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Disconnect

Disconnects from a ClickHouse database server and releases the connection.

Common Properties​

  • Name - The custom name of the node.
  • Color - The custom color of the node.
  • Delay Before (sec) - Waits in seconds before executing the node.
  • Delay After (sec) - Waits in seconds after executing node.
  • Continue On Error - Automation will continue regardless of any error. The default value is false.
info

If the ContinueOnError property is true, no error is caught when the project is executed, even if a Catch node is used.

Inputs​

  • Connection Id - The connection ID returned from the Connect node.

How It Works​

The Disconnect node closes an active ClickHouse database connection and releases its resources. When executed, the node:

  1. Validates that a connection ID is provided
  2. Retrieves the connection from the internal connection pool
  3. Closes the database connection
  4. Removes the connection from the internal pool
  5. Releases all associated resources

Requirements​

  • A valid connection ID from a previous Connect node
  • The connection must still be active (not already closed)

Error Handling​

The node will return specific errors in the following cases:

  • InvalidConnection - Connection not found (connection ID is invalid or connection was already closed)
  • Database close errors (network issues, server problems)

Usage Notes​

  • Always use Disconnect to properly clean up database connections
  • Disconnecting a connection that is no longer valid will result in an error
  • After disconnecting, the connection ID becomes invalid and cannot be reused
  • Any ongoing transactions on the connection will be rolled back automatically
  • Ensure all queries and batches are completed before disconnecting

Example​

Scenario: Close the connection after completing all database operations

Inputs:

  • Connection Id: "550e8400-e29b-41d4-a716-446655440000" (from Connect node)

Output: No output - the connection is simply closed and removed from the pool.

Best Practices​

  • Always pair Connect nodes with Disconnect nodes
  • Place Disconnect at the end of your database workflow
  • Use error handling to ensure Disconnect runs even if earlier operations fail
  • Consider using a Try-Catch-Finally pattern with Disconnect in the Finally block
  • Don't attempt to use the connection ID after disconnecting

Common Flow Pattern​

A typical ClickHouse automation flow follows this pattern:

1. Connect → Get connection ID
2. Execute Query/Non Query operations → Use connection ID
3. Disconnect → Clean up connection

For error-safe patterns:

Try:
  1. Connect
  2. Execute operations
Catch:
  - Handle errors
Finally:
  - Disconnect (always runs)

Resource Management​

  • Disconnecting releases memory and network resources
  • Failing to disconnect can lead to connection pool exhaustion
  • ClickHouse servers have connection limits - always clean up connections
  • Idle connections may be automatically closed by the server after a timeout
  • Proper disconnection helps maintain optimal server performance