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# ClickHouse


<img src="https://netdata.cloud/img/clickhouse.svg" width="150"/>


Plugin: go.d.plugin
Module: clickhouse

<img src="https://img.shields.io/badge/maintained%20by-Netdata-%2300ab44" />

## Overview

This collector retrieves performance data from ClickHouse for connections, queries, resources, replication, IO, and data operations (inserts, selects, merges) using HTTP requests and ClickHouse system tables. It monitors your ClickHouse server's health and activity.


It sends HTTP requests to the ClickHouse [HTTP interface](https://clickhouse.com/docs/en/interfaces/http), executing SELECT queries to retrieve data from various system tables.
Specifically, it collects metrics from the following tables:

- system.metrics
- system.async_metrics
- system.events
- system.disks
- system.parts
- system.processes


This collector is supported on all platforms.

This collector supports collecting metrics from multiple instances of this integration, including remote instances.


### Default Behavior

#### Auto-Detection

By default, it detects ClickHouse instances running on localhost that are listening on port 8123.
On startup, it tries to collect metrics from:

- http://127.0.0.1:8123


#### Limits

The default configuration for this integration does not impose any limits on data collection.

#### Performance Impact

The default configuration for this integration is not expected to impose a significant performance impact on the system.

## Setup


You can configure the **clickhouse** collector in two ways:

| Method                | Best for                                                                                 | How to                                                                                                                                 |
|-----------------------|------------------------------------------------------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------|
| [**UI**](#via-ui)     | Fast setup without editing files                                                         | Go to **Nodes → Configure this node → Collectors → Jobs**, search for **clickhouse**, then click **+** to add a job. |
| [**File**](#via-file) | If you prefer configuring via file, or need to automate deployments (e.g., with Ansible) | Edit `go.d/clickhouse.conf` and add a job.                                                                        |

:::important

UI configuration requires paid Netdata Cloud plan.

:::


### Prerequisites

No action required.

### Configuration

#### Options

The following options can be defined globally: update_every, autodetection_retry.


<details open><summary>Config options</summary>



| Group | Option | Description | Default | Required |
|:------|:-----|:------------|:--------|:---------:|
| **Collection** | update_every | Data collection interval (seconds). | 1 | no |
|  | autodetection_retry | Autodetection retry interval (seconds). Set 0 to disable. | 0 | no |
| **Target** | url | Target endpoint URL. | http://127.0.0.1:8123 | yes |
|  | timeout | HTTP request timeout (seconds). | 1 | no |
| **HTTP Auth** | username | Username for Basic HTTP authentication. |  | no |
|  | password | Password for Basic HTTP authentication. |  | no |
|  | bearer_token_file | Path to a file containing a bearer token (used for `Authorization: Bearer`). |  | no |
| **TLS** | tls_skip_verify | Skip TLS certificate and hostname verification (insecure). | no | no |
|  | tls_ca | Path to CA bundle used to validate the server certificate. |  | no |
|  | tls_cert | Path to client TLS certificate (for mTLS). |  | no |
|  | tls_key | Path to client TLS private key (for mTLS). |  | no |
| **Proxy** | proxy_url | HTTP proxy URL. |  | no |
|  | proxy_username | Username for proxy Basic HTTP authentication. |  | no |
|  | proxy_password | Password for proxy Basic HTTP authentication. |  | no |
| **Request** | method | HTTP method to use. | GET | no |
|  | body | Request body (e.g., for POST/PUT). |  | no |
|  | headers | Additional HTTP headers (one per line as key: value). |  | no |
|  | not_follow_redirects | Do not follow HTTP redirects. | no | no |
|  | force_http2 | Force HTTP/2 (including h2c over TCP). | no | no |
| **Functions** | functions.top_queries.disabled | Disable the [top-queries](#top-queries) function. | no | no |
|  | functions.top_queries.timeout | Query timeout (seconds). Uses collector timeout if not set. |  | no |
|  | functions.top_queries.limit | Maximum number of queries to return. | 500 | no |
| **Virtual Node** | vnode | Associates this data collection job with a [Virtual Node](https://learn.netdata.cloud/docs/netdata-agent/configuration/organize-systems-metrics-and-alerts#virtual-nodes). |  | no |


</details>


#### via UI

Configure the **clickhouse** collector from the Netdata web interface:

1. Go to **Nodes**.
2. Select the node **where you want the clickhouse data-collection job to run** and click the :gear: (**Configure this node**). That node will run the data collection.
3. The **Collectors → Jobs** view opens by default.
4. In the Search box, type _clickhouse_ (or scroll the list) to locate the **clickhouse** collector.
5. Click the **+** next to the **clickhouse** collector to add a new job.
6. Fill in the job fields, then click **Test** to verify the configuration and **Submit** to save.
    - **Test** runs the job with the provided settings and shows whether data can be collected.
    - If it fails, an error message appears with details (for example, connection refused, timeout, or command execution errors), so you can adjust and retest.


#### via File

The configuration file name for this integration is `go.d/clickhouse.conf`.

The file format is YAML. Generally, the structure is:

```yaml
update_every: 1
autodetection_retry: 0
jobs:
  - name: some_name1
  - name: some_name2
```
You can edit the configuration file using the [`edit-config`](https://github.com/netdata/netdata/blob/master/docs/netdata-agent/configuration/README.md#edit-configuration-files) script from the
Netdata [config directory](https://github.com/netdata/netdata/blob/master/docs/netdata-agent/configuration/README.md#locate-your-config-directory).

```bash
cd /etc/netdata 2>/dev/null || cd /opt/netdata/etc/netdata
sudo ./edit-config go.d/clickhouse.conf
```

##### Examples

###### Basic

A basic example configuration.

```yaml
jobs:
  - name: local
    url: http://127.0.0.1:8123

```
###### HTTP authentication

Basic HTTP authentication.

<details open><summary>Config</summary>

```yaml
jobs:
  - name: local
    url: http://127.0.0.1:8123
    username: username
    password: password

```
</details>

###### HTTPS with self-signed certificate

ClickHouse with enabled HTTPS and self-signed certificate.

<details open><summary>Config</summary>

```yaml
jobs:
  - name: local
    url: https://127.0.0.1:8123
    tls_skip_verify: yes

```
</details>

###### Multi-instance

> **Note**: When you define multiple jobs, their names must be unique.

Collecting metrics from local and remote instances.


<details open><summary>Config</summary>

```yaml
jobs:
  - name: local
    url: http://127.0.0.1:8123

  - name: remote
    url: http://192.0.2.1:8123

```
</details>



## Alerts


The following alerts are available:

| Alert name  | On metric | Description |
|:------------|:----------|:------------|
| [ clickhouse_restarted ](https://github.com/netdata/netdata/blob/master/src/health/health.d/clickhouse.conf) | clickhouse.uptime | ClickHouse has recently been restarted |
| [ clickhouse_queries_preempted ](https://github.com/netdata/netdata/blob/master/src/health/health.d/clickhouse.conf) | clickhouse.queries_preempted | ClickHouse has queries that are stopped and waiting due to priority setting |
| [ clickhouse_long_running_query ](https://github.com/netdata/netdata/blob/master/src/health/health.d/clickhouse.conf) | clickhouse.longest_running_query_time | ClickHouse has a long-running query exceeding the threshold |
| [ clickhouse_rejected_inserts ](https://github.com/netdata/netdata/blob/master/src/health/health.d/clickhouse.conf) | clickhouse.rejected_inserts | ClickHouse has INSERT queries that are rejected due to high number of active data parts for partition in a MergeTree |
| [ clickhouse_delayed_inserts ](https://github.com/netdata/netdata/blob/master/src/health/health.d/clickhouse.conf) | clickhouse.delayed_inserts | ClickHouse has INSERT queries that are throttled due to high number of active data parts for partition in a MergeTree |
| [ clickhouse_replication_lag ](https://github.com/netdata/netdata/blob/master/src/health/health.d/clickhouse.conf) | clickhouse.replicas_max_absolute_delay | ClickHouse is experiencing replication lag greater than 5 minutes |
| [ clickhouse_replicated_readonly_tables ](https://github.com/netdata/netdata/blob/master/src/health/health.d/clickhouse.conf) | clickhouse.replicated_readonly_tables | ClickHouse has replicated tables in readonly state due to ZooKeeper session loss/startup without ZooKeeper configured |
| [ clickhouse_max_part_count_for_partition ](https://github.com/netdata/netdata/blob/master/src/health/health.d/clickhouse.conf) | clickhouse.max_part_count_for_partition | ClickHouse high number of parts per partition |
| [ clickhouse_distributed_connections_failures ](https://github.com/netdata/netdata/blob/master/src/health/health.d/clickhouse.conf) | clickhouse.distributed_connections_fail_exhausted_retries | ClickHouse has failed distributed connections after exhausting all retry attempts |
| [ clickhouse_distributed_files_to_insert ](https://github.com/netdata/netdata/blob/master/src/health/health.d/clickhouse.conf) | clickhouse.distributed_files_to_insert | ClickHouse high number of pending files to process for asynchronous insertion into Distributed tables |


## Metrics

Metrics grouped by *scope*.

The scope defines the instance that the metric belongs to. An instance is uniquely identified by a set of labels.



### Per ClickHouse instance

These metrics refer to the entire monitored application.

This scope has no labels.

Metrics:

| Metric | Dimensions | Unit |
|:------|:----------|:----|
| clickhouse.connections | tcp, http, mysql, postgresql, interserver | connections |
| clickhouse.slow_reads | slow | reads/s |
| clickhouse.read_backoff | read_backoff | events/s |
| clickhouse.memory_usage | used | bytes |
| clickhouse.running_queries | running | queries |
| clickhouse.queries_preempted | preempted | queries |
| clickhouse.queries | successful, failed | queries/s |
| clickhouse.select_queries | successful, failed | selects/s |
| clickhouse.insert_queries | successful, failed | inserts/s |
| clickhouse.queries_memory_limit_exceeded | mem_limit_exceeded | queries/s |
| clickhouse.longest_running_query_time | longest_query_time | seconds |
| clickhouse.queries_latency | queries_time | microseconds |
| clickhouse.select_queries_latency | selects_time | microseconds |
| clickhouse.insert_queries_latency | inserts_time | microseconds |
| clickhouse.io | reads, writes | bytes/s |
| clickhouse.iops | reads, writes | ops/s |
| clickhouse.io_errors | read, write | errors/s |
| clickhouse.io_seeks | lseek | ops/s |
| clickhouse.io_file_opens | file_open | ops/s |
| clickhouse.replicated_parts_current_activity | fetch, send, check | parts |
| clickhouse.replicas_max_absolute_dela | replication_delay | seconds |
| clickhouse.replicated_readonly_tables | read_only | tables |
| clickhouse.replicated_data_loss | data_loss | events |
| clickhouse.replicated_part_fetches | successful, failed | fetches/s |
| clickhouse.inserted_rows | inserted | rows/s |
| clickhouse.inserted_bytes | inserted | bytes/s |
| clickhouse.rejected_inserts | rejected | inserts/s |
| clickhouse.delayed_inserts | delayed | inserts/s |
| clickhouse.delayed_inserts_throttle_time | delayed_inserts_throttle_time | milliseconds |
| clickhouse.selected_bytes | selected | bytes/s |
| clickhouse.selected_rows | selected | rows/s |
| clickhouse.selected_parts | selected | parts/s |
| clickhouse.selected_ranges | selected | ranges/s |
| clickhouse.selected_marks | selected | marks/s |
| clickhouse.merges | merge | ops/s |
| clickhouse.merges_latency | merges_time | milliseconds |
| clickhouse.merged_uncompressed_bytes | merged_uncompressed | bytes/s |
| clickhouse.merged_rows | merged | rows/s |
| clickhouse.merge_tree_data_writer_inserted_rows | inserted | rows/s |
| clickhouse.merge_tree_data_writer_uncompressed_bytes | inserted | bytes/s |
| clickhouse.merge_tree_data_writer_compressed_bytes | written | bytes/s |
| clickhouse.uncompressed_cache_requests | hits, misses | requests/s |
| clickhouse.mark_cache_requests | hits, misses | requests/s |
| clickhouse.max_part_count_for_partition | max_parts_partition | parts |
| clickhouse.parts_count | temporary, pre_active, active, deleting, delete_on_destroy, outdated, wide, compact | parts |
| distributed_connections | active | connections |
| distributed_connections_attempts | connection | attempts/s |
| distributed_connections_fail_retries | connection_retry | fails/s |
| distributed_connections_fail_exhausted_retries | connection_retry_exhausted | fails/s |
| distributed_files_to_insert | pending_insertions | files |
| distributed_rejected_inserts | rejected | inserts/s |
| distributed_delayed_inserts | delayed | inserts/s |
| distributed_delayed_inserts_latency | delayed_time | milliseconds |
| distributed_sync_insertion_timeout_exceeded | sync_insertion | timeouts/s |
| distributed_async_insertions_failures | async_insertions | failures/s |
| clickhouse.uptime | uptime | seconds |

### Per disk

These metrics refer to the Disk.

Labels:

| Label      | Description     |
|:-----------|:----------------|
| disk_name | Name of the disk as defined in the [server configuration](https://clickhouse.com/docs/en/engines/table-engines/mergetree-family/mergetree#table_engine-mergetree-multiple-volumes_configure). |

Metrics:

| Metric | Dimensions | Unit |
|:------|:----------|:----|
| clickhouse.disk_space_usage | free, used | bytes |

### Per table

These metrics refer to the Database Table.

Labels:

| Label      | Description     |
|:-----------|:----------------|
| database | Name of the database. |
| table | Name of the table. |

Metrics:

| Metric | Dimensions | Unit |
|:------|:----------|:----|
| clickhouse.database_table_size | size | bytes |
| clickhouse.database_table_parts | parts | parts |
| clickhouse.database_table_rows | rows | rows |



## Live Data

This collector exposes real-time functions for interactive troubleshooting in the Live tab.


### Top Queries

Retrieves and aggregates SQL query performance metrics from ClickHouse [system.query_log](https://clickhouse.com/docs/en/operations/system-tables/query_log) table.

This function queries the `system.query_log` table, which contains information about executed queries including timing, resource usage, and execution statistics. Queries are grouped by their normalized hash (`normalized_query_hash`) to aggregate statistics for identical query patterns with different literal values.

Use cases:
- Identify slow queries that consume the most execution time
- Find frequently executed queries that may benefit from optimization
- Analyze I/O patterns by examining read/written rows and bytes

Query text is truncated at 4096 characters for display purposes.


| Aspect | Description |
|:-------|:------------|
| Name | `Clickhouse:top-queries` |
| Require Cloud | yes |
| Performance | Queries `system.query_log` table and aggregates by `normalized_query_hash`:<br/>• On busy systems with high query throughput, the table can grow large<br/>• Default limit of 500 rows balances usefulness with performance |
| Security | Query text may contain unmasked literal values including potentially sensitive data:<br/>• Personal information in query parameters<br/>• Business data and internal identifiers<br/>• Access should be restricted to authorized personnel only |
| Availability | Available when:<br/>• The collector has successfully connected to ClickHouse<br/>• `system.query_log` table is accessible<br/>• Returns HTTP 503 if `system.query_log` is not accessible<br/>• Returns HTTP 500 if the query fails<br/>• Returns HTTP 504 if the query times out |

#### Prerequisites

##### Grant access to `system.query_log`

Ensure the Netdata user can read `system.query_log` on the target ClickHouse instance.

1. Verify `query_log` is enabled (enabled by default):

   ```sql
   SELECT * FROM system.query_log LIMIT 1;
   ```

2. If using a dedicated monitoring user, grant SELECT access:

   ```sql
   GRANT SELECT ON system.query_log TO netdata_user;
   ```

:::info

- The `query_log` table is enabled by default in ClickHouse
- Only queries with `type='QueryFinish'` are included in the results
- The `normalized_query_hash` column is used for grouping when available

:::



#### Parameters

| Parameter | Type | Description | Required | Default | Options |
|:---------|:-----|:------------|:--------:|:--------|:--------|
| Filter By | select | Select the primary sort column. The available options include total execution time, number of calls, rows read, and more. Defaults to total execution time to focus on most resource-intensive queries. | yes | totalTime |  |

#### Returns

Aggregated query statistics from `system.query_log`, grouped by normalized query hash. Each row represents a unique query pattern with cumulative metrics across all executions.

| Column | Type | Unit | Visibility | Description |
|:-------|:-----|:-----|:-----------|:------------|
| Query ID | string |  | hidden | Unique hash identifier for the normalized query pattern. Queries with identical structure but different literal values share the same hash. |
| Query | string |  |  | SQL query text from one of the executions. Truncated to 4096 characters. Use this to identify the actual SQL being executed. |
| Database | string |  |  | Database name where the query was executed. Empty string for queries without a database context or system queries. |
| User | string |  |  | ClickHouse user that executed the query. Useful for identifying query sources and implementing per-user resource monitoring. |
| Calls | integer |  |  | Total number of times this query pattern has been executed. High values indicate frequently run queries that impact overall server load. |
| Total Time | duration | milliseconds |  | Cumulative execution time across all executions. High values indicate queries that consume significant server resources over time. |
| Avg Time | duration | milliseconds |  | Average execution time per query run. Use this to compare typical performance across different query patterns. |
| Min Time | duration | milliseconds | hidden | Minimum execution time observed for a single execution. Helps identify best-case query performance. |
| Max Time | duration | milliseconds | hidden | Maximum execution time observed for a single execution. Large gaps between min and max may indicate data skew or resource contention. |
| Read Rows | integer |  |  | Total number of rows read from storage across all executions. High values suggest queries scanning large amounts of data that may benefit from better filtering or indexing. |
| Read Bytes | integer |  |  | Total bytes read from storage across all executions. Indicates I/O load and data transfer volume for the query pattern. |
| Written Rows | integer |  | hidden | Total number of rows written across all executions. Relevant for INSERT, CREATE, or materialized view queries. |
| Written Bytes | integer |  | hidden | Total bytes written across all executions. Indicates storage impact of write operations. |
| Result Rows | integer |  |  | Total number of rows returned to clients across all executions. A high ratio of read rows to result rows indicates filtering or aggregation happening on large datasets. |
| Result Bytes | integer |  | hidden | Total bytes returned to clients across all executions. Large values may indicate queries returning more data than necessary. |
| Max Memory | float |  | hidden | Maximum memory used during any single execution. High values may indicate queries at risk of hitting memory limits under load. |



## Troubleshooting

### Debug Mode

**Important**: Debug mode is not supported for data collection jobs created via the UI using the Dyncfg feature.

To troubleshoot issues with the `clickhouse` collector, run the `go.d.plugin` with the debug option enabled. The output
should give you clues as to why the collector isn't working.

- Navigate to the `plugins.d` directory, usually at `/usr/libexec/netdata/plugins.d/`. If that's not the case on
  your system, open `netdata.conf` and look for the `plugins` setting under `[directories]`.

  ```bash
  cd /usr/libexec/netdata/plugins.d/
  ```

- Switch to the `netdata` user.

  ```bash
  sudo -u netdata -s
  ```

- Run the `go.d.plugin` to debug the collector:

  ```bash
  ./go.d.plugin -d -m clickhouse
  ```

  To debug a specific job:

  ```bash
  ./go.d.plugin -d -m clickhouse -j jobName
  ```

### Getting Logs

If you're encountering problems with the `clickhouse` collector, follow these steps to retrieve logs and identify potential issues:

- **Run the command** specific to your system (systemd, non-systemd, or Docker container).
- **Examine the output** for any warnings or error messages that might indicate issues.  These messages should provide clues about the root cause of the problem.

#### System with systemd

Use the following command to view logs generated since the last Netdata service restart:

```bash
journalctl _SYSTEMD_INVOCATION_ID="$(systemctl show --value --property=InvocationID netdata)" --namespace=netdata --grep clickhouse
```

#### System without systemd

Locate the collector log file, typically at `/var/log/netdata/collector.log`, and use `grep` to filter for collector's name:

```bash
grep clickhouse /var/log/netdata/collector.log
```

**Note**: This method shows logs from all restarts. Focus on the **latest entries** for troubleshooting current issues.

#### Docker Container

If your Netdata runs in a Docker container named "netdata" (replace if different), use this command:

```bash
docker logs netdata 2>&1 | grep clickhouse
```


