In my talks, I’m using a short example that illustrates how the mechanics of my notebook-driven approach for analyzing software systems works. Now you can find the example on my blog, too. Have also a look at the original on GitHub (best viewed in desktop mode).

Context

John Doe remarked in #AP1432 that there may be too much code in our application that isn’t used at all. Before migrating the application to the new platform, we have to analyze which parts of the system are still in use and which are not.

Idea

To understand how much code isn’t used, we recorded the executed code in production with the coverage tool JaCoCo. The measurement took place between 21st Oct 2017 and 27st Oct 2017. The results were exported into a CSV file using the JaCoCo command line tool with the following command:

java -jar jacococli.jar report "C:\Temp\jacoco.exec" --classfiles \
C:\dev\repos\buschmais-spring-petclinic\target\classes --csv jacoco.csv

The CSV file contains all lines of code that were passed through during the measurement’s time span. We just take the relevant data and add an additional LINES column to be able to calculate the ratio between covered and missed lines later on.

In [1]:
import pandas as pd
coverage = pd.read_csv("../input/spring-petclinic/jacoco.csv")
coverage = coverage[['PACKAGE', 'CLASS', 'LINE_COVERED' ,'LINE_MISSED']]
coverage['LINES'] = coverage.LINE_COVERED + coverage.LINE_MISSED
coverage.head(1)
Out[1]:
PACKAGE CLASS LINE_COVERED LINE_MISSED LINES
0 org.springframework.samples.petclinic PetclinicInitializer 24 0 24

Analysis

It was stated that whole packages wouldn’t be needed anymore and that they could be safely removed. Therefore, we sum up the coverage data per class for each package and calculate the coverage ratio for each package.

In [2]:
grouped_by_packages = coverage.groupby("PACKAGE").sum()
grouped_by_packages['RATIO'] = grouped_by_packages.LINE_COVERED / grouped_by_packages.LINES
grouped_by_packages = grouped_by_packages.sort_values(by='RATIO')
grouped_by_packages
Out[2]:
LINE_COVERED LINE_MISSED LINES RATIO
PACKAGE
org.springframework.samples.petclinic.repository.jdbc 0 152 152 0.000000
org.springframework.samples.petclinic.util 13 17 30 0.433333
org.springframework.samples.petclinic.web 75 40 115 0.652174
org.springframework.samples.petclinic.model 75 33 108 0.694444
org.springframework.samples.petclinic.repository.jpa 21 7 28 0.750000
org.springframework.samples.petclinic.service 16 2 18 0.888889
org.springframework.samples.petclinic 24 0 24 1.000000

We plot the data for the coverage ratio to get a brief overview of the result.

In [3]:
%matplotlib inline
grouped_by_packages[['RATIO']].plot(kind="barh", figsize=(8,2))
Out[3]:
<matplotlib.axes._subplots.AxesSubplot at 0x1874cdde9e8>

Conclusion

The JDBC package org.springframework.samples.petclinic.repository.jdbc isn’t used at all and can be left out safely when migrating to the new platform.

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Production Coverage Demo Notebook

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