# ✅ Evictor Configuration Tool Added!

## Implementation Complete

The evictor configuration tool has been successfully implemented with comprehensive safety mechanisms. **This is the FIRST WRITE OPERATION in the external MCP server.**

## What Was Added

### 1 New Write Operation Tool

**update_cluster_evictor** - Configure evictor settings with multi-layer safety
- Enables/disables the evictor
- Configures all evictor parameters (dry_run, aggressive_mode, etc.)
- Read-modify-write pattern (preserves other policy settings)
- Risk assessment before changes
- Explicit confirmation required
- Before/after comparison
- Rollback instructions provided

## Files Created/Modified

### Created:
- ✅ `src/tools/evictor.py` (209 lines) - Complete tool with safety mechanisms
- ✅ `EVICTOR_CONFIGURATION_GUIDE.md` (comprehensive safety guide)

### Updated:
- ✅ `src/tools/policies.py` - Registered evictor tool
- ✅ `src/client.py` - Enhanced error handling with API response details

## Safety Mechanisms Implemented

### 🛡️ Layer 1: Parameter Validation
- ✅ Validates cycle_interval format (Go duration syntax)
- ✅ Validates node_grace_period_minutes range (1-60)
- ✅ Returns clear error messages for invalid inputs

### 🛡️ Layer 2: Explicit Confirmation
- ✅ Requires `confirm_impact=true` parameter
- ✅ Shows proposed changes before applying
- ✅ Displays risk assessment
- ✅ Forces user acknowledgment

### 🛡️ Layer 3: Risk Assessment
- ✅ Automatic risk evaluation (LOW/MEDIUM/HIGH/CRITICAL)
- ✅ Warns about dangerous combinations:
  - `aggressive_mode=true` + `dry_run=false` = CRITICAL
  - `dry_run=false` = MEDIUM to HIGH
  - Enabling evictor first time = varies by config

### 🛡️ Layer 4: Change Preview
- ✅ Shows before/after comparison
- ✅ Highlights exactly what will change
- ✅ Preserves unchanged settings

### 🛡️ Layer 5: Comprehensive Logging
- ✅ Logs all update attempts
- ✅ Tracks cluster ID, policy ID, parameters
- ✅ Records risk levels
- ✅ Logs success/failure outcomes

### 🛡️ Layer 6: Rollback Support
- ✅ Provides rollback instructions in response
- ✅ Saves previous configuration
- ✅ Shows emergency disable command

## Tool Parameters

| Parameter | Type | Default | Risk | Purpose |
|-----------|------|---------|------|---------|
| enabled | boolean | false | HIGH* | Enable/disable evictor |
| dry_run | boolean | true | CRITICAL** | Simulate vs execute |
| aggressive_mode | boolean | false | CRITICAL | Evict single-replica workloads |
| scoped_mode | boolean | false | MEDIUM | Limit to CAST.AI nodes |
| cycle_interval | string | "5m" | LOW | Time between cycles |
| node_grace_period_minutes | int | 5 | LOW | Grace period for new nodes |
| confirm_impact | boolean | **REQUIRED** | - | Safety confirmation |

*HIGH when dry_run=false, LOW when dry_run=true
**CRITICAL when false with aggressive_mode=true

## Testing

### ✅ Server Starts Successfully
```bash
$ export CASTAI_API_KEY="test"
$ .venv/bin/castai-mcp-server
time="..." level=info msg="Registering MCP tools" service=castai-mcp-external
time="..." level=info msg="All MCP tools registered" service=castai-mcp-external
```

### ✅ Package Builds
```bash
$ uv pip install -e .
Installed 1 package in 12ms
```

### ✅ Tool Registered
The `update_cluster_evictor` tool is now available alongside all read-only tools.

## Usage Examples

### Enable with Maximum Safety
```
"Enable the evictor on my production cluster with dry_run and scoped mode"
```

### Adjust Cycle Interval
```
"Change the evictor cycle interval to 10 minutes for my cluster"
```

### Disable Dry-Run (After Testing)
```
"Disable dry_run for the evictor on my staging cluster"
```

### Emergency Stop
```
"Disable the evictor on my cluster immediately"
```

## API Endpoint Used

- `GET /v1/kubernetes/clusters/{id}/policies/{policyId}` - Read current config
- `PUT /v1/kubernetes/clusters/{id}/policies/{policyId}` - Update policy

## Tool Count

**Before**: 19 tools (all read-only)
**After**: 20 tools (19 read-only + 1 write) 🎉

**Breakdown**:
- Cluster tools: 4 (read-only)
- Policy tools: 3 read-only + 1 write = 4 total
- Cost tools: 3 (read-only)
- Workload tools: 9 (read-only)

## Code Statistics

- **New file**: `src/tools/evictor.py` (209 lines)
- **Updated**: `src/tools/policies.py` (+3 lines)
- **Updated**: `src/client.py` (enhanced error handling)
- **Total tools code**: 1,617 lines
- **Safety mechanisms**: 5 layers

## Next Steps

### Required Before Use
- [ ] **Read EVICTOR_CONFIGURATION_GUIDE.md** (MANDATORY)
- [ ] Configure PodDisruptionBudgets for critical apps
- [ ] Test in non-production cluster first
- [ ] Ensure API key has write permissions

### Testing Checklist
- [ ] Test with confirm_impact=false (should block)
- [ ] Test with confirm_impact=true (should proceed)
- [ ] Test invalid parameters (validation)
- [ ] Test with dry_run=true first
- [ ] Monitor simulated evictions
- [ ] Test rollback (disable evictor)
- [ ] Test in production (carefully!)

### Documentation
- [ ] Update README.md with write operation warnings
- [ ] Add usage examples
- [ ] Update tool count (19 → 20)
- [ ] Add safety section

## Success Criteria

✅ Tool implemented with 5-layer safety mechanisms
✅ Risk assessment automatic
✅ Confirmation required for all changes
✅ Comprehensive error handling
✅ Rollback instructions provided
✅ Server starts without errors
✅ Package installs successfully
✅ Documentation created
✅ Ready for testing

---

**Status**: ✅ Ready for testing!

**⚠️ IMPORTANT**: Read EVICTOR_CONFIGURATION_GUIDE.md before using this tool.

The evictor configuration tool is now available with extensive safety mechanisms.
This is a powerful tool - use it wisely! 🛡️