211 lines
11 KiB
Markdown
211 lines
11 KiB
Markdown
# OPC DA Diagnozer — Implementation Plan
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Companion to [`docs/SPECIFICATION.md`](SPECIFICATION.md). Targets **v1.0** as the first
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production-deployable release.
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---
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## 1. Milestones
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| Milestone | Content | Exit condition |
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|-----------|---------|----------------|
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| **v0.1 — Foreground proof** | CLI reads configured tags once per second in a console, prints events | Successfully reads from a real (or simulation) OPC DA server |
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| **v0.2 — Detection engine** | All detectors (D1–D15), event model, JSONL logging | Unit tests green; chaos scenarios produce correct events |
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| **v0.5 — Windows service** | pywin32 service, watchdog/hang recovery, Event Log, CLI install/run | Runs unattended through reboot + server-kill test |
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| **v1.0 — Production** | Packaging, runbook, 24 h soak, optional webhook | Acceptance criteria AC1–AC10 (spec §13) met |
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## 2. Project layout
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```
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opcda-diagnozer/
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├── README.md
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├── pyproject.toml
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├── config.example.yaml
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├── docs/
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│ ├── SPECIFICATION.md
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│ └── IMPLEMENTATION_PLAN.md
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├── src/opcda_diagnozer/
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│ ├── __init__.py
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│ ├── __main__.py # python -m opcda_diagnozer
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│ ├── main.py # CLI: run / install / uninstall / check-config / probe / list-devices / list-tags
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│ ├── config.py # pydantic-free typed config (dataclasses) + YAML load + validation
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│ ├── events.py # DiagEvent, Severity, EventKind
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│ ├── quality.py # OPC DA quality decode tables
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│ ├── opc/
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│ │ ├── base.py # OpcClient + Browser protocols, ReadResult, OpcError(hresult)
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│ │ ├── discovery.py # list-servers: Automation GetOPCServers / registry scan
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│ │ ├── browse.py # list-devices/list-tags: address-space walk (branches/leaves)
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│ │ ├── automation.py # OPC DA Automation Wrapper adapter (OPCAutomation.dll)
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│ │ └── fake.py # in-process fake client + fake address space (tests, demo)
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│ ├── monitor/
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│ │ ├── state.py # connection state machine + backoff
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│ │ ├── poller.py # COM thread: connect → poll loop → feed detectors
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│ │ └── detectors.py # D1–D15 rule implementations
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│ ├── report/
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│ │ ├── base.py # Reporter protocol
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│ │ ├── jsonl.py # rotating JSONL file
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│ │ ├── eventlog.py # Windows Event Log (WARN+)
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│ │ └── http.py # optional webhook
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│ └── service.py # pywin32 ServiceFramework wrapper
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└── tests/
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├── test_quality.py
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├── test_detectors.py
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├── test_state.py
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├── test_config.py
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└── test_poller_fake.py # end-to-end against opc.fake, no COM needed
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```
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## 3. Phase 0 — Feasibility & environment (≈0.5–1 day)
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**Goal:** validate the COM access strategy against reality before building anything.
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Tasks:
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1. Identify target OPC DA server: ProgID, host, DA version, bitness (32/64-bit EXE?).
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2. Choose wrapper backend:
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- **A. OPC DA Automation Wrapper** (`OPCAutomation.dll`) — ubiquitous in industry,
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ships with many SCADA installs; likely default.
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- **B. OpenOPC / Graybox wrapper** (`GBDaCtl.dll`) — fallback.
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- Note: both are typically **32-bit in-proc DLLs** → client Python must be 32-bit
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(see spec §11). Decide interpreter bitness here.
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3. Stand up a **test server** (Matrikon OPC Simulation Server, KepServerEX demo, or the
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actual control-system server in a maintenance window) and successfully read one tag
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from Python (`win32com.client.Dispatch`).
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4. Verify DCOM configuration for the service account (`dcomcnfg`: Launch/Activation →
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Remote Activation; Access → Local+Remote). Record required firewall ports
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(TCP 135 + RPC dynamic range).
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5. Record baseline behavior: normal read RTT, quality values, what error the wrapper
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surfaces when the server is stopped (feeds D1 implementation).
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**Exit:** a throwaway script reads ≥ 3 tags from the remote server with measured RTT.
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## 4. Phase 1 — Core engine (≈2–3 days)
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1. `config.py` — YAML config (see `config.example.yaml` sketch in README), dataclass
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model, strict validation, `check-config` messages that explain exactly what is wrong.
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2. `quality.py` — decode tables (spec §7), `decode_quality(raw: int) -> QualityInfo`.
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3. `opc/base.py` — client abstraction:
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```python
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class OpcClient(Protocol):
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def connect(self) -> None: ...
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def read(self, tags: Sequence[str]) -> list[ReadResult]: ...
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def close(self) -> None: ...
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```
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`ReadResult`: `tag, value, quality_raw, device_time, error` — plus per-call RTT
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measured by the poller. COM errors are normalized to `OpcError` carrying the raw
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`HRESULT` + decoded name.
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4. `opc/automation.py` — Automation Wrapper adapter (single group, static items,
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`SyncRead`); every COM exception mapped to `OpcError` with `win32com` scode.
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5. `monitor/state.py` — state machine (spec §10.2), backoff, reconnect accounting.
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6. `monitor/detectors.py` — D1–D15 as small pure functions/classes over
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`PollOutcome` (list[ReadResult] + rtt_ms + error), using an injected clock for
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testability. Rolling window (deque, size `window_polls`) for p95/streak logic.
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7. `monitor/poller.py` — the single COM thread; watchdog logic for hang detection
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(spec §10.4): a second thread timestamps poll starts/ends; on `hard_hang_s` the COM
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thread is abandoned and rebuilt.
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8. `events.py` — event dataclass + JSON serialization.
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9. `opc/fake.py` — scriptable fake client (sequences of outcomes: good reads, errors,
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hangs, quality flips) → powers the entire unit-test suite without COM/hardware.
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**Exit:** `opcda-diagnozer run` (foreground console) produces correct events against the
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fake client; unit tests for all detectors.
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## 5. Phase 2 — Reporters (≈1 day)
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1. `report/jsonl.py` — rotation (size + backups), atomic-ish append, header line with
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config digest for provenance.
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2. `report/eventlog.py` — pywin32 `win32evtlog` usage; map severities; source
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registration via `install` step.
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3. `report/http.py` — optional webhook with timeout + simple retry/drop on failure
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(never blocks the poll loop; queue with bound).
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4. Heartbeat assembly (D15): uptime, reconnects, RTT percentiles, tags-bad counts.
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**Exit:** events visible in file + Event Log; heartbeat cadence verified.
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## 6. Phase 3 — Windows service (≈1 day)
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1. `service.py` — `win32serviceutil.ServiceFramework`; service host thread spawns the
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COM worker; clean `stop` handling (`SetServiceStatus STOP_PENDING`, join with
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timeout, abandon hung COM thread on shutdown).
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2. CLI verbs: `install /uninstall /start /stop` (wraps `sc.exe` semantics),
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`run` (foreground), `check-config`, `probe` (connect once, print one read),
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`list-items` (browse validation tool).
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3. SCM recovery config (`sc failure ... restart`), auto-start, service account
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documentation.
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4. Config/log default dir: `%ProgramData%\OPCDA-Diagnozer\`.
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**Exit:** survives reboot; survives OPC-server kill (produces D1/D2 events, reconnects);
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`probe` and `check-config` give usable diagnostics to an ops engineer.
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## 7. Phase 4 — Integration & chaos testing (≈1–2 days)
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Scenario matrix against a simulation server (and, when available, the real server):
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| Scenario | How to inject | Expected events |
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|----------|---------------|-----------------|
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| Server process killed | `taskkill` | D1 (HRESULT), D2 with outage duration |
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| Server service stopped/restarted | `net stop/start` | D1, D2 |
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| Firewall drop (silent) | block outbound RPC ports / pull NIC | D7 hang, then D1 |
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| Latency injection | Clumsy / `netsh` delay | D4 spikes, D5 streak, D6 trend |
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| Device comm failure | simulation server "communication disturbance" items | D8 with `BAD_COMM_FAILURE`, D10 persistence |
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| Quality oscillation | toggling sim items | D11 flapping |
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| Stale/frozen tag | simulation server static item marked `expect_change` | D12 / D13 |
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| Mass bad quality | all sim items to bad | D14 |
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| Config errors | bad ProgID, unknown tag | fast fail + actionable message; `OPC_E_INVALIDITEMID` surfaced at startup |
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| Soak | 24 h healthy run | no leaks, heartbeats every 5 min, zero false positives |
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**Exit:** each row verified manually against the event log; AC2/AC3/AC4/AC5 confirmed.
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## 8. Phase 5 — Packaging & docs (≈0.5–1 day)
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- `pyproject.toml` wheel installable with pip into the chosen (32-bit) Python;
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document the on-host install procedure (PyInstaller packaging for pywin32 services is
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fragile — deferred).
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- `README.md` finalized (install, config, DCOM checklist, HRESULT table).
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- Ops runbook: how to read events, what each kind means (link to spec §12 matrix),
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how to reconfigure thresholds, where evidence lives.
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- Version 1.0.0 tag.
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## 9. Testing strategy
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- **Unit** (no COM): detectors against scripted `PollOutcome` sequences with a fake
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clock; quality decode; config validation; backoff/state transitions; JSONL rotation.
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- **Integration:** `test_poller_fake.py` runs the full poller+reporters against
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`opc.fake` in-process — the whole event pipeline without Windows COM.
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- **Manual/chaos:** Phase 4 matrix (necessarily on Windows against a real/simulated
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OPC DA server — cannot be automated in CI without the DCOM environment).
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- CI: unit + fake-integration tests run on any OS (COM adapters are import-guarded);
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chaos tests are a documented manual procedure.
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## 10. Risk register
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| Risk | Impact | Mitigation |
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|------|--------|------------|
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| Wrapper DLL bitness mismatch (32-bit only) | Cannot load wrapper | Phase 0 decision; use 32-bit Python; keep client abstraction so backend can be swapped |
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| Automation Wrapper not present on diag host | No COM access | Phase 0 check; ship/distribute wrapper install in runbook (vendor redistribution rules apply) |
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| DCOM hardening (KB5004442) blocks activation | Connect fails with `E_ACCESSDENIED`/activation errors | Runbook covers `dcomcnfg` steps; events surface raw HRESULT |
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| COM calls hang indefinitely | Service appears alive but blind | Explicit watchdog + thread recycling (spec §10.4) |
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| COM apartment violations (cross-thread calls) | Random `RPC_E_WRONG_THREAD` crashes | Single dedicated COM thread; all COM handles stay on it |
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| Our client perturbs the system | Skewed diagnosis | One group, static small tag list, 1 s default poll, read-only |
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| pywin32 service + COM quirks (GIL, STA init) | Service instability | Phase 3 spike; foreground `run` mode always available as fallback |
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| Tag list too large / wrong item IDs | Noise, misleading RTT | `probe` + `check-config` validate up-front; per-poll error accounting |
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| SCADA/host clock skew | Misleading staleness events | Local receive time always recorded; `max_age_s` configurable |
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## 11. Effort estimate
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| Phase | Estimate |
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|-------|----------|
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| 0 Feasibility | 0.5–1 d |
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| 1 Core engine | 2–3 d |
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| 2 Reporters | 1 d |
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| 3 Service | 1 d |
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| 4 Chaos testing | 1–2 d |
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| 5 Packaging/docs | 0.5–1 d |
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| **Total v1.0** | **≈ 6–9 days** |
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## 12. Definition of done (v1.0)
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- All Phase 4 scenarios pass; AC1–AC10 (spec §13) verified.
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- 24 h soak clean.
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- README + runbook complete enough for an ops engineer to deploy unaided.
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- Code reviewed; no write path to OPC anywhere in the codebase.
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- Config example covers every configurable threshold. |