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Running a distributed native-cloud python app on a CoreOS cluster

September 21st, 2014 • 1 Comment

Suricate is an open source Data Science platform. As it is architected to be a native-cloud app, it is composed into multiple parts:

Up till now each part was running in a SmartOS zone in my test setup or run with Openhift Gears. But I wanted to give CoreOS a shot and slowly get into using things like Kubernetes. This tutorial hence will guide through creating: the Docker image needed, the deployment of RabbitMQ & MongoDB as well as deployment of the services of Suricate itself on top of a CoreOS cluster. We’ll use suricate as an example case here – it is also the general instructions to running distributed python apps on CoreOS.

Step 0) Get a CoreOS cluster up & running

Best done using VagrantUp and this repository.

Step 1) Creating a docker image with the python app embedded

Initially we need to create a docker image which embeds the Python application itself. Therefore we will create a image based on Ubuntu and install the necessary requirements. To get started create a new directory – within initialize a git repository. Once done we’ll embed the python code we want to run using a git submodule.

$ git init
$ git submodule add https://github.com/engjoy/suricate.git

Now we’ll create a little directory called misc and dump the python scripts in it which execute the frontend and execution node of suricate. The requirements.txt file is a pip requirements file.

 
$ ls -ltr misc/
total 12
-rw-r--r-- 1 core core 20 Sep 21 11:53 requirements.txt
-rw-r--r-- 1 core core 737 Sep 21 12:21 frontend.py
-rw-r--r-- 1 core core 764 Sep 21 12:29 execnode.py 

Now it is down to creating a Dockerfile which will install the requirements and make sure the suricate application is deployed:

 
$ cat Dockerfile
FROM ubuntu
MAINTAINER engjoy UG (haftungsbeschraenkt)

# apt-get stuff
RUN echo "deb http://archive.ubuntu.com/ubuntu/ trusty main universe" >> /etc/apt/sources.list
RUN apt-get update
RUN apt-get install -y tar build-essential
RUN apt-get install -y python python-dev python-distribute python-pip

# deploy suricate
ADD /misc /misc
ADD /suricate /suricate

RUN pip install -r /misc/requirements.txt

RUN cd suricate && python setup.py install && cd ..

Now all there is left to do is to build the image:

 
$ docker build -t docker/suricate .

Now we have a docker image we can use for both the frontend and execution nodes of suricate. When starting the docker container we will just make sure to start the right executable.

Note.: Once done publish all on DockerHub – that’ll make live easy for you in future.

Step 2) Getting RabbitMQ and MongoDB up & running as units

Before getting suricate up and running we need a RabbitMq broker and a Mongo database. These are just dependencies for our app – your app might need a different set of services. Download the docker images first:

 
$ docker pull tutum/rabbitmq
$ docker pull dockerfile/mongodb

Now we will need to define the RabbitMQ service as a CoreOS unit in a file call rabbitmq.service:

 
$ cat rabbitmq.service
[Unit]
Description=RabbitMQ server
After=docker.service
Requires=docker.service
After=etcd.service
Requires=etcd.service

[Service]
ExecStartPre=/bin/sh -c "/usr/bin/docker rm -f rabbitmq > /dev/null ; true"
ExecStart=/usr/bin/docker run -p 5672:5672 -p 15672:15672 -e RABBITMQ_PASS=secret --name rabbitmq tutum/rabbitmq
ExecStop=/usr/bin/docker stop rabbitmq
ExecStopPost=/usr/bin/docker rm -f rabbitmq

Now in CoreOS we can use fleet to start the rabbitmq service:

 
$ fleetctl start rabbitmq.service
$ fleetctl list-units
UNIT                    MACHINE                         ACTIVE  SUB
rabbitmq.service        b9239746.../172.17.8.101        active  running

The CoreOS cluster will make sure the docker container is launched and RabbitMQ is up & running. More on fleet & scheduling can be found here.

This steps needs to be repeated for the MongoDB service. But afterall it is just a change of the Exec* scripts above (Mind the port setups!). Once done MongoDB and RabbitMQ will happily run:

 
$ fleetctl list-units
UNIT                    MACHINE                         ACTIVE  SUB
mongo.service           b9239746.../172.17.8.101        active  running
rabbitmq.service        b9239746.../172.17.8.101        active  running

Step 3) Run frontend and execution nodes of suricate.

Now it is time to bring up the python application. As we have defined a docker image called engjoy/suricate in step 1 we just need to define the units for CoreOS fleet again. For the frontend we create:

 
$ cat frontend.service
[Unit]
Description=Exec node server
After=docker.service
Requires=docker.service
After=etcd.service
Requires=etcd.service

[Service]
ExecStartPre=/bin/sh -c "/usr/bin/docker rm -f suricate > /dev/null ; true"
ExecStart=/usr/bin/docker run -p 8888:8888 --name suricate -e MONGO_URI=<change uri> -e RABBITMQ_URI=<change uri> engjoy/suricate python /misc/frontend.py
ExecStop=/usr/bin/docker stop suricate
ExecStopPost=/usr/bin/docker rm -f suricate

As you can see it will use the engjoy/suricate image from above and just run the python command. The frontend is now up & running. The same steps need to be repeated for the execution node. As we run at least one execution node per tenant we’ll get multiple units for now. After bringing up multiple execution nodes and the frontend the list of units looks like:

 
$ fleetctl list-units
UNIT                    MACHINE                         ACTIVE  SUB
exec_node_user1.service b9239746.../172.17.8.101        active  running
exec_node_user2.service b9239746.../172.17.8.101        active  running
frontend.service        b9239746.../172.17.8.101        active  running
mongo.service           b9239746.../172.17.8.101        active  running
rabbitmq.service        b9239746.../172.17.8.101        active  running
[...]

Now your distributed Python app is happily running on a CoreOS cluster.

Some notes

My Software Development Environment for Python

February 21st, 2011 • Comments Off on My Software Development Environment for Python

Python is my favorite programming language for multiple reasons. Most important though is that it has a strong community, a Benevolent Dictator For Life (BDFL) and allows rapid development of high quality software. I love automation of processes wherever possible because it saves time. Here is a list of tools, methodologies, stuff I use to ensure code quality:

Tools I sometimes use during the development of code:

Thinks I would like to have replacements for:

Overall I’m pretty happy with this setup and find it good for fast coding. I usually write unittests (With test for success, failure and sanity for every routine) first before starting coding. I don’t find it a time waste but actually I’m pretty sure that the overall setup allows me to code and refactor faster.

Maybe others or you (?) also want to writeup their setups and we can start a site like The Setup for Software Development? Please Retweet and share the link!

Update: Also have a look at this Python and Dtrace blog post.

Hudson and Python

September 23rd, 2010 • 3 Comments

Regarding Continuous Integration (CI) systems I probably still like Hudson! Great tool and runs perfectly well. Just get the latest jar file and run it with java – jar hudson.jar. Now to get started you will need to install some plugins:

You can install those plugins in he management interface of hudson. When configuring the job in hudson you simple add a new “Build a free-style software project” job. Add SCM information – and than add some build steps. I had to use two:

python setup.py clean --all
python setup.py build
coverage erase
nosetests --with-coverage --cover-package=<your packages> --with-xunit
coverage xml

And a second one:

#!/bin/bash
pylint -f parseable <your packages> > pylint.txt
echo "pylint complete"

Both are external scripts. Now in the post-build section activate the JUnit test reporting and tell it to use the **/nosetests.xml file. Also activate the Cobertura Coverage report and tell it to use **/coverage.xml. Finally activate the Report Violations – and add pylint.txt in the right row.

Configure the rest of the stuff just as you like and hit the Build button. Thanks to XML the reporting tools written for java can parser the output generated for your Python project. Now you have nice reports from a Python project in Hudson!

A more detailed and great article about this topic can be found here.

Story board for agile development

July 14th, 2010 • 1 Comment

I’m a fan of software development processes. They need to be simple and easy to follow. Now one thing I like are so called task/story boards for agile development to keep track of stuff in the pipeline. What I do not like is that tool support is rather not good. Most people seem to be using ‘real’ task/story boards with paper and pen. That is not an option for me – since I’m not always in the same place 🙂

Other tools are so overblown that they are hardly usable – and again an external tool makes that the stories and their states are not stored near the source code – where the belong IMHO.

So I stumbled upon simple-kanban an easy tool where you basically can just drag and drop stories around based on their state. There is a very simple editor for editing the stories and the best feature is: It’s an single HTML file which you can check-in next to your source code in your SCM. And with the web browser integrated in eclipse even open in your IDE.

Only feature missing was that this board couldn’t store the information – you had to manually copy the stories from the editor and paste them into the HTML file, which you could save then:

Go to the data view and copy all stories. Then simply edit the source of the HTML file with an editor of your choice, preferably one which knows HTML. There you can paste the copied stories over the old ones and save the HTML file.

I didn’t like that – and since I knew of tiddlywiki, which is another single page application (SPA), which can store data, I thought I can update it. So I took the saving features from the wiki (described here BTW) and integrated them with the simple-kanban board. Now I have a save button and do not need to do nasty copy & pastes into source codes.

BTW this is how it looks in Eclipse:

Nice for small projects, your to-dos (Getting Thinks Done (GTD)) or any other stuff…

Open source & making money: two worlds?

May 17th, 2010 • 4 Comments

I’m a big fan of Open Source Software. But I can also understand that making money is important nowadays. And to be honest I feel more confident when a company is involved in the development of a tool/product/application. I think communities are great – but a company with real QA and who needs to make money out of a tool/product/application has a motivation to make the best out of the tool/product/application.

Now the question is: How do you make money with this in mind? Simply by selling support contracts? I have seen companies fail with that model.

A good idea might be to release the code in open source but as a company do development of new features in a closed repository. Make a clear release plan which shows the upcoming features (and distribute it). When a customer needs one of these upcoming features etc. he can either:

Next to that Support contracts might still be an option 🙂

Crucial point is here the right choice of a source code control system. Because the community still might develop cool features which you want in you closed repository as well…But distributed SCMs do the job…

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