concurrent-api: make context capture more generic #3183
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Motivation: Why is this change being made? Modifications: - List the changes Result: What is the result of this change?
bryce-anderson
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bryce-anderson
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Feb 5, 2025
servicetalk-concurrent-api/src/main/java/io/servicetalk/concurrent/api/CapturedContext.java
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...lk-concurrent-api/src/main/java/io/servicetalk/concurrent/api/ContextPreservingRunnable.java
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...rrent-api/src/main/java/io/servicetalk/concurrent/api/CustomCaptureAsyncContextProvider.java
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servicetalk-concurrent-api/src/main/java/io/servicetalk/concurrent/api/CapturedContext.java
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bryce-anderson
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Feb 6, 2025
| /** | ||
| * Functionality related to capturing thread-local like context for later restoration across async boundaries. | ||
| */ | ||
| interface CapturedContextProvider { |
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This is the nugget that lets users 'hook' into the context capture and restore process.
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Should be @FunctionalInterface
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...talk-concurrent-api/src/main/java/io/servicetalk/concurrent/api/CapturedContextProvider.java
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...-concurrent-api/src/main/java/io/servicetalk/concurrent/api/DefaultAsyncContextProvider.java
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| /** | ||
| * Functionality related to capturing thread-local like context for later restoration across async boundaries. | ||
| */ | ||
| interface CapturedContextProvider { |
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Should be @FunctionalInterface
idelpivnitskiy
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Feb 7, 2025
| @Override | ||
| public Scope attachContext() { | ||
| return AsyncContext.provider().attachContextMap(this); | ||
| } | ||
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| // Scope method | ||
| // Scope method. For the base async context implementation, the `prev` map instance is returned as the Scope if that | ||
| // is the context state that needs to be restored and restoring just means setting it to the thread-local. |
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Thanks for adding these clarifications!
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Motivation:
Our context capture and restore process is centered upon the ContextMap type. The AsyncContext type is only one specific type of context that applications may want to capture and restore across async boundaries. Other examples include the OTEL context, grpc context, and really any random ThreadLocal you want to preserve across async boundaries. They don't necessarily fit the same pattern as a AsycContext.
Modifications:
Further abstract the context type to a
CapturedContext. The key method isScope attachContext()which has the job of attaching whatever context it knows about. The key benefit of this abstraction is that it is very composable. We can add extensions that are simple proxy wrappers that capture the context and restore their own, while delegating to an underlying version that is ultimately rooted in what we know as the AsyncContext.Result:
More composable context capture and restore.