DM_GWPipeline_Gateway_MashupDataAccessError after deploying to test in pipeline

[KilianG]

We have the following situation:

• dashbords in a deployment pipeline.
• all workspaces / dashboards /datasets in this pipeline have the same admins /users and settings
• there are no staging variables
• all datasets use the same on premise gateway.
• The gateway admins and datasource users are the same as those for the workspaces / datasets

On development stage everything is working fine, but after deployment to test stage the refresh fails with an DM_GWPipeline_Gateway_MashupDataAccessError
All dataset settings are the same here, too- only in test there is a scheduled refresh. But even if deactivated the error stll occurs.
I tried most of the "solutions" of the other posts(restarting the gateway, setting https-mode off, set the scope of the data sources to the same value, etc.), but none of them helped. Some are no option - e.g. deleting the dashboard from the workspace, since it's embedded in several websites and with deleting/recreating the reportid would change and so cause trouble (and effort) on other (customers!) side.
As eyerything is set up identically, i don't believe it to be a problem of the gateway.

Is anybody able to help?

[lbendlin · Accepted solution]

On each gateway cluster member validate that you can reach each of the databases.

[KilianG]

Although this was the solution, i do no understand the concept behind it:
If i have to give each user of the cluster acces to each datasource anyway - why is there an option, to set access for each source?
This would mean, that if i want to have users with different Data access, i have to create new gateway clusters?

[lbendlin]

No, but you will have to create separate connections, even if it is the same exact data source.

Don't forget - gateway cluster members are zombies - they have no idea what's happening around them. All they know is to ask the gateway service if there are jobs available.  They need to have the right plumbing (network access and drivers)  but don't need to know anything about credentials. Credentials are supplied by the service as part of the job ticket.