Initially posted as an issue here: Server-side scripting & external data source
Then followed TSGal's instructions to post as a product Idea. so here it is:
Product and version: FMS 22.214.171.124 (web facing server) & FMS 126.96.36.1994 (data server; NOT web facing)
OS and version: Windows Server 2012 R2 (both servers)
Hardware: Virtual machines (both servers)
Description: Server-side script called by any means (xml web publishing, php api, PSOS, Server Scheduled Script) on the web facing server cannot use external data source pointing to a file hosted by the data server (both FileMaker files are password protected and do not have a default login).
Related: Remaining issue in FileMaker Server 13.0v2 with Perform Script on Server in multi-file solutions & PSoS and External Data Sources lead us to believe there is something problematic about relaying credentials to the files targeted by the external data sources. The identified workaround (specific to PSOS) is to open those files on the client making the PSOS call before performing that call. Our scenario forces us to trigger the script via CWP, where there is no client for us to open files prior to calling the script.
Why is this problematic: We have the web facing server listening to webhook updates from a 3rd party's web service. Upon receiving the update, via CWP a record is created in a FileMaker file hosted on the web facing server and a script is called (also via CWP) to process the data of that record. This script parses the information received from the webhook and interacts with a file located on the data server to read/update/create records as needed, via a Table Occurence using an external data source and/or by calling scripts. Exposing the data server to the web in order to have it listen directly to the webhook updates is NOT a viable option.
How to replicate: Set up two servers with password protected files on each and have a server-side running script on one interact with data from a file on the second server.
Attempts to make this work: we validated the user/password/extended privileges in both files, tried to add 'open file' script steps to the script, tried to use a prefind script when making the CWP call to attempt to open the other file 'before' the rest of the server stuff happens (trying to mimic the workaround for PSOS), all to no avail.
Workaround (if any): none. Even a 'robot' computer in the mix to run the script at scheduled intervals is not a viable workaround because in this context, we loose the proximity between the webhook update and the time the script runs (as if the webhook update triggers the script)
Expected fix: Something, ANYTHING, that would let us relay credentials over to other files targeted by an external data source. We would be ok with an 'Open File' script step where user account and password could be specified by calculation (it would be either sent as parameter or hardcoded, but that would still be better then having no single way of having those two files interact in the way that is possible via a FileMaker Pro client sitting on the same machine.