ClickHouse Server Logs In JSON Format

Can Sayin
Posted on February 10, 2023

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ClickHouse is a fast, open-source column-oriented database used to analyze large amounts of data. One of the key features of ClickHouse is its support for logging server activity in JSON format, which allows easy integration with other tools and systems.

By logging server activity in JSON format, ClickHouse provides a detailed and structured record of all server events, including queries, errors, and performance metrics. This information is valuable for understanding how the server performs and identifying any issues that need to be addressed.

In this article, we will discuss the benefits of using JSON format for logging server activity in ClickHouse and provide an example of how to set up and configure JSON logging.

Benefits of JSON Logging in ClickHouse

  1. Easy Integration with Other Tools: By logging server activity in JSON format, ClickHouse easily integrates with other tools and systems. This allows you to use the logs in a variety of ways, including analyzing performance, debugging issues, and monitoring activity.
  2. Structured Data: JSON format provides a structured way of storing data, which makes it easier to search and filter logs. This allows you to quickly find the information you need, even when dealing with large amounts of log data.
  3. Machine-Readable: JSON format is machine-readable, which means that logs can be easily processed by automated systems. This allows you to automate tasks such as log analysis and reporting.
  4. Human-Readable: While JSON format is machine-readable, it is also human-readable, making it easier for people to understand and interpret the logs. This can be useful for debugging issues and understanding the behavior of the server.

Configuring JSON Logging in ClickHouse

To configure JSON logging in ClickHouse, you will need to make changes to the server configuration file. The configuration file is usually located at /etc/clickhouse-server/config.xml on Linux systems.

To enable JSON logging, you will need to add the following lines to the configuration file:


In this example, the format the option is set to JSON, which tells ClickHouse to log server activity in JSON format. The path option specifies the location of the log file, which in this case, is /var/log/clickhouse/server.log.

After making these changes to the configuration file, you will need to restart the ClickHouse server for the changes to take effect.

Example JSON Log Entry

Here is an example of a JSON log entry from a ClickHouse server:

  "timestamp": "2022-11-28T08:43:20.000Z",
  "level": "info",
  "message": "Query completed",
  "query_id": "c0c7f000-c875-11eb-8f9c-0242ac120002",
  "query": "SELECT count(*) FROM web_traffic",
  "rows_read": 100000,
  "rows_written": 0,
  "time_elapsed": 0.123456

As a result, storing and processing the data in JSON format will facilitate your work in machine language. It will enable your employees who will work in JSON format to read and understand the file more quickly. This is just a small example of doing business in JSON format.