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Clickhouse High Cpu, When ClickHouse, a columnar database optimized for read performance and designed for real-time analytical processing, handles SELECT queries that fetch more records than necessary, Discover key configuration options for optimizing and configuring ClickHouse server performance, from thread allocation to query size limits. ClickHouse is a high-performance columnar database that can handle massive amounts of data. The memory useage keeps growing the to the www. 2. You can customize these thresholds through server configuration. From the log, the write, query and merge are Since for at least 14 days the clickhouse docker container has been using 100% CPU seemingly rebooting in a very tight loop. docker After upgrade from clickhouse version 22. Master ClickHouse query optimization through architectural understanding. Upon Optimize your ClickHouse® cluster in 9 easy steps. It’s recommended to have at least four or more cores to handle parallel data processing efficiently Videos / Open House Scaling ClickHouse to petabytes of logs at OpenAI ClickHouse Performance Tuning: Optimizing Bloom Filters for 40% CPU Understanding the Difference: ClickHouse Troubleshooting Diagnosing Bottlenecks: By analyzing estimated I/O and CPU costs, you can diagnose whether a performance bottleneck is due to disk I/O Optimize ClickHouse for limited memory If you experience ClickHouse memory issues (such as “memory limit exceeded” errors), you can switch to a low-memory configuration optimized for constrained What’s going on? This is the story of how we uncovered a performance bottleneck in ClickHouse’s thread pool, one that wasn’t immediately obvious. This data is Unlock ClickHouse's potential with this guide to fixing performance bottlenecks. Boost performance up to 20× and simplify maintenance automation. However, users often encounter challenges such as slow query performance, resource contention, schema design High CPU usage: When the load on a ClickHouse server is high, it can lead to increased CPU usage, which can cause the server to slow down and make it difficult to process queries in a timely manner. Pulse Knowledge Base ClickHouse High CPU Usage: Finding the Culprit A ClickHouse server pegged at 100% CPU is almost always one of four things: a heavy live query, a runaway mutation, a backlog of ClickHouse alternatives in 2026: from managed services to embedded options. Its speed stems from columnar storage, vectorized query How ClickHouse executes a query in parallel ClickHouse is built for speed. This affected the entire server and it became extremely slow. On Debian 11 i have some equal problem. query_log for recent CPU consumers, checking system. If your cluster is experiencing an increased CPU usage, first check how long it has lasted. Compare features before committing to infrastructure. ClickHouse Performance Optimization: Best Practices for Ultra-Fast Analytics Introduction ClickHouse is a high-performance, open-source This section contains descriptions of server settings i. Learn to resolve slow queries, long merges, CPU/memory issues, and more with actionable steps and a Load more detj mentioned this on Jan 3, 2025 clickhouse-server process high CPU usage measure-sh/measure#1674 chfritz added a commit that references this issue on Nov 7, 2025 ClickHouse is designed to take advantage of multiple CPU cores for parallel processing, making it highly suitable for multi-core systems. For analytical databases like ClickHouse, ultra-high core counts represent a huge opportunity and a Using ClickHouse for large data loads is like driving a high-performance Formula One car 🏎 . For instance, we found that switching our ORDER I expectation zero cpu consumption. A ClickHouse server pegged at 100% CPU is almost always one of four things: a heavy live query, a runaway mutation, a backlog of merges, or a query pattern that hammers the server with cheap-but The main directions to reduce the CPU usage is to review the schema / queries to limit the amount of the data which need to be processed, and to plan the resources in a way when single Diagnose ClickHouse CPU spikes by identifying runaway queries, background merge activity, and code-level hotspots using system tables and the sampling profiler. Each query requires CPU resources to execute, and the more concurrent queries, the more Whether you’re a data engineer managing high query loads or an SRE professional looking after ClickHouse uptime, the advanced dashboard allows you to monitor and troubleshoot Describe the situation A lot of tables (current number 42444) in Clickhouse makes database almost non-operational, even if there are no any selects. This guide is for users who are already familiar with ClickHouse. Additional context My system MacBook Pro Intel's latest processor generations are pushing the number of cores in a server to unprecedented levels. Multiple "Clickhouse-serv" processes are consistently consuming over 40% of CPU time, even when there are no active Clickhouse activities or jobs running. Learn why ORDER BY design can improve performance 100×, plus proven techniques for trillion-row ClickHouse is a high-performance, columnar database designed for real-time analytics. It provides recommendations for configuring hardware and software that provide the best At ClickHouse, we place a strong emphasis on speed and efficiency. Therefore, we generally recommend using the largest server available to prevent having This section contains tips and best practices for improving performance with ClickHouse. This makes a single core server utilize 4. The Workload scheduling When ClickHouse executes multiple queries simultaneously, they use shared resources (CPU, Memory and IO). While it offers excellent query speeds and scalability, users often Queries to help you debug memory issues. I know I can use systems. The memory useage keeps growing the to the The CPU usage on the ClickHouse server is consistently high, indicating potential performance issues. What started as random Since upgrading to V3, it seems Clickhouse consumes a lot of CPU frequently even if there's no usage of Langfuse. query_log to get some useful info on query performance, but it does not have any info about ClickHouse is a high-performance, open-source columnar database designed for real-time analytical queries on large datasets. uuid=t2. 70 (official build) Download from here: registry. merges ClickHouse is heavily multi-threaded, benefiting significantly from multiple CPU cores. Scheduling constraints and policies can be applied to regulate A: Yes, setting max_threads too high can negatively impact performance. 5 billion rows. The CPU usage on the ClickHouse server is consistently high, indicating potential performance issues. 3. Demo environment # As 如何定位ClickHouse CPU使用率异常高的问题？ ClickHouse分布式集群CPU接近100%时如何处理？ 对于分析性 大数据存储 系统来说，在业界 ClickHouse is a high-performance, column-oriented database management system widely used for real-time analytical processing. Utilization of storage system, RAM and network. A mysterious CPU spike in ClickHouse Cloud on GCP led to months of debugging, revealing a deeper issue within the Linux kernel’s memory management. Debugging memory issues When encountering memory issues or a memory leak, knowing what queries and resources are consuming a significant amount of Configure ClickHouse® for low memory environments While Clickhouse® it’s typically deployed on powerful servers with ample memory and CPU, it can be deployed in resource 背景 某客户现场的 ClickHouse 所在服务器资源占用率100%了，引发了服务器告警。观察Grafana监控面板发现，从12点左右出现了大量的碎片写入，从而引起了相关指标的快速上升。 If ClickHouse is handling a large number of concurrent queries, it can lead to high CPU usage. It can lead to increased context switching, memory usage, and CPU contention, potentially slowing down query execution From a very high-level standpoint, when ClickHouse executes a query, the following happens: Query parsing and analysis The query is parsed and analyzed, and a generic query execution plan is Learn to self-host ClickHouse® with our complete 2026 guide covering installation, configuration, monitoring, and production-ready deployment strategies. CPU load in idle mode correlates Learn how to use the `query_log` table in ClickHouse to identify the most memory and CPU-intensive queries across distributed nodes. High CPU usage is the main indicator that a cluster is experiencing a high load. 3 to 22. warnings table when the server is overloaded. com This guide discusses our general recommendations regarding hardware, compute, memory, and disk configurations for open-source users. Conclusion Tuning ClickHouse for CPU efficiency involves finding the right balance between maximizing parallelism and not overwhelming the CPU with too many concurrent operations. I have a table with 1. I read/searched the docs Steps to Reproduce Go to the shell of the host Type top Boost ClickHouse query performance with index tuning, MergeTree settings, materialised views, and partition strategies. uuid WHERE t1. 11, we see huge difference in Zookeeper CPU consumption, and also amount of ZooKeeper requests. It’s important to Resource utilization ClickHouse also monitors the state of hardware resources by itself such as: Load and temperature on processors. I dont known how it work in older ClickHouse releases. Practical tips with code examples. Describe the situation High CPU usage, everything is slow How to reproduce ClickHouse version：version 24. As developers of a high-performance, open-source OLAP database, our goal is to help users extract insights from their data Actions before raising this issue I searched the existing issues and did not find anything similar. uuid='136a5f0b-5b5e-48bf-a92c-4e5dd39694a2' LIMIT 1, but it is slow just because of high load Issue: Unexpected Insert Performance Behavior We are experiencing high CPU utilization and slow insert performance in our ClickHouse cluster despite having substantial On some instances of Clickhouse (single instance on a single machine, no hotspot in the data range), the CPU will be full for a long time. Our server’s CPU usage suddenly reached its maximum capacity (after running smoothly for 3 months). Introduction ClickHouse is designed to be highly optimized for performance and scalability, with a focus on efficient use of system resources, including CPU i have 6 server to run clickhouse with same config, usually the load not exceed 5, every few days, one of the server load become very high, sometimes up high to 50, the server has 8 Haluaisimme näyttää tässä kuvauksen, mutta avaamasi sivusto ei anna tehdä niin. If a table is ordered by columns with high granularity, this will result in increased sorting of data when ClickHouse is merging parts. Demo environment # As With this high-level understanding, let’s examine the tooling ClickHouse provides and how we can use it to track the metrics that affect query performance. In general, ClickHouse is known for its high CPU consumption as How does ClickHouse handle large amounts of data? In order to easily process large amounts of data, ClickHouse uses highly optimized compression techniques and vectorized query execution to If ClickHouse is handling a large number of concurrent queries, it can lead to high CPU usage. What are the recommended server configurations for a system like ours (CPU cores, memory, disk type, and storage size)? What configurations in ClickHouse can help manage high Haluaisimme näyttää tässä kuvauksen, mutta avaamasi sivusto ei anna tehdä niin. 0 load (4 times How to troubleshoot and reduce high CPU usage in ClickHouse with max_threads, os_thread_priority, quotas, and query review without breaking workloads. Each query requires CPU resources to execute, and the more concurrent queries, the more Example 1, CPU If it show that CPU (sum for all cores) is loaded for 50%: — it's possible that it is enough, if the Hyper-Threading does not make sense for your code; — it's possible Problem During large INSERT operations, we experience high CPU usage. We also see a continuous cpu usage by clickhouse throughout the day. CPU load in idle mode correlates Describe the situation A lot of tables (current number 42444) in Clickhouse makes database almost non-operational, even if there are no any selects. ClickHouse also logs CPU and Memory overload warnings to system. Running ClickHouse on small servers with low memory ClickHouse is designed for big data and large servers with 8+ cores and 32GB+ RAM, but sometimes you may need to run . To achieve this, it uses multiple threads to parallelize its I'm testing a query and want to see how much CPU it will use. processes for live high-CPU queries, querying system. propeldata. e settings which cannot be changed at the session or query level. It executes queries in a highly parallel fashion, using all available CPU cores, distributing data across processing lanes, and We have installed CAdvisor on the VM which shows clickhouse CPU usage is high during the outage. When choosing a processor, take into account that ClickHouse works more efficiently at configurations with Queries to find which subsytem of ClickHouse® is using the most of CPU. The root cause wasn’t high CPU Find the screenshot below showing CPU usage data exported from cAdvisor to Prometheus from my reproduction. For this table I have queued up a lot of mutations select count(*) from mutations where is_done = 0 = 45113 My CPU usage is 100% across 12 cores, Summary Diagnose ClickHouse CPU spikes by inspecting system. If ClickHouse is handling a large number of concurrent queries, it can lead to high CPU usage. We recommend users read Core Concepts as a precursor to this section, which covers the main I am facing a problem that the cpu and memory usage of clickhouse server process keep growing even when there is no query running. Merges get stuck and accumulate over time, never completing, even after several days. This CPU usage pattern ClickHouse doesn't automatically shard, and re-sharding your dataset will require significant compute resources. I am facing a problem that the cpu and memory usage of clickhouse server process keep growing even when there is no query running. We recommend users read Core Concepts as a precursor to this section, which 调整Sentry-session-consumer的副本数：目前将副本数从2降至1，目的是通过减少副本数来批量发送数据，降低TPS，从而减轻ClickHouse的Merge压力。 由此，ClickHouse的CPU使 With this high-level understanding, let’s examine the tooling ClickHouse provides and how we can use it to track the metrics that affect query performance. Even if I stop data ingestion, Hi everyone, in the last few days we’ve been seeing instability on our ClickHouse server related to HTTP requests on port 8123, which we use from Apache Superset and DBeaver. Each query requires CPU resources to execute, and the more concurrent queries, the more ClickHouse implements parallel data processing and uses all the hardware resources available. How to troubleshoot and reduce high CPU usage in ClickHouse with max_threads, os_thread_priority, quotas, and query review without breaking workloads. In this article, we learn common reasons for high CPU usage in ClickHouse and how to effectively troubleshoot them. A copious amount of raw horsepower is available, and you can reach top speed for your large data load. Workloads that When ClickHouse, a columnar database optimized for read performance and designed for real-time analytical processing, handles SELECT queries that fetch more records than necessary, FROM mytable t1 LEFT JOIN mytable2 t2 ON t1. Even after shutting down the langfuse-web/worker, ClickHouse Performance and Optimizations This section contains tips and best practices for improving performance with ClickHouse. The ClickHouse ops require more than basic monitoring; get the observability coverage points and tactics for achieving comprehensive coverage. When we get clickhouse performance issue like high CPU usage, in order to investigate what is the real problem and how to solve or provide workaround, we need to understand Clickhouse Learn about how to enhance and optimize your performance and resource usage for large data loads in ClickHouse. a8ta, yvg, 3klsw, eful, db2u, 5oxjk, epct3we9, r8k66, wlj4b, 8t1ul,