Rick Duggan
85 lines
4.0 KiB
Markdown
85 lines
4.0 KiB
Markdown
# Code push Notes
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Just place to keep running notes about our development of codepush for Flutter.
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## Server push vs. code push
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Dynamically changing the application a user experiences (even just to show
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their login name or shopping cart balance, etc) is necessary in any modern
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server-associated application. This is trivial on the web (where users always
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fetch the latest version of your application from your servers), but not for
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installed applications, like we use on mobile phones.
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One approach is sending new configuration data to clients. This works for
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changing layouts, showing profile information, etc. However, it does not work
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for changing the application logic (fixing bugs, etc). For the purposes of this
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doc I'm referring to data-only delivery as "server push" and code+data delivery
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as "code push".
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Every single large application on mobile phones that I'm aware of uses code push
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in some form. One reason for this is update frequency. It is not uncommon for
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a mobile application to have a new release every week or two, yet users
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sometimes lag months (or years) in their app updates. This means that if an
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application has a server component which might be tied to a specific version of
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an application, that server component must be able to handle multiple versions
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of the application going back years. This is a huge burden for developers and
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eventually results in a worse end user experience than if the an application
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required less developer effort to maintain.
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## Code push approaches
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Many approaches one could take:
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1. Compile Release Flutter with DartVM in JIT mode\
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Implementation Difficulty: Medium\
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Application Performance: Unreliable (due to JIT compiles), but good once warmed up.\
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Platform Restrictions: Some restrict executing dynamically compiled code (either technically or by store agreement)
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1. Replace libapp.so with new libapp.so\
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Implementation Difficulty: Simple\
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Application Performance: Great (AOT level performance)\
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Platform Restrictions: Some restrict loading dynamic libraries (either technically or by store agreement)\
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Developer Experience: OK (need to recompile for each platform)\
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Notes:
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* A naive implementation has large update sizes (can be mitigated)
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1. Flutter Web (JS or WASM) + C++ Engine\
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Implementation Difficulty: Hard (no known implementations)\
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Application Performance: Unknown, likely good? (JS JIT level performance)\
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Platform Restrictions: None known.\
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Notes:
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* No per-platform work for developers.
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* Possible developer headaches due to Dart -> JS compilation quirks.
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1. Flutter Web (JS or WASM) in a WebView\
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Implementation Difficulty: Medium\
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Application Performance: Poor (untested)\
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Platform Restrictions: None known.
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1. (Custom) Dart Interpreter (for some or all application code)\
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Implementation Difficulty: Hard\
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Application Performance: Unknown\
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Developer Experience: Unknown\
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Platform Restrictions: None known.\
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Pros:
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* There have been several implementations of this approach, I'm not aware
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of any being publicly available/supported at this time.
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* Defining a boundary between AOT and Interpreter code is very hard.
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Shorebird takes the approach of building the correct developer experience and
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underlying infrastructure first, with plans to (likely dynamically) provide
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multiple code push implementations to customers, depending on their needs and
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the needs/restrictions of their target platforms. We will likely implement
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several of the above approaches for code push.
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## Other known over-the-air update implementations
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* https://github.com/microsoft/code-push
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* https://github.com/Tencent/tinker
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* https://github.com/expo/expo/tree/main/packages/expo-updates
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* https://github.com/hydro-sdk/hydro-sdk
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* https://pub.dev/packages/rfw
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* https://pub.dev/packages/flutter_eval
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* https://github.com/google/omaha
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* http://code.google.com/p/update-engine/
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* https://sparkle-project.org/
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* https://learn.microsoft.com/en-us/windows/msix/overview
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* https://hydraulic.software/
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Did we forget some? Patches welcome!
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