Handling proxy support

2023-02-17

This article describes how you can enable proxy support in your Power Query custom connector using the Power Query SDK.

Windows proxy settings

First you'll need to set up the proxy settings in Windows. There are two ways to set up the proxy, either through Internet Options or the Network & internet setting.

Internet Options

From the Windows start menu, search for and open Internet Options.
Select the Connections tab.
Select LAN settings.
In the Proxy sever section, configure the proxy server.

Network & internet

From the Windows start menu, select the Settings icon.
In Settings, select Network & Internet (Windows 10), or select the Open Navigation icon and then select Network & internet (Windows 11).
Select Proxy.
Under the Manual proxy setup section, toggle the Use a proxy server button (Windows 10), or select the Set up button and toggle the Use a proxy server button (Windows 11).
Configure the address and port.

Enabling proxy support

A Web.DefaultProxy function has been added to the extensibility module. Third-party M connectors can use this function to fetch the web proxy settings to be set in the driver properties (when the proxy is enabled as described in Windows proxy settings).

The proxy information can be set in the connection string against the connection parameter, which can differ by connectors. Proxy credentials (username and password) aren't supported. Web.DefaultProxy takes in the serverUri/host as the parameter and returns a record containing the proxy URI as the ProxyUri field of a record. To get the constituent parts of the URI (for example: scheme, host, port) inside the connector, use Uri.Parts.

If the proxy isn't configured, Web.DefaultProxy returns an empty record.

Example usage

Example 1

To use Web.DefaultProxy in the connector code, a boolean type variable can be used to opt in or out of using this functionality. In this example, Web.DefaultProxy is invoked in the connector code if the optional boolean parameter UseWebDefaultProxy is set to true (defaults to false).

UseWebDefaultProxyOption = options[UseWebDefaultProxy]?,
ProxyUriRecord = if UseWebDefaultProxyOption then Web.DefaultProxy(Host) else null,
ProxyOptions = if Record.FieldCount(ProxyUriRecord) > 0 then
      [
            Proxy = ProxyUriRecord[ProxyUri]
      ]
      else [],
      ...

Once the UseWebDefaultProxy is set to true and ProxyUriRecord is fetched, a record can be created to set the Proxy (configuration parameter supported by the driver, which can vary) with the ProxyUri field returned by Web.DefaultProxy. It can be named something like ProxyOptions. This record can then be appended to the base ConnectionString, and include the proxy details along with it.

Databases = Odbc.DataSource(ConnectionString & ProxyOptions, Options)

Example 2

If there are multiple configuration parameters used by the driver for setting the proxy details (like host and port details being handled separately), Uri.Parts can be used.

UseWebDefaultProxyOption = options[UseWebDefaultProxy]?,
ProxyRecord = if UseWebDefaultProxyOption then Web.DefaultProxy(Host) else null,
UriRecord = if ProxyRecord <> null then Uri.Parts(ProxyRecord) else null,
ProxyOptions = if UriRecord <> null then
    [
        ProxyHost = UriRecord[Scheme] & "://" & UriRecord[Host],
        ProxyPort = UriRecord[Port]
    ]
    else [],
    ...

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