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Technical Lag in Software
Ecosystems
Ahmed Zerouali
The 18th Belgium-Netherlands Software Evolution Workshop
November 28-29, 2019 - VUB, Brussels
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/background
Credits: libraries.io 3

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/background
Not updateUpdate “If I go there will be trouble,
And if I stay it will be double,
So come on and let me know:
Should I Stay Or Should I Go? ”
The Clash
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/background
Technical lag*: the difference between deployed
software packages and the ideal available packages.
1.0.1 1.2.0 2.0.12.0.0 2.1.0
Technical lag
Deployed Ideal
Releases of a
used software
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/background
Measurement: bugs, vulnerabilities, version updates,
line of code, commits, etc.
Gold standard/IDEAL: stability, security, functionality,
etc.
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/example
up-to-date
1.0.1
3.6.0
1.2.0
4.0.0
allowed
dependent
package P
required
package D
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/example
outdated
1.0.1 1.2.0 2.0.1
3.6.0
4.0.0
2.0.0
allowed
4.1.0
missing updates
dependent
package P
required
package D
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/example
package.json
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/dependency
network
Credits: https://exploring-data.com/vis/npm-packages-dependencies/ 10

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/dependency
tree
Credits: https://exploring-data.com/vis/npm-packages-dependencies/ 11

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/technical lag
framework
● is a set of component releases
● is a set of possible lag values
● ideal : → is a function returning the “ideal” component release
● delta : x → is a function computing the difference between two
component releases
● agg : is a function aggregating the results of a set of lags
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/technical lag
framework
Given a technical lag framework , we define:
Technical lag
Aggregated Technical lag
Let D C be a set of components, then:
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/case studies
- npm packages : the whole registry
- Debian-based Docker images
Goal: Analyze technical lag in software ecosystems.
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/results
/npm packages
- npm packages have a median version lag of 14 versions (2 majors, 2 minors , 10 patches)
- Technical lag is increasing over time.
- Version constraints (e.g, ^1.0.0), are the main reason behind the technical lag.
- Development dependencies have slightly more technical lag than runtime dependencies
For direct dependencies
versions
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/results
/npm applications For direct dependencies
Time lag induced by direct dependencies in GitHub applications:
Technical lag in GitHub applications is higher than in npm
package releases
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/results
/Docker images
- Debian packages have a median version lag of 1 version
- Debian-based images have a median version lag of 6 versions.
- Technical lag depends on the Debian version used in the image
- Different dimensions of technical lag are complementary
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/conclusion
- The technical lag could help open source software developers and deployers to keep their
software in a healthy shape.
- TL can be a proxy for the effort needed to deploy the ideal version.
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