Support multiple hosts in provider configuration

postgresql/proxy_driver.go

@@ -4,7 +4,9 @@ import (
 	"context"
 	"database/sql"
 	"database/sql/driver"
+	"errors"
 	"net"
+	"strings"
 	"time"
 
 	"github.com/lib/pq"
@@ -20,14 +22,82 @@ func (d proxyDriver) Open(name string) (driver.Conn, error) {
 }
 
 func (d proxyDriver) Dial(network, address string) (net.Conn, error) {
-	dialer := proxy.FromEnvironment()
-	return dialer.Dial(network, address)
+	return d.DialTimeout(network, address, 0)
 }
 
 func (d proxyDriver) DialTimeout(network, address string, timeout time.Duration) (net.Conn, error) {
-	ctx, cancel := context.WithTimeout(context.TODO(), timeout)
-	defer cancel()
-	return proxy.Dial(ctx, network, address)
+	var ctx context.Context
+	var cancel context.CancelFunc
+	if timeout > 0 {
+		ctx, cancel = context.WithTimeout(context.Background(), timeout)
+		defer cancel()
+	} else {
+		ctx = context.Background()
+	}
+
+	// Only handle TCP networks for multi-host splitting
+	if !strings.HasPrefix(network, "tcp") {
+		return proxy.Dial(ctx, network, address)
+	}
+
+	hosts, port, err := parseAddress(address)
+	if err != nil {
+		// If parsing fails, fall back to trying the original address
+		return proxy.Dial(ctx, network, address)
+	}
+
+	var lastErr error
+	for _, host := range hosts {
+		addr := net.JoinHostPort(host, port)
+		conn, err := proxy.Dial(ctx, network, addr)
+		if err == nil {
+			return conn, nil
+		}
+		lastErr = err
+
+		// Check if context expired
+		select {
+		case <-ctx.Done():
+			return nil, ctx.Err()
+		default:
+		}
+	}
+	if lastErr != nil {
+		return nil, lastErr
+	}
+	return nil, errors.New("no hosts available")
+}
+
+func parseAddress(address string) ([]string, string, error) {
+	host, port, err := net.SplitHostPort(address)
+	if err == nil {
+		if strings.Contains(host, ",") {
+			return strings.Split(host, ","), port, nil
+		}
+		return []string{host}, port, nil
+	}
+
+	// Fallback for when net.SplitHostPort fails (e.g. mixed bracketed and unbracketed hosts)
+	lastColon := strings.LastIndex(address, ":")
+	if lastColon == -1 {
+		return nil, "", err
+	}
+
+	port = address[lastColon+1:]
+	hostPart := address[:lastColon]
+
+	if strings.Contains(hostPart, ",") {
+		hosts := strings.Split(hostPart, ",")
+		// Clean up brackets if present so net.JoinHostPort doesn't double them
+		for i, h := range hosts {
+			if len(h) > 2 && h[0] == '[' && h[len(h)-1] == ']' {
+				hosts[i] = h[1 : len(h)-1]
+			}
+		}
+		return hosts, port, nil
+	}
+
+	return nil, "", err
 }
 
 func init() {

postgresql/proxy_driver_test.go

@@ -0,0 +1,83 @@
+package postgresql
+
+import (
+	"net"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestParseAddress(t *testing.T) {
+	tests := []struct {
+		input       string
+		expectHosts []string
+		expectPort  string
+		expectErr   bool
+	}{
+		{
+			input:       "host1:5432",
+			expectHosts: []string{"host1"},
+			expectPort:  "5432",
+			expectErr:   false,
+		},
+		{
+			input:       "host1,host2:5432",
+			expectHosts: []string{"host1", "host2"},
+			expectPort:  "5432",
+			expectErr:   false,
+		},
+		{
+			input:       "[::1]:5432",
+			expectHosts: []string{"::1"}, // net.SplitHostPort strips brackets
+			expectPort:  "5432",
+			expectErr:   false,
+		},
+		{
+			input:       "[::1],localhost:5432",
+			expectHosts: []string{"::1", "localhost"}, // manual split strips brackets
+			expectPort:  "5432",
+			expectErr:   false,
+		},
+		{
+			input:       "host1,[::1]:5432",
+			expectHosts: []string{"host1", "::1"},
+			expectPort:  "5432",
+			expectErr:   false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.input, func(t *testing.T) {
+			hosts, port, err := parseAddress(tt.input)
+			if tt.expectErr {
+				assert.Error(t, err)
+			} else {
+				assert.NoError(t, err)
+				assert.Equal(t, tt.expectHosts, hosts)
+				assert.Equal(t, tt.expectPort, port)
+			}
+		})
+	}
+}
+
+func TestReconstruction(t *testing.T) {
+	// Verify that net.JoinHostPort reconstructs correctly from what parseAddress returns
+	tests := []string{
+		"host1:5432",
+		"host1,host2:5432",
+		"[::1]:5432",
+		"[::1],localhost:5432",
+	}
+
+	for _, input := range tests {
+		hosts, port, err := parseAddress(input)
+		assert.NoError(t, err)
+		for _, h := range hosts {
+			addr := net.JoinHostPort(h, port)
+			// Sanity check on address format
+			_, _, err := net.SplitHostPort(addr)
+			assert.NoError(t, err, "JoinHostPort produced invalid address: %s", addr)
+		}
+	}
+}
+