Provide more accurate information about versioning for in-flight instances

[SimonLuckenuik]

I consider this topic has being very important, easy to forget and tricky to debug, so I would like to have more information to prevent any issues. By reading the document, it sounds that once you go in Production with your code, it should not change at all since any small logic change is breaking for the replay. My remarks are around the fact that I don't want to lose data and keep my in-fligh instances running, considering that some workflows we have will be running for weeks.

For in-flight instances and versioning:

• Provide more information about the impact of changing the HubName? What will happen to the tasks part of the previous HubName, are they still being executed or they will be pending forever?
• Provide complex examples with step-by-step examples of how to resolve the versioning issue. If I create a workflow that is meant to run for several weeks and involve multiple steps (and multiple versions of the code), what is the appropriate approach to follow? Examples:
  • Create multiple orchestrators and execute them as Sub-Orchestrators
  • Do not create long running workflows that are expected to live for a long time
• Provide best practices of code organization/flow to ease transition from one version to another. Examples:
  • minimize the amount of logic inside the orchestrator and move it inside activities to prevent replay errors.
  • provide complex types as Input and Output of activities in order to have more control over serialization breaking changes
• Provide more information about renaming the Function approach. Do I need the same orchestrator code, but just change "Foo" for "Foo2" and everything will work correctly?
• For "Deploy all the updates as entirely new functions (new names)" --> I guess we need to keep both the new and old function to make sure previous version continue to work correctly?
• What is the impact of adding or removing "WaitForExternalEvent" calls?
• What is the impact of having a do-while that continously "WaitForExternalEvent" vs replay/versioning?

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Document Details

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• ID: ae9ac6a0-6b49-c116-7fa4-59e104edf2d2
• Version Independent ID: bb8f7436-91ca-36ef-1ce8-7d2b9fcf5b50
• Content: Versioning in Durable Functions - Azure
• Content Source: articles/azure-functions/durable-functions-versioning.md
• Service: functions
• Product: unspecified
• GitHub Login: @cgillum
• Microsoft Alias: azfuncdf

[mimckitt]

@SimonLuckenuik Thanks for the feedback! I have assigned the issue to the content author to investigate further and update the document as appropriate.

[SimonLuckenuik]

@cgillum Could you please point me to the updated documentation?

[cgillum]

@SimonLuckenuik I'm impressed that you're still interested in following up on this docs issue even after ~515 days (apparently this was the oldest still-open docs issue for Functions)! :) I just checked and the updates should be published now. You can find the updated content here: https://docs.microsoft.com/en-us/azure/azure-functions/durable/durable-functions-versioning.

You can also see the diff here: https://github.com/MicrosoftDocs/azure-docs/commit/1ce14d7eb0e434a4634b1879fbb129bb18eb1707#diff-422d3f2958314dc5fe55203073f37052

You may be slightly disappointed because I didn't make all the updates you requested. I tried to fit in as much as I could efficiently, though at the same time I wanted to be careful about providing too much guidance. My worry is that providing too much information about in-place updates may cause more folks to attempt them (and shoot themselves in the foot). I'd rather try to encourage readers to go down the side-by-side deployment path.

I'm open to updating this information further if you think it's necessary. If so, please open a new issue and can follow up there.

FYI @anthonychu

[SimonLuckenuik]

@cgillum, I just raised a follow-up issue on versioning directly in the Durable Functions repo to have proper visibility. It would be nice if some developers could share how they are handling versioning as well.