Yet Another Raspberry Pi Cluster

The slides of a lecture/presentation on 2016-03-20 @ Chemnitzer Linux Tage

Christian Prior

Slides available

http://www.helotism.de \ ⏎
/business/marketing/presentation/CLT_2016-03-20

## about me ![](/business/marketing/presentation/images/about-cpr.svg) https://www.facebook.com/profile.php?id=100010639868228 https://github.com/cprior

Content of today's presentation

[Maker] CNC, CAD&CAM development boards power supply [SysAdmin] Config Mgt monitoring [Data Analysis] data provider visualization [Documentation]

Helotism

Wiktionary.org: Helotism (zoology): A form of mutualism in which one species is forced to perform tasks for another, for their mutual benefit.

The Goals

keeping up with IT changes
solid Linux sysadmin skills are the foundation for "Big Data"
getting most out of these boards
getting ahead of the complexity curve

The Roadmap

The Repo

https://github.com/helotism

all-in one repo

hardware
software
promotion

Issues welcome! ;)

##Jekyll Website helotism.de ```YAML #_config.yml destination: ./business/marketing/website/_site ```

## ERP ![](/business/production/HowThingsAreMade.svg)

TOGAF: Architecture Development Method

P Prerequisites
A Vision
B Business Plan/Action
C Information System Plan/Actual
D Technology Plan/Actual
E Opportunities and Solutions
F Migration Planning
G Implementation Governance
H Change Management
R Requirements

##TOGAF: "Domains" & Building Blocks ![](/business/planning/images/PRDV_TOGAF-Cube_BusinessDataApplicationTechnology.jpg)

##Maker - DXF - chipping vs. 3D-printing - CAD4c Computer-Aided Design for clamping

Enthusiast's Small Batch Manufacturing

Development Boards

The market for development boards is confusing: https://en.wikipedia.org/wiki/Comparison_of_single-board_computers is a good overview.

##Development Boards: Common Features - Computation: Processor and Memory - Communication through Ethernet/… - Powersupply: Consumption, buttons - Interaction via GPIO - Fixture: Mounting holes and dimensions - Storage: SD cards and beyond - Synchronization: RTC time

Dimensions

-> see repo

##Power Consumption Rule of thumb: - 1 Pi idle == 2.5W (5V * 0,5 A) - 1 Pi under load, no USB == 5W (5V * 1 A) Caveat: GPIO-pins are no USB ports ;) - 5V passed straight through from USB - 3.3V rail max 50mA - GPIO pins 16ma in total

Minnowboard

UEFI

##Operating System 1. archlinuxarm.org * all saltstack dependencies met 2. archlinuxarm.org * up-to-date systemd (229-3 in march 2016) 3. archlinuxarm.org * pre-compiled ;) 4. Raspbian/DietPi/Debian Jessie * Raspbian "Jessie" December 2015, systemd "216"

##Circuits ![](/technology/logical/images/MIT_CircuitsElectronics_Lec1_outline.svg)

##Alles wegabstrahieren! ![](/business/marketing/presentation/images/cpr_travel_pictures_2013-08-28_IMG_0533_1024-360.jpg)

##Noise ![](/technology/logical/images/ElectricalWireNoise.svg)

##Discretization ![](/technology/logical/images/ElectricalDiscretization.svg)

##Debouncing ![](/technology/logical/images/ElectricalSwitchDebounce.svg)

##Powersupply - prevent brown-out - one switch for all boards

##On-Off-Switch - hardware - code ![](/technology/physical/myrack-v0.5/circuit/helotism_powersupply_bb_640x312.png) [raspberry-pi-geek.com On-Off-Switch](http://www.raspberry-pi-geek.com/Archive/2013/01/Adding-an-On-Off-switch-to-your-Raspberry-Pi "Adding an On/Off switch to your Raspberry Pi")

##scale out

##Python logic… ```Python b = mraa.Gpio(20) b.dir(mraa.DIR_IN) b.isr(mraa.EDGE_FALLING, handleInterrupt, handleInterrupt) ``` ```Python def handleInterrupt(args): #print("handleInterrupt") button20.pressed = True #that's a fact, but... button20.pressed_debounced = False interrupted_at = datetime.datetime.now() debounce_until = interrupted_at + datetime.timedelta(0,3) while True: if (datetime.datetime.now() > debounce_until): #print("past debounce") journal.send('GPIO20 pressed DEBOUNCED.', FIELD2='GPIO20') button20.pressed_debounced = True return else: #print("not debounced yet") journal.send('GPIO20 pressed, not debounced', FIELD2='GPIO20') time.sleep(0.5) #inside this interrupt handler only ```

##…and systemd daemonization. ```INI [Unit] Description=An GPIO interrupt listener After=local-fs.target [Service] Type=simple ExecStart=/bin/bash -c 'cd /opt/helotism/powersupply-env; \ source bin/activate; \ python ./mraa_interrupt.py' [Install] WantedBy=multi-user.target ```

##SaltStack Ecosystem ![](/application/physical/images/saltstack-ecosystem.svg)

##SaltStack top file ```YAML base: # environment 'web*': # targeted minions - apache # state file 'apache.sls' ``` - the top.sls is a special state file as "entry point" into the fileserver - "apache" references ```./apache.sls``` file

##SaltStack state file ```YAML #apache.sls {% if grains['os'] == 'Debian' %} apache: apache2 {% elif grains['os'] == 'RedHat' %} apache: httpd {% endif %} ``` - Jinja2 template language - one should read the fine manual: http://jinja.pocoo.org/docs/dev/

##SaltStack environments ```YAML file_roots: dev: - /srv/salt/dev base: - /srv/salt ``` - environments are configured in the master config file

##SaltStack fileserver ```YAML fileserver_backend: #first filename match wins - roots - git gitfs_remotes: - git://github.com/example/first.git - https://github.com/example/second.git - root: salt #subdirectory - mountpoint: salt://sub/dir - base: myTag05 #git branch - file:///root/third #top_file_merging_strategy: merge #same #env_order: ['base', 'dev', 'prod'] ``` - these are powerful configuration mechanisms: "infrastructure as code" served from a Git repo - many ways to segment or override

##Sample Salt Usage ```bash #remote execution? salt '*' cmd.run 'uname -a' ``` ```bash #listing and accepting keys salt-key -L salt-key -A ``` ```bash #salt.modules.test.ping salt '*' test.ping ``` ```bash #targeting by grains salt -G 'os:(RedHat|Debian)' test.ping ``` ```bash #more sound than test.ping salt-run manage.up ``` ```bash #apply common.sls on all (accepted) minions salt '*' state.sls common #This is the "endgame" in salt salt '*' state.highstate #remote execution! salt '*' cmd.run 'uname -a' ```

##ToDo: Scale-down and Simplify - three RPi 2 or RPi3 - bootstrap.sh script from ArchLinux ARM iso to "cluster" - keep formfactor to a minimum - still a switch is needed - and a button - and a RTC

##ToDo: More Hardware Diversity - PINE64 - GBit ethernet wanted

##ToDo: Config Mgt and IoT ![Microsoft Applications on Linux](/business/marketing/presentation/images/kickstarter_micro-python.jpg)