Implementing Quality on Java projects

Vincent MassolCommitter XWikiCTO XWiki SAS

@vmassolSaturday, April 20, 13

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

Saturday, April 20, 13

What is Quality?

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The XWiki project in summary• 9 years old

• 28 active committers

• 7 committers do 80% of work

• 700K NCLOC

• 11 commits/day

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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)

Saturday, April 20, 13

Quality Tip #1API Stability

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The Problem

Class Not Found or Method Not Found

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API Stability - Deprecations/** * ... * @deprecated since 2.4M1 use {@link #transform( * Block, TransformationContext)} */@Deprecatedvoid transform(XDOM dom, Syntax syntax) throws TransformationException;

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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>...

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API Stability - CLIRR (2/2)

Example from XWiki 5.0M1 Release notes

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

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API Stability - Legacy ModuleAspect Weaving

+ “Legacy” Profile

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

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API Stability - Young APIs

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

+ max duration for keeping the annotation!

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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 without breaking compatibility•Java 8 and Virtual Extension/Defender methods

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

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Quality Tip #2JAR Hell

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The Problem

Class Not Found or Method Not Found or not working feature

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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> ...

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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!Saturday, April 20, 13

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!

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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>

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Quality Tip #3Test Coverage

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The Problem

More bugs reported, overall quality goes down and harder to

debug software

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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>}

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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

testSaturday, April 20, 13

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?

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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!

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Quality Tip #4Functional Testing

Stability

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The Problem

Too many false positives leading to developers not

paying attention to CI emails anymore... leading to failing

software

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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)

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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 = truemessages.each { message -> if (manager.logContains(message.get(0))) { manager.addWarningBadge(message.get(1)) manager.createSummary("warning.gif").appendText(...) manager.buildUnstable() shouldSendEmail = false }}

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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)}

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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

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Results

+ use the Scriptler plugin to automate configuration for all jobs

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Quality Tip #5Bug Fixing Day

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The Problem

Bugs increasing, even simple to fix

ones, devs focusing too much on new features (i.e. scope creep)

vs fixing what existsBugs created vs closed

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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 730 days (we need to catch up with 6 bugs!)

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Results

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Conclusion

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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)

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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

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