feat: add multi call routing strategy (#26)

* feat: add multicall routing strategy
    * Updated proxyd config to accept a routing strategy parameter 
    * Added multicall routing strategies
    * Refactored backendGroup.Forward to handle multiple types of routing strategies
    * Background.ForwardToBackend now will return results via a channel

proxyd/config.go

@@ -6,6 +6,8 @@ import (
 	"os"
 	"strings"
 	"time"
+
+	"github.com/ethereum/go-ethereum/log"
 )
 
 type ServerConfig struct {
@@ -107,11 +109,54 @@ type BackendConfig struct {
 
 type BackendsConfig map[string]*BackendConfig
 
+type RoutingStrategy string
+
+func (b *BackendGroupConfig) ValidateRoutingStrategy(bgName string) bool {
+
+	// If Consensus Aware is Set and Routing RoutingStrategy is populated fail
+	if b.ConsensusAware && b.RoutingStrategy != "" {
+		log.Warn("consensus_aware is now deprecated, please use routing_strategy = consensus_aware")
+		log.Crit("Exiting consensus_aware and routing strategy are mutually exclusive, they cannot both be defined")
+	}
+
+	// If Consensus Aware is Set set RoutingStrategy to consensus_aware
+	if b.ConsensusAware {
+		b.RoutingStrategy = ConsensusAwareRoutingStrategy
+		log.Info("consensus_aware is now deprecated, please use routing_strategy = consenus_aware in the future")
+	}
+
+	switch b.RoutingStrategy {
+	case ConsensusAwareRoutingStrategy:
+		return true
+	case MulticallRoutingStrategy:
+		return true
+	case FallbackRoutingStrategy:
+		return true
+	case "":
+		log.Info("Empty routing strategy provided for backend_group, using fallback strategy ", "name", bgName)
+		b.RoutingStrategy = FallbackRoutingStrategy
+		return true
+	default:
+		return false
+	}
+}
+
+const (
+	ConsensusAwareRoutingStrategy RoutingStrategy = "consensus_aware"
+	MulticallRoutingStrategy      RoutingStrategy = "multicall"
+	FallbackRoutingStrategy       RoutingStrategy = "fallback"
+)
+
 type BackendGroupConfig struct {
 	Backends []string `toml:"backends"`
 
 	WeightedRouting bool `toml:"weighted_routing"`
 
+	RoutingStrategy RoutingStrategy `toml:"routing_strategy"`
+
+	/*
+		Deprecated: Use routing_strategy config to create a consensus_aware proxyd instance
+	*/
 	ConsensusAware          bool         `toml:"consensus_aware"`
 	ConsensusAsyncHandler   string       `toml:"consensus_handler"`
 	ConsensusPollerInterval TOMLDuration `toml:"consensus_poller_interval"`

proxyd/integration_tests/block_height_zero_and_network_errors_test.go

@@ -72,7 +72,7 @@ func setupBlockHeightZero(t *testing.T) (map[string]*bhZeroNodeContext, *proxyd.
 	bg := svr.BackendGroups["node"]
 
 	require.NotNil(t, bg)
-	require.NotNil(t, bg.Consensus)
+	require.NotNil(t, bg.Consensus, "Expected Consenus Poller to be intialized")
 	require.Equal(t, 2, len(bg.Backends))
 
 	// convenient mapping to access the nodes