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The ClickStack Open Source architecture is built around three core components: ClickHouse, ClickStack UI, and a OpenTelemetry (OTel) collector. A MongoDB instance provides storage for the application state. Together, they provide a high-performance, open-source observability stack optimized for logs, metrics, and traces.

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ClickHouse: the database engine

At the heart of ClickStack is ClickHouse, a column-oriented database designed for real-time analytics at scale. It powers the ingestion and querying of observability data, enabling:
  • Sub-second search across terabytes of events
  • Ingestion of billions of high-cardinality records per day
  • High compression rates of at least 10x on observability data
  • Native support for semi-structured JSON data, allowing dynamic schema evolution
  • A powerful SQL engine with hundreds of built-in analytical functions
ClickHouse handles observability data as wide events, allowing for deep correlation across logs, metrics, and traces in a single unified structure.

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OpenTelemetry collector: data ingestion

ClickStack includes a pre-configured OpenTelemetry (OTel) collector to ingest telemetry in an open, standardized way. You can send data using the OTLP protocol via:
  • gRPC (port 4317)
  • HTTP (port 4318)
The collector exports telemetry to ClickHouse in efficient batches. It supports optimized table schemas per data source, ensuring scalable performance across all signal types.

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ClickStack UI: the interface

ClickStack UI is the user interface for ClickStack. It offers:
  • Natural language and Lucene-style search
  • Live tailing for real-time debugging
  • Unified views of logs, metrics, and traces
  • Session replay for frontend observability
  • Dashboard creation and alert configuration
  • SQL query interface for advanced analysis
Designed specifically for ClickHouse, ClickStack UI combines powerful search with intuitive workflows, enabling you to spot anomalies, investigate issues, and gain insights fast.

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MongoDB: application state

ClickStack uses MongoDB to store application-level state, including:
  • Dashboards
  • Alerts
  • User profiles
  • Saved visualizations
This separation of state from event data ensures performance and scalability while simplifying backup and configuration. This modular architecture enables ClickStack to deliver an out-of-the-box observability platform that is fast, flexible, and open-source.