secrets/dataops/clickhouse_connection.md

ClickHouse Database Connection Guide

Connection Details

• Host: localhost
• Port: 9000 (HTTP), 9004 (HTTPS), 9009 (Native TCP)
• Protocol: HTTP/TCP (ClickHouse native)
• Default Database: default
• Health Check: clickhouse-client --query "SELECT version()"

Authentication

• Default User: default (no password)
• Access: Localhost only, no authentication required
• Security: Development mode - add authentication for production

ClickHouse-CLI Examples

# Connect to ClickHouse
clickhouse-client

# Show databases
SHOW DATABASES;

# Create nova database
CREATE DATABASE nova_analytics;

# Basic query
SELECT version(), now(), currentDatabase();

# Table operations
CREATE TABLE nova_analytics.events (
    timestamp DateTime,
    event_type String,
    data String
) ENGINE = MergeTree()
ORDER BY timestamp;

INSERT INTO nova_analytics.events VALUES 
(now(), 'session_start', '{"user": "test"}');

SELECT * FROM nova_analytics.events;

HTTP API Examples

# Health check via HTTP
curl "http://localhost:8123/?query=SELECT%20version()"

# Create table via HTTP
curl -X POST "http://localhost:8123/?query=CREATE%20TABLE%20test%20(id%20UInt32)%20ENGINE%20%3D%20Memory"

# Insert data
curl -X POST "http://localhost:8123/?query=INSERT%20INTO%20test%20VALUES%20(1)%2C%20(2)%2C%20(3)"

# Query data
curl "http://localhost:8123/?query=SELECT%20*%20FROM%20test"

Python Client Example

from clickhouse_driver import Client

# Connect to ClickHouse
client = Client(
    host='localhost',
    port=9000,
    user='default',
    database='default'
)

# Execute queries
version = client.execute('SELECT version()')
print(f"ClickHouse version: {version[0][0]}")

# Create analytics table
client.execute('''
CREATE TABLE IF NOT EXISTS nova_analytics.metrics (
    timestamp DateTime,
    metric_name String,
    value Float64,
    tags String
) ENGINE = MergeTree()
ORDER BY (metric_name, timestamp)
''')

# Insert metrics data
client.execute('''
INSERT INTO nova_analytics.metrics VALUES
(now(), 'memory_usage', 75.5, '{"host": "vast1"}'),
(now(), 'cpu_usage', 45.2, '{"host": "vast1"}')
''')

# Query analytics
results = client.execute('''
SELECT 
    metric_name,
    avg(value) as avg_value,
    max(timestamp) as last_seen
FROM nova_analytics.metrics 
GROUP BY metric_name
''')

for row in results:
    print(f"Metric: {row[0]}, Avg: {row[1]:.2f}, Last: {row[2]}")

Configuration Notes

• Data Directory: /data/data/clickhouse/data/
• Log Directory: /data/data/clickhouse/logs/
• Max Memory: 50GB (configurable)
• Backup Location: /data/adaptai/backups/clickhouse/
• Port Configuration:
  • 8123: HTTP interface
  • 9000: Native TCP interface
  • 9004: HTTPS interface
  • 9009: Native TCP with SSL

Performance Tuning

-- Monitor system metrics
SELECT * FROM system.metrics LIMIT 10;

-- Check query performance
SELECT 
    query,
    elapsed,
    read_rows,
    memory_usage
FROM system.processes;

-- Table sizes and parts
SELECT 
    database,
    table,
    sum(bytes) as size_bytes
FROM system.parts 
GROUP BY database, table
ORDER BY size_bytes DESC;

Health Checks

# Basic connectivity
clickhouse-client --query "SELECT 1"

# System health
clickhouse-client --query "SELECT * FROM system.metrics WHERE metric LIKE '%memory%'"

# Disk usage
clickhouse-client --query "
SELECT 
    name,
    free_space,
    total_space,
    formatReadableSize(free_space) as free,
    formatReadableSize(total_space) as total
FROM system.disks
"

# Active queries
clickhouse-client --query "SELECT query, elapsed FROM system.processes"

Security

• ❗ Localhost binding only
• ❗ No authentication configured (development mode)
• ❗ Add password authentication for production
• ❗ Monitor disk usage on /data partition
• ❗ Regular backups recommended
• ❗ Consider enabling SSL for encrypted connections

Backup Procedures

# Create backup
clickhouse-client --query "BACKUP DATABASE nova_analytics TO '/data/adaptai/backups/clickhouse/nova_analytics_backup'"

# Restore backup
clickhouse-client --query "RESTORE DATABASE nova_analytics FROM '/data/adaptai/backups/clickhouse/nova_analytics_backup'"

# Manual file backup
sudo rsync -av /data/data/clickhouse/data/ /data/adaptai/backups/clickhouse/full_backup/

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Last Updated: September 4, 2025