No more disks: the architecture behind stateless compute in ClickHouse Cloud

Tom Schreiber
21 min readintermediate
--
View Original

Overview

The article discusses the transition of ClickHouse Cloud to a fully stateless compute architecture, enabled by the introduction of a Shared Catalog. This architectural change eliminates local disk dependencies, allowing for faster, elastic, and resilient compute operations across various data formats.

What You'll Learn

1

How to implement stateless compute architecture in cloud environments

2

Why decoupling metadata from local storage improves scalability

3

How to utilize the Shared Catalog for enhanced DDL operations

Prerequisites & Requirements

  • Understanding of cloud-native architectures and distributed systems
  • Experience with ClickHouse or similar database systems(optional)

Key Questions Answered

What are the benefits of a stateless compute architecture in ClickHouse Cloud?
The stateless compute architecture in ClickHouse Cloud offers benefits such as faster provisioning, resilience in operations like DROP commands, and the ability to handle DDL operations with high concurrency. This architecture eliminates local disk dependencies, allowing compute nodes to spin up and down quickly without the need for syncing data.
How does the Shared Catalog improve DDL operations?
The Shared Catalog centralizes metadata management, enabling atomic DDL operations and resilient deletion processes. It allows for cloud-scale DDL coordination, ensuring consistent metadata state across nodes, which enhances performance and reliability during high concurrency scenarios.
What challenges does ClickHouse face with local disk dependencies?
Local disk dependencies in ClickHouse lead to issues such as slow scaling, manual orchestration for metadata setup, and fragile failure recovery. These challenges hinder the system's ability to efficiently manage compute resources in a cloud environment, necessitating a shift to a stateless architecture.

Technologies & Tools

Some links below are affiliate links. We may earn a commission if you make a purchase.

Database
Clickhouse
Used as the underlying database system for stateless compute architecture.
Backend
Keeper
Used for managing metadata and ensuring consistency across compute nodes.

Key Actionable Insights

1
Transitioning to a stateless compute architecture can significantly reduce operational overhead.
By eliminating local disk dependencies, organizations can streamline their cloud infrastructure, allowing for faster scaling and improved resource management.
2
Implementing a Shared Catalog can enhance DDL operations and metadata management.
This approach allows for atomic operations and better coordination across distributed systems, which is crucial for maintaining data integrity in high-concurrency environments.
3
Utilizing distributed caching mechanisms can greatly improve query performance.
By caching frequently accessed data across nodes, systems can reduce latency and improve responsiveness, especially in cloud-native applications.

Common Pitfalls

1
Failing to decouple metadata from local storage can lead to scalability issues.
When metadata is tightly coupled with local storage, it creates bottlenecks during scaling operations, making it difficult to manage resources efficiently in cloud environments.
2
Over-reliance on local caching can hinder performance in distributed systems.
Local caching may not be effective in a cloud-native architecture where compute nodes can change frequently, necessitating a more robust distributed caching solution.

Related Concepts

Cloud-native Architectures
Distributed Systems
Data Lake Integration
Metadata Management