Real-Time MySQL to ClickHouse Replication Guide

Real-time replication from MySQL to ClickHouse ensures your analytics stay up-to-date by syncing changes as they occur. This method is ideal for scenarios like fraud detection, operational monitoring, and live dashboards, where even small delays can impact decision-making. By offloading analytical queries to ClickHouse, you reduce the load on MySQL while benefiting from ClickHouse's speed and efficiency.

Key Steps to Set Up Replication:

1. Prepare MySQL: Enable binary logging, set GTID mode, and create a replication user.
2. Choose ClickHouse Deployment: Options include self-managed, ClickHouse Cloud, or Tinybird.
3. Select a Replication Method:
   • MaterializedMySQL: Built-in ClickHouse feature for direct replication.
   • Debezium with Kafka: Flexible but complex setup for advanced use cases.
   • Maxwell’s Daemon: Lightweight and simple for smaller projects.
   • Tinybird: Managed solution for quick and low-maintenance integration.

Best Practices:

• Monitor replication lag and validate data consistency regularly.
• Allocate sufficient resources to prevent performance bottlenecks.
• Test schema changes in staging environments to avoid disruptions.

Hosting Options:

• Self-Managed ClickHouse: Full control but requires expertise.
• ClickHouse Cloud: Managed infrastructure with flexibility.
• Tinybird: Simplifies analytics with built-in APIs and managed scaling.

Your choice of tools and hosting depends on your team's expertise, operational needs, and scalability requirements.

Replicating data between transactional databases and ClickHouse®

Prerequisites and Environment Setup

To get started, you'll need to configure both your MySQL source and ClickHouse® destination based on your deployment choice: self-managed, ClickHouse Cloud, or Tinybird. Afterward, ensure your MySQL and ClickHouse® setups include the necessary configurations for smooth replication.

Configure MySQL for Replication

Your MySQL instance must be properly configured to support real-time replication using Change Data Capture (CDC). Here's what you'll need to do:

• Enable binary logging and set the format
  Add the following lines to your MySQL configuration file:

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  log-bin=mysql-bin  
  binlog_format=ROW  
  

• Set binlog retention period
  To allow time for troubleshooting or backfilling, specify a retention period:

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  expire_logs_days=7  
  

• Enable GTID mode
  Use Global Transaction Identifiers for more reliable replication:

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  gtid_mode=ON  
  enforce_gtid_consistency=ON  
  

• Set binlog_row_image to FULL
  Log complete row images for updates:

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  binlog_row_image=FULL  
  

• Assign a unique server ID
  Ensure your MySQL instance has a unique identifier:

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  server-id=1  
  

• Create a replication user
  Use the following SQL commands to create a dedicated user for replication:

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  CREATE USER 'replication_user'@'%' IDENTIFIED WITH mysql_native_password BY 'secure_password';  
  GRANT REPLICATION SLAVE, REPLICATION CLIENT, SELECT, RELOAD ON *.* TO 'replication_user'@'%';  
  FLUSH PRIVILEGES;  
  

• Set timezone to UTC
  Avoid potential data conversion issues by setting the default timezone:

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  default-time-zone='+00:00'  
  

Set Up the ClickHouse Environment

With MySQL ready for CDC, the next step is configuring ClickHouse® based on your chosen deployment.

• Self-managed ClickHouse®
  For a self-managed setup, you'll need to manually install ClickHouse® (version 21.8 or later), configure the network, set up storage, manage access controls, and plan for backups.

• ClickHouse Cloud
  This managed service simplifies infrastructure tasks. After creating a service through the ClickHouse Cloud console, configure network access and user credentials. The platform handles server provisioning, basic scaling, and monitoring.

• Tinybird
  Tinybird takes care of infrastructure complexities. Once you sign up and create a workspace, you can start ingesting data right away using APIs or connectors. The platform automatically manages ClickHouse® configurations, scaling, and maintenance.

Regardless of the deployment option, ensure your ClickHouse® environment is set up to accept connections from MySQL and any intermediary tools. Proper network connectivity and security configurations are essential to ensure reliable replication.

Prerequisites Comparison

The table below highlights the key differences among the three deployment options:

Each option comes with its own pros and cons. Self-managed ClickHouse® gives you full control but requires significant effort and expertise. ClickHouse Cloud strikes a balance by offering partial management, while Tinybird focuses on simplicity and quick deployment for developers.

Replication Methods and Tools

With your environment ready, the next step is deciding how to replicate data from MySQL to ClickHouse. The right method depends on your technical needs, team expertise, and infrastructure setup.

Change Data Capture (CDC) Basics

Change Data Capture (CDC) is the foundation of real-time replication between MySQL and ClickHouse. It works by monitoring MySQL's binary logs (binlogs) to track every insert, update, or delete operation. These changes are then parsed and converted into a format that ClickHouse can process.

CDC offers a major advantage over batch processing by delivering near real-time replication. This means analytics queries can run on data that's just seconds old, enabling scenarios like fraud detection, live dashboards, or personalized user experiences - all of which depend on up-to-date information.

Another benefit is reduced strain on your MySQL production database. Instead of running resource-intensive analytical queries directly on your transactional system, those queries can be executed on ClickHouse, which is designed for high-performance analytics.

Now that you understand how CDC works, let’s compare the tools available for implementing it.

Replication Tools Comparison

Each CDC tool comes with its own strengths and trade-offs. Here’s a breakdown of some popular options:

MaterializedMySQL Engine
This is ClickHouse’s built-in solution for MySQL replication. It creates a special database that syncs automatically with your MySQL source. It handles schema changes and data type conversions, all configured through SQL commands within ClickHouse. While it’s simple to set up, it requires close monitoring during high data loads and may struggle with complex schema changes.

Debezium with Kafka Connect
Debezium provides a robust solution by capturing changes from MySQL and publishing them to Kafka topics. With a Kafka Connect sink, these changes are written to ClickHouse. This setup offers excellent fault tolerance, scalability, and the option to transform data in transit. However, managing Kafka clusters, monitoring components, and configuring schema registries can add significant complexity - something teams with existing Kafka expertise are better equipped to handle.

Maxwell’s Daemon
For a lightweight option, Maxwell’s Daemon reads MySQL binlogs and outputs JSON messages to destinations like Kafka or HTTP endpoints. It’s simpler than a full Debezium setup but lacks features like advanced schema evolution and exactly-once delivery.

Tinybird’s Streaming Ingestion
Tinybird takes a managed approach, allowing you to stream MySQL changes directly to its platform via HTTP endpoints or Kafka connectors. This eliminates the need to maintain CDC tools or ClickHouse infrastructure yourself. Tinybird handles scaling, monitoring, and other operational tasks, making it a quick and low-maintenance option.

The best tool for your needs depends on your existing infrastructure and expertise. Teams with Kafka experience often lean toward Debezium for its flexibility, while those looking for a fast and low-maintenance solution might prefer Tinybird or the MaterializedMySQL engine for simpler use cases.

Step-by-Step Replication Setup

Here's how to set up real-time MySQL to ClickHouse® replication using either the MaterializedMySQL engine or Debezium with Kafka Connect. Both methods have their strengths, so choose based on your specific needs.

Set Up MaterializedMySQL Engine

The MaterializedMySQL engine offers a straightforward way to sync MySQL data with ClickHouse®. It creates a special database in ClickHouse® that stays synchronized with your MySQL source automatically.

To get started, create a MaterializedMySQL database by running this SQL command in ClickHouse®:

CREATE DATABASE mysql_replica 
ENGINE = MaterializedMySQL('mysql_host:3306', 'source_database', 'username', 'password')
SETTINGS 
    materialized_mysql_tables_list = 'users,orders,products',
    materialized_mysql_skip_unsupported_tables = 1;

Replace the placeholders (mysql_host, source_database, etc.) with your actual MySQL server details. Here's what the key settings do:

• materialized_mysql_tables_list: Specifies the tables to replicate.
• materialized_mysql_skip_unsupported_tables: Skips tables with unsupported data types, preventing replication failures.

If you're working with a large database, the initial sync can take hours. Check the progress using this query:

SELECT * FROM system.materialized_mysql_tables WHERE database = 'mysql_replica';

The engine automatically handles schema changes like adding new columns. However, changes like dropping columns or modifying primary keys may pause replication, requiring you to recreate the database.

Data type mapping happens automatically as well. For example, MySQL's JSON and ENUM types are converted to String in ClickHouse®. If you notice unexpected data formats, check the logs for details on these conversions.

Configure Debezium with Kafka Connect

For more flexibility and fault tolerance, you can use Debezium with Kafka Connect. This approach streams MySQL changes to ClickHouse® via Kafka, offering more control over the replication process.

Start by creating a JSON configuration file named mysql-source.json:

{
  "name": "mysql-source-connector",
  "config": {
    "connector.class": "io.debezium.connector.mysql.MySqlConnector",
    "database.hostname": "mysql_host",
    "database.port": "3306",
    "database.user": "debezium_user",
    "database.password": "debezium_password",
    "database.server.id": "184054",
    "database.server.name": "mysql_server",
    "database.include.list": "ecommerce",
    "table.include.list": "ecommerce.users,ecommerce.orders,ecommerce.products",
    "database.history.kafka.bootstrap.servers": "kafka:9092",
    "database.history.kafka.topic": "schema-changes.mysql"
  }
}

Deploy this source connector using the Kafka Connect REST API:

curl -X POST http://kafka-connect:8083/connectors \
  -H "Content-Type: application/json" \
  -d @mysql-source.json

Debezium creates Kafka topics for each table using the format mysql_server.database.table. Use tools like kafka-topics or kafka-console-consumer to verify that the topics are being created and populated.

Next, configure the ClickHouse® sink connector. Create a file called clickhouse-sink.json:

{
  "name": "clickhouse-sink-connector",
  "config": {
    "connector.class": "com.clickhouse.kafka.connect.ClickHouseSinkConnector",
    "tasks.max": "1",
    "topics": "mysql_server.ecommerce.users,mysql_server.ecommerce.orders",
    "clickhouse.server.url": "http://clickhouse:8123",
    "clickhouse.server.user": "default",
    "clickhouse.server.password": "",
    "clickhouse.server.database": "replicated_data",
    "clickhouse.table.name": "{topic}",
    "key.converter": "org.apache.kafka.connect.json.JsonConverter",
    "value.converter": "org.apache.kafka.connect.json.JsonConverter"
  }
}

Deploy the sink connector the same way:

curl -X POST http://kafka-connect:8083/connectors \
  -H "Content-Type: application/json" \
  -d @clickhouse-sink.json

Important: Unlike MaterializedMySQL, this method doesn't automatically create tables in ClickHouse®. You'll need to manually define the tables to match your MySQL schema. For example:

CREATE TABLE replicated_data.users (
    id UInt32,
    name String,
    email String,
    created_at DateTime
) ENGINE = MergeTree()
ORDER BY id;

Monitor and Handle Errors

Whether you use MaterializedMySQL or Debezium, consistent monitoring is key to ensuring smooth replication.

For MaterializedMySQL, use these queries to monitor status and identify issues:

-- Check replication status
SELECT * FROM system.materialized_mysql_tables 
WHERE database = 'mysql_replica';

-- Monitor replication lag
SELECT table, last_written_time, rows_written 
FROM system.materialized_mysql_tables 
WHERE database = 'mysql_replica';

Common issues include connection timeouts, unsupported schema changes, and disk space limitations. If replication stops, check the ClickHouse® logs for error details. Restarting the MaterializedMySQL database often resolves connection issues, while schema-related problems may require recreating the database.

For Debezium, monitor Kafka Connect and individual connectors using their status commands. You can also track Kafka consumer groups to ensure data is flowing correctly.

Data consistency checks are essential for both methods. Run periodic comparisons between MySQL and ClickHouse® to verify accuracy:

-- Compare row counts
SELECT 'mysql' as source, COUNT(*) as rows FROM mysql_replica.users
UNION ALL  
SELECT 'original' as source, COUNT(*) as rows FROM mysql('mysql_host:3306', 'source_db', 'users', 'user', 'password');

Set up alerts for replication lag. While most systems can handle a lag of 30–60 seconds, real-time dashboards may require sub-10-second delays. Also, keep an eye on disk usage in ClickHouse®, as frequent small inserts from replication can quickly consume storage.

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Managed Services Comparison: Tinybird vs ClickHouse Cloud vs Self-Managed ClickHouse®

Once you've set up replication, the next step is deciding how to host ClickHouse®. This choice is pivotal for keeping your real-time analytics running smoothly - a central focus of this guide. Your decision between self-managed ClickHouse®, ClickHouse Cloud, and Tinybird will influence your operational workload, development speed, and overall expenses. Let’s dig into how each option stacks up against common workload requirements.

What to Consider

When evaluating your hosting options, key factors include setup, performance, scalability, security, compliance, and pricing. Each platform handles these differently:

• Setup and Performance: Self-managed ClickHouse® gives you complete hardware control but requires you to configure servers and manage dependencies. ClickHouse Cloud simplifies this by handling infrastructure for you while delivering solid managed performance. Tinybird goes a step further, abstracting both infrastructure and database management while providing automatic optimization.

• Scalability: With a self-managed setup, you're responsible for capacity planning and cluster management. ClickHouse Cloud offers automatic scaling with some configuration flexibility, while Tinybird dynamically adjusts resources to match workload demands without manual intervention.

• Security and Compliance: Self-managed deployments let you tailor security settings but require expertise to implement them correctly. ClickHouse Cloud provides managed certificates, network isolation, and enterprise-grade security. Tinybird includes SOC2 Type II and HIPAA compliance out of the box, along with role-based access control (RBAC), requiring no extra setup.

• Pricing: Self-managed setups often have predictable infrastructure costs but may involve hidden operational expenses. ClickHouse Cloud uses a consumption-based pricing model that can fluctuate based on usage. Tinybird offers transparent, usage-based pricing, making it easier to project costs upfront.

Feature Comparison Table

When to Choose Tinybird

While the table offers a quick comparison, let’s unpack why Tinybird might be the right fit for certain scenarios. Tinybird shines in real-time analytics use cases, especially when powering dashboards, user-facing tools, or API-driven applications.

One standout feature is Tinybird’s CLI, which supports local development using the ClickHouse® engine. This allows developers to test queries and API endpoints before deploying them. By treating analytics as code, Tinybird integrates seamlessly with Git workflows, making analytics development feel like traditional software engineering.

Tinybird is particularly appealing to startups and scaling companies. It allows you to start small with basic plans and scale operations over time, transitioning to dedicated infrastructure as your needs grow. This gradual scaling contrasts with self-managed solutions, which often require significant upfront investments in hardware and expertise.

Another major benefit is speed. With Tinybird, you can skip the weeks typically spent on configuring replication, setting up monitoring tools, and building custom API layers. Instead, you can focus on your analytics logic while Tinybird takes care of optimization, scaling, and security.

For industries with strict compliance requirements, Tinybird’s built-in certifications like SOC2 and HIPAA can save significant time and effort during audits and regulatory checks. This eliminates the need for extensive compliance work, which is often necessary with self-managed infrastructure.

That said, Tinybird may not be the best option if you need complete control over hardware, have specific network requirements, or already have a team with deep ClickHouse® expertise. In such cases, a self-managed solution might make more sense. Similarly, ClickHouse Cloud is a strong choice for teams that want managed infrastructure while still maintaining flexibility to build custom application layers and APIs.

Ultimately, the decision isn’t just about where to host ClickHouse® - it’s about how much of the analytics stack you want to handle yourself versus relying on a managed solution. Tinybird offers a turnkey approach for teams prioritizing real-time analytics, while the other options provide more control at the cost of added complexity.

Best Practices and Key Points

Ensuring stable and efficient replication is essential for handling production workloads. Building on the replication setup you already have, these practices can help maintain long-term reliability.

Maintain Reliable Replication

To keep replication running smoothly, consider these key steps:

• Monitor replication lag: Use ClickHouse®'s system.replicated_fetches table to track lag, and set up alerts if it exceeds 30 seconds. Adjust this threshold based on your specific needs.
• Test schema changes carefully: Always validate schema updates in a staging environment. For large tables, use online schema-change tools. If you're using MaterializedMySQL, be aware that certain DDL operations may require manual adjustments to ensure consistency.
• Allocate sufficient resources: ClickHouse® should have 2–3× the storage capacity of your MySQL setup, along with enough RAM to prevent lag and timeouts. Keep an eye on CPU usage, especially during peak times - if it consistently exceeds 70%, it’s time to scale up.
• Automate recovery and maintain backups: Have a plan for automated recovery and keep recent backups of both MySQL binlogs and ClickHouse® data. This is particularly important to address issues like network outages, disk space shortages, or misconfigurations.

By taking these steps, you can proactively address potential replication challenges before they escalate.

Avoid Common Problems

Some issues can derail replication if not addressed early. Here’s how to sidestep common pitfalls:

• Don’t ignore replication lag spikes: Even occasional increases in lag might signal deeper problems, such as limited disk I/O, network bottlenecks, or poorly optimized ClickHouse® table structures. Investigate and resolve these quickly to avoid compounding issues.
• Stick to one replication method: Mixing replication methods can lead to conflicts and data inconsistencies. If you need to switch methods, plan a full migration instead of running systems in parallel.
• Handle data type mismatches carefully: MySQL’s flexible data types can cause problems when mapped to ClickHouse®, which has stricter type requirements. Pay close attention to timestamps, decimal precision, and nullable fields. Test edge cases thoroughly, especially with older MySQL schemas that might include unexpected data formats.
• Manage binlog expiration and disk usage: Set binlog_expire_logs_seconds to at least 604800 seconds (7 days) and monitor disk space to avoid running out of storage.

Final Recommendations

Here are some additional tips to help you succeed:

• Start simple and build gradually: Begin with basic replication for a small set of critical tables. Once you’ve confirmed the system’s reliability, expand its scope and add optimizations like custom partitioning or materialized views.
• Evaluate your team’s expertise: Running a self-managed ClickHouse® setup requires deep technical knowledge. If your team lacks experience, consider managed solutions like ClickHouse Cloud or Tinybird to reduce implementation time and operational risks.
• Factor in total cost of ownership: While self-managed setups might seem cost-effective upfront, they often involve significant long-term expenses for engineering, monitoring, maintenance, and troubleshooting. Weigh these costs against the benefits of managed services.
• Plan for scalability: Design your architecture to handle 3–5× your current data volume without major overhauls. This approach can save you from expensive and disruptive migrations later.

Ultimately, your choice between self-managed ClickHouse®, ClickHouse Cloud, and Tinybird depends on your team’s goals. Self-managed setups give you maximum control if you have the expertise. ClickHouse Cloud offers a balance of managed infrastructure and flexibility for development. Meanwhile, Tinybird is ideal for teams focused on speed to market and analytics rather than infrastructure management.

FAQs

What factors should I consider when deciding between self-managed ClickHouse®, ClickHouse Cloud, and Tinybird for real-time MySQL to ClickHouse® replication?

When choosing between self-managed ClickHouse®, ClickHouse Cloud, and Tinybird for real-time MySQL to ClickHouse® replication, it all boils down to how much control you need, how easy you want the process to be, and the resources your team can dedicate.

Self-managed ClickHouse® offers unmatched flexibility and customization. However, it demands a high level of expertise and ongoing maintenance, making it a better option for organizations with specialized engineering teams that can handle the workload.

On the other hand, ClickHouse Cloud streamlines the process by providing a managed solution. It’s perfect for teams that want top-notch performance but don’t want to deal with the hassle of managing infrastructure.

Then there's Tinybird, which takes simplicity to the next level. It eliminates infrastructure management entirely, catering to developers who need to rapidly build and scale real-time analytics APIs without diving into the nitty-gritty of database operations.

What is Change Data Capture (CDC), and how does it enable real-time data replication compared to batch processing?

What Is Change Data Capture (CDC)?

Change Data Capture (CDC) is a technique used to monitor and record changes - like inserts, updates, and deletions - in a database as they happen or very shortly afterward. By analyzing database logs or transaction streams, CDC identifies these changes and syncs them with target systems. This process helps maintain data consistency without unnecessary delays.

Unlike traditional batch processing, CDC focuses only on transferring the data that has been updated. This approach cuts down on network usage, speeds up updates for real-time analytics, and reduces the chances of relying on outdated information. It's especially useful for applications that demand quick insights or support operational decisions on the fly.

What challenges might arise when replicating MySQL data to ClickHouse® in real time, and how can you address them?

Replicating MySQL data to ClickHouse® in real time isn’t without its hurdles. You’ll need to ensure a steady and reliable data flow, handle updates and deletions without creating conflicts, and scale to accommodate large volumes of data. If these challenges aren’t managed properly, they can result in delays or even data loss.

To tackle these issues, tools like Debezium or mysql_ch_replicator can make a big difference. These high-performance change data capture (CDC) solutions are built to support efficient real-time replication. On the ClickHouse® side, using ReplacingMergeTree tables can simplify handling updates and maintaining data consistency. Beyond the tools, success also depends on having a well-configured setup, strong infrastructure, and ongoing monitoring to keep latency low and ensure your replication stays reliable.