Open database connection when needed

Overview

By default, Etlworks opens all database Connections referenced in the Flow before the Flow execution starts. It closes all Connections and coordinates distributed transactions when the Flow stops, successfully or with an error. 

It works perfectly well but creates a problem when the database Connection is parametrized using {tokens}. When the Flow starts, the values of the tokens (global variables) are not available yet, so the Flow fails before it even starts executing the transformations.

To solve this problem, Etlworks allows configuring a database Connection to be opened when needed. When needed means that the Flow defers opening the Connection to the moment when it is requested by the ETL Flow.  

Process

Here's how you can configure a database connection to be opened when needed:

Step 1. Open database Connection.

Step 2. Scroll to the Metadata section and enable Open connection when needed.

Limitations

The Connection configured with {tokens} is not going to work in Explorer, Mapping, and test transformation, regardless of the state of Open connection when needed.