how to write maintainable software...2014/05/21 · how to write maintainable software a crash...

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www.softwarezaken.nl

HOW TO WRITE MAINTAINABLE SOFTWARE A crash course in code quality and software maintainability Sieuwert van Otterloo [email protected] 06-10509674 @entreprenl

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About Sieuwert van Otterloo Current activities: •  Startup enthusiast (investor, journalist) •  Software expert (court-registered IT expert, scrum

coach, software auditor) •  Strategy consultant (McKinsey & Company, Eden

McCallum)

Claims to fame: •  Has assessed 100+ IT systems (election software, railway software,

insurance and banking systems and ATM software) •  Has interviewed more than 100 startup founders to give better advice.

The goal is to interview founders from all NL-based startups •  First round investor in several startups (SOWISO, Buzzoek, Kidswatcher,

Arete Caerus, Plot Projects, SellanApp)

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Computer issues delay flights in Los Angeles

LOS ANGELES (AP) — Flights to and from airports in the Los Angeles area were grounded for more than an hour Wednesday due to a computer failure at an air traffic control facility in the region, the Federal Aviation Administration said. The problems rippled nationwide. Dozens of planes heading into the region were diverted elsewhere, and flights scheduled to take off to the Los Angeles area were held on the ground across the country. […] A notice posted on the FAA website said planes were not allowed to depart Los Angeles because of a failure within the agency's En Route Automation Modernization system, also known as ERAM. […]

The ERAM system is critical to the FAA's plans to transition from a radar-based air traffic control system to satellite-based navigation, but its rollout is years behind schedule and hundreds of millions of dollars over budget. ERAM is replacing another computer system that was so old that most of the technicians who understood its unique computer language have retired.

May 1, 2014 8:51 AM

http://news.yahoo.com/computer-issues-delay-flights-los-angeles-234300027.html

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Build a system

Write a program

Ideal position of this course in your personal learning plan

Listen

Do

Agile / Scrum basics

Learn to code

How to write maintainable

software

Startup weekend

Scaling agile

Lean startup

Join / start a startup

Grow and build a business Make IT decisions

Management techniques

Mastering Lean

Security

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Agenda

•  The motivation: Why software maintainability is important

•  The destination: What does maintainable code look like

•  The road: How to put quality into the software development process

•  The roadblocks: How to deal with quality assessments

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Why software is important

Marc Andreessen Founder of Netscape, Venture capitalist

Software is eating the world: •  Today, the world's largest bookseller, Amazon, is a software

company •  Today's largest video service by number of subscribers is a

software company: Netflix. •  Today's dominant music companies are software companies,

too: Apple's iTunes, Spotify and Pandora. •  Today's fastest growing entertainment companies are

videogame makers •  The best new movie production company in many decades,

Pixar, was a software company. •  Today's largest direct marketing platform is a software

company—Google. •  Today's fastest growing telecom company is Skype •  LinkedIn is today's fastest growing recruiting company..

Source: Wall street journal, August 20 2011

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Team growth

Selling your company

Buy another

company

Software maintainability is important for scaling startups

Idea

MVP

Product / market fit

Reduce risk of chaos

Need to pass due diligence

process

Need to sanitize and

integrate

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The classic view on software costs

Conservative example: •  The system needs 15% maintenance per year •  The system grows 10% per year •  System lasts 10 years

Result: maintenance costs are 140% higher than development cost

!"!!!! !15!!!17!!

!18!!!20!!

!22!!!24!!

!27!!

!29!!

!32!!

!35!!

!239!!

100!

0!25!50!75!

100!125!150!175!200!225!250!275!

build! Year!1! Year!2! Year!3! Year!4! Year!5! Year!6! Year!7! Year!8! Year!9! Year!10! Total!

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Agile view on software quality: technical debt

•  Technical debt are issues that the customer cannot see, but the developers can

•  You can either clean it up (refactor) or work around it •  If you do not clean up, you pay interest

0.0#

5.0#

10.0#

15.0#

20.0#

25.0#

Sprint#1#

Sprint#2#

Sprint#3#

Sprint#4#

Sprint#5#

Sprint#6#

Sprint#7#

Sprint#8#

Sprint#9#

Sprint#10#

Sprint#11#

Sprint#12#

Story&po

ints&

Development&speed&&

without#refactoring#

With#refactoring#0.0#

50.0#

100.0#

150.0#

200.0#

250.0#

300.0#

350.0#

400.0#

Sprint#1#

Sprint#2#

Sprint#3#

Sprint#4#

Sprint#5#

Sprint#6#

Sprint#7#

Sprint#8#

Sprint#9#

Sprint#10#

Sprint#11#

Sprint#12#

Sprint#13#

Sprint#14#

Sprint#15#

Sprint#16#

Sprint#17#

Sprint#18#

Sprint#19#

Sprint#20#

Story&po

ints&

Value&delivered&&

without#refactoring#

With#refactoring#

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Agenda

•  The motivation: Why SW maintainability is important




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Volume

Very small Nice and small

Hard to handle

Impossible

< 10.000 lines of code

< 100.000 lines of code

Less than 500.000 lines of code

>500.000 lines of code

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Understanding the scale Small system (60.000 LoC) Huge system (600.000 LoC)

Annual maintenance: 9 personmonths

Annual maintenance: 90

personmonths

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System volume

0"1" 1"

6"7"

5"

10"8"

12"

18"

11"10"

1" 1" 1"0"

0"2"4"6"8"

10"12"14"16"18"20"

A"100+

200"

B"200+

500"

C"500+

1k"

D"1k+2k"

E"2k+5k"

F"5k+10k"

G"10k+20k

"

H"20k+50k

"

I"50k+100k

"

J"100k

+200k"

K"200k

+500k"

L"500k

+1M"

M"1M

+2M"

N"2M+5M

"

O"5M+10M

"

P"10M

+up"

Nr.$o

f$systems$

Volume$in$lines$of$code$

System$volume$

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Example of a very small program

#!/bin/perl -sp0777i<X+d*lMLa^*lN%0]dsXx++lMlN/dsM0<j]dsj!$/=unpack('H*',$_);$_=`echo 16dio\U$k"SK$/SM$n\EsN0p[lN*1!lK[d2%Sa2/d0$^Ixp"|dc`;s/\W//g;$_=pack('H*',/((..)*)$/)!

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Use of technologies

Java

Simple stack

Java

Complicated stack

Javascript Shell

C

‘Legacy’ stack

XML

PL/SQL

php perl

Java XSLT

x86

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Duplication

Found 185 duplicate lines in the following files: Between lines 29 and 235 in /java/jabref-2.9.2/src/java/net/sf/jabref/export/layout/format/FormatChars.java Between lines 31 and 239 in /java/jabref-2.9.2/src/java/net/sf/jabref/oo/OOPreFormatter.java Found 194 duplicate lines in the following files: Between lines 130 and 397 in /java/jose-144-source/java/de/jose/util/Metaphone2.java Between lines 129 and 396 in /java/jose-144-source/java/de/jose/util/Metaphone.java

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Complexity: decision points per method

Source: SweetHome 3D, fileOBJWriter.java

Best: less than 7 decision points per method (128 paths)

Mediocre: less than 10 (1024 paths)

This code: 36 decision points ( 68,719,476,736

paths)

public boolean equals(Object obj) { if (obj instanceof ComparableAppearance) {

Appearance appearance2 = ((ComparableAppearance)obj).appearance; ……..

if (!color1.equals(color2)) {! return false;!

} else if (material1.getShininess() != material2.getShininess()) {! return false;!

} else if (material1.getClass() != material2.getClass()) {! return false;!

} else if (material1.getClass() == OBJMaterial.class) {! OBJMaterial objMaterial1 = (OBJMaterial)material1;!

OBJMaterial objMaterial2 = (OBJMaterial)material2;! if (objMaterial1.isOpticalDensitySet() ^ objMaterial2.isOpticalDensitySet()) {!

return false;! } else if (objMaterial1.isOpticalDensitySet() && objMaterial2.isOpticalDensitySet()!

&& objMaterial1.getOpticalDensity() != objMaterial2.getOpticalDensity()) {!

return false;!

} else if (objMaterial1.isIlluminationModelSet() ^ objMaterial2.isIlluminationModelSet()) {!

return false;! } else if (objMaterial1.isIlluminationModelSet() && objMaterial2.isIlluminationModelSet()! && objMaterial1.getIlluminationModel() != objMaterial2.getIlluminationModel()) {! return false;!

} else if (objMaterial1.isSharpnessSet() ^ objMaterial2.isSharpnessSet()) {! return false;!

} else if (objMaterial1.isSharpnessSet() && objMaterial2.isSharpnessSet()!

&& objMaterial1.getSharpness() != objMaterial2.getSharpness()) {! return false;!

}! }!

}! }!

}! }!

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Other important aspects

•  Missing exception handling •  TODO comments •  Long ‘do-it-all’ files •  Memory actions and leaks •  Safe use of user strings •  Complex queries •  Code copyrighted by others

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Typical quality model (SIG)

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Benchmarking quality

Raw measurements of your system

Averaging

% score for each component Overall % score

Measurement of open source systems

“120 violations of type X”

“Aspect X is better than 55% of

systems”

“Maintainability is better than 60% of

systems”

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Agenda





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Joint code ownership

•  Everyone in the team should feel comfortable explaining each line of code

•  All founders should be interested in the code on which the company runs

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Create daily feedback

•  Integrate and test a working system at least every two weeks

•  Agree on basic code quality standards Structure

Tools

Mindset

•  Create a fully automated daily build process •  Use automated tools in the build process (checkstyle,

FxCop, Simian, PMD, Sonar) •  Configure automated checks in the IDE (Visual studio)

•  Monitor issues daily as a lead developer •  Address root causes of issues in retrospectives:

•  Training needs for new and current developers •  Important refactoring actions •  Adjustments to quality standards

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Five steps for a quality program

1. Make strategy and technology choices

2. Set quality standards and architecture rules

3. Start measuring

4. Create good new code

5. Clean up old code

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Agenda





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Top 4 situations when assessments / audits happen

1. A large company buys your service

3. Someone invests in your company

4. Someone buys your company

2. You are supplier in a delayed/troubled

project

Product focus Company focus

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Software Risk Assessment process

System context and

business strategy

Risks

Quality

Economics

Is the input for determining … Are the basis

for…

Conclusions

Code review

Recommen-dations

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How not to deal with an assessment

Develop a system as fast as possible at minimal cost

OK, here it is

Can you audit the system?

What quality standards did you demand?

What quality standards did you use?

None, we focused on cost and speed

We asked nothing special, but we expect a fit for use system conforming to industry best practices

Client Supplier Assessor

Let’s report a lot of findings to show that we worked really hard

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A better way to deal with assessments

Develop a system as fast as possible at minimal cost Here is our own standard, is that good

enough for you?

What quality standards did you use?

We agreed on this standard. We checked to code and it complies. Let us know if you

find any issues

We worked really hard and have these findings

Well done! We do not see major risks, but if needed we have a quality process and

can fix these in the next release.

The quality is what has been agreed, and will be even better in the next release

Client Supplier Assessor

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How to deal with due diligence

1.  Keep it short by starting late: Do not start the assessment before the other deal details are sorted out

2.  Ensure the goal is limited: For instance to determine whether the software has issues that cannot be fixed and cause major risks

3.  Ensure involvement: Auditors should listen to your side, share and discuss findings before reporting any issues.

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Conclusions

•  Software quality is important for any growing or grown company •  You can achieve quality with the right agile development process

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Thank you!

•  These slides will be made available on www.softwarezaken.nl

•  If you have any questions, contact me •  I can be hired for additional workshops, coaching and

consulting on any of the topics below:

IT strategy

maintainable software

Starting with agile / scrum

Lean startup

Secure software development

Call or mail me: [email protected] +31 6 1050 9674

Lean startup for corporates

Startup search & selection

IT contracts IT management

for non-IT

how to write maintainable software...2014/05/21 · how to write maintainable software a crash...

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