fix(simulation): make create_simulation idempotent to prevent duplicate sims#690
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alreadyhavefeel wants to merge 1 commit into
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fix(simulation): make create_simulation idempotent to prevent duplicate sims#690alreadyhavefeel wants to merge 1 commit into
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…te sims Creating a simulation was not idempotent: each POST /api/simulation/create minted a fresh sim_<uuid>. The frontend wraps createSimulation in requestWithRetry(..., 3, 1000), so a slow/timed-out first request triggers a retry that creates a second identical simulation for the same project+graph (observed: two sims created ~2s apart). Guard against this by reusing an existing, not-yet-run simulation for the same project_id + graph_id (and matching platform flags) when status is CREATED/PREPARING/READY and current_round == 0. A force_new=True escape hatch preserves the ability to intentionally create a fresh simulation. Verified: repeated /create calls now return the same simulation_id instead of spawning duplicates. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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Problem
Creating a simulation is not idempotent. Each
POST /api/simulation/createmints a freshsim_<uuid>viaSimulationManager.create_simulation. The frontend calls it throughrequestWithRetry(() => service.post('/api/simulation/create', data), 3, 1000)(frontend/src/api/simulation.js), so when the first request is slow or times out, the automatic retry fires a second create for the same project + graph.Result: two identical simulations for the same project/graph, created ~2 seconds apart (matching the 1000 ms retry interval), which is confusing in the Simulation History UI.
Fix
Add an idempotency guard at the top of
create_simulation: before minting a new id, reuse an existing simulation for the sameproject_id+graph_id(and matchingenable_twitter/enable_reddit) when it has not been run yet —current_round == 0and status inCREATED/PREPARING/READY.A
force_new=Trueparameter is added as an escape hatch for callers that deliberately want a brand-new simulation.This makes the POST safe to retry (the real root cause is a non-idempotent POST behind an auto-retry).
Verification
Repeated
POST /api/simulation/createfor the same project now returns the samesimulation_idinstead of spawning duplicates.Scope
Single-file change:
backend/app/services/simulation_manager.py. No API signature change (the new param is optional and defaults to current behavior for fresh projects).