config_reload
1 Commits
| Author | SHA1 | Message | Date | |
|---|---|---|---|---|
Ben Roberts
|
fe399e2f03 |
Support for reloading config file on HUP signal
Implemented dynamic configuration reloading for gocast via SIGHUP signal handling. This allows updating BGP configuration, applications, and agent settings without service restart.
**Location:** `main.go:29-46`
Enhanced the existing signal handler to process SIGHUP:
```go
switch sig {
case syscall.SIGHUP:
log.Info("Received SIGHUP, reloading configuration")
if err := mon.Reload(*config); err != nil {
log.Errorf("Failed to reload configuration: %v", err)
} else {
log.Info("Configuration reloaded successfully")
}
case os.Interrupt, syscall.SIGTERM:
log.Info("Received shutdown signal, cleaning up")
mon.CloseAll()
cancel()
return
}
```
**Key Features:**
- Non-blocking: Uses goroutine to handle signals
- Graceful: SIGINT/SIGTERM still trigger clean shutdown
- Logged: All reload attempts are logged with success/failure status
**Location:** `controller/monitor.go:343-420`
Main reload orchestration method:
```go
func (m *MonitorMgr) Reload(configPath string) error
```
**Process Flow:**
1. Read new configuration from file
2. Compare with current configuration
3. If BGP config changed:
- Withdraw all announced routes
- Shutdown old BGP controller
- Start new BGP controller
- Re-announce routes for healthy apps
4. If Consul config changed:
- Initialize new Consul monitor
5. Update agent settings
6. Reload applications (add/remove/update)
**Thread Safety:**
- Uses existing `monMu` mutex for monitor map access
- Atomic BGP controller replacement
- No race conditions during reload
**Location:** `controller/monitor.go:422-475`
```go
func (m *MonitorMgr) bgpConfigChanged(old, new c.BgpConfig) bool
```
Comprehensive comparison of:
- Local AS, Peer AS, Peer IPs
- BGP origin
- Multi-hop settings (including nil checks)
- MD5 passwords and environment variables
- Per-peer communities
- Global communities
**Important:** Deep comparison ensures even minor changes are detected.
**Location:** `controller/monitor.go:477-532`
```go
func (m *MonitorMgr) reloadApps(oldApps, newApps []c.AppConfig)
```
Intelligent app management:
- **Remove:** Apps no longer in config (source="config" only)
- **Update:** Apps with changed configuration (VIP, monitors, NAT, communities)
- **Add:** New apps in configuration
**Key Behavior:**
- Consul-discovered apps are NOT removed during reload
- Only config-defined apps are managed
- Config changes trigger remove + re-add
1. **TestBgpConfigChanged**
- Tests all BGP configuration change scenarios
- Validates detection of AS, peer, MD5, community changes
- Includes nil multi-hop pointer checks
2. **TestEqualStringSlices**
- Tests slice comparison helper
- Validates empty, identical, and different slices
3. **TestReload** (Integration, requires root)
- Full reload cycle with BGP AS change
- App removal verification
- BGP controller replacement validation
4. **TestReloadAddApp** (Integration)
- Tests adding new app via reload
- Validates app registration
5. **TestReloadMD5Change** (Integration)
- Tests MD5 password change detection
- Validates BGP controller restart
**Decision:** Reload BGP configuration requires full controller restart.
**Rationale:**
- GoBGP library doesn't support modifying peers dynamically
- Simplifies implementation
- Ensures clean state
- Brief interruption is acceptable for infrequent config changes
**Alternative Considered:** Per-peer updates
- Complex to implement correctly
- Partial state issues
- Not supported well by GoBGP library
**Decision:** Log errors but don't crash; maintain old state on failure.
**Rationale:**
- Availability over correctness for config errors
- Admin can fix config and retry
- Better than service downtime
- Logs provide clear error messages
1. **BGP Interruption**
- Full BGP restart causes brief routing interruption
- All routes withdrawn and re-announced
- May impact traffic during reload
2. **No Atomic BGP Updates**
- Cannot add/remove single peer without full restart
- All peers affected even if one changes
3. **No Config Validation**
- Invalid config is detected during reload
- No pre-validation before applying
- Syntax errors require manual fix and retry
4. **No Rollback**
- Failed reload leaves service in potentially inconsistent state
- Manual intervention required to restore
- No automatic rollback to previous config
These changes were written using AI LLM
Authored-By: Claude Code (Sonnet 4.5)
|