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Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
147 lines
6.7 KiB
Markdown
147 lines
6.7 KiB
Markdown
# HTTP, Scheduling, And Resilience
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HTTP, scheduling, and resilience are extension modules layered on top of workflow core, management, runtime, and expressions.
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## HTTP Module
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Start in [src/modules/Elsa.Http](../../src/modules/Elsa.Http).
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[HttpFeature](../../src/modules/Elsa.Http/Features/HttpFeature.cs) owns:
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- inbound HTTP endpoint workflows
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- outbound HTTP request activities
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- route matching and route table updates
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- HTTP bookmark payloads
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- HTTP request/response content parsing and writing
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- downloadable content handling
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- file cache and zip management
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- correlation and workflow instance ID selectors
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- HTTP activity descriptors and UI hints
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- HTTP resilience strategy registration
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- HTTP ingress source registration for graceful shutdown
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The public module extension is [UseHttp](../../src/modules/Elsa.Http/Extensions/ModuleExtensions.cs).
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## Inbound HTTP Workflows
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The inbound path is:
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```mermaid
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flowchart LR
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Request["ASP.NET request"] --> Middleware["HttpWorkflowsMiddleware"]
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Middleware --> RouteTable["IRouteTable / IRouteMatcher"]
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RouteTable --> Lookup["IHttpWorkflowLookupService"]
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Lookup --> Runtime["Workflow runtime"]
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Runtime --> Activity["HttpEndpoint activity"]
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Activity --> Response["HTTP response activity"]
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```
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Important files:
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- [HttpWorkflowsMiddleware](../../src/modules/Elsa.Http/Middleware/HttpWorkflowsMiddleware.cs)
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- [HttpEndpoint](../../src/modules/Elsa.Http/Activities/HttpEndpoint.cs)
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- [HttpEndpointBase](../../src/modules/Elsa.Http/Activities/HttpEndpointBase.cs)
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- [RouteMatcher](../../src/modules/Elsa.Http/Services/RouteMatcher.cs)
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- [RouteTable](../../src/modules/Elsa.Http/Services/RouteTable.cs)
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- [DefaultRouteTableUpdater](../../src/modules/Elsa.Http/Services/DefaultRouteTableUpdater.cs)
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- [HttpWorkflowLookupService](../../src/modules/Elsa.Http/Services/HttpWorkflowLookupService.cs)
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Hosts enable middleware with [UseWorkflows](../../src/modules/Elsa.Http/Extensions/ApplicationBuilderExtensions.cs).
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## Outbound HTTP
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Outbound HTTP activities:
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- [SendHttpRequest](../../src/modules/Elsa.Http/Activities/SendHttpRequest.cs)
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- [FlowSendHttpRequest](../../src/modules/Elsa.Http/Activities/FlowSendHttpRequest.cs)
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- [DownloadHttpFile](../../src/modules/Elsa.Http/Activities/DownloadHttpFile.cs)
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Supporting services include `HttpClientFileDownloader`, content factories, content parsers, and downloadable content handlers.
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## HTTP Security And Faults
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HTTP endpoint authorization and faults are configurable through `HttpFeature`:
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- [AuthenticationBasedHttpEndpointAuthorizationHandler](../../src/modules/Elsa.Http/Handlers/AuthenticationBasedHttpEndpointAuthorizationHandler.cs)
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- [AllowAnonymousHttpEndpointAuthorizationHandler](../../src/modules/Elsa.Http/Handlers/AllowAnonymousHttpEndpointAuthorizationHandler.cs)
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- [DefaultHttpEndpointFaultHandler](../../src/modules/Elsa.Http/Handlers/DefaultHttpEndpointFaultHandler.cs)
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- [DetailedHttpEndpointFaultHandler](../../src/modules/Elsa.Http/Handlers/DetailedHttpEndpointFaultHandler.cs)
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The module registers authorization services because the authentication-based handler requires them.
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## HTTP Tests
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Good test entry points:
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- [test/unit/Elsa.Http.UnitTests](../../test/unit/Elsa.Http.UnitTests)
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- [test/integration/Elsa.Http.IntegrationTests](../../test/integration/Elsa.Http.IntegrationTests)
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- [test/component/Elsa.Workflows.ComponentTests/Scenarios/Activities/Http](../../test/component/Elsa.Workflows.ComponentTests/Scenarios/Activities/Http)
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- [test/component/Elsa.Workflows.ComponentTests/Scenarios/HttpWorkflows](../../test/component/Elsa.Workflows.ComponentTests/Scenarios/HttpWorkflows)
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## Scheduling Module
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Start in [src/modules/Elsa.Scheduling](../../src/modules/Elsa.Scheduling).
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[SchedulingFeature](../../src/modules/Elsa.Scheduling/Features/SchedulingFeature.cs) registers:
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- local scheduler
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- cron parser
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- trigger scheduler
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- bookmark scheduler
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- workflow scheduler
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- tenant schedule updater
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- create-schedules background task
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- `ScheduleWorkflows` handlers
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- Cron trigger payload validator
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- scheduled-trigger ingress source for graceful shutdown
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- scheduling activities through workflow management
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The public extension is [UseScheduling](../../src/modules/Elsa.Scheduling/Extensions/ModuleExtensions.cs).
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## Scheduling Concepts
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Scheduled workflows typically create trigger or bookmark payloads that the scheduler can wake later. Important files:
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- [Bookmarks](../../src/modules/Elsa.Scheduling/Bookmarks)
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- [Services](../../src/modules/Elsa.Scheduling/Services)
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- [Handlers](../../src/modules/Elsa.Scheduling/Handlers)
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- [StartupTasks](../../src/modules/Elsa.Scheduling/StartupTasks)
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- [TriggerPayloadValidators](../../src/modules/Elsa.Scheduling/TriggerPayloadValidators)
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The scheduler integrates with tenancy by reacting to tenant activation/deletion events.
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## Resilience Module
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Start in [src/modules/Elsa.Resilience](../../src/modules/Elsa.Resilience) and [Elsa.Resilience.Core](../../src/modules/Elsa.Resilience.Core).
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[ResilienceFeature](../../src/modules/Elsa.Resilience/Features/ResilienceFeature.cs) registers:
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- activity descriptor modifier for resilient activities
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- resilience strategy catalog
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- strategy config evaluator
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- resilient activity invoker
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- configuration strategy source
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- retry attempt recorders/readers
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- transient exception detector and strategy
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- FastEndpoints assembly for resilience descriptors/testing endpoints
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HTTP registers [HttpResilienceStrategy](../../src/modules/Elsa.Http/Resilience/HttpResilienceStrategy.cs) with resilience in `HttpFeature.Configure()`.
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## Resilience Concepts
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Core contracts:
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- [IResilienceStrategy](../../src/modules/Elsa.Resilience.Core/Contracts/IResilienceStrategy.cs)
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- [IResilientActivity](../../src/modules/Elsa.Resilience.Core/Contracts/IResilientActivity.cs)
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- [IResilientActivityInvoker](../../src/modules/Elsa.Resilience.Core/Contracts/IResilientActivityInvoker.cs)
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- [IRetryAttemptRecorder](../../src/modules/Elsa.Resilience.Core/Contracts/IRetryAttemptRecorder.cs)
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- [ITransientExceptionDetector](../../src/modules/Elsa.Resilience.Core/Contracts/ITransientExceptionDetector.cs)
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Use resilience when an activity performs IO that can fail transiently. Keep strategy types registered by the owning module.
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The resilience testing endpoint `GET /elsa/api/simulate-response` is included in the module. It requires `exec:resilience:simulate-response` (or wildcard `exec:resilience` or `exec:*`) and is intended for integration-testing resilience strategies, not for production traffic.
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## Cross-Cutting Graceful Shutdown
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HTTP and Scheduling both register runtime ingress sources so graceful shutdown can pause new external work. When adding a new external event source, implement and register an `IIngressSource` in the owning module, then add runtime tests that prove pause/resume/drain behavior.
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