a818b5110e
Module.Apply() enumerated _features.Values directly while calling feature.Apply(). A feature whose Apply() introduces another feature — Module.Configure<T>() directly, or via a helper such as AddActivity<T>() which configures WorkflowManagementFeature — mutated that collection mid-enumeration and threw "Collection was modified; enumeration operation may not execute", naming nothing about features. Whether it fired depended on whether the other feature happened to be installed already, so a module built or did not based on unrelated host config. The module already treats introduction-during-apply as supported: the ConfigureFeature loop iterates a snapshot for exactly this reason, and Configure<T>() has an _isApplying branch that creates, resolves and configures a feature introduced mid-Apply. Only the final apply loop missed the same treatment, so make it tolerant rather than diagnose a constraint the code does not hold. The apply loop now runs in rounds until no new features appear, each round topologically sorted so a late feature's dependencies apply before it. Hosted services are registered in a single pass after that loop, then moved back to the index the block previously occupied: registering late is needed so features contributed during Apply() are included and ordered by priority, while keeping the position matters because features register hosted services directly from Apply() — WorkflowRuntimeFeature adds DrainOrchestratorHostedService that way — and module-managed services must keep starting first, or a priority such as ActivateTenants at -1 would silently start ordering after them. Adds Elsa.Features.UnitTests, covering the introduced feature applying, a three-deep introduction chain, dependency ordering, hosted service registration and priority ordering for late arrivals, the installed- feature registry, and no double-apply, plus guards for pre-existing ordering behaviour. Closes #7944 Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> |
||
|---|---|---|
| .. | ||
| activities-and-authoring.md | ||
| architecture.md | ||
| bpmn-workflows.md | ||
| build-run-operate.md | ||
| diagnostics-console-logs.md | ||
| diagnostics-structured-logs.md | ||
| expressions-and-scripting.md | ||
| extension-guide.md | ||
| health-checks.md | ||
| http-scheduling-resilience.md | ||
| identity-tenancy-security.md | ||
| module-system.md | ||
| opentelemetry-workflows.md | ||
| output-converters.md | ||
| persistence.md | ||
| README.md | ||
| repository-map.md | ||
| specs-and-adrs.md | ||
| testing-guide.md | ||
| workflow-api.md | ||
| workflow-core.md | ||
| workflow-management.md | ||
| workflow-runtime.md | ||
Elsa Core Wiki
This wiki is a repo-local, code-grounded map of Elsa Core. It is intended for contributors who need the same kind of fast orientation that a DeepWiki-style generated wiki gives: what the system is, where the important code lives, how the pieces connect, and how to safely extend or test them.
The source of truth is still the code, specs, ADRs, and tests. Each page links back to the relevant files so you can jump from explanation to implementation.
Start Here
Elsa Core is a modular .NET workflow engine. The main solution is Elsa.sln. Production code lives under src, tests under test, specifications under specs, and architecture decisions under doc/adr.
The shortest mental model:
- An application calls
services.AddElsa(...). - Elsa builds an
IModuleand configures feature objects. - Features register services, activities, API endpoints, middleware, hosted services, and persistence stores.
- Workflow definitions are created by code, JSON, imported files, or providers.
- The runtime starts, resumes, dispatches, and persists workflow instances.
- APIs, SignalR hubs, HTTP endpoint activities, diagnostics, and persistence packages layer around that core.
flowchart LR
App["Host app"] --> Module["Elsa module system"]
Module --> Core["Workflow core"]
Module --> Management["Workflow management"]
Module --> Runtime["Workflow runtime"]
Module --> Api["Workflow API"]
Module --> Extensions["HTTP, Scheduling, Expressions, Identity, Tenants"]
Management --> Persistence["Stores / EF Core providers"]
Runtime --> Persistence
Runtime --> Logs["Execution logs and diagnostics"]
Api --> Studio["Elsa Studio / API clients"]
Page Map
| Page | Use it for |
|---|---|
| Repository Map | Top-level folders, projects, and where to look first. |
| Architecture | The main system layers and request/execution flow. |
| Module System | How IModule, FeatureBase, feature dependencies, and shell features work. |
| Workflow Core | Activities, execution contexts, pipelines, variables, bookmarks, graphs, and flowchart execution. |
| Workflow Management | Workflow definitions, instances, import/export, materializers, validation, and activity descriptors. |
| Workflow Runtime | Dispatch, triggers, bookmarks, queues, background activity scheduling, graceful shutdown, and recovery. |
| Workflow API | FastEndpoints, route prefixing, API categories, SignalR, and client-facing contracts. |
| Activities And Authoring | How workflows are authored in C#, JSON, ElsaScript, and host methods. |
| Output Converters | How to register, configure, validate, discover, and operate bound-value converters. |
| Expressions And Scripting | Expression evaluators and language feature packages. |
| HTTP, Scheduling, And Resilience | Inbound HTTP workflows, outbound HTTP, scheduled triggers, and resilience strategies. |
| Persistence | In-memory stores, EF Core stores, provider packages, migrations, and multi-provider rules. |
| Diagnostics Structured Logs | ILogger capture, live feed, REST/SignalR surface, redaction, and SQLite persistence. |
| Diagnostics Console Logs | Raw stdout/stderr capture, live feed, REST/SignalR surface, and redaction. |
| Health Checks | Elsa runtime readiness probes, liveness/readiness mapping, and Kubernetes probe guidance. |
| Identity, Tenancy, And Security | Users, applications, roles, API keys, tenant resolution, and authorization touch points. |
| Testing Guide | Test project layout, fixture choices, and targeted commands. |
| Extension Guide | How to add features, activities, expression providers, stores, endpoints, and ingress sources. |
| OpenTelemetry Workflow Instrumentation | First-party workflow and activity traces and metrics emitted through System.Diagnostics. |
| Specs And ADRs | How current specs and ADRs explain design intent. |
| Build, Run, And Operate | Build commands, sample hosts, runtime knobs, Docker notes, and operational endpoints. |
Source Landmarks
- Main public entry: src/modules/Elsa/Extensions/DependencyInjectionExtensions.cs
- Default umbrella feature: src/modules/Elsa/Features/ElsaFeature.cs
- Module implementation: src/common/Elsa.Features/Implementations/Module.cs
- Core workflow feature: src/modules/Elsa.Workflows.Core/Features/WorkflowsFeature.cs
- Management feature: src/modules/Elsa.Workflows.Management/Features/WorkflowManagementFeature.cs
- Runtime feature: src/modules/Elsa.Workflows.Runtime/Features/WorkflowRuntimeFeature.cs
- API feature: src/modules/Elsa.Workflows.Api/Features/WorkflowsApiFeature.cs
- Reference server: src/apps/Elsa.Server.Web/Program.cs
- Structured-log persistence design: specs/005-structured-log-persistence/plan.md
Contributor Workflow
Use targeted reads first, then targeted tests. For most changes, start with the relevant module page, inspect the linked feature class and contracts, add or update tests in the matching test/unit, test/integration, or test/component project, and run the narrowest dotnet test command that proves the behavior.
When changing public behavior, update the related README, spec quickstart, or wiki page in the same PR. This repository is strongly modular, so the best changes keep ownership boundaries clear.