openclaw - 💡(How to fix) Fix MCP stdio server processes not properly cleaned up (process leak) [1 comments, 2 participants]

Description

When using MCP servers configured in stdio mode (e.g., MemPalace mempalace-mcp.exe), the Gateway creates a new process for each MCP call but does not properly terminate them after use. This causes process accumulation over time.

Environment

• OS: Windows_NT 10.0.26200 (x64)
• OpenClaw version: [please fill in]
• Node.js: v22.21.1

Configuration

{
  "mcp": {
    "servers": {
      "mempalace": {
        "command": "C:\\path\\to\\mempalace-mcp.exe",
        "args": ["--palace", "C:\\path\\to\\palace"],
        "env": { "PYTHONUTF8": "1" }
      }
    }
  }
}

Expected Behavior

• Each MCP stdio process should terminate after completing its call
• Only the currently active process should remain running

Actual Behavior

• Multiple mempalace-mcp.exe processes accumulate over time
• Processes are created at regular intervals (approximately every 30 minutes based on usage)
• Old processes are never terminated, only new ones are created
• Memory usage grows linearly with process count (~7MB per process)

Process List Example

Impact

• Resource leak: ~7MB per leaked process
• After 4+ hours of usage: 20+ processes consuming ~140MB memory
• Each process remains zombie-style, not doing anything

Investigation Notes

• This is NOT a MemPalace issue - MemPalace MCP server is designed for stdio mode only
• All leaked processes have the same parent: QClaw.exe (the OpenClaw Gateway)
• The issue appears to be in how OpenClaw manages stdio MCP subprocess lifecycle

Suggested Fix

1. Ensure stdio MCP processes are properly terminated after each call
2. Implement process pool management for frequently-used MCP servers
3. Add monitoring/logging for MCP process lifecycle events

Workaround

A cleanup script that kills old mempalace-mcp.exe processes while keeping the newest one:

$processes = Get-Process -Name "mempalace-mcp" | Sort-Object StartTime
if ($processes.Count -gt 1) {
    $toKeep = $processes[-1]
    $processes[0..($processes.Count - 2)] | Stop-Process -Force
}