From 12603a1a5c978638a4fb794bd667f4fec7778933 Mon Sep 17 00:00:00 2001
From: Alex Newman <thedotmack@gmail.com>
Date: Fri, 12 Dec 2025 21:22:00 -0500
Subject: [PATCH] docs: add PM2 to Bun migration documentation to Mintlify
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Add comprehensive technical documentation explaining the v7.1.0 migration from PM2 to Bun-based process management and better-sqlite3 to bun:sqlite database driver.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
---
 .../architecture/pm2-to-bun-migration.mdx     | 551 ++++++++++++++++++
 docs/public/docs.json                         |   3 +-
 2 files changed, 553 insertions(+), 1 deletion(-)
 create mode 100644 docs/public/architecture/pm2-to-bun-migration.mdx

diff --git a/docs/public/architecture/pm2-to-bun-migration.mdx b/docs/public/architecture/pm2-to-bun-migration.mdx
new file mode 100644
index 00000000..01ba4582
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+++ b/docs/public/architecture/pm2-to-bun-migration.mdx
@@ -0,0 +1,551 @@
+---
+title: "PM2 to Bun Migration"
+description: "Complete technical documentation for the process management and database driver migration in v7.1.0"
+---
+
+# PM2 to Bun Migration: Complete Technical Documentation
+
+**Version**: 7.1.0
+**Date**: December 2025
+**Migration Type**: Process Management (PM2 → Bun) + Database Driver (better-sqlite3 → bun:sqlite)
+
+## Executive Summary
+
+Claude-mem version 7.1.0 introduces two major architectural migrations:
+
+1. **Process Management**: PM2 → Custom Bun-based ProcessManager
+2. **Database Driver**: better-sqlite3 npm package → bun:sqlite runtime module
+
+Both migrations are **automatic** and **transparent** to end users. The first time a hook fires after updating to 7.1.0+, the system performs a one-time cleanup of legacy PM2 processes and transitions to the new architecture.
+
+### Key Benefits
+
+- **Simplified Dependencies**: Removes PM2 and better-sqlite3 npm packages
+- **Improved Cross-Platform Support**: Better Windows compatibility
+- **Faster Installation**: No native module compilation required
+- **Built-in Runtime**: Leverages Bun's built-in process management and SQLite
+- **Reduced Complexity**: Custom ProcessManager is simpler than PM2 integration
+
+### Migration Impact
+
+- **Data Preservation**: User data, settings, and database remain unchanged
+- **Automatic Cleanup**: Old PM2 processes automatically terminated (all platforms)
+- **No User Action Required**: Migration happens automatically on first hook trigger
+- **Backward Compatible**: SQLite database format unchanged (only driver changed)
+
+## Architecture Comparison
+
+### Old System (PM2-based)
+
+<AccordionGroup>
+<Accordion title="Process Management (PM2)">
+**Component**: PM2 (Process Manager 2)
+- **Package**: `pm2` npm dependency
+- **Process Name**: `claude-mem-worker`
+- **Management**: External PM2 daemon manages lifecycle
+- **Discovery**: `pm2 list`, `pm2 describe` commands
+- **Auto-restart**: PM2 automatically restarts on crash
+- **Logs**: `~/.pm2/logs/claude-mem-worker-*.log`
+- **PID File**: `~/.pm2/pids/claude-mem-worker.pid`
+
+**Lifecycle Commands**:
+```bash
+pm2 start <script>           # Start worker
+pm2 stop claude-mem-worker   # Stop worker
+pm2 restart claude-mem-worker # Restart worker
+pm2 delete claude-mem-worker  # Remove from PM2
+pm2 logs claude-mem-worker    # View logs
+```
+
+**Pain Points**:
+- Additional npm dependency required
+- PM2 daemon must be running
+- Potential conflicts with other PM2 processes
+- Windows compatibility issues
+- Complex configuration for simple use case
+</Accordion>
+
+<Accordion title="Database Driver (better-sqlite3)">
+**Component**: better-sqlite3
+- **Package**: `better-sqlite3` npm package (native module)
+- **Installation**: Requires native compilation (node-gyp)
+- **Windows**: Requires Visual Studio build tools + Python
+- **Import**: `import Database from 'better-sqlite3'`
+
+**Installation Requirements**:
+- Node.js development headers
+- C++ compiler (gcc/clang on Mac/Linux, MSVC on Windows)
+- Python (for node-gyp)
+- Windows: Visual Studio Build Tools
+</Accordion>
+</AccordionGroup>
+
+### New System (Bun-based)
+
+<AccordionGroup>
+<Accordion title="Process Management (Custom ProcessManager)">
+**Component**: Custom ProcessManager (`src/services/process/ProcessManager.ts`)
+- **Package**: Built-in Bun APIs (no external dependency)
+- **Process Spawn**: `Bun.spawn()` with detached mode
+- **Management**: Direct process control via PID file
+- **Discovery**: PID file + process existence check + HTTP health check
+- **Auto-restart**: Hook-triggered restart on failure detection
+- **Logs**: `~/.claude-mem/logs/worker-YYYY-MM-DD.log`
+- **PID File**: `~/.claude-mem/.worker.pid`
+- **Port File**: `~/.claude-mem/.worker.port` (new)
+
+**Lifecycle Commands**:
+```bash
+npm run worker:start    # Start worker
+npm run worker:stop     # Stop worker
+npm run worker:restart  # Restart worker
+npm run worker:status   # Check status
+npm run worker:logs     # View logs
+```
+
+**Core Mechanisms**:
+
+1. **PID File Management**:
+   - File: `~/.claude-mem/.worker.pid`
+   - Content: Process ID (e.g., "35557")
+   - Validation: Process existence via `kill(pid, 0)` signal
+
+2. **Port File Management**:
+   - File: `~/.claude-mem/.worker.port`
+   - Content: Two lines (port number, PID)
+   - Purpose: Track port binding and validate PID match
+
+3. **Health Checking**:
+   - Layer 1: PID file exists?
+   - Layer 2: Process alive? (`kill(pid, 0)`)
+   - Layer 3: HTTP health check (`GET /health`)
+   - All three must pass for "healthy" status
+
+**Advantages**:
+- No external dependencies
+- Simpler codebase (direct control)
+- Better error handling and validation
+- Platform-agnostic (Bun handles platform differences)
+</Accordion>
+
+<Accordion title="Database Driver (bun:sqlite)">
+**Component**: bun:sqlite
+- **Package**: Built into Bun runtime (no npm package)
+- **Installation**: None required (comes with Bun ≥1.0)
+- **Platform**: Works anywhere Bun works
+- **Import**: `import { Database } from 'bun:sqlite'`
+- **API**: Similar to better-sqlite3 (synchronous)
+
+**Installation Requirements**:
+- Bun ≥1.0 (automatically installed if missing)
+- No native compilation required
+- No platform-specific build tools needed
+
+**Compatibility**:
+- SQLite database format: **Unchanged**
+- Database file: `~/.claude-mem/claude-mem.db` (same location)
+- Query syntax: **Identical** (both use SQLite SQL)
+</Accordion>
+</AccordionGroup>
+
+## Migration Mechanics
+
+### One-Time PM2 Cleanup
+
+The migration system uses a marker-based approach to perform PM2 cleanup exactly once.
+
+**Implementation**: `src/shared/worker-utils.ts:73-86`
+
+```typescript
+// Clean up legacy PM2 (one-time migration)
+const pm2MigratedMarker = join(DATA_DIR, '.pm2-migrated');
+
+if (!existsSync(pm2MigratedMarker)) {
+  try {
+    spawnSync('pm2', ['delete', 'claude-mem-worker'], { stdio: 'ignore' });
+    // Mark migration as complete
+    writeFileSync(pm2MigratedMarker, new Date().toISOString(), 'utf-8');
+    logger.debug('SYSTEM', 'PM2 cleanup completed and marked');
+  } catch {
+    // PM2 not installed or process doesn't exist - still mark as migrated
+    writeFileSync(pm2MigratedMarker, new Date().toISOString(), 'utf-8');
+  }
+}
+```
+
+### Migration Trigger Points
+
+<Steps>
+<Step title="Hook Execution">
+SessionStart, UserPromptSubmit, or PostToolUse hooks execute using new 7.1.0 code
+</Step>
+<Step title="Worker Status Check">
+`ensureWorkerRunning()` checks if `~/.claude-mem/.worker.pid` exists (it doesn't for first run after update)
+</Step>
+<Step title="Start Worker Decision">
+Worker not running → Call `startWorker()`
+</Step>
+<Step title="Migration Check">
+Check if `~/.claude-mem/.pm2-migrated` exists
+</Step>
+<Step title="PM2 Cleanup">
+Execute `pm2 delete claude-mem-worker` (errors ignored), create marker file
+</Step>
+<Step title="New Worker Start">
+Spawn new Bun-managed worker process with PID and port files
+</Step>
+</Steps>
+
+### Marker File
+
+**Location**: `~/.claude-mem/.pm2-migrated`
+
+**Content**: ISO 8601 timestamp
+```
+2025-12-13T00:18:39.673Z
+```
+
+**Purpose**:
+- One-time migration flag
+- Prevents repeated PM2 cleanup on every start
+- Persists across restarts and reboots
+
+**Lifecycle**:
+- Created: First hook trigger after update to 7.1.0+ (all platforms)
+- Updated: Never
+- Deleted: Never (user could manually delete to force re-migration)
+
+## User Experience Timeline
+
+### First Session After Update
+
+<Note>
+This is the critical migration moment. The process takes approximately 2-5 seconds.
+</Note>
+
+**Step-by-Step Execution**:
+
+1. **Hook fires** (SessionStart most common)
+2. **Worker status check**: No PID file → worker not running
+3. **Migration check**: No marker file → run PM2 cleanup
+4. **PM2 cleanup**: `pm2 delete claude-mem-worker` (old worker terminated)
+5. **Marker creation**: `~/.claude-mem/.pm2-migrated` with timestamp
+6. **New worker start**: Bun process spawned, PID/port files created
+7. **Verification**: Process check + HTTP health check
+8. **Hook completes**: Claude Code session starts normally
+
+**User Observable Behavior**:
+- Slight delay on first startup (PM2 cleanup + new worker spawn)
+- No error messages (cleanup failures silently handled)
+- Worker appears running via `npm run worker:status`
+- Old PM2 worker no longer in `pm2 list`
+
+### Subsequent Sessions
+
+After migration completes, every hook trigger follows the fast path:
+
+1. PID file exists? **YES**
+2. Process alive? **YES**
+3. HTTP health check? **SUCCESS**
+4. Result: Worker already running, done (~50ms)
+
+No migration logic runs on subsequent sessions.
+
+## Platform-Specific Behavior
+
+### Platform Comparison
+
+| Feature | macOS | Linux | Windows |
+|---------|-------|-------|---------|
+| PM2 Cleanup | Attempted | Attempted | Attempted |
+| Marker File | Created | Created | Created |
+| Process Signals | POSIX (native) | POSIX (native) | Bun abstraction |
+| Bun Support | Full | Full | Full |
+| PID File | Yes | Yes | Yes |
+| Port File | Yes | Yes | Yes |
+| Health Check | HTTP | HTTP | HTTP |
+| Migration Delay | ~2-5s first time | ~2-5s first time | ~2-5s first time |
+
+### Platform Notes
+
+<Tabs>
+<Tab title="macOS">
+- POSIX signal handling works natively
+- Bun fully supported
+- No platform-specific workarounds needed
+</Tab>
+<Tab title="Linux">
+- Identical behavior to macOS
+- POSIX signal handling
+- Works on Ubuntu, Debian, RHEL, CentOS, Arch
+- Alpine may require glibc (not musl)
+</Tab>
+<Tab title="Windows">
+- PM2 cleanup now runs (safe due to try/catch)
+- Bun abstracts signal handling differences
+- Path module handles Windows separators
+- File locking handled by SQLite
+</Tab>
+</Tabs>
+
+## Observable Changes
+
+### Command Changes
+
+| Old (PM2) | New (Bun) | Notes |
+|-----------|-----------|-------|
+| `pm2 list` | `npm run worker:status` | Shows worker status |
+| `pm2 start <script>` | `npm run worker:start` | Start worker |
+| `pm2 stop claude-mem-worker` | `npm run worker:stop` | Stop worker |
+| `pm2 restart claude-mem-worker` | `npm run worker:restart` | Restart worker |
+| `pm2 delete claude-mem-worker` | `npm run worker:stop` | Remove worker |
+| `pm2 logs claude-mem-worker` | `npm run worker:logs` | View logs |
+| `pm2 describe claude-mem-worker` | `npm run worker:status` | Detailed status |
+| `pm2 monit` | No equivalent | PM2-specific monitoring |
+
+### File Location Changes
+
+**Logs**:
+```
+Old: ~/.pm2/logs/claude-mem-worker-out.log
+     ~/.pm2/logs/claude-mem-worker-error.log
+
+New: ~/.claude-mem/logs/worker-YYYY-MM-DD.log
+```
+
+**PID Files**:
+```
+Old: ~/.pm2/pids/claude-mem-worker.pid
+
+New: ~/.claude-mem/.worker.pid
+```
+
+**Process State**:
+```
+Old: PM2 daemon memory (pm2 save)
+
+New: ~/.claude-mem/.worker.pid
+     ~/.claude-mem/.worker.port
+     ~/.claude-mem/.pm2-migrated (all platforms)
+```
+
+**Database** (unchanged):
+```
+Same: ~/.claude-mem/claude-mem.db
+```
+
+### User-Visible Changes
+
+**Before Update**:
+```bash
+$ pm2 list
+┌────┬────────────────────┬─────────┬─────────┬──────────┐
+│ id │ name               │ status  │ restart │ uptime   │
+├────┼────────────────────┼─────────┼─────────┼──────────┤
+│ 0  │ claude-mem-worker  │ online  │ 0       │ 2d 5h    │
+└────┴────────────────────┴─────────┴─────────┴──────────┘
+```
+
+**After Update**:
+```bash
+$ pm2 list
+# Empty - worker no longer managed by PM2
+
+$ npm run worker:status
+Worker is running
+PID: 35557
+Port: 37777
+Uptime: 2h 15m
+```
+
+### Orphaned Files
+
+After migration, these PM2 files may remain (safe to delete):
+
+```
+~/.pm2/                    # Entire PM2 directory
+~/.pm2/logs/               # Old logs
+~/.pm2/pids/               # Old PID files
+~/.pm2/pm2.log             # PM2 daemon log
+~/.pm2/dump.pm2            # PM2 process dump
+```
+
+**Cleanup (optional)**:
+```bash
+# Remove PM2 entirely (if not used for other processes)
+pm2 kill
+rm -rf ~/.pm2
+
+# Or just remove claude-mem logs
+rm -f ~/.pm2/logs/claude-mem-worker-*.log
+rm -f ~/.pm2/pids/claude-mem-worker.pid
+```
+
+## File System State
+
+### State Directory Structure
+
+**Before Migration** (PM2 system):
+```
+~/.claude-mem/
+├── claude-mem.db          # Database (unchanged)
+├── chroma/                # Vector embeddings (unchanged)
+├── logs/                  # Application logs (unchanged)
+└── settings.json          # User settings (unchanged)
+
+~/.pm2/
+├── logs/
+│   ├── claude-mem-worker-out.log
+│   └── claude-mem-worker-error.log
+├── pids/
+│   └── claude-mem-worker.pid
+└── pm2.log
+```
+
+**After Migration** (Bun system):
+```
+~/.claude-mem/
+├── claude-mem.db          # Database (same file)
+├── chroma/                # Vector embeddings (unchanged)
+├── logs/
+│   └── worker-2025-12-13.log  # New log format
+├── settings.json          # User settings (unchanged)
+├── .worker.pid            # NEW: Process ID
+├── .worker.port           # NEW: Port + PID
+└── .pm2-migrated          # NEW: Migration marker (all platforms)
+
+~/.pm2/                    # Orphaned (safe to delete)
+├── logs/                  # Old logs (no longer written)
+├── pids/                  # Old PID (no longer updated)
+└── pm2.log                # PM2 daemon log (not used)
+```
+
+## Edge Cases and Troubleshooting
+
+### Scenario 1: Migration Fails (PM2 Still Running)
+
+<Warning>
+This is rare but can happen if PM2 has watch mode enabled or the process is manually restarted.
+</Warning>
+
+**Symptoms**:
+- `pm2 list` still shows `claude-mem-worker`
+- Port conflict errors in logs
+- Worker fails to start
+
+**Resolution**:
+```bash
+# Manual cleanup
+pm2 delete claude-mem-worker
+pm2 save  # Persist the deletion
+
+# Force re-migration (optional)
+rm ~/.claude-mem/.pm2-migrated
+
+# Restart worker
+npm run worker:restart
+```
+
+### Scenario 2: Stale PID File (Process Dead)
+
+**Symptoms**:
+- `npm run worker:status` shows "not running"
+- `.worker.pid` file exists
+- Process ID doesn't exist
+
+**Automatic Recovery**: Next hook trigger detects dead process and starts a fresh worker.
+
+**Manual Resolution**:
+```bash
+rm ~/.claude-mem/.worker.pid
+rm ~/.claude-mem/.worker.port
+npm run worker:start
+```
+
+### Scenario 3: Port Already in Use
+
+**Error**: `EADDRINUSE: address already in use`
+
+**Resolution**:
+```bash
+# Check what's using the port
+lsof -i :37777
+
+# Kill the process
+kill -9 <PID>
+
+# Restart worker
+npm run worker:restart
+```
+
+### Common Error Messages
+
+| Error | Cause | Resolution |
+|-------|-------|------------|
+| `EADDRINUSE` | Port already in use | `lsof -i :37777` then kill conflicting process |
+| `No such process` | Stale PID file | Automatic cleanup on next hook trigger |
+| `pm2: command not found` | PM2 not installed | None needed (error is caught and ignored) |
+| `Invalid port X` | Port validation failed | Update `CLAUDE_MEM_WORKER_PORT` in settings |
+
+## Developer Notes
+
+### Testing the Migration
+
+```bash
+# 1. Install old version (with PM2)
+git checkout <pre-7.1.0-tag>
+npm install && npm run build && npm run sync-marketplace
+
+# 2. Start PM2 worker
+pm2 start plugin/scripts/worker-cli.js --name claude-mem-worker
+
+# 3. Update to new version
+git checkout main
+npm install && npm run build && npm run sync-marketplace
+
+# 4. Trigger hook
+node plugin/scripts/session-start-hook.js
+
+# 5. Verify migration
+pm2 list  # Should NOT show claude-mem-worker
+cat ~/.claude-mem/.pm2-migrated  # Should exist
+npm run worker:status  # Should show Bun worker running
+```
+
+### Architecture Decisions
+
+**Why Custom ProcessManager Instead of PM2?**
+1. **Simplicity**: Direct control, no external daemon
+2. **Dependencies**: Remove npm dependency
+3. **Cross-platform**: Bun handles platform differences
+4. **Bundle Size**: Reduce plugin package size
+5. **Control**: Fine-grained error handling and validation
+
+**Why One-Time Marker Instead of Always Running PM2 Delete?**
+1. **Performance**: Avoid unnecessary process spawning
+2. **Idempotency**: Migration runs exactly once
+3. **Debugging**: Timestamp shows when migration occurred
+4. **Simplicity**: Clear migration state
+
+**Why Run PM2 Cleanup on All Platforms?**
+1. **Quality Migration**: Clean up orphaned processes
+2. **Consistency**: Same behavior across all platforms
+3. **Safety**: Error handling already in place (try/catch)
+4. **No Downside**: If PM2 not installed, error is caught and ignored
+
+## Summary
+
+The migration from PM2 to Bun-based ProcessManager is a **one-time, automatic, transparent** transition that:
+
+1. **Removes external dependencies** (PM2, better-sqlite3)
+2. **Simplifies architecture** (direct process control)
+3. **Improves cross-platform support** (especially Windows)
+4. **Preserves user data** (database, settings, logs unchanged)
+5. **Requires no user action** (automatic on first hook trigger)
+
+**Key Migration Moment**: First hook trigger after update to 7.1.0+
+**Duration**: ~2-5 seconds (one-time delay)
+**Impact**: Seamless transition, user-invisible
+**Rollback**: Not needed (migration is forward-only, safe)
+
+For most users, the migration will be completely transparent - they'll see no errors, no data loss, and experience improved reliability and simpler troubleshooting going forward.
diff --git a/docs/public/docs.json b/docs/public/docs.json
index 7837d537..dacd99c4 100644
--- a/docs/public/docs.json
+++ b/docs/public/docs.json
@@ -70,7 +70,8 @@
           "architecture/hooks",
           "architecture/worker-service",
           "architecture/database",
-          "architecture/search-architecture"
+          "architecture/search-architecture",
+          "architecture/pm2-to-bun-migration"
         ]
       }
     ]