Add graph reinit on failure

[atobiszei]

No description provided.

[Copilot]

Pull request overview

Adds automatic MediaPipe graph reinitialization on inference failure when using the graph queue/pool, to prevent returning an errored (“poisoned”) graph instance back to the pool for reuse.

Changes:

• Introduces GraphHelper::reinitialize() plus an RAII GraphReinitGuard that rebuilds a fresh CalculatorGraph unless dismissed on the success path.
• Hooks the guard into queue-based unary and streaming inference paths to trigger graph rebuild after failures.
• Moves per-graph shutdown logic into GraphHelper’s destructor and simplifies GraphQueue destructor.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
src/mediapipe_internal/mediapipegraphexecutor.hpp	Adds GraphReinitGuard around queue-path inference and dismisses it on success.
src/mediapipe_internal/graphqueue.hpp	Adds GraphHelper destructor, reinitialize() declaration, and new GraphReinitGuard type.
src/mediapipe_internal/graphqueue.cpp	Implements GraphHelper shutdown + reinit logic; defaults GraphQueue destructor.

Comments suppressed due to low confidence (2)

src/mediapipe_internal/graphqueue.cpp:142

• reinitialize() sets graph to nullptr on ObserveOutputStream failure (graph.reset()). The next request acquiring this GraphHelper will dereference graphHelper->graph in GraphIdGuard (graph(*graphHelper->graph)), which can crash if graph is null. Ensure reinitialize() always leaves a non-null graph, or update acquisition logic to detect nullptr and rebuild/replace before use.

        if (!absStatus.ok()) {
            SPDLOG_ERROR("Graph reinitialize: ObserveOutputStream failed: {}", absStatus.ToString());
            graph.reset();
            return;
        }

src/mediapipe_internal/graphqueue.cpp:162

• reinitialize() sets graph to nullptr on StartRun failure (graph.reset()). The next request acquiring this GraphHelper will dereference graphHelper->graph in GraphIdGuard (graph(*graphHelper->graph)), which can crash if graph is null. Ensure reinitialize() always leaves a non-null graph, or update acquisition logic to detect nullptr and rebuild/replace before use.

    if (!absStatus.ok()) {
        SPDLOG_ERROR("Graph reinitialize: StartRun failed: {}", absStatus.ToString());
        graph.reset();
        return;
    }

[dkalinowski]

Unit test that will ensure failed graphs are reusable is missing