# Load Test Issue Analysis - 100 Students Failed

## 🔴 Issue 1: Chrome User Data Directory Conflict (FIXED)

### Error
```
SessionNotCreatedException: session not created: probably user data directory is already in use, 
please specify a unique value for --user-data-dir argument
```

### Root Cause
- **Problem**: All 30 Chrome browsers were trying to use the same user data directory
- **Result**: Chrome instances conflicted with each other and failed to start
- **Impact**: 100% failure rate (all browsers crashed at startup)

### Solution Applied ✅
- **Fix**: Each browser now gets a **unique temporary user data directory**
- **Implementation**: `tempfile.mkdtemp(prefix=f'chrome_user_data_{user_id}_')`
- **Cleanup**: Temp directories are automatically cleaned up after driver quits

### Status
✅ **FIXED** - This issue is now resolved in the code

---

## 🔴 Issue 2: Metrics Interval Confusion (CLARIFICATION)

### Your Question
> "how can we get metrics interval at 10,10, because it's continuous process, all the Students should work simultaneously"

### Clarification

**`--metrics-interval 10` does NOT mean:**
- ❌ Students run in batches of 10
- ❌ Only 10 students run at a time
- ❌ Students wait for each other

**`--metrics-interval 10` ACTUALLY means:**
- ✅ **Print metrics every 10 students complete**
- ✅ All students run **simultaneously** (30 at a time with 30 workers)
- ✅ Metrics are just printed for visibility, not controlling execution

### How It Works

```
Timeline:
0s:  Start 30 browsers (workers=30)
5s:  Student 1 completes → metrics NOT printed (1 < 10)
8s:  Student 2 completes → metrics NOT printed (2 < 10)
...
15s: Student 10 completes → ✅ METRICS PRINTED (10 % 10 == 0)
20s: Student 11 completes → metrics NOT printed
...
30s: Student 20 completes → ✅ METRICS PRINTED (20 % 10 == 0)
```

**All 30 browsers are running simultaneously!** The metrics interval just controls when you see the progress report.

### Visual Explanation

```
With --workers 30:
┌─────────────────────────────────────────┐
│  Browser 1  │ Browser 2  │ Browser 3   │  ← All start at same time
│  Browser 4  │ Browser 5  │ Browser 6   │
│  ...        │ ...        │ ...        │
│  Browser 28 │ Browser 29 │ Browser 30 │
└─────────────────────────────────────────┘
     ↓           ↓           ↓
  Running    Running    Running
  (simultaneously, not in batches!)
```

---

## 📊 What Actually Happened

### Execution Flow
1. ✅ Script started successfully
2. ✅ Loaded 100 students from CSV
3. ✅ Started 30 concurrent browsers (workers=30)
4. ❌ **Chrome user data directory conflict** → All browsers failed to start
5. ❌ All 100 students failed within 60 seconds

### Error Breakdown
- **User 1, 3, 4, etc.**: `SessionNotCreatedException` (user data dir conflict)
- **User 2, etc.**: `InvalidSessionIdException` (browser crashed after conflict)

### Why So Fast?
- All failures happened at **browser startup** (within seconds)
- No students even reached the backend
- This is a **local Chrome configuration issue**, NOT a backend issue

---

## ✅ Solution Applied

### Code Changes
1. **Added unique user data directory** for each browser:
   ```python
   user_data_dir = tempfile.mkdtemp(prefix=f'chrome_user_data_{user_id}_')
   options.add_argument(f'--user-data-dir={user_data_dir}')
   ```

2. **Added cleanup** for temp directories after driver quits

### Test Again
```bash
./scripts/PC1_100_students.sh
```

**Expected Result**: Browsers should start successfully now!

---

## 🎯 Is This a Backend Issue?

### Answer: **NO** - This is a local Chrome configuration issue

**Evidence:**
- ❌ No students reached the backend (all failed at browser startup)
- ❌ Error is `SessionNotCreatedException` (Chrome issue, not API issue)
- ❌ All failures happened within seconds (before any API calls)

**Backend was never tested** because browsers couldn't even start!

---

## 📈 Next Steps

1. **Test again with the fix**:
   ```bash
   ./scripts/PC1_100_students.sh
   ```

2. **If it works**, then proceed with 3 PCs (300 students)

3. **Monitor backend** during the test:
   - Check backend logs
   - Monitor API response times
   - Check database performance
   - Monitor server resources (CPU, RAM)

---

## 💡 Understanding Metrics Interval

### Current Behavior (Correct)
- **30 workers** = 30 browsers running simultaneously
- **Metrics interval 10** = Print progress every 10 completions
- **All students process in parallel**, not sequentially

### If You Want Different Behavior

**Option 1: Print metrics more frequently**
```bash
--metrics-interval 5  # Print every 5 completions
```

**Option 2: Print metrics less frequently**
```bash
--metrics-interval 20  # Print every 20 completions
```

**Option 3: Print only at the end**
```bash
--metrics-interval 1000  # Print only at the end (if < 1000 students)
```

**Note**: This does NOT change how students run - they still run simultaneously!

---

## ✅ Summary

1. **Issue 1 (FIXED)**: Chrome user data directory conflict → Each browser now has unique directory
2. **Issue 2 (CLARIFIED)**: Metrics interval is just for printing, not batching
3. **Backend**: Was never tested (browsers failed before reaching backend)
4. **Next**: Test again with the fix to actually test backend capacity

**The fix is ready - test again!** 🚀