MVP
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Marcelo
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AVAILABILITY_ZERO_FIX.md
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AVAILABILITY_ZERO_FIX.md
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# Fix: Availability Shows 0% After Production Start
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## Date: November 27, 2025
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---
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## 🔍 PROBLEM DESCRIPTION
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**Symptom:** When starting production via the START button, Availability and OEE immediately show **0%** and only become non-zero after the first scrap prompt or after several machine cycles.
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**User Impact:** Dashboard shows misleading KPIs at production start, making it appear the machine is offline when it's actually preparing to run.
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---
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## 📊 ROOT CAUSE ANALYSIS
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### Timeline of Events
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1. **User clicks START button**
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- `global.set("trackingEnabled", true)` ✓
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- `global.set("productionStartTime", Date.now())` ✓
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- `global.set("operatingTime", 0)` ✓
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- `global.set("lastMachineCycleTime", Date.now())` ✓ (via Init node)
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2. **Calculate KPIs runs immediately** (triggered by START action)
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- `trackingEnabled = true` ✓
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- `productionStartTime = <timestamp>` ✓
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- `operatingTime = 0` ❌ (no cycles yet)
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- `timeSinceLastCycle = 0` ✓
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3. **Availability calculation logic check:**
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```javascript
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if (!trackingEnabled || timeSinceLastCycle > BRIEF_PAUSE_THRESHOLD) {
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// NOT this branch (trackingEnabled=true, timeSince=0)
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} else if (trackingEnabled && productionStartTime && operatingTime > 0) {
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// ❌ FAILS HERE - operatingTime is 0!
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// Normal calculation: (operatingTime / elapsedSec) * 100
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} else {
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// ✓ FALLS TO HERE
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// Uses: prevKPIs.availability || 0
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// Result: 0% (since lastKPIValues was cleared or is null)
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}
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```
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4. **Result:** Availability = 0%, OEE = 0%
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### Why Theories Were Correct
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✅ **Theory 1: First KPI Run Before Valid Cycle**
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- Calculate KPIs executes immediately after START
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- No machine cycles have occurred yet
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- `operatingTime = 0` fails the check on line 22
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✅ **Theory 2: timeSinceLastCycle Logic**
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- Not the issue in this case (timeSince = 0 at start)
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- But could be an issue if `lastMachineCycleTime` was stale from previous run
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- Our Init node prevents this by setting it to `Date.now()`
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✅ **Theory 3: Manual Seeding Overwritten**
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- Correct - any manual `operatingTime` value would be replaced by first cycle
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- But the real issue is the check `operatingTime > 0` preventing calculation
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---
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## 🎯 THE FIX
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### Strategy: Optimistic Availability on Production Start
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**Principle:** When production JUST started and no cycles have occurred yet, assume **100% availability** (optimistic assumption) until real data proves otherwise.
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**Reasoning:**
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- Machine was just told to START - assume it's ready
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- First cycle will provide real data within seconds
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- Better UX: Show 100% → real value, rather than 0% → real value
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- Avoids false alarm of "machine offline"
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### Code Changes
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**Location:** Calculate KPIs function, Availability calculation section
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**Before (4 branches):**
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```javascript
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if (!trackingEnabled || timeSinceLastCycle > BRIEF_PAUSE_THRESHOLD) {
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// Branch 1: Legitimately stopped
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msg.kpis.availability = 0;
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} else if (trackingEnabled && productionStartTime && operatingTime > 0) {
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// Branch 2: Normal calculation
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availability = (operatingTime / elapsedSec) * 100;
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} else {
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// Branch 3: Brief pause fallback
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availability = prevKPIs.availability || 0; // ❌ Returns 0 on first run!
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}
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```
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**After (5 branches):**
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```javascript
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if (!trackingEnabled || timeSinceLastCycle > BRIEF_PAUSE_THRESHOLD) {
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// Branch 1: Legitimately stopped
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msg.kpis.availability = 0;
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} else if (trackingEnabled && productionStartTime && operatingTime > 0) {
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// Branch 2: Normal calculation (has real cycle data)
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availability = (operatingTime / elapsedSec) * 100;
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} else if (trackingEnabled && productionStartTime) {
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// Branch 3: NEW - Production just started, no cycles yet
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msg.kpis.availability = 100; // ✅ Optimistic!
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node.warn('[Availability] Production starting - showing 100% until first cycle');
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} else {
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// Branch 4: Brief pause fallback
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availability = prevKPIs.availability || 0;
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}
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```
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### Logic Flow Chart
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```
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START clicked
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↓
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trackingEnabled = true
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productionStartTime = now
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operatingTime = 0
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↓
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Calculate KPIs runs
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↓
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Check: trackingEnabled? YES
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Check: timeSinceLastCycle > 5min? NO
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Check: operatingTime > 0? NO ←── KEY CHECK
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↓
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NEW BRANCH: trackingEnabled && productionStartTime?
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↓ YES
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Availability = 100% (optimistic) ✅
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↓
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Display on dashboard: OEE and Availability show 100%
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↓
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First machine cycle occurs (within 1-3 seconds)
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↓
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operatingTime becomes > 0
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↓
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Next KPI calculation uses REAL data
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↓
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Availability = (operatingTime / elapsedSec) * 100 ✅
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```
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---
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## ✅ EXPECTED BEHAVIOR AFTER FIX
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### Before Fix
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```
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User clicks START
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↓
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Dashboard immediately shows:
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Availability: 0%
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OEE: 0%
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Wait 3-5 seconds for first cycle...
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↓
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Dashboard updates:
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Availability: 95%
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OEE: 85%
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```
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**Problem:** False alarm - looks like machine is offline
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### After Fix
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```
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User clicks START
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↓
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Dashboard immediately shows:
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Availability: 100% ← Optimistic assumption
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OEE: 90-100% ← Based on quality/performance
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First cycle occurs (1-3 seconds)
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↓
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Dashboard updates with REAL data:
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Availability: 95% ← Actual calculated value
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OEE: 85% ← Based on real performance
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```
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**Improvement:** Smooth transition, no false "offline" alarm
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---
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## 🧪 TESTING INSTRUCTIONS
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### Test 1: Fresh Production Start
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1. Ensure no work order is active
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2. Start a new work order
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3. Click START button
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4. **Expected:** Availability immediately shows 100%
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5. Wait for first machine cycle (1-3 seconds)
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6. **Expected:** Availability updates to real calculated value
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### Test 2: Monitor Debug Logs
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1. Open Node-RED debug panel
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2. Click START
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3. **Expected to see:**
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```
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[START] Cleared kpiBuffer for fresh production run
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[Availability] Production starting - showing 100% until first cycle
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```
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4. After first cycle:
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```
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AVAILABILITY CHECK ➤
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trackingEnabled: true
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operatingTime: <some value > 0>
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```
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### Test 3: Verify Actual Calculation Takes Over
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1. Start production
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2. Let machine run for 10-20 cycles
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3. **Expected:** Availability should reflect real performance (likely 85-98%)
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4. Submit scrap
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5. **Expected:** Availability should NOT drop to 0% (brief pause logic)
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### Test 4: Stop Detection Still Works
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1. Start production
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2. Let run for 1 minute
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3. Click STOP (or let trackingEnabled become false)
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4. Wait 5+ minutes
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5. **Expected:** Availability drops to 0% (legitimate stop)
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---
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## 📝 ALTERNATIVE APPROACHES CONSIDERED
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### Option 1: Seed operatingTime = 0.001
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**Rejected:** Gets overwritten by first cycle calculation
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### Option 2: Delay Calculate KPIs until first cycle
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**Rejected:** Requires complex flow rewiring, delays all KPI visibility
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### Option 3: Show "N/A" or "--" instead of 0%
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**Rejected:** Requires UI changes, doesn't solve the core logic issue
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### Option 4: Use 50% as starting value
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**Rejected:** Arbitrary, 100% is more optimistic and clear
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### Option 5 (CHOSEN): Add dedicated branch for "just started" state
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**✅ Accepted:**
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- Minimal code change (one extra `else if`)
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- Clear logic separation
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- No impact on existing behavior
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- Easy to understand and maintain
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---
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## 🔒 SAFETY CHECKS
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### What Could Go Wrong?
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**Q:** What if machine actually can't start (offline, error)?
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**A:** First cycle will never occur, but `timeSinceLastCycle` will eventually exceed 5 minutes, triggering the "long pause" logic that sets availability to 0%.
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**Q:** What if operatingTime never increases?
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**A:** Same as above - after 5 minutes, availability will correctly drop to 0%.
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**Q:** Does this affect quality or performance KPIs?
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**A:** No - they have separate calculation logic. Quality = good/total, Performance = cycles/target.
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**Q:** What if user clicks START/STOP repeatedly?
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**A:** Each START resets `productionStartTime` and `operatingTime`, so the optimistic 100% will show each time until cycles prove otherwise. This is correct behavior.
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---
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## 🔄 ROLLBACK INSTRUCTIONS
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If issues occur:
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```bash
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cd /home/mdares/.node-red/projects/Plastico/
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cp flows.json.backup_20251127_124628 flows.json
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# Restart Node-RED
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```
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Or manually revert the Calculate KPIs function:
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- Remove the new `else if (trackingEnabled && productionStartTime)` branch
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- Restore the original 3-branch logic
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---
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## 📊 METRICS TO MONITOR
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After deployment, monitor:
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- **Time to first real availability value** (should be 1-3 seconds)
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- **False 0% occurrences** (should be eliminated)
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- **Long pause detection** (should still work after 5+ min idle)
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- **User feedback** on perceived responsiveness
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---
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## FILES MODIFIED
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- `/home/mdares/.node-red/projects/Plastico/flows.json`
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- Calculate KPIs function node (ID: `00b6132848964bd9`)
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- Added 5th logic branch for production start state
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---
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**Status: FIX COMPLETE ✅**
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**Risk Level: LOW** (Isolated change, all existing branches preserved)
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**Deployment: READY**
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