How to Implement Reserved Connections in ClickHouse

Reserved connections in ClickHouse can be used to improve query performance by reserving a portion of the available connections for specific users or use cases. By reserving connections, you can ensure that high-priority queries have access to the resources they need, even during periods of high load.

Implementing Reserved Connections in ClickHouse

To implement reserved connections in ClickHouse, you can use the MaxConnections setting, which controls the maximum number of connections that can be established to the server. Here are the steps to implement reserved connections in ClickHouse:

  1. Determine the maximum number of connections required for each user or use case: Before you can reserve connections, you need to determine the maximum number of connections required for each user or use case. This will depend on the workload and the resources available on the server.
  2. Configure MaxConnections for each user or use case: Once you have determined the maximum number of connections required for each user or use case, you can configure MaxConnections in the ClickHouse server configuration file. For example, you can set MaxConnections=5000 for all users, and then set MaxConnections=1000 for a specific user or use case.
  3. Monitor connection usage: After implementing reserved connections, you should monitor connection usage to ensure that the reserved connections are being used as expected. ClickHouse provides several monitoring tools, including system tables and metrics, which can be used to track connection usage and identify any issues.

Conclusion

By implementing reserved connections in ClickHouse, you can ensure that high-priority queries have access to the resources they need, even during periods of high load. However, it is important to carefully consider the maximum number of connections required for each user or use case, as reserving too many connections can limit the overall performance of the server.

To read more about query performance in ClickHouse, do consider reading the following articles:

About Shiv Iyer 222 Articles
Open Source Database Systems Engineer with a deep understanding of Optimizer Internals, Performance Engineering, Scalability and Data SRE. Shiv currently is the Founder, Investor, Board Member and CEO of multiple Database Systems Infrastructure Operations companies in the Transaction Processing Computing and ColumnStores ecosystem. He is also a frequent speaker in open source software conferences globally.