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Pull request Compare This branch is even with apache:trunk.
omkreddy and ijuma MINOR: Close ZooKeeperClient if waitUntilConnected fails during const…
…ruction (#5411)

This has always been an issue, but the recent upgrade to ZooKeeper
3.4.13 means it is also an issue when an unresolvable ZK
address is used, causing some tests to leak threads.

The change in behaviour in ZK 3.4.13 is that no exception is thrown
from the ZooKeeper constructor in case of an unresolvable address.
Instead, ZooKeeper tries to re-resolve the address hoping it becomes
resolvable again. We eventually throw a
`ZooKeeperClientTimeoutException`, which is similar to the case
where the the address is resolvable but ZooKeeper is not

Reviewers: Ismael Juma <>
Latest commit 5db2f99 Jul 22, 2018
Failed to load latest commit information.
bin KAFKA-2983: Remove Scala consumers and related code (#5230) Jun 19, 2018
checkstyle MINOR: Remove deprecated ZkUtils usage from EmbeddedKafkaCluster (#5324) Jul 19, 2018
clients KAFKA-6897; Prevent KafkaProducer.send from blocking when producer is… Jul 21, 2018
config KAFKA-5540: Deprecate internal converter configs (KIP-174) May 29, 2018
connect MINOR: FileStreamSinkTask should create file if it doesn't exist (#5406) Jul 21, 2018
core MINOR: Close ZooKeeperClient if waitUntilConnected fails during const… Jul 22, 2018
docs KAFKA-7177; Update 2.0 documentation to reflect changed quota behavio… Jul 21, 2018
examples KAFKA-2983: Remove Scala consumers and related code (#5230) Jun 19, 2018
gradle KAFKA-4994; Remove findbugs suppression for OffsetStorageWriter (#5385) Jul 19, 2018
jmh-benchmarks MINOR: Fix needless GC + Result time unit in JMH Sep 18, 2017
log4j-appender/src MINOR: Use static imports in KafkaLog4jAppender Jul 18, 2017
streams KAFKA-5037 Follow-up: move Scala test to Java (#5399) Jul 20, 2018
tests MINOR: Add thread dumps if broker node cannot be stopped (#5373) Jul 20, 2018
tools/src HOTFIX: KAFKA-7097; Set create time default to -1L in VerifiableProducer Jun 29, 2018
vagrant MINOR: fix Vagrant VM setup (#5178) Jun 17, 2018
.gitignore KAFKA-6782: solved the bug of restoration of aborted messages for Glo… Jun 12, 2018
.travis.yml MINOR: Add HttpMetricsReporter for system tests Nov 9, 2017 KAFKA-2321; Introduce Jul 27, 2015
HEADER trivial fix to add missing license header using .gradlew licenseForma… Feb 7, 2014
LICENSE KAFKA-3314: Add CDDL license to LICENSE and NOTICE file Mar 3, 2016
NOTICE MINOR: Update copyright year in NOTICE Feb 5, 2018 MINOR: Exclude Committer Checklist section from commit message Nov 10, 2017 KAFKA-4423: Drop support for Java 7 (KIP-118) and update deps (#5046) May 22, 2018 MINOR: Fix for the location of the executable file in the … Jun 5, 2018
Vagrantfile MINOR: use jdk8 to build/run system tests (#4925) Apr 26, 2018
build.gradle MINOR: Update build.gradle and to upload streams-scala_2.12 ( Jul 19, 2018
doap_Kafka.rdf MINOR: Remove <release> tag from doap file May 12, 2016 MINOR: need to update system test version after version bump (#5156) Jun 6, 2018 KAFKA-4459: Run rat checks in Jenkins script Jun 1, 2017 MINOR: Bump version to 2.1.0-SNAPSHOT (#5153) Jun 6, 2018 MINOR: Update build.gradle and to upload streams-scala_2.12 ( Jul 19, 2018 MINOR: Change version format in release notes python code Nov 3, 2017
settings.gradle KAFKA-6776: ConnectRestExtension Interfaces & Rest integration (KIP-285) May 30, 2018
wrapper.gradle KAFKA-1490 remove gradlew initial setup output from source distributi… Sep 23, 2014

Apache Kafka

See our web site for details on the project.

You need to have Gradle and Java installed.

Kafka requires Gradle 4.5 or higher.

Java 8 should be used for building in order to support both Java 8 and Java 10 at runtime.

First bootstrap and download the wrapper

cd kafka_source_dir

Now everything else will work.

Build a jar and run it

./gradlew jar

Follow instructions in

Build source jar

./gradlew srcJar

Build aggregated javadoc

./gradlew aggregatedJavadoc

Build javadoc and scaladoc

./gradlew javadoc
./gradlew javadocJar # builds a javadoc jar for each module
./gradlew scaladoc
./gradlew scaladocJar # builds a scaladoc jar for each module
./gradlew docsJar # builds both (if applicable) javadoc and scaladoc jars for each module

Run unit/integration tests

./gradlew test # runs both unit and integration tests
./gradlew unitTest
./gradlew integrationTest

Force re-running tests without code change

./gradlew cleanTest test
./gradlew cleanTest unitTest
./gradlew cleanTest integrationTest

Running a particular unit/integration test

./gradlew -Dtest.single=RequestResponseSerializationTest core:test

Running a particular test method within a unit/integration test

./gradlew core:test --tests kafka.api.ProducerFailureHandlingTest.testCannotSendToInternalTopic
./gradlew clients:test --tests org.apache.kafka.clients.MetadataTest.testMetadataUpdateWaitTime

Running a particular unit/integration test with log4j output

Change the log4j setting in either clients/src/test/resources/ or core/src/test/resources/

./gradlew -i -Dtest.single=RequestResponseSerializationTest core:test

Generating test coverage reports

Generate coverage reports for the whole project:

./gradlew reportCoverage

Generate coverage for a single module, i.e.:

./gradlew clients:reportCoverage

Building a binary release gzipped tar ball

./gradlew clean
./gradlew releaseTarGz

The above command will fail if you haven't set up the signing key. To bypass signing the artifact, you can run:

./gradlew releaseTarGz -x signArchives

The release file can be found inside ./core/build/distributions/.

Cleaning the build

./gradlew clean

Running a task on a particular version of Scala (either 2.11.x or 2.12.x)

Note that if building the jars with a version other than 2.11.12, you need to set the SCALA_VERSION variable or change it in bin/ to run the quick start.

You can pass either the major version (eg 2.11) or the full version (eg 2.11.12):

./gradlew -PscalaVersion=2.11 jar
./gradlew -PscalaVersion=2.11 test
./gradlew -PscalaVersion=2.11 releaseTarGz

Running a task for a specific project

This is for core, examples and clients

./gradlew core:jar
./gradlew core:test

Listing all gradle tasks

./gradlew tasks

Building IDE project

Note that this is not strictly necessary (IntelliJ IDEA has good built-in support for Gradle projects, for example).

./gradlew eclipse
./gradlew idea

The eclipse task has been configured to use ${project_dir}/build_eclipse as Eclipse's build directory. Eclipse's default build directory (${project_dir}/bin) clashes with Kafka's scripts directory and we don't use Gradle's build directory to avoid known issues with this configuration.

Building the jar for all scala versions and for all projects

./gradlew jarAll

Running unit/integration tests for all scala versions and for all projects

./gradlew testAll

Building a binary release gzipped tar ball for all scala versions

./gradlew releaseTarGzAll

Publishing the jar for all version of Scala and for all projects to maven

./gradlew uploadArchivesAll

Please note for this to work you should create/update ${GRADLE_USER_HOME}/ (typically, ~/.gradle/ and assign the following variables


Publishing the streams quickstart archetype artifact to maven

For the Streams archetype project, one cannot use gradle to upload to maven; instead the mvn deploy command needs to be called at the quickstart folder:

cd streams/quickstart
mvn deploy

Please note for this to work you should create/update user maven settings (typically, ${USER_HOME}/.m2/settings.xml) to assign the following variables

<settings xmlns=""

Installing the jars to the local Maven repository

./gradlew installAll

Building the test jar

./gradlew testJar

Determining how transitive dependencies are added

./gradlew core:dependencies --configuration runtime

Determining if any dependencies could be updated

./gradlew dependencyUpdates

Running code quality checks

There are two code quality analysis tools that we regularly run, findbugs and checkstyle.


Checkstyle enforces a consistent coding style in Kafka. You can run checkstyle using:

./gradlew checkstyleMain checkstyleTest

The checkstyle warnings will be found in reports/checkstyle/reports/main.html and reports/checkstyle/reports/test.html files in the subproject build directories. They are also are printed to the console. The build will fail if Checkstyle fails.


Findbugs uses static analysis to look for bugs in the code. You can run findbugs using:

./gradlew findbugsMain findbugsTest -x test

The findbugs warnings will be found in reports/findbugs/main.html and reports/findbugs/test.html files in the subproject build directories. Use -PxmlFindBugsReport=true to generate an XML report instead of an HTML one.

Common build options

The following options should be set with a -P switch, for example ./gradlew -PmaxParallelForks=1 test.

  • commitId: sets the build commit ID as .git/HEAD might not be correct if there are local commits added for build purposes.
  • mavenUrl: sets the URL of the maven deployment repository (file://path/to/repo can be used to point to a local repository).
  • maxParallelForks: limits the maximum number of processes for each task.
  • showStandardStreams: shows standard out and standard error of the test JVM(s) on the console.
  • skipSigning: skips signing of artifacts.
  • testLoggingEvents: unit test events to be logged, separated by comma. For example ./gradlew -PtestLoggingEvents=started,passed,skipped,failed test.
  • xmlFindBugsReport: enable XML reports for findBugs. This also disables HTML reports as only one can be enabled at a time.

Running in Vagrant

See vagrant/


Apache Kafka is interested in building the community; we would welcome any thoughts or patches. You can reach us on the Apache mailing lists.

To contribute follow the instructions here: