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…e captive fix Dispatch observer (Ports & Adapters): - Abstractions: IMediatorDispatchObserver port — one observation scope per dispatch wrapping the WHOLE pipeline (pre/post-processors included), with no Activity dependency in the core. - OpenTelemetry: MediatorDispatchTracingObserver adapter replaces MediatorTracingBehavior (deleted) — opens the span once per dispatch. Zero overhead for non-OTel apps: the observer is null on the hot path (a single field-null check in Handle). - MediatorBuilder.AddDispatchObserver; the generator forces a chain when an observer is registered so handler-only requests are still observed. Chain-lifetime captive fix: - PrecompilePipelines now folds the HANDLER's lifetime into the chain lifetime, not only the pipeline components. A Singleton chain wrapping a Transient/Scoped handler captured it (and its scoped deps, e.g. an injected IMediator) for the application lifetime -> "Cannot consume scoped service from singleton" at BuildServiceProvider. The chain is now Scoped when the handler is non-singleton, and still Singleton (zero-alloc, pre-linked once) when everything it wraps is singleton. - Observer-forced chains no longer pin allSingleton=false; the folded lifetimes decide, so a singleton handler keeps a cached Singleton chain. Docs: ADR-0001 + dispatch-pipeline.md (chain lifetime = lowest of handler + components).
A handler with constructor dependencies was always registered Transient,
so under scope-per-request (one DI scope per HTTP request) it was
re-resolved and re-allocated every request - ~24 B + ~6.5 ns each,
against the zero-allocation premise.
RegisterMediatorHandlers now stages each dependency-carrying request
handler (recording the descriptor it created plus the dependency types).
The finalization step - PrecompilePipelines or the single-call AddMediator
- runs HandlerLifetimeOptimizer.Apply once every registration is present,
raising each handler to the longest SAFE lifetime its dependencies allow:
- Singleton when every dependency is a singleton (cached, zero-alloc per
request, and via the chain-lifetime fold a cached Singleton chain too)
- Scoped when any dependency is scoped
- Transient (unchanged) when any dependency is transient or unregistered
Running at finalization makes it order-independent: a dependency
registered AFTER RegisterMediatorHandlers (the common composition-root
order) is still seen. A reference-identity guard upgrades a handler only
while the generator's own descriptor is still the winning registration, so
any user re-registration - including an identical AddTransient that pins
Transient - is respected. [HandlerLifetime(...)] pins a lifetime
explicitly. No reflection: only registered ServiceDescriptor.Lifetime
values are read, so it is AOT/trim-safe and never touches the dispatch hot
path (generated dispatch IL is byte-identical).
Tests: HandlerLifetimeOptimizerTests (logic, order-independence, reference
guard, idempotency) and HandlerLifetimeAutoDetectionTests (end-to-end
through the generated path). Full OSS suite green.
…erver seam Handle() delegated the 3-way dispatch switch to HandleCore(); despite the AggressiveInlining hint the JIT did not inline it, adding a real call to every chain dispatch. Peel the cold observer path off first and run the switch inline in Handle() (as it was pre-seam); HandleCore() now serves only the cold observer paths. The no-observer hot path is back to a single field-null check + the inline switch. No behavior change: 555 OSS tests green (incl. 101 OpenTelemetry adapter tests).
…erver seam Handle() delegated the 3-way dispatch switch to HandleCore(); despite the AggressiveInlining hint the JIT did not inline it, adding a real call to every chain dispatch. Peel the cold observer path off first and run the switch inline in Handle() (as it was pre-seam); HandleCore() now serves only the cold observer paths. The no-observer hot path is back to a single field-null check + the inline switch. No behavior change: 555 OSS tests green (incl. 101 OpenTelemetry adapter tests).
…dler-lifetime release core + Abstractions 1.3.0-rc.1 -> 1.3.0-rc.2; OpenTelemetry 1.1.0-rc.2 -> 1.1.0-rc.3; FluentValidation + HybridCache 1.0.9-rc.1 -> 1.0.9-rc.2. Version-string only; carries the already-committed dispatch-observer seam + order-independent handler DI-lifetime auto-detection. Build green (0 errors).
…mmary (Ports & Adapters)
Contributor
SummarySummary
CoverageDSoftStudio.Mediator - 98.4%
DSoftStudio.Mediator.Abstractions - 91.3%
DSoftStudio.Mediator.FluentValidation - 100%
DSoftStudio.Mediator.Generators - 91.9%
DSoftStudio.Mediator.HybridCache - 100%
DSoftStudio.Mediator.OpenTelemetry - 96.8%
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Highlights
feat(core): dispatch-observer seam (Ports & Adapters)
Exposes the request-dispatch lifecycle as an optional observation port (
IMediatorDispatchObserver) so an external adapter (e.g. the OpenTelemetry bridge) can wrap the WHOLE pipeline — pre-processors, behaviors, handler, post-processors. A pipeline behavior cannot do this because pre-/post-processors run OUTSIDE the behavior chain. The mediator itself never observes or traces; it only exposes the boundary. Includes the chain-lifetime captive-dependency fix.feat(di): order-independent handler DI-lifetime auto-detection
A request handler is raised from the Transient default to the longest SAFE lifetime its constructor dependencies allow — Singleton when every dependency is a singleton, Scoped when any dependency is scoped; a stateless handler (no constructor parameters) is Singleton. Staged at registration and applied at finalization (
PrecompilePipelines) so dependencies registered BEFORE or AFTER the handler are both seen, with a reference-identity guard that respects any user re-registration.[HandlerLifetime]opts out.perf(dispatch): keep the PipelineChainHandler hot path flat under the observer seam
The observation port adds no overhead on the dispatch hot path when no observer is attached.
Release / versions
DSoftStudio.Mediator(core) +DSoftStudio.Mediator.Abstractions: 1.3.0-rc.2DSoftStudio.Mediator.OpenTelemetry: 1.1.0-rc.3DSoftStudio.Mediator.FluentValidation+DSoftStudio.Mediator.HybridCache: 1.0.9-rc.2Validation
Full OSS solution builds green (0 errors); test suite green.