Infrastructure

Co-evolution of Infrastructure and Source Code

- An Empirical Study

Yujuan Jiang, Bram Adams MCIS lab Polytechnique Montreal, Canada

Server 1: Ubuntu

Server 2: centOS

Infrastructure Code Automates Environment Setup

Commit Build

Deploy

Deploy

Automate Instantiation of Web Server with Puppet & Chef

# Chef snippet case node[:platform] when “ubuntu” package “httpd-v1” do version “2.4.12” action: install end when “centOS” package “httpd-v2” do version “2.2.29” action: install end end

# Puppet snippet case $platform{ ‘ubuntu’: { package {‘httpd-v1’: ensure => “2.4.12” } } ‘centOS’: { package {‘httpd-v2’: ensure => “2.2.29” } } }

Infrastructure Code Widely Used by Large Companies

Uses Both Chef & Puppet + Large Data Set of 262 Repos

How much effort do you need to pay to maintain infrastructure code?

Preliminary & Research Questions

TestInf

Inf

PQ1: How many !infrastructure files !

does a project have?

PQ2: How many !infrastructure files !change per month?

PQ3: How large !are infrastructure !system changes?

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Bld

Prod

Test

Tester

Production !developer

Build developerInfrastructure !

developer

RQ1: How tight is the coupling !between infrastructure code and !

other kinds of code?RQ2: Who changes !

infrastructure code?

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Prod Other

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Collect all files !from repos

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ProdProdProdTestTestTest

OtherOther

Other

Classify files into 5 groups !(“Other” deserted) !

for each project

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Split projects into 2 groups-!Multi & Single

Commit co-change Ownership coupling

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Statistical visualization

Monthly change ratio

Average churn

Preliminary analysis

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Build developer

Tester

Infrastructure !developer? ?

RQs: coupling relation

Approach

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OtherOther

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for each project

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Average churn


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Build developer

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Approach

Prod BldTest

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Prod Other

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OtherOther

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for each project

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Average churn


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Build developer

Tester



Approach

Prod BldTest

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Prod Other

Test


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OtherOther

Other


for each project

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Average churn


Inf

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Build developer

Tester



Approach

Prod BldTest

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Prod Other

Test


InfInfInfBldBldBld


OtherOther

Other


for each project

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Average churn


Inf

Bld

Prod

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Build developer

Tester



Approach

Prod BldTest

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Prod Other

Test


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OtherOther

Other


for each project

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Average churn


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Build developer

Tester



Approach

Case Study Results

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! PQ1: Infrastructure files almost as large as source code and test files!

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File Size !(LOC)

Infrastructure Build Production Test

1100

10000

2,486

Infrastructure Build Production Test

54

2991 2768

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Case Study Results

! PQ2: The monthly change for infrastructure files has a

median value of 0.28

Infrastructure vs BuildInfrastructure & Build Production & Test

Comparable to production, and!

Higher than Build & Test!0.28 0.28

0.180.21

The proportion of files

changed per month

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Case Study Results

Infrastructure vs Build Production vs Test

! PQ3: Average churn per file is the highest across all file

categoriesAverage MCF

(Monthly Churn/File)

Infrastructure & Build Production & Test

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Case Study Results

Using Confidence to Measure Coupling!

Beer? Diapers?

Association Rules

! RQ1: The changes to Infrastructure files are tightly coupled with the changes to Test

and Production files.!

0.0

0.1

0.2

0.3

0.4

0.5

Infrastructure <=> Build Infrastructure <=> Production Infrastructure <=> Test

LegendProbability that left requires changes to right

Vice versa

Implication of Infrastructure !to other Category Code Change

0.2637

0.4583

0.03470.1085 0.0885

0.2578

RQ1: The most common reasons for the coupling between Infrastructure and Test are

“Integration” and “Update”.!

INTEGRATION!(e.g.: enabling new !

test modules !or integrating new !

test cases)

UPDATE (e.g.: changed a global !

variable valu)

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Case Study Results

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Case Study Results

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developerCheck out !our paper !please! :)

Data & Analytics

Infrastructure