See our web site for details on the project.
You need to have Java installed.
We build and test Apache Kafka with Java 8, 11, 17 and 21. We set the release parameter in javac and scalac
to 8 to ensure the generated binaries are compatible with Java 8 or higher (independently of the Java version
used for compilation). Java 8 support project-wide has been deprecated since Apache Kafka 3.0, Java 11 support for
the broker and tools has been deprecated since Apache Kafka 3.7 and removal of both is planned for Apache Kafka 4.0 (
see KIP-750 and
KIP-1013 for more details).
Scala 2.12 and 2.13 are supported and 2.13 is used by default. Scala 2.12 support has been deprecated since Apache Kafka 3.0 and will be removed in Apache Kafka 4.0 (see KIP-751 for more details). See below for how to use a specific Scala version or all of the supported Scala versions.
./gradlew jar
Follow instructions in https://kafka.apache.org/quickstart
./gradlew srcJar
./gradlew aggregatedJavadoc
./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
./gradlew test # runs both unit and integration tests
./gradlew unitTest
./gradlew integrationTest
./gradlew test --rerun
./gradlew unitTest --rerun
./gradlew integrationTest --rerun
./gradlew clients:test --tests RequestResponseTest
I=0; while ./gradlew clients:test --tests RequestResponseTest --rerun --fail-fast; do (( I=$I+1 )); echo "Completed run: $I"; sleep 1; done
./gradlew core:test --tests kafka.api.ProducerFailureHandlingTest.testCannotSendToInternalTopic
./gradlew clients:test --tests org.apache.kafka.clients.MetadataTest.testTimeToNextUpdate
By default, there will be only small number of logs output while testing. You can adjust it by changing the log4j.properties file in the module's src/test/resources directory.
For example, if you want to see more logs for clients project tests, you can modify the line in clients/src/test/resources/log4j.properties
to log4j.logger.org.apache.kafka=INFO and then run:
./gradlew cleanTest clients:test --tests NetworkClientTest
And you should see INFO level logs in the file under the clients/build/test-results/test directory.
By default, each failed test is retried once up to a maximum of five retries per test run. Tests are retried at the end of the test task. Adjust these parameters in the following way:
./gradlew test -PmaxTestRetries=1 -PmaxTestRetryFailures=5
See Test Retry Gradle Plugin for more details.
Generate coverage reports for the whole project:
./gradlew reportCoverage -PenableTestCoverage=true -Dorg.gradle.parallel=false
Generate coverage for a single module, i.e.:
./gradlew clients:reportCoverage -PenableTestCoverage=true -Dorg.gradle.parallel=false
./gradlew clean releaseTarGz
The release file can be found inside ./core/build/distributions/.
Sometimes it is only necessary to rebuild the RPC auto-generated message data when switching between branches, as they could fail due to code changes. You can just run:
./gradlew processMessages processTestMessages
Using compiled files:
KAFKA_CLUSTER_ID="$(./bin/kafka-storage.sh random-uuid)"
./bin/kafka-storage.sh format -t $KAFKA_CLUSTER_ID -c config/kraft/server.properties
./bin/kafka-server-start.sh config/kraft/server.properties
Using docker image:
docker run -p 9092:9092 apache/kafka:3.7.0
Using compiled files:
./bin/zookeeper-server-start.sh config/zookeeper.properties
./bin/kafka-server-start.sh config/server.properties
Since ZooKeeper mode is already deprecated and planned to be removed in Apache Kafka 4.0, the docker image only supports running in KRaft mode
./gradlew clean
Note that if building the jars with a version other than 2.13.x, you need to set the SCALA_VERSION variable or change it in bin/kafka-run-class.sh to run the quick start.
You can pass either the major version (eg 2.12) or the full version (eg 2.12.7):
./gradlew -PscalaVersion=2.12 jar
./gradlew -PscalaVersion=2.12 test
./gradlew -PscalaVersion=2.12 releaseTarGz
Invoke the gradlewAll script followed by the task(s):
./gradlewAll test
./gradlewAll jar
./gradlewAll releaseTarGz
This is for core, examples and clients
./gradlew core:jar
./gradlew core:test
Streams has multiple sub-projects, but you can run all the tests:
./gradlew :streams:testAll
./gradlew tasks
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.
The recommended command is:
./gradlewAll publish
For backwards compatibility, the following also works:
./gradlewAll uploadArchives
Please note for this to work you should create/update ${GRADLE_USER_HOME}/gradle.properties (typically, ~/.gradle/gradle.properties) and assign the following variables
mavenUrl=
mavenUsername=
mavenPassword=
signing.keyId=
signing.password=
signing.secretKeyRingFile=
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, ${USER_HOME}/.m2/settings.xml) to assign the following variables
<settings xmlns="http://maven.apache.org/SETTINGS/1.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/SETTINGS/1.0.0
https://maven.apache.org/xsd/settings-1.0.0.xsd">
...
<servers>
...
<server>
<id>apache.snapshots.https</id>
<username>${maven_username}</username>
<password>${maven_password}</password>
</server>
<server>
<id>apache.releases.https</id>
<username>${maven_username}</username>
<password>${maven_password}</password>
</server>
...
</servers>
...
The recommended command to build for both Scala 2.12 and 2.13 is:
./gradlewAll publishToMavenLocal
For backwards compatibility, the following also works:
./gradlewAll install
./gradlew -PskipSigning=true :streams:publishToMavenLocal
If needed, you can specify the Scala version with -PscalaVersion=2.13.
./gradlew testJar
There are two code quality analysis tools that we regularly run, spotbugs and checkstyle.
Checkstyle enforces a consistent coding style in Kafka. You can run checkstyle using:
./gradlew checkstyleMain checkstyleTest spotlessCheck
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 printed to the console. The build will fail if Checkstyle fails.
The import order is a part of static check. please call spotlessApply to optimize the imports of Java codes before filing pull request :
./gradlew spotlessApply
Spotbugs uses static analysis to look for bugs in the code. You can run spotbugs using:
./gradlew spotbugsMain spotbugsTest -x test
The spotbugs warnings will be found in reports/spotbugs/main.html and reports/spotbugs/test.html files in the subproject build
directories. Use -PxmlSpotBugsReport=true to generate an XML report instead of an HTML one.
We use JMH to write microbenchmarks that produce reliable results in the JVM.
See jmh-benchmarks/README.md for details on how to run the microbenchmarks.
The gradle dependency debugging documentation mentions using the dependencies or dependencyInsight tasks to debug dependencies for the root project or individual subprojects.
Alternatively, use the allDeps or allDepInsight tasks for recursively iterating through all subprojects:
./gradlew allDeps
./gradlew allDepInsight --configuration runtimeClasspath --dependency com.fasterxml.jackson.core:jackson-databind
These take the same arguments as the builtin variants.
./gradlew dependencyUpdates
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/repocan be used to point to a local repository).maxParallelForks: maximum number of test processes to start in parallel. Defaults to the number of processors available to the JVM.maxScalacThreads: maximum number of worker threads for the scalac backend. Defaults to the lowest of8and the number of processors available to the JVM. The value must be between 1 and 16 (inclusive).ignoreFailures: ignore test failures from junitshowStandardStreams: 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.xmlSpotBugsReport: enable XML reports for spotBugs. This also disables HTML reports as only one can be enabled at a time.maxTestRetries: maximum number of retries for a failing test case.maxTestRetryFailures: maximum number of test failures before retrying is disabled for subsequent tests.enableTestCoverage: enables test coverage plugins and tasks, including bytecode enhancement of classes required to track said coverage. Note that this introduces some overhead when running tests and hence why it's disabled by default (the overhead varies, but 15-20% is a reasonable estimate).keepAliveMode: configures the keep alive mode for the Gradle compilation daemon - reuse improves start-up time. The values should be one ofdaemonorsession(the default isdaemon).daemonkeeps the daemon alive until it's explicitly stopped whilesessionkeeps it alive until the end of the build session. This currently only affects the Scala compiler, see gradle/gradle#21034 for a PR that attempts to do the same for the Java compiler.scalaOptimizerMode: configures the optimizing behavior of the scala compiler, the value should be one ofnone,method,inline-kafkaorinline-scala(the default isinline-kafka).noneis the scala compiler default, which only eliminates unreachable code.methodalso includes method-local optimizations.inline-kafkaadds inlining of methods within the kafka packages. Finally,inline-scalaalso includes inlining of methods within the scala library (which avoids lambda allocations for methods likeOption.exists).inline-scalais only safe if the Scala library version is the same at compile time and runtime. Since we cannot guarantee this for all cases (for example, users may depend on the kafka jar for integration tests where they may include a scala library with a different version), we don't enable it by default. See https://www.lightbend.com/blog/scala-inliner-optimizer for more details.
See tests/README.md.
See vagrant/README.md.
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:
React
Typescript
Django
Laravel
Facebook
Microsoft
Google
Alibaba
D3
Tencent