Bound the /__hot-reload__ long-poll duration#1395
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The /__hot-reload__ debug endpoint blocked a request thread indefinitely until a code change triggered a reload, and Flask's dev server ran unthreaded, so a single in-flight poll serialized all other requests. Cap the poll at a max duration (client already retries) and run the dev server threaded so one slow/long connection can't starve everyone else. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01SH7W9VinxHv8yMEwfW1yXX
The threaded dev server change surfaces an unrelated latent race in MemoryStateSessionBackend (unsynchronized check-then-act on a shared dict) that needs its own fix first. Splitting this out as a separate improvement; the bounded hot-reload poll stands on its own. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01SH7W9VinxHv8yMEwfW1yXX
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Summary
/__hot-reload__debug endpoint blocked its request indefinitely until a code change triggered a reload. Combined with Flask's dev server processing one request at a time by default, a single in-flight poll could serialize (or in the worst case, freeze) every other request against the app for as long as that connection stayed open._MAX_POLL_SECONDS = 25inmesop/server/server_debug_routes.py) so no single request can hold a connection open indefinitely. If the counter hasn't changed by the deadline, the endpoint returns the unchanged counter instead of continuing to block.mesop/web/src/services/channel.ts) to only trigger a hot reload when the returned counter actually differs from what it last saw, and to otherwise immediately re-poll. This keeps behavior identical for real reload events while making the timeout-and-retry path a no-op rather than a spurious reload.Not included
threaded=Trueto Mesop's built-in dev-server.run()calls (CLI, Colab/notebook, and themesoppip binary) as a complementary fix. That's been reverted for now: it surfaces a separate, unrelated latent race inMemoryStateSessionBackend(unsynchronized check-then-act on a shared in-memory dict) that needs its own fix first. Tracking that as a follow-up rather than bundling it here.Test plan
_MAX_POLL_SECONDStemporarily shrunk) that an unchanged counter times out and returns the same value after the bounded duration, and that a counter bump mid-poll still returns promptly with the new value.Co-Authored-By: Claude Sonnet 5 noreply@anthropic.com
Claude-Session: https://claude.ai/code/session_01SH7W9VinxHv8yMEwfW1yXX