About the Modern C++ Kafka API

Introduction

The Modern C++ Kafka API is a layer of C++ wrapper based on librdkafka (the C part), with high quality, but more friendly to users.

• By now, modern-cpp-kafka is compatible with librdkafka v1.9.0.

KAFKA is a registered trademark of The Apache Software Foundation and
has been licensed for use by modern-cpp-kafka. modern-cpp-kafka has no
affiliation with and is not endorsed by The Apache Software Foundation.

Why it's here

The librdkafka is a robust high performance C/C++ library, widely used and well maintained.

Unfortunately, to maintain C++98 compatibility, the C++ interface of librdkafka is not quite object-oriented or user-friendly.

Since C++ is evolving quickly, we want to take advantage of new C++ features, thus make the life easier for developers. And this led us to create a new C++ API for Kafka clients.

Eventually, we worked out the modern-cpp-kafka, -- a header-only library that uses idiomatic C++ features to provide a safe, efficient and easy to use way of producing and consuming Kafka messages.

Features

• Header-only

  • Easy to deploy, and no extra library required to link

• Ease of Use

  • Interface/Naming matches the Java API

  • Object-oriented

  • RAII is used for lifetime management

  • librdkafka's polling and queue management is now hidden

• Robust

  • Verified with kinds of test cases, which cover many abnormal scenarios (edge cases)

    • Stability test with unstable brokers

    • Memory leak check for failed client with in-flight messages

    • Client failure and taking over, etc.

• Efficient

  • No extra performance cost (No deep copy introduced internally)

  • Much better (2~4 times throughput) performance result than those native language (Java/Scala) implementation, in most commonly used cases (message size: 256 B ~ 2 KB)

Build

• No need to build for installation

• To build its tools/tests/examples, you should

  • Specify library locations with environment variables

    • LIBRDKAFKA_ROOT -- librdkafka headers and libraries

    • GTEST_ROOT -- googletest headers and libraries

    • BOOST_ROOT -- boost headers and libraries

    • SASL_LIBRARYDIR/SASL_LIBRARY -- if SASL connection support is wanted

    • RAPIDJSON_INCLUDE_DIRS -- addons/KafkaMetrics requires rapidjson headers

  • Create an empty directory for the build, and cd to it

  • Build commands

    • Type cmake path-to-project-root

    • Type make (could follow build options with -D)

      • BUILD_OPTION_USE_ASAN=ON -- Use Address Sanitizer

      • BUILD_OPTION_USE_TSAN=ON -- Use Thread Sanitizer

      • BUILD_OPTION_USE_UBSAN=ON -- Use Undefined Behavior Sanitizer

      • BUILD_OPTION_CLANG_TIDY=ON -- Enable clang-tidy checking

      • BUILD_OPTION_GEN_DOC=ON -- Generate documentation as well

      • BUILD_OPTION_DOC_ONLY=ON -- Only generate documentation

      • BUILD_OPTION_GEN_COVERAGE=ON -- Generate test coverage, only support by clang currently

    • Type make install

Install

• Include the include/kafka directory in your project

• To work together with modern-cpp-kafka API, the compiler should support

  • Option 1: C++17

  • Option 2: C++14 (with pre-requirements)

    • Need boost headers (for boost::optional)

    • GCC only (with optimization, e.g. -O2)

How to Run Tests

• Unit test (tests/unit)

  • The test could be run with no Kafka cluster depolyed

• Integration test (tests/integration)

  • The test should be run with Kafka cluster depolyed

  • The environment variable KAFKA_BROKER_LIST should be set

    • E.g. export KAFKA_BROKER_LIST=127.0.0.1:29091,127.0.0.1:29092,127.0.0.1:29093

• Robustness test (tests/robustness)

  • The test should be run with Kafka cluster depolyed locally

  • The environment variable KAFKA_BROKER_LIST should be set

  • The environment variable KAFKA_BROKER_PIDS should be set

    • Make sure the test runner gets the privilege to stop/resume the pids

    • E.g. export KAFKA_BROKER_PIDS=61567,61569,61571

• Additional settings for clients

  • The environment variable KAFKA_CLIENT_ADDITIONAL_SETTINGS could be used for customized test environment

    • Especially for Kafka cluster with SASL(or SSL) connections

    • E.g. export KAFKA_CLIENT_ADDITIONAL_SETTINGS="security.protocol=SASL_PLAINTEXT;sasl.kerberos.service.name=...;sasl.kerberos.keytab=...;sasl.kerberos.principal=..."

To Start

• Tutorial

  • Confluent Blog Debuting a Modern C++ API for Apache Kafka

  • KafkaProducer Quick Start

  • KafkaConsumer Quick Start

• User's Manual

  • Kafka Client API

  • Kafka Client Properties

    • In most cases, the Properties settings for modern-cpp-kafka are identical with librdkafka configuration

    • With following exceptions

      • KafkaConsumer

        • Properties with random string as default

          • client.id

          • group.id

        • More properties than librdkafka

          • max.poll.records (default: 500): The maxmum number of records that a single call to poll() would return

        • Property which overrides the one from librdkafka

          • enable.auto.commit (default: false): To automatically commit the previously polled offsets on each poll operation

        • Properties not supposed to be used (internally shadowed by modern-cpp-kafka)

          • enable.auto.offset.store

          • auto.commit.interval.ms

      • KafkaProducer

        • Properties with random string as default

          • client.id

      • Log level

        • The default log_level is NOTICE (5) for all these clients

• Test Environment (ZooKeeper/Kafka cluster) Setup

  • Start the servers

How to Achieve High Availability & Performance

• Kafka Broker Configuration

• Good Practices to Use KafkaProducer

• Good Practices to Use KafkaConsumer

• How to Make KafkaProducer Reliable

Other References

• Java API for Kafka clients

  • org.apache.kafka.clients.producer

  • org.apache.kafka.clients.consumer

  • org.apache.kafka.clients.admin