fix: pool backup failover on reconnect, perfect dropper scripts, bcrypt password hashing

server/internal/pool/proxy.go

@@ -84,6 +84,14 @@ type Proxy struct {
 	reconnecting    bool
 	reconnectDelay  time.Duration
 	verboseTraffic  bool
+
+	// Pool failover: if the active config fails on reconnect, cycle through
+	// these alternatives before giving up. The primary Config is always index -1
+	// (the original); backups are tried in order.  primaryConfig preserves the
+	// original so we can reset after a full round fails.
+	primaryConfig  Config
+	backupConfigs  []Config
+	backupIdx      int // next backup to try
 }
 
 type PendingShare struct {
@@ -116,6 +124,7 @@ type Config struct {
 func NewProxy(cfg *Config) *Proxy {
 	return &Proxy{
 		config:         cfg,
+		primaryConfig:  *cfg,
 		stopCh:         make(chan struct{}),
 		shareQueue:     make(chan *PendingShare, 100),
 		pendingResults: make(map[int]*pendingShareResult),
@@ -123,6 +132,14 @@ func NewProxy(cfg *Config) *Proxy {
 	}
 }
 
+// SetBackupConfigs registers fallback pool configs tried in order when the
+// active config fails on reconnect.  Call before Start().
+func (p *Proxy) SetBackupConfigs(backups []Config) {
+	p.mu.Lock()
+	p.backupConfigs = backups
+	p.mu.Unlock()
+}
+
 func (p *Proxy) SetReconnectDelay(d time.Duration) {
 	if d > 0 {
 		p.mu.Lock()
@@ -702,18 +719,64 @@ func (p *Proxy) reconnect() {
 	default:
 	}
 
-	if err := p.connect(); err != nil {
-		log.Printf("[Pool] Reconnect failed: %v", err)
-		if p.onError != nil {
-			p.onError(fmt.Errorf("pool reconnect failed: %w", err))
+	// Build the full candidate list: [current primary] + backup configs.
+	// If the primary fails we rotate through backups so the fleet keeps hashing
+	// even when the configured pool is down.
+	p.mu.RLock()
+	primary := p.primaryConfig
+	backups := append([]Config(nil), p.backupConfigs...) // copy
+	startIdx := p.backupIdx
+	p.mu.RUnlock()
+
+	candidates := make([]Config, 0, 1+len(backups))
+	candidates = append(candidates, primary)
+	candidates = append(candidates, backups...)
+
+	total := len(candidates)
+	for i := 0; i < total; i++ {
+		// Rotate: try startIdx (last successful backup) before falling back to primary
+		idx := (startIdx + i) % total
+		cfg := candidates[idx]
+
+		p.mu.Lock()
+		*p.config = cfg
+		p.mu.Unlock()
+
+		if err := p.connect(); err != nil {
+			label := "primary"
+			if idx > 0 {
+				label = fmt.Sprintf("backup#%d (%s:%d)", idx, cfg.Host, cfg.Port)
+			}
+			log.Printf("[Pool] Reconnect to %s failed: %v", label, err)
+			continue
 		}
-		time.Sleep(30 * time.Second)
-		select {
-		case <-p.stopCh:
-			return
-		default:
-			p.scheduleReconnect()
+
+		// Succeeded — remember where we are so next reconnect starts here
+		p.mu.Lock()
+		p.backupIdx = idx
+		p.mu.Unlock()
+		if idx > 0 {
+			log.Printf("[Pool] Now connected to backup#%d (%s:%d)", idx, cfg.Host, cfg.Port)
 		}
+		return
+	}
+
+	// All candidates failed
+	if p.onError != nil {
+		p.onError(fmt.Errorf("all pool endpoints unreachable (%d tried)", total))
+	}
+	// Restore primary so next cycle starts fresh
+	p.mu.Lock()
+	*p.config = primary
+	p.backupIdx = 0
+	p.mu.Unlock()
+
+	time.Sleep(30 * time.Second)
+	select {
+	case <-p.stopCh:
+		return
+	default:
+		p.scheduleReconnect()
 	}
 }