Technical Reference

This Connector SDK Technical Reference covers the following topics:

• On this page:
  • SDK runtime environment
  • Limitations and notes
• On separate pages, it also covers the following detailed sections:
  • Connector SDK CLI Commands
  • Connector SDK Code Reference
    • Required declarations
    • Supported Methods
    • Supported Operations
    • Connector SDK Logging
  • Connector SDK Supported Data Type

SDK runtime environment

The Connector SDK runtime environment executes your submitted Python script in an isolated environment. It installs the libraries listed in the requirements.txt file, and after installation, it runs the provided Python script.

Python version support

We support the following Python versions:

• 3.14
• 3.13
• 3.12
• 3.11
• 3.10

While patch versions are usually compatible, a specific patch version can be critical for any Python library your code depends on. The exact patch versions for 3.14, 3.13, 3.12, 3.11, and 3.10 are listed below:

• 3.14.0
• 3.13.7
• 3.12.11
• 3.11.13
• 3.10.18

Python setup notes

Python may be global or managed in a virtual environment (venv). To verify your setup:

python --version

To activate a virtual environment:

• in macOS/Linux:

  python -m venv .venv
  source .venv/bin/activate
  

• in Windows (PowerShell):

  python -m venv .venv
  .venv\Scripts\Activate.ps1
  

• in Windows (Command Prompt):

  python -m venv .venv
  .venv\Scripts\activate.bat
  

See our Using Environment Variables With the Connector SDK guide for details on how to use environment variables.

Pre-installed DB drivers

We pre-install the msodbcsql17 and msodbcsql18 drivers for connecting to Microsoft SQL Server. We also pre-install libpq5 and libpq-dev, which are required to support psycopg and psycopg2 respectively.

Pre-installed packages

We pre-install the following packages when running your code:

• fivetran_connector_sdk:latest
• requests:2.32.5
• grpcio:1.76.0
• grpcio-tools:1.76.0

System resources

The environment running your code has:

• 1 GB of RAM
• Less than 0.5 vCPUs of an 8 Core N2 or equivalent machine
• 64-bit Linux (amd64) platform.

Our production infrastructure allows for some variation in resources available to your connections at any given moment, load balancing across multiple connections.

Handling Python version upgrades and End of Life

We are constantly expanding the list of supported Python versions. If you need support for a particular version, submit a feature request.

Each year, the oldest minor version of Python reaches its End of Life (EOL). When Python.org stops supporting a particular minor version, we discontinue support for that version of Python as well. You are required to migrate to a newer minor version for your connections to work.

To help you take timely action, we show a warning on the connection dashboard 90 days prior to the EOL date. We also send email notifications about it. If you do not migrate to a newer version, your connections stop working after the EOL date and you see an error on your connection dashboard. In most cases, updating the Python version from the CLI or the setup form is enough. However, if anything breaks, you are required to fix the code and redeploy it. Additionally, we disallow creating new connections 60 days before the EOL date. This applies to any minor Python version approaching End of Life.

If a new patch version is available, we work on adding support for it at the earliest. Once supported, newly created connections are configured to use the latest patch version. We do not immediately remove support for an existing connection using an older patch that's already uploaded and running. Instead, we work with you to transition to an updated, supported Python patch version.

Limitations

History mode

Currently, the Connector SDK does not support History Mode. You can mimic its behavior by including a timestamp column as part of a composite primary key.

Notes

Hybrid Deployment

If you are using a destination set up for Hybrid Deployment model, you can specify a custom hybrid agent (different from that used by the destination) using the CLI parameter --hybrid-deployment-agent-id <ID>. For more information about deploying your custom connector, see Deploy Your Custom Connector section.

System behavior

• Fivetran infers schema when not defined.
• The None values are inferred as NULL and NaN values are inferred as FLOAT.
• Long syncs should periodically call checkpoint() to persist state.