CHANGELOG.md

@@ -6,6 +6,32 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ---
 
+## [6-25-26] — v1.6.0
+
+Optional dual-send mirror so a standby server stays a live replica.
+
+### Added — Mirror (dual-send)
+- **Post every heartbeat and event to a second ("mirror") server in addition to the primary.**  When `MIRROR_API_URL` and/or `MIRROR_SFM_URL` are set, each heartbeat POST and each forwarded Blastware event is *also* sent to the mirror destination — letting a standby box (e.g. the office NAS) stay a continuous replica of prod during a migration so the eventual cutover is a non-event.  **Default off** — blank URLs mean existing 1.5.x installs don't change behaviour after an auto-update.
+- **Heartbeat mirror (best-effort).**  After the primary `send_api_payload`, the same payload is fired at `MIRROR_API_URL` when set.  It is fully wrapped and bounded by the existing API timeout — the mirror can **never** delay or fail the primary heartbeat; its outcome is ignored except for a debug log line.
+- **Event mirror (reliable, isolated).**  Events are re-forwarded to `MIRROR_SFM_URL` through a *separate* sha256 state file (`MIRROR_SFM_STATE_FILE`, blank → `<log dir>/sfm_forwarded_mirror.json`) so the mirror tracks its own delivery independently of the primary forwarder.  Before each mirror pass a quick reachability probe (~3 s) checks the mirror server; if it's down the pass is skipped and retried next tick rather than blocking the loop on per-event timeouts.  Skipped events stay pending in the mirror state and deliver once the mirror returns — **no data loss**.
+- **Isolation invariant.**  Nothing on the mirror path can delay or fail the primary: its own state file, its own try/except, the reachability guard + bounded timeouts, and all exceptions swallowed-and-logged.  The primary path stays exactly as reliable as before.  The mirror rides along with the primary — there is no separate enable flag (heartbeat-mirror active iff the primary heartbeat is on *and* `MIRROR_API_URL` is set; event-mirror active iff primary forwarding is on *and* `MIRROR_SFM_URL` is set).
+- **Mirror fields in the Settings dialog**: `Mirror API URL` + `Mirror SFM URL` (blank = off).
+- New unit tests in `test_event_forwarder.py` covering mirror reachability, the down-mirror skip, separate-state idempotency, and the isolation invariant (a mirror failure leaves the primary's result + state untouched).
+
+### Configuration
+
+New `[agent]` keys (all default-off — existing 1.5.x deployments don't change behaviour on auto-update):
+
+| Key | Default | Notes |
+|---|---|---|
+| `MIRROR_API_URL` | empty | Second heartbeat base URL, e.g. `http://10.0.0.x:8001` (blank = off) |
+| `MIRROR_SFM_URL` | empty | Second SFM base URL, e.g. `http://10.0.0.x:8200` (blank = off) |
+| `MIRROR_SFM_STATE_FILE` | `<log dir>/sfm_forwarded_mirror.json` | Override location of the mirror's forwarded-sha256 state file |
+
+### Operational (migration seeding)
+
+To make the mirror re-deliver only the gap since a one-time replica snapshot, copy the primary state file to the mirror state file and drop entries whose `forwarded_at` is after the snapshot.  SFM-side dedup covers any overlap.  See `docs/mirror-dual-send-design.md`.
+
 ## [5-11-26] — v1.5.0
 
 First release of the SFM event forwarder.

README.md

@@ -1,4 +1,4 @@
-# Series 3 Watcher v1.5.0
+# Series 3 Watcher v1.6.0
 
 Monitors Instantel **Series 3 (Minimate)** call-in activity on a Blastware server. Runs as a **system tray app** that starts automatically on login, reports heartbeats to terra-view, and self-updates from Gitea.
 
@@ -124,6 +124,27 @@ Combine both for a fully controlled rollout: seed-state to skip the deep archive
 
 ---
 
+## Mirror (Dual-Send) — v1.6.0+
+
+The watcher can post every heartbeat and event to a **second ("mirror") server** in addition to the primary — useful for keeping a standby box (e.g. the office NAS) as a continuous replica during a server migration, so the eventual cutover is a non-event. **Default off.**
+
+The mirror rides along with the primary — there is no separate enable flag:
+
+- **Heartbeat mirror** is active when `API_ENABLED = true` **and** `MIRROR_API_URL` is set. After the primary heartbeat POST, the same payload is fired at the mirror.
+- **Event mirror** is active when `SFM_FORWARD_ENABLED = true` **and** `MIRROR_SFM_URL` is set. Events are re-forwarded to the mirror using a **separate** sha256 state file (`MIRROR_SFM_STATE_FILE`, blank → `<log dir>/sfm_forwarded_mirror.json`).
+
+**The mirror can never delay or fail the primary.** The heartbeat mirror is fully wrapped and bounded by the API timeout. The event mirror runs a quick reachability probe (~3 s) first and skips the pass if the mirror server is down — skipped events stay pending in the mirror state and deliver when it returns, so nothing is lost. All mirror exceptions are swallowed-and-logged; the primary path stays exactly as reliable as before.
+
+| Key | Description |
+|-----|-------------|
+| `MIRROR_API_URL` | Second heartbeat base URL, e.g. `http://10.0.0.x:8001` (blank = off) |
+| `MIRROR_SFM_URL` | Second SFM base URL, e.g. `http://10.0.0.x:8200` (blank = off) |
+| `MIRROR_SFM_STATE_FILE` | Path to the mirror's sha256 state file. Blank → `<log dir>/sfm_forwarded_mirror.json` |
+
+**Seeding for a migration.** To re-deliver only the gap since a one-time replica snapshot, copy the primary state file to the mirror state file and drop entries whose `forwarded_at` is after the snapshot. SFM-side dedup covers any overlap. See [`docs/mirror-dual-send-design.md`](docs/mirror-dual-send-design.md).
+
+---
+
 ## Tray Icon
 
 | Colour | Meaning |
@@ -167,7 +188,7 @@ where the corresponding server-side work lives.
 
 ## Versioning
 
-Follows **Semantic Versioning**. Current release: **v1.5.0**.
+Follows **Semantic Versioning**. Current release: **v1.6.0**.
 See `CHANGELOG.md` for full history.
 
 ---

installer.iss

@@ -3,7 +3,7 @@
 
 [Setup]
 AppName=Series 3 Watcher
-AppVersion=1.5.0
+AppVersion=1.6.0
 AppPublisher=Terra-Mechanics Inc.
 DefaultDirName={pf}\Series3Watcher
 DefaultGroupName=Series 3 Watcher

series3_tray.py

@@ -1,5 +1,5 @@
 """
-Series 3 Watcher — System Tray Launcher  v1.5.0
+Series 3 Watcher — System Tray Launcher  v1.6.0
 Requires: pystray, Pillow, tkinter (stdlib)
 
 Run with:  pythonw series3_tray.py   (no console window)

series3_watcher.py

@@ -253,7 +253,7 @@ def scan_latest(
 
 
 # --- API heartbeat / SFM telemetry helpers ---
-VERSION = "1.5.0"
+VERSION = "1.6.0"
 
 
 def _read_log_tail(log_file: str, n: int = 25) -> Optional[list]:

settings_dialog.py

@@ -1,5 +1,5 @@
 """
-Series 3 Watcher — Settings Dialog  v1.5.0
+Series 3 Watcher — Settings Dialog  v1.6.0
 
 Provides a Tkinter settings dialog that doubles as a first-run wizard.