Possible exception on configuration reload - Collection was modified; enumeration operation may not execute.

[mzakrzewski]

Describe the bug

I'm currently researching an invalid operation exception in an application when binding configuration. I haven't conclusively narrowed it down but my research so far raises concern for how the ConfigServerConfigurationProvider is implemented. This application is using env variables, cloud foundry configuration and config server configuration providers.

Based on changes made in the framework configuration providers (i.e. dotnet/extensions#1202), and seeing that the AddConfigServerClientSettings method in ConfigServerConfigurationProvider is directly changing the Data dictionary, I believe there is the potential that a configuration reload() could result in an InvalidOperationException.

To my knowledge, we're not calling Reload() on configuration when this is being encountered, but I thought it best to let you know that there may be an issue with how this is implemented: https://github.com/SteeltoeOSS/Steeltoe/blob/main/src/Configuration/src/ConfigServerBase/ConfigServerConfigurationProvider.cs#L422

Expected behavior

I would expect a call to reload configuration would not throw an invalid operation exception because a collection has been modified.

Environment (please complete the following information):

• Steeltoe Version: 3.0.2
• Platform: Cloud Foundry
• OS: Linux
• .NET Version: .net core 3.1.13
• Any other library versions to note: N/A

[TimHess]

Quick investigation reveals that the potential for this kind of issue was removed in #185 but then reintroduced by #270 ... looks like a bug to me, @mzakrzewski do you want to submit a PR?

Note: this should be fixed in the 2.x branch first and later merged to main (3.x)

[mzakrzewski]

Yep, I'll submit a PR; hopefully this week. Thanks.