27 au 29 mars 2013

Implementing Quality on Java projects

Vincent Massol Committer XWiki

XWiki SAS !

@vmassol

Vincent Massol

• Speaker Bio

• CTO XWiki SAS

• Your Projects

• XWiki (community-driven open source project)

• Past: Maven, Apache Cargo, Apache Cactus, Pattern Testing

• Other Credentials:

• LesCastCodeurs podcast

• Creator of OSSGTP open source group in Paris

• 3 books: JUnit in Action, Maven: A Developer’s Notebook, BBWM

What is Quality?

The XWiki project in summary

• 9 years old

• 28 active committers

• 7 committers do 80% of work

• 700K NCLOC

• 11 commits/day

• 16 mails/day

• 65% TPC

Examples of Quality actions

• Coding rules (Checkstyle, ...)

• Test coverage

• Track bugs

• Don’t use Commons Lang 2.x

• Use SLF4J and don’t draw Log4J/JCL in dependencies

• Automated build

• Automated unit tests

• Stable automated functional tests

• Ensure API stability

• Code reviews

• License header checks

• Release with Java 6

• Ensure javadoc exist

• Prevent JAR hell

• Release often (every 2 weeks)

• Collaborative design

• Test on supported environments (DB & Browsers)

27 au 29 mars 2013

Quality Tip #1 !

API Stability

The Problem

Class Not Found or Method Not Found

API Stability - Deprecations

/**! * ...! * @deprecated since 2.4M1 use {@link #transform(! * Block, TransformationContext)}! */!@Deprecated!void transform(XDOM dom, Syntax syntax)! throws TransformationException;!!!

API Stability - CLIRR (1/2)<plugin>! <groupId>org.codehaus.mojo</groupId>! <artifactId>clirr-maven-plugin</artifactId>! <configuration>! <ignored>! <difference>! <differenceType>7006</differenceType>! <className>org/xwiki/.../MetaDataBlock</className>! <method>org.xwiki....block.Block clone()</method>! <to>org.xwiki.rendering.block.MetaDataBlock</to>! <justification>XDOM#clone() doesn't clone the meta! data</justification>! </difference>!...

API Stability - CLIRR (2/2)

Example from XWiki 5.0M1 Release notes

<plugin>! <groupId>org.apache.maven.plugins</groupId>! <artifactId>maven-javadoc-plugin! <configuration>! <excludePackageNames>*.internal.*! </excludePackageNames>

API Stability - Internal PackageJavadoc

CLIRR<plugin>! <groupId>org.codehaus.mojo</groupId>! <artifactId>clirr-maven-plugin</artifactId>! <excludes>! <exclude>**/internal/**</exclude>! <exclude>**/test/**</exclude>

<plugin>! <groupId>org.codehaus.mojo</groupId>! <artifactId>aspectj-maven-plugin</...>!...! <configuration>! <weaveDependencies>! <weaveDependency>! <groupId>org.xwiki.rendering</...>! <artifactId>xwiki-rendering-api</...>!...

API Stability - Legacy Module

Aspect Weaving

+ “Legacy” Profile

API Stability - Young APIs

/**! * ...! * @since 5.0M1! */!@Unstable(<optional explanation>)!public EntityReference createEntityReference(String name,...)!{!...!}

+ max duration for keeping the annotation!

API Stability - Next steps

• Annotation or package for SPI?

• Better define when to use the @Unstable annotation

• Not possible to add a new method to an existing Interface

• Java 8 and Virtual Extension/Defender methods

interface TestInterface {!  public void testMe();!  public void newMethod() default {!    System.out.println("Default from interface");!  }!}

27 au 29 mars 2013

Quality Tip #2 !

JAR Hell

The Problem

Class Not Found or Method Not Found or not working feature

No duplicate classes @ runtime<plugin>! <groupId>com.ning.maven.plugins</groupId>! <artifactId>maven-duplicate-finder-plugin</artifactId>! <executions>! <execution>! <phase>verify</phase>! <goals>! <goal>check</goal>! </goals>! <configuration>! <failBuildInCaseOfConflict>true</...>! <exceptions>! ...

Surprising results...

• Commons Beanutils bundles some classes from Commons Collections, apparently to avoid drawing a dependency to it...

• Xalan bundles a lot of other projects (org/apache/xml/**, org/apache/bcel/**, JLex/**, java_cup/**, org/apache/regexp/**). In addition, it even has these jars in its source tree without any indication about their versions...

• stax-api, geronimo-stax-api_1.0_spec and xml-apis all draw javax.xml.stream.* classes

• xmlbeans and xml-apis draw incompatible versions of org.w3c.dom.* classes

14 exceptions in total!

Maven: dependency version issue<dependencies>! <dependency>! <groupId>org.slf4j</groupId>! <artifactId>slf4j-api</artifactId>! <version>1.4.0</version>! </dependency>! <dependency>! <groupId>ch.qos.logback</groupId>! <artifactId>logback-classic</artifactId>! <version>0.9.9</version>! <!-- Depends on org.slf4j:slf4j-api:1.5.0 -->! </dependency>!</dependencies>

Will run logback 0.9.9 with slf4J-api 1.4.0 instead of 1.5.0!

Maven: ensure correct version<plugin>! <groupId>org.apache.maven.plugins</groupId>! <artifactId>maven-enforcer-plugin</artifactId>! <executions>! <execution>! <id>enforce-version-compatibility</id>! <phase>verify</phase>! <goals>! <goal>enforce</goal>! </goals>! <configuration>! <rules>! <requireUpperBoundDeps/>! </rules>

27 au 29 mars 2013

Quality Tip #3 !

Test Coverage

The Problem

More bugs reported, overall quality goes down and harder to debug

software

Use Jacoco to fail the build<plugin>! <groupId>org.jacoco</groupId>! <artifactId>jacoco-maven-plugin</artifactId>! <executions>! <execution><id>jacoco-prepare</id>! <goals><goal>prepare-agent</goal></goals>! </execution>! <execution><id>jacoco-check</id>! <goals><goal>check</goal></goals>! </execution>! </executions>! <configuration>! <check>! <instructionRatio>${xwiki.jacoco.instructionRatio}</...>! </check>}

Strategy

• When devs add code (and thus tests), increase the TPC percentage

• Put the Jacoco check in “Quality” Maven Profile

• Have a CI job to execute that profile regularly

• About 15% overhead compared to build without checks

• “Cheat mode”: Add easier-to-write test

Quizz Time!

[INFO] --- jacoco-maven-plugin:0.6.2.201302030002:check (jacoco-check)[INFO] All coverage checks have been met.

[INFO] --- jacoco-maven-plugin:0.6.2.201302030002:check (jacoco-check) ![WARNING] Insufficient code coverage for INSTRUCTION: 75.52% < 75.53%

Step 1: Building on my local machine gives the following:

Step 2: Building on the CI machine gave:

Non determinism! Why?

Quizz Answer

private Map componentEntries = new ConcurrentHashMap();!...!for (Map.Entry entry : componentEntries.entrySet())!{! if (entry.getValue().instance == component) {!  key = entry.getKey();!    oldDescriptor = entry.getValue().descriptor;!    break;!  }!}

... because the JVM is non deterministic!

27 au 29 mars 2013

Quality Tip #4 !

Functional Testing Stability (with Jenkins)

The Problem

Too many false positives leading to developers not paying attention to CI

emails anymore... leading to failing software

False positives examples

• The JVM has crashed

• VNC is down (we run Selenium tests)

• Browser crash (we run Selenium tests)

• Git connection issue

• Machine slowness (if XWiki cannot start under 2 minutes then it means the machine has some problems)

• Nexus is down (we deploy our artifacts to a Nexus repository)

• Connection issue (Read time out)

Step 1: Groovy PostBuild Plugin (1/2)def messages = [! [".*A fatal error has been detected by the Java Runtime Environment.*",! "JVM Crash", "A JVM crash happened!"],! [".*Error: cannot open display: :1.0.*",! "VNC not running", "VNC connection issue!"],! ...!] def shouldSendEmail = true!messages.each { message ->! if (manager.logContains(message.get(0))) {! manager.addWarningBadge(message.get(1))! manager.createSummary("warning.gif").appendText(...)! manager.buildUnstable()! shouldSendEmail = false! }!}

Step 1: Groovy PostBuild Plugin (2/2)

... continued from previous slide...!!if (!shouldSendEmail) {! def pa = new ParametersAction([! new BooleanParameterValue("noEmail", true)! ])! manager.build.addAction(pa)!}

Step 2: Mail Ext Plugin

import hudson.model.*!!build.actions.each { action ->! if (action instanceof ParametersAction) {! if (action.getParameter("noEmail")) {! cancel = true! }! }!}

Pre-send Script

Results

+ use the Scriptler plugin to automate configuration for all jobs

27 au 29 mars 2013

Quality Tip #5 !

Bug Fixing Day

The Problem

Bugs increasing, even simple to fix ones, devs focusing too much on new

features (i.e. scope creep) vs fixing what exists

Bugs created vs closed

Bug Fixing Day

• Every Thursday

• Goal is to close the max number of bugs

• Triaging: Can be closed with Won’t fix, Duplicate, Cannot Reproduce, etc

• Close low hanging fruits in priority

• Started with last 365 days then with last 547 days and currently with last 1500 days (we need to catch up with 22 bugs!)

• Today is BFD#40 (and I’m missing it!)

Results (1/2)

As many bugs closed over past 4 years than created!

Results (2/2)

27 au 29 mars 2013

Conclusion

Parting words

• Slowly add new quality check over time

• Everyone must be on board

• Favor Active Quality (i.e. make the build fail) over Passive checks

• Be ready to adapt/remove checks if found not useful enough

• Quality brings some risks:

• Potentially less committers for your project (especially open source)

• Project seen as “less fun”

Be proud of your Quality!

“I have offended God and mankind because my work didn't reach the quality it should have.”

Leonardo da Vinci, on his death bed