ClickHouse Monitoring Overview
ClickHouse is a powerful column-oriented database optimized for real-time analytics and high-throughput data ingestion. UptimeDock provides comprehensive monitoring for your ClickHouse clusters, helping you maintain optimal performance and prevent issues before they impact your users.
What is ClickHouse Monitoring?
ClickHouse monitoring involves continuously tracking the health, performance, and resource utilization of your ClickHouse database instances. Unlike traditional OLTP databases, ClickHouse is designed for analytical workloads and has unique characteristics that require specialized monitoring approaches.
With UptimeDock's ClickHouse monitoring, you get:
- Real-time query performance tracking - Monitor query execution times, identify slow queries, and optimize your analytical workloads
- Memory utilization alerts - Get notified when memory usage exceeds thresholds to prevent out-of-memory errors
- Disk space monitoring - Track storage consumption and predict when you'll need to scale
- Cluster health visibility - Monitor replication status, partition health, and merge operations
Why Monitor ClickHouse?
ClickHouse's columnar architecture and append-only design make it incredibly fast for analytical queries, but also introduce unique challenges:
Unlike PostgreSQL or MySQL, ClickHouse handles updates and deletes differently. Data modifications are processed asynchronously through mutations, which can impact performance if not monitored properly.
Key reasons to monitor your ClickHouse instances:
- Prevent query timeouts - Long-running queries can consume significant resources and affect other operations
- Optimize merge operations - ClickHouse continuously merges data parts in the background; inefficient merges can cause performance degradation
- Manage disk space - Analytical databases often grow quickly; monitoring helps you plan capacity
- Ensure data integrity - Track replication lag and detect issues in distributed setups
- Control costs - Identify inefficient queries that consume excessive resources
Key Metrics to Monitor
UptimeDock tracks the following key metrics for your ClickHouse databases:
Query Performance
Query performance is critical for analytical workloads. We monitor:
- Query execution time - Average, P95, and P99 latency for your queries
- Queries per second (QPS) - Track query throughput over time
- Failed queries - Detect and alert on query errors
- CPU utilization per query - Identify resource-intensive queries
-- Example: Find slow queries in ClickHouse
SELECT
query_id,
query,
query_duration_ms,
read_rows,
read_bytes
FROM system.query_log
WHERE query_duration_ms > 1000
ORDER BY query_duration_ms DESC
LIMIT 10Set appropriate query timeout limits in your ClickHouse configuration. Long-running queries can block other operations and consume cluster resources.
Memory & Resources
ClickHouse can consume significant memory for complex queries. We track:
- Total memory usage - Current memory consumption across the cluster
- Memory per query - Identify queries that use excessive memory
- Background operations - Track memory used by merges and mutations
- Max memory threshold - Alert before hitting memory limits
| Metric | Warning Threshold | Critical Threshold |
|---|---|---|
| Memory Usage | 70% | 85% |
| Active Queries | 50 | 100 |
| Merge Operations | 20 | 50 |
Disk Space
Disk space monitoring is essential for capacity planning:
- Total disk usage - Track storage across all data directories
- Database sizes - Monitor growth per database
- Table sizes - Identify large tables that may need archiving
- Compression ratios - Track storage efficiency
- Part counts - Monitor for excessive parts that indicate merge issues
Running out of disk space can cause data loss and cluster instability. Configure alerts well before reaching capacity limits (recommended: alert at 80% usage).
Getting Started
Follow these guides to set up ClickHouse monitoring:
- Quick Setup Guide – Step-by-step instructions to create your first ClickHouse check
- Database Configuration – Required permissions and query logging setup
- Network Access & IP Whitelist – Configure firewall and whitelist UptimeDock IPs
Use read-only credentials for monitoring. UptimeDock only needs SELECT permissions on system tables to collect metrics. See Database Configuration for details.
Metrics & Monitoring
Learn how to analyze and optimize your ClickHouse database:
- Query Performance – Track query execution times, identify slow queries, analyze resource usage
- Memory & Resources – Monitor memory usage, set up alerts, prevent OOM errors
- Disk Space Management – Track storage by database and table, manage capacity