Class: ClickhouseRuby::ConnectionPool

Inherits:
Object
  • Object
show all
Defined in:
lib/clickhouse_ruby/connection_pool.rb

Overview

Thread-safe connection pool for managing multiple ClickHouse connections

Features:

  • Thread-safe checkout/checkin with mutex

  • Configurable pool size and timeout

  • Automatic health checks before returning connections

  • with_connection block pattern for safe usage

  • Idle connection cleanup

Examples:

Basic usage with block (recommended)

pool = ClickhouseRuby::ConnectionPool.new(config)
pool.with_connection do |conn|
  response = conn.post('/query', 'SELECT 1')
end

Manual checkout/checkin (use with caution)

conn = pool.checkout
begin
  response = conn.post('/query', 'SELECT 1')
ensure
  pool.checkin(conn)
end

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(config, size: nil, timeout: nil) ⇒ ConnectionPool

Creates a new connection pool

Parameters:

  • config (Configuration) —

    connection configuration

  • size (Integer) (defaults to: nil) —

    maximum pool size (default from config)

  • timeout (Integer) (defaults to: nil) —

    wait timeout in seconds (default from config)



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# File 'lib/clickhouse_ruby/connection_pool.rb', line 41

def initialize(config, size: nil, timeout: nil)
  @config = config
  @size = size || config.pool_size
  @timeout = timeout || config.pool_timeout
  @connection_options = config.to_connection_options

  # Pool state
  @available = [] # Connections available for checkout
  @in_use = []             # Connections currently checked out
  @all_connections = []    # All connections ever created

  # Synchronization
  @mutex = Mutex.new
  @condition = ConditionVariable.new

  # Stats
  @total_checkouts = 0
  @total_timeouts = 0
  @created_at = Time.now
end

Instance Attribute Details

#size ⇒ Integer (readonly)

Returns maximum number of connections in the pool.

Returns:

  • (Integer) —

    maximum number of connections in the pool



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# File 'lib/clickhouse_ruby/connection_pool.rb', line 31

def size
  @size
end

#timeout ⇒ Integer (readonly)

Returns timeout in seconds when waiting for a connection.

Returns:

  • (Integer) —

    timeout in seconds when waiting for a connection



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# File 'lib/clickhouse_ruby/connection_pool.rb', line 34

def timeout
  @timeout
end

Instance Method Details

#available_count ⇒ Integer

Returns the number of currently available connections

Returns:

  • (Integer) 


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# File 'lib/clickhouse_ruby/connection_pool.rb', line 169

def available_count
  @mutex.synchronize { @available.size }
end

#checkin(connection) ⇒ void

This method returns an undefined value.

Returns a connection to the pool

Parameters:

  • connection (Connection) —

    the connection to return



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# File 'lib/clickhouse_ruby/connection_pool.rb', line 147

def checkin(connection)
  return unless connection

  @mutex.synchronize do
    @in_use.delete(connection)

    # Only return healthy connections to the available pool
    if connection.healthy? && !connection.stale?
      @available << connection
    else
      # Disconnect unhealthy connections
      safe_disconnect(connection)
      @all_connections.delete(connection)
    end

    @condition.signal
  end
end

#checkout ⇒ Connection

Checks out a connection from the pool

If no connections are available and the pool is at capacity, waits up to @timeout seconds for one to become available.

Returns:

Raises:



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# File 'lib/clickhouse_ruby/connection_pool.rb', line 103

def checkout
  deadline = Time.now + @timeout

  @mutex.synchronize do
    loop do
      # Try to get an available connection
      if (conn = get_available_connection)
        @in_use << conn
        @total_checkouts += 1
        return conn
      end

      # Try to create a new connection if under capacity
      if @all_connections.size < @size
        conn = create_connection
        @in_use << conn
        @total_checkouts += 1
        return conn
      end

      # Wait for a connection to be returned
      remaining = deadline - Time.now
      if remaining <= 0
        @total_timeouts += 1
        # Publish pool timeout event
        Instrumentation.publish(Instrumentation::EVENTS[:pool_timeout], {
          pool_id: object_id,
          wait_time_ms: @timeout * 1000,
          pool_size: @size,
          in_use: @in_use.size,
        },)
        raise PoolTimeout, "Could not obtain a connection from the pool within #{@timeout} seconds " \
                           "(pool size: #{@size}, in use: #{@in_use.size})"
      end

      @condition.wait(@mutex, remaining)
    end
  end
end

#cleanup(max_idle_seconds = 300) ⇒ Integer

Removes idle/unhealthy connections from the pool

Parameters:

  • max_idle_seconds (Integer) (defaults to: 300) —

    maximum idle time before removal

Returns:

  • (Integer) —

    number of connections removed



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# File 'lib/clickhouse_ruby/connection_pool.rb', line 217

def cleanup(max_idle_seconds = 300)
  removed = 0

  @mutex.synchronize do
    @available.reject! do |conn|
      if conn.stale?(max_idle_seconds) || !conn.healthy?
        safe_disconnect(conn)
        @all_connections.delete(conn)
        removed += 1
        true
      else
        false
      end
    end
  end

  removed
end

#detailed_stats ⇒ Hash

Returns detailed pool statistics for monitoring

Provides comprehensive metrics suitable for Prometheus/StatsD export.

Examples:

pool.detailed_stats
# => {
#   capacity: 5,
#   connections: { total: 5, available: 3, in_use: 2 },
#   utilization_percent: 40.0,
#   checkouts: { total: 1000, rate_per_minute: 16.7 },
#   timeouts: { total: 5, rate_per_minute: 0.08 },
#   uptime_seconds: 3600
# }

Returns:

  • (Hash) —

    detailed pool statistics



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# File 'lib/clickhouse_ruby/connection_pool.rb', line 296

def detailed_stats
  @mutex.synchronize do
    uptime = Time.now - @created_at
    uptime_minutes = uptime / 60.0

    in_use = @in_use.size
    available = @available.size
    total = @all_connections.size
    utilization = total.positive? ? (in_use.to_f / total * 100).round(2) : 0.0

    checkout_rate = uptime_minutes.positive? ? (@total_checkouts / uptime_minutes).round(2) : 0.0
    timeout_rate = uptime_minutes.positive? ? (@total_timeouts / uptime_minutes).round(4) : 0.0

    {
      capacity: @size,
      connections: {
        total: total,
        available: available,
        in_use: in_use,
      },
      utilization_percent: utilization,
      checkouts: {
        total: @total_checkouts,
        rate_per_minute: checkout_rate,
      },
      timeouts: {
        total: @total_timeouts,
        rate_per_minute: timeout_rate,
      },
      uptime_seconds: uptime.round(2),
    }
  end
end

#exhausted? ⇒ Boolean

Checks if all connections are currently in use

Returns:

  • (Boolean) 


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# File 'lib/clickhouse_ruby/connection_pool.rb', line 190

def exhausted?
  @mutex.synchronize do
    @available.empty? && @all_connections.size >= @size
  end
end

#health_check ⇒ Hash

Pings all available connections to check health

Returns:

  • (Hash) —

    status report



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# File 'lib/clickhouse_ruby/connection_pool.rb', line 239

def health_check
  @mutex.synchronize do
    healthy = 0
    unhealthy = 0

    @available.each do |conn|
      if conn.ping
        healthy += 1
      else
        unhealthy += 1
      end
    end

    {
      available: @available.size,
      in_use: @in_use.size,
      total: @all_connections.size,
      capacity: @size,
      healthy: healthy,
      unhealthy: unhealthy,
    }
  end
end

#in_use_count ⇒ Integer

Returns the number of connections currently in use

Returns:

  • (Integer) 


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# File 'lib/clickhouse_ruby/connection_pool.rb', line 176

def in_use_count
  @mutex.synchronize { @in_use.size }
end

#inspect ⇒ String

Returns a string representation of the pool

Returns:

  • (String) 


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# File 'lib/clickhouse_ruby/connection_pool.rb', line 333

def inspect
  @mutex.synchronize do
    "#<#{self.class.name} size=#{@size} available=#{@available.size} in_use=#{@in_use.size}>"
  end
end

#shutdown ⇒ void

This method returns an undefined value.

Closes all connections and resets the pool

This should be called when shutting down the application.



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# File 'lib/clickhouse_ruby/connection_pool.rb', line 201

def shutdown
  @mutex.synchronize do
    (@available + @in_use).each do |conn|
      safe_disconnect(conn)
    end

    @available.clear
    @in_use.clear
    @all_connections.clear
  end
end

#stats ⇒ Hash

Returns pool statistics

Returns:

  • (Hash) —

    pool statistics



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# File 'lib/clickhouse_ruby/connection_pool.rb', line 266

def stats
  @mutex.synchronize do
    {
      size: @size,
      available: @available.size,
      in_use: @in_use.size,
      total_connections: @all_connections.size,
      total_checkouts: @total_checkouts,
      total_timeouts: @total_timeouts,
      uptime_seconds: (Time.now - @created_at).round(2),
    }
  end
end

#total_count ⇒ Integer

Returns the total number of connections (available + in use)

Returns:

  • (Integer) 


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# File 'lib/clickhouse_ruby/connection_pool.rb', line 183

def total_count
  @mutex.synchronize { @all_connections.size }
end

#with_connection {|Connection| ... } ⇒ Object

Executes a block with a checked-out connection

This is the recommended way to use the pool. The connection is automatically returned to the pool when the block completes, even if an exception is raised.

Yields:

Returns:

  • (Object) —

    the block’s return value

Raises:



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# File 'lib/clickhouse_ruby/connection_pool.rb', line 71

def with_connection
  started_at = Instrumentation.monotonic_time
  conn = checkout
  wait_time_ms = Instrumentation.duration_ms(started_at)

  # Publish pool checkout event
  Instrumentation.publish(Instrumentation::EVENTS[:pool_checkout], {
    pool_id: object_id,
    wait_time_ms: wait_time_ms,
    connection_id: conn.object_id,
  },)

  begin
    yield conn
  ensure
    checkin(conn)
    # Publish pool checkin event
    Instrumentation.publish(Instrumentation::EVENTS[:pool_checkin], {
      pool_id: object_id,
      connection_id: conn.object_id,
    },)
  end
end