ALL --args=net.ifnames=0" \
    --run-command "systemctl enable sshd" \
    --run-command "useradd stack -m -p ''" \    --mkdir /root/.ssh \
    --copy-in ifcfg-eth0:/etc/sysconfig/network-scripts/ \
    --copy-in ifcfg-eth1:/etc/sysconfig/network-scripts/ \
    --ssh-inject stack:file:$VMSSHKEY \

The Problem:

As you may have noticed above, the newline trailing our conditional is being absorbed when the template is rendered. A quick review of Jinja template docs[1]  tells us that this is expected behavior, ‘If an application configures Jinja to trim_blocks, the first newline after a template tag is removed automatically (like in PHP).’

Template Two

The trim_blocks issue is easily resolved with Jinja by prepending the conditinoal, ‘You can manually disable the lstrip_blocks behavior by putting a plus sign (+) at the start of a block.’

virt-customize -a ~{{ supplemental_user }}/ipa.qcow2 \
    --root-password password:test1234 \
    --install openssh-server \
    --run-command "xfs_growfs /" \
    --run-command "echo 'GRUB_CMDLINE_LINUX=\"console=tty0 crashkernel=auto no_timer_check net.ifnames=0 console=ttyS0,115200n8\"' >> /etc/default/grub" \
    --run-command "grubby --update-kernel=ALL --args=net.ifnames=0" \
    --run-command "systemctl enable sshd" \
    {%+ if supplemental_user != 'root' %}--run-command "useradd {{ supplemental_user }} -m -p ''" \{% endif %}  # <-- Note the "{%+ .."
    --mkdir /root/.ssh \
    --copy-in ifcfg-eth0:/etc/sysconfig/network-scripts/ \
    --copy-in ifcfg-eth1:/etc/sysconfig/network-scripts/ \
    --ssh-inject {{ supplemental_user }}:file:$VMSSHKEY \

Output From Template Two:

FAILED! => {"changed": false, "failed": true, "msg": "AnsibleError: template error while templating string: tag name expected. String: <snip>

The Next Problem:

This is unexpected, we followed Jinja’s docs, right? A quick look at the docs for Ansible’s template module[2] tell us that we need to set the `trim_blocks` parameter to false when calling the template module. Unfortunately, this feature was added in Ansible 2.3.

Template Three

What do you do if your library is pinned to an earlier release of Ansible? You use an expression to interpret python directly. However if you have lots of special characters, like we do here in this complicated bash template, you will have to be very careful when you form your expression.

# NOTE(hrybacki): The ugly is formed as such because Ansible <2.3 lacks the ability to control
#                 whitespace trimming in Jinja templates. This results in the inability to form
#                 a proper newline. http://docs.ansible.com/ansible/template_module.html#options
virt-customize -a ~{{ supplemental_user }}/ipa.qcow2 \
    --root-password password:test1234 \
    --install openssh-server \
    --run-command "xfs_growfs /" \
    --run-command "echo 'GRUB_CMDLINE_LINUX=\"console=tty0 crashkernel=auto no_timer_check net.ifnames=0 console=ttyS0,115200n8\"' >> /etc/default/grub" \
    --run-command "grubby --update-kernel=ALL --args=net.ifnames=0" \
    --run-command "systemctl enable sshd" \
    {{ "--run-command \"useradd " + supplemental_user + " -m -p ''\" \\" if supplemental_user != 'root' else "\\" }}
    --mkdir /root/.ssh \
    --copy-in ifcfg-eth0:/etc/sysconfig/network-scripts/ \
    --copy-in ifcfg-eth1:/etc/sysconfig/network-scripts/ \
    --ssh-inject {{ supplemental_user }}:file:$VMSSHKEY \

Output From Template Three:

# NOTE(hrybacki): The odd conditional is formed as such because ansible 2.2 does not support
#                 trim_blocks option for Jinja templates preventing us from being able to
#                 form a proper newline.
virt-customize -a ~stack/ipa.qcow2 \
    --root-password password:test1234 \
    --install openssh-server \
    --run-command "xfs_growfs /" \
    --run-command "echo 'GRUB_CMDLINE_LINUX=\"console=tty0 crashkernel=auto no_timer_check net.ifnames=0 console=ttyS0,115200n8\"' >> /etc/default/grub" \
    --run-command "grubby --update-kernel=ALL --args=net.ifnames=0" \
    --run-command "systemctl enable sshd" \
    --run-command "useradd stack -m -p ''" \
    --mkdir /root/.ssh \
    --copy-in ifcfg-eth0:/etc/sysconfig/network-scripts/ \
    --copy-in ifcfg-eth1:/etc/sysconfig/network-scripts/ \
    --ssh-inject stack:file:$VMSSHKEY \

Relevant Links:

[1] – http://jinja.pocoo.org/docs/2.9/templates/#whitespace-control
[2] – http://docs.ansible.com/ansible/template_module.html#options


Standing up OpenStack with FreeIPA and TLS Everywhere using TripleO-Quickstart

UPDATE: 24-May-2017

The three reviews[3] mentioned in the original post have merged and this feature is now part of OOOQ/OOOQ-E. I have updated the deployment script[10] on GitHub for your convenience.

Original Post:

Over the past month, I have been working with TripleO-Quickstart (OOOQ)[1] and TripleO-Quickstart-Extras (OOOQ-E)[2] to automate the deployment of a FreeIPA server and enable TLS Everywhere. There three reviews[3] on review.openstack.org that comprise the majority of my work. All of this is coming to a head after many, many months of work from my teammates Ozz[4], Rob[5], and Ade[6] who put together all the leg work in relevant libraries and communities. Without their effort and headaches, this wouldn’t be possible.

Automating this process is a big deal. Once this it is streamlined this will allow for greatly expanding the security and compliance coverage throughout OpenStack CI. Needless to say, I am pretty excited to be working on this topic. Without any further ado, here is the present workflow to conduct a deployment:


  1. One machine is set up[7] as the controller from which you will call OOOQ to conduct the deployment. I am deploying from a ThinkPad T450S running Fedora 24.
  2. Once machine, referred to as the virthost, 1 quad core CPU, 24GB of memory, and 160 GB of free space. Running with fewer resources is possible but not tested, and will likely result in difficult errors difficult to diagnose.

Preparing Our Environment To deploy:

The first thing we need to do is pull down the OOOQ and OOOQ-E repositories.

cd ~/git

git clone https://github.com/openstack/tripleo-quickstart

git clone https://github.com/openstack/tripleo-quickstart-extras

Next we have to pull down the two reviews required to run the code that hasn’t been merged yet.

cd ~/git/tripleo-quickstart

git fetch https://git.openstack.org/openstack/tripleo-quickstart refs/changes/23/453223/17 && git checkout FETCH_HEAD

cd ~/git/tripleo-quickstart-extras

git fetch https://git.openstack.org/openstack/tripleo-quickstart-extras refs/changes/98/436198/18 && git checkout FETCH_HEAD

In order to ensure that we use our local version of OOOQ-E, we must modify tripleo-quickstart/quickstart-extras-requirements.txt to the repo on our file system.

cd ~/git/tripleo-quickstart

sed -e ‘s/.*#/file:\/\/\/~\/git\/tripleo-quickstart-extras\/#/’ quickstart-extras-requirements.txt

Now, let’s go ahead and create a special working directory to house our deployment data, artifacts, and keep our modified repos clean in the process.

export WORKING_DIR=~/.quickstart-freeipa


cp -rf ~/git/tripleo-quickstart $WORKING_DIR

At this point we are ready to deploy. The only thing we have to do is ensure that we can ssh into our virthost from the controller as root. This is a requirement for Ansible.


cd ~/git/tripleo-quickstart

export VIRTHOST=<your virthost’s IP or FQDN>

bash quickstart.sh \

–bootstrap \

–ansible-debug \

–no-clone \

–playbook quickstart-extras.yml \

–working-dir $WORKING_DIR \

–release master \

–config $WORKING_DIR/config/general_config/ipa.yml \

–nodes $WORKING_DIR/config/nodes/1ctlr_1comp_1supp.yml \

–tags “all” \


After calling quickstart.sh, you will see OOOQ take over and begin installing all the necessary libraries for deployment. After completing it’s environment preparations, it will call the Ansible playbook, quickstart-extras.yml[7]. Pay close attention to the two config files we are explicitly using, ipa.yml[8] and 1ctlr_1comp_1supp.yml[9]. These two configuration files specify how OOOQ deploys a single compute, control, and supplemental node (housing the FreeIPA server), as well as sets all of the various flags needed for the FreeIPA server and enabling TLS Everywhere.

The deployment itself should take around two hours to complete. While we are adding some additional time fetching the Centos image, provisioning the supplemental node, and deploying the FreeIPA server itself — the majority of the deployment time still lands on installing the undercloud and deploying the overcloud.

After deployment has completed — you have full access to the undercloud:

ssh -F $WORKING_DIR/ssh.config.ansible undercloud

as well as the supplemental node which is running the FreeIPA server:

ssh -F $WORKING_DIR/ssh.config.ansible supplemental

Please note that a log of the FreeIPA server deployment can be located on the supplemental node at ~/deploy_freeipa.log. The IPA server admin password can be located in either the Ansible logs (look for freeipa_admin_password) or in the deployment script ~/deploy_freeipa.sh (look for CA_ADMIN_PASSWORD).


Once the reviews[3] have merged, this process will be come much simpler. In the meantime, I have a created a simple bash script[10] which automates all of the above steps requiring only a single parameter, the virthost.

git clone https://gist.github.com/6cf1e6bc32085dd358365f44267f7188.git

chmod +x ./6cf1e6bc32085dd358365f44267f7188/run_oooq_with_ipa.sh

./6cf1e6bc32085dd358365f44267f7188/run_oooq_with_ipa.sh <your virthost’s IP or FQDN>

Relevant Links:

[1] – https://github.com/openstack/tripleo-quickstart

[2] – https://github.com/openstack/tripleo-quickstart-extras

[3] – https://review.openstack.org/#/q/topic:bug/1662923

[4] – http://jaormx.github.io/

[5] – https://blog-rcritten.rhcloud.com/

[6] – https://vakwetu.wordpress.com/

[7] – https://github.com/openstack/tripleo-quickstart/blob/master/playbooks/quickstart-extras.yml

[8] – https://review.openstack.org/#/c/451523/27/config/general_config/ipa.yml

[9] – https://review.openstack.org/#/c/451523/27/config/nodes/1ctlr_1comp_1supp.yml

[10] – https://gist.github.com/HarryRybacki/6cf1e6bc32085dd358365f44267f7188


Using a custom ssh config with Ansible’s synchronize module

Have you ever needed to specify which ssh config file rsync should use when called from Ansible’s synchronize module? I have and it was not obvious how to do so.

At work we use Ansible to deploy OpenStack in our CI infrastructure. The playbooks my work (mostly) revolve around follow TripleO. The resulting deployment will create a custom ssh.config.ansible file that specifies how to properly tunnel from the baremetal machine OpenStack was installed on to a virtual undercloud host and several virtual overcloud hosts residing on it. This config is explicitly called in our ansible.cfg.  But, this is very important information is not transferred over when Ansible executes the synchronize module. The resulting call will raise an error that looks similar to:

cmd: rsync --delay-updates -F --compress --archive --rsh 'ssh -i 
    /home/.../.ssh/id_rsa -S none -o StrictHostKeyChecking=no' \
    --out-format='<<CHANGED>>%i %n%L' "/path/to/sync/from/" \
msg: ssh: Could not resolve hostname undercloud: No address associated with hostname
 rsync: connection unexpectedly closed (0 bytes received so far) [sender]
 rsync error: unexplained error (code 255) at io.c(226) [sender=3.1.1]

The use_ssh_args parameter for the synchronize would resolve the issue but it is only available in ansible 2.0 or greater. However, there is a simple solution if you are forced to use Ansible <= 2.0.

You can specify which ssh config to use in the rsync_opts parameter, as I have below, and everything should work as one would expect.

- name: copy custom fork of tempest to the undercloud
 src: "{{base_dir}}/tempest/"
 dest: "{{ instack_user_home }}/tempest"
 recursive: true
 rsync_opts: -e 'ssh -F "{{ base_dir }}"/khaleesi/ssh.config.ansible'

Hopefully this tip can help save you some time and possibly a headache.


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Deploying an OpenStack undercloud/overcloud on a single server from my laptop with Ansible.

During the summer of 2014 I worked on the OpenStack Keystone component while interning at Red Hat. Fast forward to the end of October 2015 and I once again find myself working on OpenStack for Red Hat — this time on the RDO[1] Continuous Integration (CI) team. Since re-joining Red Hat I’ve developed a whole new level of respect not only for the wide breadth of knowledge required to work on this team but for deploying OpenStack in general.

The list of deployment options for OpenStack[2a,b,c,d] is long and has a colorful history. Furthermore, there are probably only a handful of people who have developed and or used more than any given handful. I have the fortune of working with, or at least within the proximity of, several of these folks. However, even with that advantage, I find wrapping my head around all of the moving parts involved in deploying OpenStack confusing. This was a prime source of frustrations during my first several weeks back at Red Hat. Routinely I found myself having to accept the magic of a given deployment tool in order move forward with my tasks.

Presently, the RDO CI team uses Khaleesi[3][4], and by proxy Ansible, as one of the deployment tools for automating builds with Jenkins[5]. During this walkthrough I will follow the deployment steps as outlined in Khaleesi’s cookbook[6] to deploy OpenStack using RDO-Manager[7] on a single, baremetal CentOS 7.2 server.


  1. One machine is set up[8] as the controller from which you will generate the necessary Ansible configuration and execute the appropriate playbooks within Khaleesi. In my case this is a ThinkPad X1 running Fedora 22 — my work laptop.
    1. Note: Make sure you follow all of the steps in the Khaleesi setup guide on the controller or you will run into problems when trying to use ksgen or Ansible.
  2. One machine with a minimum of 1 quad core CPU, 12 GB of memory, and 120 GB of free space, as outlined by the RDO-Manager docs[9], that is running a clean install of CentOS 7.2
    1. Note: Because our installer, RDO-Manager, is based off of TripleO[2d] we do in fact need to use a baremetal machine for this. I couldn’t find a detailed explanation specifying the exact reasons anywhere but the limitation is noted in both the TripleO docs[c] as well as the Khaleesi docs[10]

My setup meeting the two above requirements looks looks like this:

Screenshot from 2016-01-11 17-57-38


Okay, let us move to the actual setup. We will be picking up at the Configuration[11] portion of the Khaleesi cookbook. Remember that all of these commands are to be run from the machine you installed Khaleesi on — the Thinkpad X1 in my case.

    cp ansible.cfg.example ansible.cfg
    touch ssh.config.ansible
    echo "" >> ansible.cfg
    echo "[ssh_connection]" >> ansible.cfg
    echo "ssh_args = -F ssh.config.ansible" >> ansible.cfg

We begin by copying over the Ansible config in version control, with some defaults needed across Khaleesi use cases, and then telling Ansible to use the config file that will be generated by Khaleesi, ssh.config.ansible

    ssh-copy-id root@<ip address of baremetal virt host>  # x.x.x.49 in my example

ssh-copy-id allows us to easily transfer your ssh keys to the CentOS box. This tool has quickly become one of my gotos as I am constantly provisioning systems and removes many of the possible human errors involved in key transfers.

    export TEST_MACHINE=<ip address of baremetal virt host>  # x.x.x.49 in my example

The playbook we will end up calling, khaleesi/playbooks/full-job-no-test.yml will expect that the TEST_MACHINE environment variable has been set and will use it while generating the hosts file used by Ansible.

    ksgen --config-dir settings generate \
        --provisioner=manual \
        --product=rdo \
        --product-version=liberty \
        --product-version-build=last_known_good \
        --product-version-repo=delorean \
        --distro=centos-7.0 \
        --installer=rdo_manager \
        --installer-env=virthost \
        --installer-images=build \
        --installer-network-isolation=none \
        --installer-network-variant=ml2-vxlan \
        --installer-post_action=none \
        --installer-topology=minimal \
        --installer-tempest=smoke \
        --workarounds=enabled \
        --extra-vars @../khaleesi-settings/hardware_environments/virt/network_configs/none/hw_settings.yml \

Note: If you see warnings similar to the line directly below, don’t worry. There is a set of defaults and it is simply informing you which it will be using if no respective parameter was handed to it when called.

    settings.py:105|       _load_defaults() | WARNING: '--installer-network' hasn't been provided, using 'neutron' as default

Remember that tool we installed from within the Khaleesi repository? That was ksgen, a tool that generates a file, ksgen_settings.yml in our case, which contains most of the variables used by Ansible during the execution of Khaleesi’s playbooks. The parameters above line up with files underneath khaleesi/settings and pull in the variables respectively while magically handling any conflicts that may arise. For example, `–provisioner=manual` will include all variables located within khaleesi/settings/provisioner/manual.yml as well as khaleesi/settings/provisioner/common/common.yml as indicated by the include statement at the top of the aforementioned manual.yml.

This is a pretty basic setup. A few of the parameters are of particular note, namely:


We have provisioned the CentOS box ourselves as opposed to using say Beaker or Foreman (both of which are supported provisioners by Khaleesi)


RDO-Manager is our tool of choice here for the actual installation of OpenStack on our CentOS box.


Our undercloud/overcloud deployment will be installed on virtual machines running on the CentOS box, TEST_MACHINE. Accordingly, Khaleesi will need to use respective virthost playbooks — as opposed to baremetal playbooks were we to install our nodes on actual boxes. 

   --extra-vars @../khaleesi-settings/…

Once upon a time all of the settings files that reside underneath khaleesi/settings lived in another repository aptly named khaleesi-settings. It still exists, we use it internally for storing sensitive data needed for our CI infrastructure that we wouldn’t want public, and it retains some things like the virtual networking settings needed for ml2-vxlan argument passed to ksgen. Why exactly does khaleesi-settings still exist upstream? To be frank, I’m not quite sure but I’ll update this post when I have a rational answer.

The result of calling ksgen is a concise YAML file, ksgen_settings.yml — you can rename it whatever you want just be sure to pass it to your ansible-playbook calls accordingly. This file is infinitely useful and will quickly become your best friend whenever you have to troubleshoot failures with Ansible.


Now we are ready to call Khaleesi’s playbook khaleesi/playbook/full-job-no-test.yml which will provision TEST_MACHINE, which is minimal in our case as we’ve already manually done so, and then use RDO-Manager to deploy an undercloud and overcloud in virtual machines that are hosted on our CentOS box.

    ansible-playbook -vv --extra-vars @ksgen_settings.yml -i local_hosts playbooks/full-job-no-test.yml

If Ansible doesn’t throw an error within the first 10 seconds, indicating something is likely messed up in either you Ansible config file or in ksgen_settings.yml, feel free to go and stretch your legs as these playbooks can take awhile to finish up. The console output at the end of the playbooks execution should look similar to:

    PLAY [Global post install] ****************************************************
                        [[ previous play time: 0:00:02.259124 = 2.26s / 3836.33s ]]
    skipping: no hosts matched

    PLAY RECAP ********************************************************************
    host0                      : ok=126  changed=81   unreachable=0    failed=0
    localhost                  : ok=21   changed=7    unreachable=0    failed=0
    overcloud-cephstorage-0    : ok=1    changed=1    unreachable=0    failed=0
    overcloud-controller-0     : ok=2    changed=2    unreachable=0    failed=0
    overcloud-novacompute-0    : ok=1    changed=1    unreachable=0    failed=0
    undercloud                 : ok=123  changed=74   unreachable=0    failed=0

                        [[ previous task time: 0:00:00.029086 = 0.03s / 3836.35s ]]
                        [[ previous play time: 0:00:00.018960 = 0.02s / 3836.35s ]]
                 [[ previous playbook time: 1:03:56.350566 = 3836.35s / 3836.35s ]]
                       [[ previous total time: 1:03:56.350779 = 3836.35s / 0.00s ]]

You should now have a fully functional undercloud and overcloud running on TEST_MACHINE that is similar to the grossly simplified graphic below.
Screenshot from 2016-01-11 17-57-54

Conveniently, you can log directly into the undercloud from the root Khaleesi directory by using the ssh config generated by Khaleesi.

    ssh -F ssh.config.ansible undercloud
    Warning: Permanently added 'x.x.x.49' (ECDSA) to the list of known hosts.
    Warning: Permanently added 'undercloud' (ECDSA) to the list of known hosts.
    Last login: Wed Jan 13 18:33:22 2016 from gateway
    [stack@instack ~]$ ls


Once you wrap up doing whatever it is you want to do with your new deployment, wiping out the overcloud and and performing cleanup is as simple as calling another of Khaleesi’s playbooks.

    ansible-playbook -vv --extra-vars @ksgen_settings.yml -i hosts playbooks/cleanup.yml

Final Thoughts:

Ansible, and Khaleesi, make it very easy to deploy OpenStack in a reproducible manner — if you have everything configured correctly beforehand. The vast majority of time I spend fixing problems while working with Khaleesi come down to mistakes related to configurations.

From the 40 or so lines we’ve entered into our shells an enormous number of subsequent actions have taken place through Khaleesi’s playbooks. I could spend days diving into each one of them. I’m sure I will eventually but it’s nice to know that I can do so as time permits me to do so thanks to Khaleesi and Ansible.

Things I’d like to write more about in the future:

  1. A more in depth breakdown of what is happening in each of the playbooks used during this deployment — or a deployment of a similar nature.
  2. Khaleesi’s purpose, history, and potential future.
  3. The product pipeline from OpenStack (upstream) -> RDO -> Red Hat OpenStack, aka RHOS, (downstream) and others.
  4. Anything you as an audience would like to hear more about related to my work.


[1] – https://www.rdoproject.org/rdo/faq/

[2a] – Devstack: http://docs.openstack.org/developer/devstack/

[2b] – Staypuft: https://github.com/theforeman/staypuft

[2c] – Packstack: https://wiki.openstack.org/wiki/Packstack

[2d] – TripleO: https://wiki.openstack.org/wiki/TripleO

[3] – https://github.com/redhat-openstack/khaleesi

[4] – http://khaleesi.readthedocs.org/en/master/khaleesi.html

[5] – https://jenkins-ci.org/

[6] – http://khaleesi.readthedocs.org/en/master/cookbook.html

[7] – https://repos.fedorapeople.org/repos/openstack-m/rdo-manager-docs/liberty/

[8] – http://khaleesi.readthedocs.org/en/master/khaleesi.html#prerequisites

[9] – https://repos.fedorapeople.org/repos/openstack-m/rdo-manager-docs/liberty/environments/virtual.html#minimum-system-requirements

[10] – http://khaleesi.readthedocs.org/en/master/cookbook.html#installation

[11] – http://khaleesi.readthedocs.org/en/master/cookbook.html#configuration


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Graduation (Yester)Day

Last night I received a neat little email from the University of North Carolina at Greensboro. I’ll leave out the verbose output from legal and finance and get to the fun bits that in short read:

Dear Harry

On behalf of the University Registrar’s Office, it is my pleasure to inform you that we have completed the final processing of your academic record.

Congratulations, all degree requirements have been met as of the posted graduation date, December 10th, 2015.

What a thrill it is to know that I have finally completed that damned degree. It was about a year ago that I decided to not return to school in January for the lone remaining class I required, Biology 101 (why is it always a gen. ed. class?). Instead I rode off to the great, mountainous North that is Charlottesville, Virginia.

Living in what will possibly be my favorite apartment ever, I worked as a web application developer for a small non-profit that I had previously interned with — CoS (the Center for Open Science). To them and in particular Dr. Jeffrey Spies and Dr. Joshua Carp I will be forever grateful. The slightly less than a year that I spent in that cozy, gorgeous city was one of great professional and personal development. But all states in life, aside from death I suppose, are transitionary and in October I moved back down to the warm and humid North Carolina to what has been one of my favorite cities of all time — Raleigh.

Too me Raleigh is bikes, beer, coding, music, and friends. More than that, Raleigh is the perfect blending of them in an active city that is neither too large nor too small. It is, at least for now, a good base of operations and one which I want to leave better off than I found it. I don’t know how long I’ll be here. I don’t know how long I’ll be at Red hat. But, I do know that I’m happy to have completed my undergraduate degree, be actively contributing to the open source community professionally,  and living in a city that feels like home.

I suppose I should change the blog description now.

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API Testing with Flask: Post

Have you ever tried to test POST requests to an API written with Flask? Today I was going through an old code base writing unittests that should have been written eons ago when I ran into a snag. The issue stemmed when I tried manually setting the headers Content-Type.

But before we get to that, let me show you the skeleton of the Flask route I was testing:

@app.route('/someendpoint/' methods=['POST'])
def some_endpoint():
    """API endpoint for submitting data to

    :return: status code 405 - invalid JSON or invalid request type
    :return: status code 400 - unsupported Content-Type or invalid publisher
    :return: status code 201 - successful submission
    # Ensure post's Content-Type is supported
    if request.headers['content-type'] == 'application/json':
        # Ensure data is a valid JSON
            user_submission = json.loads(request.data)
        except ValueError:
            return Response(status=405)
        ... some magic stuff happens
        if everything_went_well:
            return Response(status=201)
            return Response(status=405)

    # User submitted an unsupported Content-Type
        return Response(status=400)

Ignoring the magic, everything seems in order. So, lets go ahead and write a quick unittest that posts an invalid json.

    def test_invalid_JSON(self):
        """Test status code 405 from improper JSON on post to raw"""
        response = self.app.post('/someendpoint',
                                data="This isn't a json... it's a string!")
        self.assertEqual(response.status_code, 405)

Cool, let’s run it!

    self.assertEqual(response.status_code, 405)
    AssertionError: 400 != 405

A quick glance at the code and I realize I’ve forgotten to set the headers Content-Type! Wait. How do I set the Content-Type? That’s a good question. After searching around for people who had run into similar problems this is what I came up with:

    def test_invalid_JSON(self):
        """Test status code 405 from improper JSON on post to raw"""
        response = self.app.post('/someendpoint',
                                data="This isn't a json... it's a string!",
        self.assertEqual(response.status_code, 405)

Let’s try this again.

    self.assertEqual(response.status_code, 405)
    AssertionError: 400 != 405

Hmmm, okay. Next, I decided to inspect the request coming into the flask app and found something odd in request.headers:

    Host: localhost
    Content-Length: 10

Why is the Content-Type empty? Another search gave hinted at another possible solution. Why not just build the headers dict inline?

    headers=dict(content-type='application/json') # But that's not right. We can't have '-' in a key.

By this point I’ve become agitated. Neither the Flask docs themselves nor various forums have been of much use. Then I stumbled across this.

Perhaps I missed something in the docs. Either way, I learned that you can hand the Content-Type as a parameter to the post method. It works and it looks much cleaner. Let’s revise my initial unittest accordinlgy:

    def test_invalid_JSON(self):
        """Test status code 405 from improper JSON on post to raw"""
        response = self.app.post('/raw',
                                data="not a json",
        self.assertEqual(response.status_code, 405)

And, let’s run this one last time and look at the request as it comes though.

    Tests passed
    Host: localhost
    Content-Length: 10
    Content-Type: application/json

Much better. Now, back to testing!


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Currently, I am attempting to trim my CV down to a length appropriate for a resume. To be honest, it’s not as easy as I would have thought. Wouldn’t it be more simple if a resume could just simply read the following:

Favorite language: Python. Why? It’s awesome and so is the community it’s built up around it.

Favorite IDE: None. I like Vim (shhhh emacs lovers). Again, why? It’s quick, powerful, and I can use it on any of my machines or while I’m remoted into some server. I value consistency.

Favorite OS: Hands down, any of the Linux derivatives. Does this require justification? Nope.

Favorite place to code: Anywhere with a nice view and lots of natural light.

Anything other questions? Let’s discuss this over a coffee or tea. And don’t forget to checkout my Github account!



Everyone makes mistakes: Even the web’s inventor

Earlier today, while reading over Interactive Data Visualization for the Web, I came across an interesting fact I would like to share. We all know the preamble for web addresses, http://. I couldn’t fathom how many times I’ve typed it myself. Apparently the creator of the world wide web, Tim Berners-Lee, regrets making this part of the standard as he stated during an interview with the New York Times. To summarize, he equated it to be a convention of programmers at the time.

I wonder how many double slashes have been typed, printed, and read since the standards creation. But hey, there is always room for improvement, right?

As an aside, I highly recommend the aforementioned book, Interactive Data Visualization for the Web. Written by Scott Murray, it provides an excellent introduction to data visualization with D3 and basic web programming. What makes this even more cool? O’reilly is offering an online version of the book that includes interactive examples and it’s free! Click the previous link to view the book directly or visit this O’reilly page for more information on about the paper version!

“First make something work. Then, make it work better.” – Anonymous


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The Division Of Generation Y

Many of my private thoughts put down as words.