feat: add support for epoch-based deadline extensions for host I/O#138
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ruslanti merged 2 commits intoMay 13, 2026
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- Introduced `epoch_pause_ms` to track elapsed host I/O time and extend execution deadlines. - Enhanced `StoreBuilder` with `epoch_pause_ms` and `max_external_duration_ms` configuration. - Updated HTTP backends to deposit I/O time into shared counters and refund guest execution ticks. - Integrated `epoch_deadline_callback` for dynamic deadline adjustments.
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Pull request overview
This PR introduces epoch-based deadline extensions by tracking wall-clock time spent in host I/O (notably outbound HTTP) and using that “credit” to extend Wasmtime epoch deadlines, while also adding configurable slack to the outer Tokio timeout.
Changes:
- Added a shared
epoch_pause_mscounter to store state and integrated aepoch_deadline_callbackto extend deadlines based on accumulated host I/O time. - Wired HTTP execution paths/backends to deposit elapsed outbound HTTP time (ms) into
epoch_pause_ms. - Expanded tracing context on request handling and ensured spawned tasks inherit the current tracing span.
Reviewed changes
Copilot reviewed 5 out of 5 changed files in this pull request and generated 4 comments.
Show a summary per file
| File | Description |
|---|---|
| crates/runtime/src/store.rs | Adds epoch pause counter plumbing, max external duration slack, and installs an epoch deadline callback to extend/trap dynamically. |
| crates/runtime/src/lib.rs | Stores the shared counter on Data and deposits wasi-http outbound request wall time into it. |
| crates/http-service/src/lib.rs | Adds an extra span field for request handling tracing. |
| crates/http-service/src/executor/wasi_http.rs | Wires a shared epoch pause counter into the store builder and backend; instruments spawned task with current span. |
| crates/http-service/src/executor/http.rs | Wires a shared epoch pause counter into the store builder and backend for the non-wasi-http executor path. |
| crates/http-backend/src/lib.rs | Deposits outbound HTTP wall time (request + body read) into the shared epoch pause counter. |
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epoch_pause_msto track elapsed host I/O time and extend execution deadlines.StoreBuilderwithepoch_pause_msandmax_external_duration_msconfiguration.epoch_deadline_callbackfor dynamic deadline adjustments.