TimeWarp.State.Telemetry 12.0.0-beta.5

TimeWarp.State.Telemetry

OpenTelemetry instrumentation for the TimeWarp.State mediator pipeline. Each dispatched action becomes a span with type names, duration, and success/failure — the observation half of Redux DevTools, on any OTel backend (Aspire dashboard, Jaeger, Seq, Application Insights).

Time-travel, commit, and import/export stay out of this package. Those need a dev-only back-channel; OTLP is one-directional.

Install

dotnet add package TimeWarp.State.Telemetry

The package weaves TelemetryBehavior<TAction, TResponse> into ClientPipeline the same way StateTransactionBehavior is woven (generated mediator, closed types visible to the trimmer). Order 350 sits inside StateTransactionBehavior (300) and outside RenderSubscriptionsPostProcessor (400): handler failures are recorded as Error before the transaction restores state and swallows the exception. Span duration is handler + render, not clone or Redux DevTools JS.

Register

builder.Services.AddGeneratedMediator<ClientPipeline>();
builder.Services.AddTimeWarpState();
builder.Services.AddTimeWarpStateTelemetry();

builder.Services.AddOpenTelemetry()
  .WithTracing(tracing =>
  {
    tracing.AddSource(TimeWarpStateTelemetry.ActivitySourceName);
    tracing.AddAspNetCoreInstrumentation();
    tracing.AddOtlpExporter(); // reads OTEL_EXPORTER_OTLP_* (Aspire sets these)
  });

AddTimeWarpStateTelemetry uses TryAdd* so a host can replace options or the snapshot cache.

What a span contains

Default (no payload):

An action that triggers HTTP is the parent of that HTTP span when the handler runs under Activity.Current.

Opt-in snapshots

Snapshots are off unless all of these are true:

1. An Activity listener is attached (ActivitySource.HasListeners()).
2. The span is sampled (IsAllDataRequested).
3. TimeWarpStateTelemetryOptions.IncludeSnapshots is true.
4. Caller-supplied JsonSerializerOptions.TypeInfoResolver returns JsonTypeInfo for the state type.

builder.Services.AddTimeWarpStateTelemetry(options =>
{
  options.IncludeSnapshots = true;
  options.JsonSerializerOptions = timeWarpStateJsonOptions; // TypeInfoResolver required
  options.MaxSnapshotChars = 16_384;
});

Or set TypeInfoResolver on TimeWarpStateOptions.JsonSerializerOptions (the same options Store and persistence use). This package never calls new JsonSerializerOptions() and never JsonSerializer.Serialize(object) on an open TState.

Events (not span attributes):

• First JSON for a state type in the scope: state.snapshot with tag snapshot.json
• Later unequal JSON: state.diff with the new JSON (string compare of the full JSON, no reflection property walk)
• Equal JSON: no event
• MaxSnapshotChars truncates only the event payload and sets boolean tag snapshot.truncated

Performance

The dispatch hot path with no listener is ActivitySource.HasListeners() (false) and next(). No GetState, no JSON, no snapshot cache.

With a listener, StartActivity returns null when the sampler drops the span; that path also skips snapshots.

Security

State JSON may contain user data. Defaults emit no payload. Enable snapshots only in local/dev, pair them with sampling, and redact via JsonConverter / source-generated context (omit secrets, tokens, PII). Truncation (MaxSnapshotChars) is a size cap, not redaction.

Do not enable IncludeSnapshots in production unless the OTel backend is access-controlled and payloads are redacted.

AOT / trimming

• IsAotCompatible=true on this package.
• Default spans use typeof names only.
• Snapshots require caller JsonTypeInfo (typically a JsonSerializerContext).
• No Type.GetType, no AssemblyQualifiedName, no GetProperties walk.
• Time-travel / LoadStatesFromJson is not in this package.

Blazor Server

Works out of the box: the circuit runs .NET, so ActivitySource spans export over OTLP to the Aspire dashboard (or any backend).

Blazor WebAssembly / browser telemetry

WASM process telemetry is the JS OpenTelemetry SDK, not this ActivitySource. That is maintained SDK code, not the custom redux-dev-tools.ts / timewarp-state.ts bridge.

Aspire dashboard browser telemetry (OTLP/HTTP + CORS):

• When the AppHost launches both the app and the dashboard, CORS for the OTLP HTTP endpoint is configured automatically. See Enable browser telemetry.
• A standalone dashboard needs DASHBOARD__OTLP__CORS__ALLOWEDORIGINS set to the WASM origin (for example https://localhost:7001).

This JS is not the C# trimmer’s problem.

Redux DevTools

Use this package for the observation half (action log, timing, snapshots). Keep UseReduxDevTools only if you still need time-travel / commit / import-export in the browser extension. A dedicated control channel is a follow-on; that path is AOT-hostile.

Sample

samples/04-telemetry/ is a Blazor Server counter that exports action spans. Run it against the Aspire dashboard (see that sample’s overview).