Master- /Diplomstudium:Software Engineering - Internet Computing

Master's Thesis Presentation

Configuration Management with Libelektra

Bernhard Denner

Technische Universität WienFaculty of Informatics

Institute of Computer Languages Supervisor: Ao.Univ.-Prof.Dipl.-Ing. Dr.techn. Franz Puntigam

Co-Supervisor: Univ.Ass.Dipl.-Ing. Dr.techn. Markus Raab

Introduction and Motivation

Configuration Management (CM) Tools - Automatic and reproducible management of computer systems - Desired system state defined by code

Configuration Files - Plain text - Different formats: INI, XML, JSON, custom

Approach

Results

ERB

KDB

500 1000 1500 2000 2500 3000 3500

RQ: How does our approach perform against existing Puppet file modification concepts?

Case Study: - Is our solution ready for real-world scenarios?

User Study: - Does our solution increase the usabiltiy and maintainability? - Intra-subject SW-experiment - 4 Puppet programming tasks in up to 3 variants - Measure task duration times - Subjective impressions of participants (voting from 1 - 5)

Combine Puppet + Libelektra - Puppet as frontend to express needs - Libelektra as backend to modify configuration files

Puppet extension puppet-libelektra - Treat configuration settings as first class citizen - One language construct to define configuration settings for different configuration file formats - Brings all features of Libelektra to Puppet

puppet-libelektra extends Puppet DSL by two new types: - kdbkey defines a single configuration setting, with optional metadata (validation properties...) - kdbmount describes how Libelektra should integrate a configuration file, if not already done by the application

Problem - How to handle configuration file changes in a uniform way? - Abstraction for configuration settings? - Syntax and semantic awareness?

Libelektra: configuration framework - Configuration settings as key-value pairs - Hierarchical shared key space - Plugin architecture, extensible

kdbmount { 'system/sw/myapp': file => '/etc/myapp/config.ini', plugins => ['ini', 'range', 'enum']}

kdbkey { 'system/sw/myapp/instances': ensure => present, value => ${instance_count}, comments => 'configures the number ...', check => { 'range' => '1-10' }}

Methods

Kontakt: bernhard.denner@gmail.com, markus@libelektra.org, https://libelektra.org

Case Studypuppet-libelektra was used to manage a continuous integration and Web-hosting system

User StudySW-experiment with 14 subjects, all students without Puppet experience - significant shorter development times for creating or updating configuration files compared to other general purpose strategies - almost at the same level with format specific strategies - no productivity improvement in code maintenance

general purpose strategies KDB ERB AUG

... puppet-libelektra

... Ruby ERB template engine

... Augeas

format specific: HOST INI

... edit /etc/hosts files

... edit INI files

ERBHOST

INIAUGKDB

1 2 3 4 5

Create new configuration files from scratch

Maintenance of existing Puppet code

Subjective Usability Ratings

Task duration time (seconds)

Usability rating: 1 (very good) ... 5 (very bad)

ERB

KDB

1000 2000 3000 4000

Update configuration files

HOST/INIAUGKDB

1000 2000 3000 4000

Backend SystemMain System

Apache Web Server

libelektra.orgwebpage

sub-domainredirects

Jenkinsreverse proxy

JenkinsBuild Server

Docker

Build slavesBuild slavesBuild Slave

Build System

Build slaves

Build System

Build slaves

Build System

Build Slave

Snippet-sharingREST Backend

Build Slave

Puppet Agent

Module

puppet-libelektra

libelektra-core

system/sw/myapp system/network/hosts

hostsini

/etc/myapp/config.ini

[general]instances = 5domain = example.com

[logging]log_level = info

/etc/hosts

127.0.0.1 localhost

192.168.1.3 bbnode1 node1192.168.1.4 bbnode2 node2192.168.1.10 bbclient1 client1

Puppet - Open source CM-tool - Declariative domain specific language (DSL) - Modify configuration files in different ways

CM-ToolAgent

CM-ToolAgent

CM-ToolAgent

package { 'firefox': ensure => installed}

file { '/etc/resolv.conf': ensure => file, content => "search ${domain}"}

abstraction

high

low

enforce