The Pipeline Framework

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Archived Docsv26.5.2

Replay And Live Topology ​

TPF exposes three different observability surfaces:

  1. Prometheus/Grafana metrics for live throughput, latency, inflight, queue pressure, and retry pressure
  2. Tempo tracing for live topology, trace drill-down, and span relationships
  3. Replay viewer for deterministic post-run playback

They answer different questions. Do not treat them as interchangeable.

Replay artifact ​

The offline artifact is replay JSON.

It is emitted by the framework replay exporter and contains:

  • pipeline topology from META-INF/pipeline/replay-topology.json
  • ordered execution events
  • a curated runtime configuration snapshot under runParameters
  • lineage fields such as itemId and parentItemIds
  • trace correlation fields such as traceId, spanId, and parentSpanId
  • viewer-oriented semantics such as:
    • start
    • emit
    • retry
    • error
    • success
    • cache_hit
    • reject

Replay JSON is the supported offline input for the TPF replay viewer.

Live versus offline ​

Live ​

  • OTLP trace/span export into Tempo or another tracing backend
  • Prometheus metric scraping
  • Grafana dashboards and Explore views backed by Tempo or Prometheus

Offline ​

  • replay JSON written by the framework replay exporter

Replay JSON is not a collector input and it is not a live transport. It is a deterministic playback artifact.

For csv-payments, the repo keeps those concerns in separate modular E2E lanes:

  • replay lane: writes replay JSON and validates offline playback inputs
  • Tempo lane: exports live spans to a dedicated LGTM stack and queries Tempo directly

Prometheus polling versus traces ​

Prometheus polling only affects metrics freshness.

  • Tracing is push-based: spans and span events are exported in real time to the configured tracing backend.
  • Metrics are scrape-based: dashboard freshness depends on the Prometheus scrape interval and query window.

So:

  • live topology comes from Tempo/tracing
  • live heat and pressure come from Prometheus metrics
  • post-run playback comes from replay JSON

Framework outputs ​

TPF emits:

  • META-INF/pipeline/replay-topology.json
  • tpf.pipeline.run spans
  • tpf.step spans
  • step span events:
    • tpf.step.start
    • tpf.step.emit
    • tpf.step.retry
    • tpf.step.success
    • tpf.step.error
    • tpf.step.cache_hit
    • tpf.step.reject

Replay JSON is written from the same runtime semantics by the framework replay exporter.

Await unit note:

Await boundaries park the owning QUEUE_ASYNC execution on a durable await unit and resume from that unit after completion admission. Current replay output remains step/event focused; first-class await unit lifecycle visibility in replay and related observability surfaces is tracked in #313. For the implementation model, see Await Unit Runtime.

Replay exporter configuration ​

Replay export is gated behind framework configuration:

properties
pipeline.telemetry.enabled=true
pipeline.telemetry.tracing.enabled=true
pipeline.telemetry.tracing.per-item=true
pipeline.telemetry.replay.enabled=true
pipeline.telemetry.replay.exporter=file
pipeline.telemetry.replay.file.path=/absolute/path/to/replay.json

If any prerequisite is missing, replay export stays off and the runtime logs one warning instead of partially activating replay work on the hot path.

Replay viewer ​

The supported replay viewer is published from the docs site at:

  • /replay-viewer/

Compatibility entrypoint:

  • /replay-viewer/index.html

It ships with built-in datasets and also accepts imported replay JSON files generated from your own runs.

The viewer exposes:

  • CSV Payments built-in
  • Search built-in pre-warm
  • Search built-in
  • Custom replay

The viewer uses a video-first layout:

  • the replay canvas as the main player surface
  • a persistent shell link back to /guide/operations/observability/replay
  • a metadata strip below the player for dataset, pipeline, duration, topology, and event summary
  • hover or tap-revealed player chrome over the canvas for transport controls, the scrubber, and inline speed radios
  • bottom-right utility icons for replay source, replay info, and player fullscreen
  • modal panes for source selection/import and Run parameters plus Legend

Custom replay is only exposed inside the replay-source modal. Selecting a source there stages the choice, and the viewer only switches when Load dataset is pressed.

Closing the modal or re-entering the page from browser history resets staged source state back to the active replay. Older replay files without runParameters remain loadable and show Run parameters unavailable.

The canonical viewer source lives in:

  • tools/replay-viewer/

Example-specific generation ​

Example commands and artifact locations are intentionally kept out of this page.

Use the example READMEs for concrete generation flows:

  • examples/csv-payments/README.md
  • examples/search/README.md

LGTM / Grafana discovery ​

LGTM Dev Services discovers dashboards stored under META-INF/grafana/ with the grafana-dashboard-*.json naming convention.

That discovery rule applies to example dashboards, not to replay JSON. Replay is a framework capability and the viewer is a separate docs-owned surface.