# Diagnostics Structured Logs

`Elsa.Diagnostics.StructuredLogs` captures semantic `ILogger` events from an Elsa host, redacts sensitive data, keeps a recent queryable buffer, exposes REST endpoints, and streams live events to Studio over SignalR.

Start in [src/modules/Elsa.Diagnostics.StructuredLogs](../../src/modules/Elsa.Diagnostics.StructuredLogs).

## Scope

This module captures structured `ILogger` records only. It does not capture raw stdout/stderr console streams, traces, metrics, or OpenTelemetry spans. Raw console output is covered by the sibling [Elsa.Diagnostics.ConsoleLogs](../../src/modules/Elsa.Diagnostics.ConsoleLogs) module — see [Diagnostics Console Logs](diagnostics-console-logs.md).

## Feature Wiring

[StructuredLogsFeature](../../src/modules/Elsa.Diagnostics.StructuredLogs/Features/StructuredLogsFeature.cs):

- registers FastEndpoints assembly
- calls `AddStructuredLogsServices`
- adds FastEndpoints from the module

[AddStructuredLogsServices](../../src/modules/Elsa.Diagnostics.StructuredLogs/Extensions/ServiceCollectionExtensions.cs) registers:

- SignalR
- `StructuredLogsOptions`
- source registry
- redactor
- in-memory store
- in-memory live feed
- default provider facade
- subscription manager
- `StructuredLogLoggerProvider` as an `ILoggerProvider`

## Core Contracts

| Contract | Purpose |
| --- | --- |
| [IStructuredLogProvider](../../src/modules/Elsa.Diagnostics.StructuredLogs/Contracts/IStructuredLogProvider.cs) | REST/SignalR facade used by endpoints and clients. |
| [IStructuredLogStore](../../src/modules/Elsa.Diagnostics.StructuredLogs/Contracts/IStructuredLogStore.cs) | Queryable storage abstraction. |
| [IStructuredLogLiveFeed](../../src/modules/Elsa.Diagnostics.StructuredLogs/Contracts/IStructuredLogLiveFeed.cs) | Live event publication/subscription abstraction. |
| [IStructuredLogSink](../../src/modules/Elsa.Diagnostics.StructuredLogs/Contracts/IStructuredLogSink.cs) | Event ingestion boundary. |
| [IStructuredLogRedactor](../../src/modules/Elsa.Diagnostics.StructuredLogs/Contracts/IStructuredLogRedactor.cs) | Redacts properties and text before storage/live delivery. |
| [IStructuredLogSourceRegistry](../../src/modules/Elsa.Diagnostics.StructuredLogs/Contracts/IStructuredLogSourceRegistry.cs) | Tracks source metadata and health. |
| [IStructuredLogStorageDiagnostics](../../src/modules/Elsa.Diagnostics.StructuredLogs/Contracts/IStructuredLogStorageDiagnostics.cs) | Provider-neutral diagnostics such as dropped durable writes. |

## Event Flow

```mermaid
sequenceDiagram
    participant App as App ILogger
    participant Provider as StructuredLogLoggerProvider
    participant Redactor as IStructuredLogRedactor
    participant Store as IStructuredLogStore
    participant Feed as IStructuredLogLiveFeed
    participant Hub as StructuredLogsHub
    participant Studio as Studio

    App->>Provider: Log event + scopes
    Provider->>Redactor: redact event
    Redactor->>Store: append event
    Redactor->>Feed: publish event
    Feed->>Hub: live event
    Hub->>Studio: SignalR stream
    Studio->>Store: recent query through REST
```

## In-Memory Provider

The default provider keeps recent logs in process:

- [InMemoryStructuredLogStore](../../src/modules/Elsa.Diagnostics.StructuredLogs/Providers/InMemory/InMemoryStructuredLogStore.cs)
- [InMemoryStructuredLogLiveFeed](../../src/modules/Elsa.Diagnostics.StructuredLogs/Providers/InMemory/InMemoryStructuredLogLiveFeed.cs)
- [RingBuffer](../../src/modules/Elsa.Diagnostics.StructuredLogs/Providers/InMemory/RingBuffer.cs)

This is bounded and process-local. In clustered deployments, each node has its own source identity and in-memory history unless durable/shared persistence is configured.

## REST And SignalR Surface

REST endpoints:

- `GET|POST /elsa/api/diagnostics/structured-logs/recent`
- `GET /elsa/api/diagnostics/structured-logs/sources`
- `GET /elsa/api/diagnostics/structured-logs/storage`

Endpoint code is under [Endpoints/StructuredLogs](../../src/modules/Elsa.Diagnostics.StructuredLogs/Endpoints/StructuredLogs).

SignalR:

- Hub: [StructuredLogsHub](../../src/modules/Elsa.Diagnostics.StructuredLogs/RealTime/StructuredLogsHub.cs)
- Client contract: [IStructuredLogsClient](../../src/modules/Elsa.Diagnostics.StructuredLogs/RealTime/IStructuredLogsClient.cs)
- Mapping: [MapStructuredLogsHub](../../src/modules/Elsa.Diagnostics.StructuredLogs/Extensions/EndpointRouteBuilderExtensions.cs)
- App extension: [UseStructuredLogs](../../src/modules/Elsa.Diagnostics.StructuredLogs/Extensions/ApplicationBuilderExtensions.cs)

The README states the hub is mapped at `/elsa/hubs/diagnostics/structured-logs`.

## Authorization

The endpoints require `read:diagnostics:structured-logs`, defined in [StructuredLogsPermissions](../../src/modules/Elsa.Diagnostics.StructuredLogs/Permissions/StructuredLogsPermissions.cs). The SignalR hub requires an authenticated user.

## Redaction

Events pass through `IStructuredLogRedactor` before buffering or streaming. Configuration lives in [StructuredLogsOptions](../../src/modules/Elsa.Diagnostics.StructuredLogs/Options/StructuredLogsOptions.cs). Extend sensitive property names and text patterns there.

## SQLite Persistence

Durable SQLite storage is available through the relational and SQLite packages:

- design plan: [specs/005-structured-log-persistence/plan.md](../../specs/005-structured-log-persistence/plan.md)
- quickstart: [specs/005-structured-log-persistence/quickstart.md](../../specs/005-structured-log-persistence/quickstart.md)
- relational package: [Elsa.Diagnostics.StructuredLogs.Persistence.Relational](../../src/modules/Elsa.Diagnostics.StructuredLogs.Persistence.Relational)
- SQLite package: [Elsa.Diagnostics.StructuredLogs.Persistence.Sqlite](../../src/modules/Elsa.Diagnostics.StructuredLogs.Persistence.Sqlite)

Configuration example from the SQLite README:

```csharp
services.AddElsa(elsa =>
{
    elsa.UseStructuredLogs(structuredLogs =>
    {
        structuredLogs.UseSqliteStorage("Data Source=elsa-structured-logs.db", sqlite =>
        {
            sqlite.RunMigrationsOnStartup = true;
            sqlite.Relational.WriteQueue.Capacity = 10_000;
            sqlite.Relational.WriteQueue.BatchSize = 100;
        });
    });
});
```

## Relational Persistence Design

[AddRelationalStructuredLogPersistence](../../src/modules/Elsa.Diagnostics.StructuredLogs.Persistence.Relational/Extensions/RelationalStructuredLogsServiceCollectionExtensions.cs) registers:

- `RelationalStructuredLogMapper`
- `RelationalStructuredLogSqlBuilder`
- `RelationalStructuredLogStore`
- `StructuredLogWriteBuffer`
- `StructuredLogRetentionService`
- `IStructuredLogStore` as the write buffer
- `IStructuredLogWriteBuffer`
- `IStructuredLogStorageDiagnostics`
- hosted service for the write buffer

The write buffer uses a bounded queue. If the queue is full, newest events are dropped and the dropped-write count is reported through storage diagnostics.

## SQLite Provider Boundary

[AddSqliteStructuredLogPersistence](../../src/modules/Elsa.Diagnostics.StructuredLogs.Persistence.Sqlite/Extensions/SqliteStructuredLogsModuleExtensions.cs) supplies provider-specific services:

- `IRelationalStructuredLogConnectionFactory`
- `IRelationalStructuredLogDialect`
- `IStructuredLogSchemaMigrator`
- startup migration/cleanup hosted service

The core structured logs package must remain unaware of SQLite. Future relational providers should copy this boundary: provider package supplies connection factory, dialect, migrator, and option binding; relational package supplies shared store behavior.

## Tests

Relevant tests:

- [test/unit/Elsa.Diagnostics.StructuredLogs.UnitTests](../../test/unit/Elsa.Diagnostics.StructuredLogs.UnitTests)
- [test/integration/Elsa.Diagnostics.StructuredLogs.IntegrationTests](../../test/integration/Elsa.Diagnostics.StructuredLogs.IntegrationTests)
- [test/unit/Elsa.Diagnostics.StructuredLogs.Persistence.Relational.UnitTests](../../test/unit/Elsa.Diagnostics.StructuredLogs.Persistence.Relational.UnitTests)
- [test/integration/Elsa.Diagnostics.StructuredLogs.Persistence.Sqlite.IntegrationTests](../../test/integration/Elsa.Diagnostics.StructuredLogs.Persistence.Sqlite.IntegrationTests)

Run targeted structured-log tests before broader builds when touching this area.