rpc: allow sharing the in-flight Semaphore across ExecutionContexts#7647
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The cap added in #7614 was scoped per-ExecutionContext: setMaxInFlight stored an int in the ctx message map and withInFlightSlot lazily created a Semaphore from it. Each independent ExecutionContext therefore got its own Semaphore, which made the cap a per-ctx cap rather than the host-wide cap callers like Moderne SaaS and the mod CLI expect when they create one InMemoryExecutionContext per repo and run several in parallel. Replace the int-message + lazy-create plumbing with a Semaphore-valued message and an explicit setInFlightSemaphore(Semaphore) setter. Callers that want a host-wide cap construct one Semaphore at the orchestrator level and install the same instance on every participating context. The old setMaxInFlight(int) is kept as a convenience for the single-ctx case but its Javadoc now spells out that it is not host-wide. withInFlightSlot runs the work unthrottled if no Semaphore is installed, preserving the "unbounded by default" behavior. Adds RewriteRpcExecutionContextViewTest covering: no-op default, fresh Semaphore from setMaxInFlight, per-ctx isolation (the misuse pattern), true sharing across many ctx/threads, and permit release on exception.
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Summary
setMaxInFlight(int)from rpc: cap concurrent in-flight requests via ExecutionContext #7614 stored an int on theExecutionContextand lazily built theSemaphoreinsidewithInFlightSlot. Each independentExecutionContexttherefore ended up with its ownSemaphore, so the cap was per-ctx, not host-wide.setInFlightSemaphore(Semaphore)so callers that want a true host-wide cap can construct oneSemaphoreonce at the orchestrator level and install the same instance on every participating context (e.g. one per repo task running in parallel).setMaxInFlight(int)as a single-ctx convenience but document that it is not host-wide.withInFlightSlotis unthrottled when noSemaphoreis installed, matching the prior "unbounded by default" baseline.This unblocks Moderne's
mod runand the SaaS recipe-worker from honoring a true process-wide rewrite-rpc concurrency cap; the wiring on those sides is in follow-up PRs.Test plan
RewriteRpcExecutionContextViewTestcovers: no-op default, fresh-Semaphore-from-setMaxInFlight, per-ctx isolation (the misuse pattern callers hit today), true sharing across many ctx/threads, permit release on exception../gradlew :rewrite-core:test --tests '*Rpc*'green locally.