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 v1.7.0.

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
- 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

Other References

Java API for Kafka clients

plachta11b / modern-cpp-kafka