31 lines
2.0 KiB
Markdown
31 lines
2.0 KiB
Markdown
---
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summary: "Command queue design that serializes auto-reply command execution"
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read_when:
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- Changing auto-reply execution or concurrency
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---
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# Command Queue (2025-11-25)
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We now serialize command-based auto-replies (WhatsApp Web listener) through a tiny in-process queue to prevent multiple commands from running at once, while allowing safe parallelism across sessions.
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## Why
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- Some auto-reply commands are expensive (LLM calls) and can collide when multiple inbound messages arrive close together.
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- Serializing avoids competing for terminal/stdin, keeps logs readable, and reduces the chance of rate limits from upstream tools.
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## How it works
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- `src/process/command-queue.ts` holds a lane-aware FIFO queue and drains each lane synchronously.
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- `runEmbeddedPiAgent` enqueues by **session key** (lane `session:<key>`) to guarantee only one active run per session.
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- Each session run is then queued into a **global lane** (`main` by default) so overall parallelism is capped by `agent.maxConcurrent`.
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- When verbose logging is enabled, queued commands emit a short notice if they waited more than ~2s before starting.
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- Typing indicators (`onReplyStart`) still fire immediately on enqueue so user experience is unchanged while we wait our turn.
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## Scope and guarantees
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- Applies only to config-driven command replies; plain text replies are unaffected.
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- Default lane (`main`) is process-wide for inbound + main heartbeats; set `agent.maxConcurrent` to allow multiple sessions in parallel.
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- Additional lanes may exist (e.g. `cron`) so background jobs can run in parallel without blocking inbound replies.
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- Per-session lanes guarantee that only one agent run touches a given session at a time.
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- No external dependencies or background worker threads; pure TypeScript + promises.
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## Troubleshooting
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- If commands seem stuck, enable verbose logs and look for “queued for …ms” lines to confirm the queue is draining.
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- `enqueueCommand` exposes a lightweight `getQueueSize()` helper if you need to surface queue depth in future diagnostics.
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