Implement Multi-Proxy and Load Balancer Strategy Support

This commit introduces significant updates to enhance the handling of proxies within the server configuration and adds support for load balancing strategies.

Changes:
- Updated API tests to reflect changes from a single `Proxy` to a list of `Proxies`.
- Adjusted initialization and configuration of proxies in `run.go` to support multiple proxies and load balancer strategies.
- Updated configuration files to include new fields for multiple proxies and load balancer strategies.
- Enhanced global configuration validation for clients, pools, and proxies.
- Added new `loadBalancer` section in `gatewayd.yaml` for rules and strategies.
- Implemented load balancing strategy selection and Round Robin strategy.
- Added tests for load balancer strategies.
- Added new error type `ErrorCodeLoadBalancerStrategyNotFound`.
- Improved proxy connection handling and added informative comments.

Configuration Example:
- Updated `gatewayd.yaml` to reflect new support for multiple proxies and load balancer strategies.
- Ensure to update your configuration files accordingly.

Testing:
- Updated existing tests and added new tests for multi-proxy and load balancing functionality.
- Verified configuration validation for proxies and load balancers.

Impact:
- Improved flexibility and scalability of server configuration.
- Enabled robust proxy management and efficient load distribution.

api/api_helpers_test.go

@@ -49,7 +49,7 @@ func getAPIConfig() *API {
 			context.Background(),
 			network.Server{
 				Logger:         logger,
-				Proxy:          defaultProxy,
+				Proxies:        []network.IProxy{defaultProxy},
 				PluginRegistry: pluginReg,
 				PluginTimeout:  config.DefaultPluginTimeout,
 				Network:        "tcp",

api/api_test.go

@@ -333,7 +333,7 @@ func TestGetServers(t *testing.T) {
 			Options: network.Option{
 				EnableTicker: false,
 			},
-			Proxy:            proxy,
+			Proxies:          []network.IProxy{proxy},
 			Logger:           zerolog.Logger{},
 			PluginRegistry:   pluginRegistry,
 			PluginTimeout:    config.DefaultPluginTimeout,

api/healthcheck_test.go

@@ -69,7 +69,7 @@ func Test_Healthchecker(t *testing.T) {
 			Options: network.Option{
 				EnableTicker: false,
 			},
-			Proxy:            proxy,
+			Proxies:          []network.IProxy{proxy},
 			Logger:           zerolog.Logger{},
 			PluginRegistry:   pluginRegistry,
 			PluginTimeout:    config.DefaultPluginTimeout,

cmd/run.go

@@ -871,6 +871,18 @@ var runCmd = &cobra.Command{
 		// Create and initialize servers.
 		for name, cfg := range conf.Global.Servers {
 			logger := loggers[name]
+
+			var serverProxies []network.IProxy
+			for _, proxyName := range cfg.Proxies {
+				proxy, exists := proxies[proxyName]
+				if !exists {
+					// This may occur if a proxy referenced in the server configuration does not exist.
+					logger.Error().Str("proxyName", proxyName).Msg("failed to find proxy configuration")
+					return
+				}
+				serverProxies = append(serverProxies, proxy)
+			}
+
 			servers[name] = network.NewServer(
 				runCtx,
 				network.Server{
@@ -885,14 +897,15 @@ var runCmd = &cobra.Command{
 						// Can be used to send keepalive messages to the client.
 						EnableTicker: cfg.EnableTicker,
 					},
-					Proxy:            proxies[name],
-					Logger:           logger,
-					PluginRegistry:   pluginRegistry,
-					PluginTimeout:    conf.Plugin.Timeout,
-					EnableTLS:        cfg.EnableTLS,
-					CertFile:         cfg.CertFile,
-					KeyFile:          cfg.KeyFile,
-					HandshakeTimeout: cfg.HandshakeTimeout,
+					Proxies:                  serverProxies,
+					Logger:                   logger,
+					PluginRegistry:           pluginRegistry,
+					PluginTimeout:            conf.Plugin.Timeout,
+					EnableTLS:                cfg.EnableTLS,
+					CertFile:                 cfg.CertFile,
+					KeyFile:                  cfg.KeyFile,
+					HandshakeTimeout:         cfg.HandshakeTimeout,
+					LoadbalancerStrategyName: cfg.LoadBalancer.Strategy,
 				},
 			)
 

config/config.go

@@ -160,6 +160,8 @@ func (c *Config) LoadDefaults(ctx context.Context) *gerr.GatewayDError {
 		CertFile:         "",
 		KeyFile:          "",
 		HandshakeTimeout: DefaultHandshakeTimeout,
+		Proxies:          []string{Default},
+		LoadBalancer:     LoadBalancer{Strategy: DefaultLoadBalancerStrategy},
 	}
 
 	c.globalDefaults = GlobalConfig{
@@ -413,7 +415,7 @@ func (c *Config) ValidateGlobalConfig(ctx context.Context) *gerr.GatewayDError {
 	}
 
 	var errors []*gerr.GatewayDError
-	configObjects := []string{"loggers", "metrics", "clients", "pools", "proxies", "servers"}
+	configObjects := []string{"loggers", "metrics", "servers"}
 	sort.Strings(configObjects)
 	var seenConfigObjects []string
 
@@ -441,18 +443,16 @@ func (c *Config) ValidateGlobalConfig(ctx context.Context) *gerr.GatewayDError {
 		seenConfigObjects = append(seenConfigObjects, "metrics")
 	}
 
+	clientConfigGroups := make(map[string]bool)
 	for configGroup := range globalConfig.Clients {
+		clientConfigGroups[configGroup] = true
 		if globalConfig.Clients[configGroup] == nil {
 			err := fmt.Errorf("\"clients.%s\" is nil or empty", configGroup)
 			span.RecordError(err)
 			errors = append(errors, gerr.ErrValidationFailed.Wrap(err))
 		}
 	}
 
-	if len(globalConfig.Clients) > 1 {
-		seenConfigObjects = append(seenConfigObjects, "clients")
-	}
-
 	for configGroup := range globalConfig.Pools {
 		if globalConfig.Pools[configGroup] == nil {
 			err := fmt.Errorf("\"pools.%s\" is nil or empty", configGroup)
@@ -461,10 +461,6 @@ func (c *Config) ValidateGlobalConfig(ctx context.Context) *gerr.GatewayDError {
 		}
 	}
 
-	if len(globalConfig.Pools) > 1 {
-		seenConfigObjects = append(seenConfigObjects, "pools")
-	}
-
 	for configGroup := range globalConfig.Proxies {
 		if globalConfig.Proxies[configGroup] == nil {
 			err := fmt.Errorf("\"proxies.%s\" is nil or empty", configGroup)
@@ -473,10 +469,6 @@ func (c *Config) ValidateGlobalConfig(ctx context.Context) *gerr.GatewayDError {
 		}
 	}
 
-	if len(globalConfig.Proxies) > 1 {
-		seenConfigObjects = append(seenConfigObjects, "proxies")
-	}
-
 	for configGroup := range globalConfig.Servers {
 		if globalConfig.Servers[configGroup] == nil {
 			err := fmt.Errorf("\"servers.%s\" is nil or empty", configGroup)
@@ -489,6 +481,50 @@ func (c *Config) ValidateGlobalConfig(ctx context.Context) *gerr.GatewayDError {
 		seenConfigObjects = append(seenConfigObjects, "servers")
 	}
 
+	// ValidateClientsPoolsProxies checks if all configGroups in globalConfig.Pools and globalConfig.Proxies
+	// are referenced in globalConfig.Clients.
+	if len(globalConfig.Clients) != len(globalConfig.Pools) || len(globalConfig.Clients) != len(globalConfig.Proxies) {
+		err := goerrors.New("clients, pools, and proxies do not have the same number of objects")
+		span.RecordError(err)
+		errors = append(errors, gerr.ErrValidationFailed.Wrap(err))
+	}
+
+	// Check if all proxies are referenced in client configuration
+	for configGroup := range globalConfig.Proxies {
+		if !clientConfigGroups[configGroup] {
+			err := fmt.Errorf(`"proxies.%s" not referenced in client configuration`, configGroup)
+			span.RecordError(err)
+			errors = append(errors, gerr.ErrValidationFailed.Wrap(err))
+		}
+	}
+
+	// Check if all pools are referenced in client configuration
+	for configGroup := range globalConfig.Pools {
+		if !clientConfigGroups[configGroup] {
+			err := fmt.Errorf(`"pools.%s" not referenced in client configuration`, configGroup)
+			span.RecordError(err)
+			errors = append(errors, gerr.ErrValidationFailed.Wrap(err))
+		}
+	}
+
+	// Each server configuration should have at least one proxy defined.
+	// Each proxy in the server configuration should be referenced in proxies configuration.
+	for serverName, server := range globalConfig.Servers {
+		if len(server.Proxies) == 0 {
+			err := fmt.Errorf(`"servers.%s" has no proxies defined`, serverName)
+			span.RecordError(err)
+			errors = append(errors, gerr.ErrValidationFailed.Wrap(err))
+			continue
+		}
+		for _, proxyName := range server.Proxies {
+			if _, exists := c.globalDefaults.Proxies[proxyName]; !exists {
+				err := fmt.Errorf(`"servers.%s" references a non-existent proxy "%s"`, serverName, proxyName)
+				span.RecordError(err)
+				errors = append(errors, gerr.ErrValidationFailed.Wrap(err))
+			}
+		}
+	}
+
 	sort.Strings(seenConfigObjects)
 
 	if len(seenConfigObjects) > 0 && !reflect.DeepEqual(configObjects, seenConfigObjects) {

config/constants.go

@@ -89,10 +89,11 @@ const (
 	DefaultHealthCheckPeriod = 60 * time.Second // This must match PostgreSQL authentication timeout.
 
 	// Server constants.
-	DefaultListenNetwork    = "tcp"
-	DefaultListenAddress    = "0.0.0.0:15432"
-	DefaultTickInterval     = 5 * time.Second
-	DefaultHandshakeTimeout = 5 * time.Second
+	DefaultListenNetwork        = "tcp"
+	DefaultListenAddress        = "0.0.0.0:15432"
+	DefaultTickInterval         = 5 * time.Second
+	DefaultHandshakeTimeout     = 5 * time.Second
+	DefaultLoadBalancerStrategy = "ROUND_ROBIN"
 
 	// Utility constants.
 	DefaultSeed = 1000

config/types.go

@@ -96,6 +96,10 @@ type Proxy struct {
 	HealthCheckPeriod time.Duration `json:"healthCheckPeriod" jsonschema:"oneof_type=string;integer"`
 }
 
+type LoadBalancer struct {
+	Strategy string `json:"strategy"`
+}
+
 type Server struct {
 	EnableTicker     bool          `json:"enableTicker"`
 	TickInterval     time.Duration `json:"tickInterval" jsonschema:"oneof_type=string;integer"`
@@ -105,6 +109,8 @@ type Server struct {
 	CertFile         string        `json:"certFile"`
 	KeyFile          string        `json:"keyFile"`
 	HandshakeTimeout time.Duration `json:"handshakeTimeout" jsonschema:"oneof_type=string;integer"`
+	Proxies          []string      `json:"proxies"`
+	LoadBalancer     LoadBalancer  `json:"loadBalancer"`
 }
 
 type API struct {

errors/errors.go

@@ -53,6 +53,7 @@ const (
 	ErrCodeMsgEncodeError
 	ErrCodeConfigParseError
 	ErrCodePublishAsyncAction
+	ErrorCodeLoadBalancerStrategyNotFound
 )
 
 var (
@@ -194,6 +195,10 @@ var (
 		ErrCodePublishAsyncAction, "error publishing async action", nil,
 	}
 
+	ErrLoadBalancerStrategyNotFound = &GatewayDError{
+		ErrorCodeLoadBalancerStrategyNotFound, "The specified load balancer strategy does not exist.", nil,
+	}
+
 	// Unwrapped errors.
 	ErrLoggerRequired = errors.New("terminate action requires a logger parameter")
 )

gatewayd.yaml

@@ -46,19 +46,51 @@ clients:
     backoff: 1s # duration
     backoffMultiplier: 2.0 # 0 means no backoff
     disableBackoffCaps: false
+  default-2:
+    network: tcp
+    address: localhost:5433
+    tcpKeepAlive: False
+    tcpKeepAlivePeriod: 30s # duration
+    receiveChunkSize: 8192
+    receiveDeadline: 0s # duration, 0ms/0s means no deadline
+    receiveTimeout: 0s # duration, 0ms/0s means no timeout
+    sendDeadline: 0s # duration, 0ms/0s means no deadline
+    dialTimeout: 60s # duration
+    # Retry configuration
+    retries: 3 # 0 means no retry and fail immediately on the first attempt
+    backoff: 1s # duration
+    backoffMultiplier: 2.0 # 0 means no backoff
+    disableBackoffCaps: false
 
 pools:
   default:
     size: 10
+  default-2:
+    size: 10
 
 proxies:
   default:
     healthCheckPeriod: 60s # duration
+  default-2:
+    healthCheckPeriod: 60s # duration
 
 servers:
   default:
     network: tcp
     address: 0.0.0.0:15432
+    proxies:
+      - "default"
+      - "default-2"
+    loadBalancer:
+      strategy: ROUND_ROBIN
+      # Not yet implemented.
+      # loadBalancingRules:
+      #   - condition: "default"
+      #     percentages:
+      #       - proxy: "default"
+      #         percentage: 70
+      #       - proxy: "default-2"
+      #         percentage: 30
     enableTicker: False
     tickInterval: 5s # duration
     enableTLS: False

network/constants.go

@@ -0,0 +1,6 @@
+package network
+
+// Load balancing strategies.
+const (
+	RoundRobinStrategy = "ROUND_ROBIN"
+)

network/loadbalancer.go

@@ -0,0 +1,18 @@
+package network
+
+import (
+	gerr "github.com/gatewayd-io/gatewayd/errors"
+)
+
+type LoadBalancerStrategy interface {
+	GetNextProxy() IProxy
+}
+
+func NewLoadBalancerStrategy(server *Server) (LoadBalancerStrategy, *gerr.GatewayDError) {
+	switch server.LoadbalancerStrategyName {
+	case RoundRobinStrategy:
+		return NewRoundRobin(server), nil
+	default:
+		return nil, gerr.ErrLoadBalancerStrategyNotFound
+	}
+}

network/loadbalancer_test.go

@@ -0,0 +1,40 @@
+package network
+
+import (
+	"errors"
+	"testing"
+
+	gerr "github.com/gatewayd-io/gatewayd/errors"
+)
+
+func TestNewLoadBalancerStrategy(t *testing.T) {
+	serverValid := &Server{
+		LoadbalancerStrategyName: RoundRobinStrategy,
+		Proxies:                  []IProxy{MockProxy{}},
+	}
+
+	// Test case 1: Valid strategy name
+	strategy, err := NewLoadBalancerStrategy(serverValid)
+	if err != nil {
+		t.Errorf("Expected no error, got %v", err)
+	}
+
+	_, ok := strategy.(*RoundRobin)
+	if !ok {
+		t.Errorf("Expected strategy to be of type RoundRobin")
+	}
+
+	// Test case 2: InValid strategy name
+	serverInvalid := &Server{
+		LoadbalancerStrategyName: "InvalidStrategy",
+		Proxies:                  []IProxy{MockProxy{}},
+	}
+
+	strategy, err = NewLoadBalancerStrategy(serverInvalid)
+	if !errors.Is(err, gerr.ErrLoadBalancerStrategyNotFound) {
+		t.Errorf("Expected ErrLoadBalancerStrategyNotFound, got %v", err)
+	}
+	if strategy != nil {
+		t.Errorf("Expected strategy to be nil for invalid strategy name")
+	}
+}

network/round-robin.go

@@ -0,0 +1,20 @@
+package network
+
+import "sync/atomic"
+
+type RoundRobin struct {
+	proxies []IProxy
+	next    atomic.Uint32
+}
+
+func NewRoundRobin(server *Server) *RoundRobin {
+	return &RoundRobin{proxies: server.Proxies}
+}
+
+func (r *RoundRobin) GetNextProxy() IProxy {
+	proxiesLen := uint32(len(r.proxies))
+
+	nextIndex := r.next.Add(1)
+
+	return r.proxies[nextIndex%proxiesLen]
+}