Block Aggregator

Block Aggregator is a data loader that subscribes to Kafka topics, aggregates the Kafka messages into blocks that follow the Clickhouse’s table schemas, and then inserts the blocks into ClickHouse. Block Aggregator provides exactly-once delivery guarantee to load data from Kafka to ClickHouse. Block Aggregator utilizes Kafka’s metadata to keep track of blocks that are intended to send to ClickHouse, and later uses this metadata information to deterministically re-produce ClickHouse blocks for re-tries in case of failures. The identical blocks are guaranteed to be deduplicated by ClickHouse.

Please refer to the article and the presentation for more detail.

Features

No data loss/duplication when loading data from Kafka to ClickHouse
Support multi-shard and multi-datacenter ClickHouse deployment model
Support Kafka message consumption from multiple Kafka clusters
Loading of multiple ClickHouse tables from one Kafka topic with multiple Kafka partitions
Monitoring with over one hundred metrics:
- Kafka message processing rate
- Block insertion rate and failure rate
- Block size distribution
- Block loading time distribution
- Kafka metadata commit time and failure rate
- Whether abnormal message consumption behaviors happened (such as message offset re-wound or skipped)

Supported Platforms

Ubuntu (tested on 18.04)

The Mac environment can support build and run Block Aggregator on its earlier version but not on the current version.

How to Build

The build enviroment requires Utuntu 18.04.

At the top directory of the repo, follow these steps:

Step 1: Install External dependencies

The dependencies include cmake 3.16, gcc 10.3 and Boost Library 1.75.0.

./external-deps-ubuntu.sh

Step 2: Build and install dependent library modules

This includes building the dependent libraries from the source code, including protobuf, flatbuffer, librdkafka and ClickHouse. The current ClickHouse version chosen is v21.8.3.44-lts.

./deps.sh

Notes: building ClickHouse from source code may take more than two hours and the build of ClickHouse includes both release build and debug build. Thus if no need to build Block Aggregator's debug build and only the ClickHouse release build is needed, then in deps.sh, change the following function:

ClickHouse () {
    ClickHouse_ 'Debug' true
    ClickHouse_ 'Release'
}

to become:

ClickHouse () {
    ClickHouse_ 'Release' true
}

Step 3: Bootstrap

This is to generate the cmake related build scripts

rm -rf ./cmake-build-*
./bootstrap.sh

If to build unit tests in addition, then run the following command:

rm -rf ./cmake-build-*
./bootstrap.sh -DUNITTEST=ON

Step 4: Build

To build in release mode:

cmake --build ./cmake-build-release -- -j8 VERBOSE=1

Or, to build the debug version:

cmake --build ./cmake-build-debug -- -j8 VERBOSE=1

The built application is located at cmake-build-release (or cmake-build-debug), named NuColumnarAggr.

If we issue earlier with ./bootstrap.sh -DUNITTEST=ON, then we can build both the application and the unit test suites. In the release mode, we can invoke:

cmake --build ./cmake-build-release -- -j8 VERBOSE=1 install

or in the debug mode:

cmake --build ./cmake-build-debug -- -j8 VERBOSE=1 install

All of the unit test suites related executables are built and installed under the directory: run-test/deployed.

Notes: In the debug mode, building the application executable or each of the test executables can take more than 15 minutes, because linking to the debug version of ClickHouse libraries is slow. Future release will consolidate the current test suites into small number of test executables.

Run Unit Tests

Step 1: Test Framework Preparation on Kafka, ZooKeeper and ClickHouse

We need to make sure that a Kafka process, a ZooKeeper process, and a ClickHouse server with ClickHouse version 21.8, are accessible from a Linux-based test environment.

The Kafaka process and the ZooKeeper process can be set up by download a kafka binary distribution, such as [kafka_2.11-2.1.1.tgz] (https://kafka.apache.org/downloads).

The ClickHouse server can be set up via [the ClickHouse installation guide] (https://clickhouse.com/docs/en/getting-started/install/)

The IP address information related to the Kafka process, the ZooKeeper process and the ClickHouse server process need to be updated to the configuration files located under run-tests/conf

example_aggregator_config.xml
example_aggregator_config_with_tls.json
example_aggregator_config_for_distributed_locking.json

Step 2: Loading Table Schema for Testing Related Tables

Follow the instructions given in the readme file to load the table schema for all of the testing related tables into the ClickHouse server process.

Step 3: Run Unit Tests

Invoke the following command to run all of the unit tests:

cd ./run-tests; . ./set_env.sh; ./runtests.sh

Integration Tests

An integration test example to launch one Block Aggregator instance and consume Kafka message batches can be found under the directory run-tests/scripts/simple_kafka_producer. Please refer to the steps in [the readme file] (./run-tests/scripts/simple_kafka_produce/readme.txt) to invoke the scripts and check the loaded rows in ClickHouse.

Docker Build

Follow the instructions given in the readme file to build the docker image.

Contributing to This Project

We welcome contributions. If you find any bugs, potential flaws and edge cases, improvements, new feature suggestions or discussions, please submit issues or pull requests.

Contact

Jun Li (junli5@ebay.com)

License Information

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

https://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

3rd Party Code

URL: https://github.com/ClickHouse/ClickHouse
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Originally licensed under the Apache 2.0 license.
URL: https://github.com/google/farmhash.git
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Originally licensed under the MIT license.
URL: https://github.com/google/protobuf
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Copyright 2008 Google Inc.
URL: https://github.com/google/flatbuffers
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Originally licensed under the Apache 2.0 license.
URL: https://github.com/edenhill/librdkafka
License Information: https://github.com/edenhill/librdkafka/blob/master/LICENSE
Copyright 2012-2020, Magnus Edenhill.
URL: https://github.com/google/glog/
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Copyright 2008, Google Inc.
URL: https://github.com/jupp0r/prometheus-cpp
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Originally licensed under the MIT license.
URL: https://github.com/urcu/userspace-rcu
License Information: https://github.com/urcu/userspace-rcu/blob/master/LICENSE
Originally licensed under the LGPLv2.1 license
URL: https://github.com/nlohmann/json
License Information: https://github.com/nlohmann/json/blob/develop/LICENSE.MIT
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URL: https://github.com/arun11299/cpp-jwt
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URL: https://chromium.googlesource.com/breakpad/breakpad.git
License Information: https://chromium.googlesource.com/breakpad/breakpad.git/+/refs/heads/main/LICENSE
Copyright 2006 Google Inc.
URL: https://downloads.sourceforge.net/project/tclap
License Information: https://sourceforge.net/p/tclap/code/ci/1.4/tree/COPYING
Copyright 2003-2012 Michael E. Smoot, 2004-2016 Daniel Aarno, 2017-2021 Google LLC
URL: https://github.com/emcrisostomo/fswatch
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Copyright 2002-present Jason Evans, 2007-2012 Mozilla Foundation, 2009-present Facebook Inc.
URL: https://github.com/google/googletest
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Originally licensed under the BSD 3-Clause "New" or "Revised" License

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