Fix RPC error and change log statement

Former-commit-id: 54da8e259e6abae30c61dc6301cbfeeb0ede8570 [formerly 31f207fb38d4a1699dc60c294cf99a1673b54ab7]
Former-commit-id: c70fc84a836a6b03bcaf07b5fe7a9eb5c116e0da

sharding/client/client.go

@@ -79,30 +79,28 @@ func MakeClient(ctx *cli.Context) *ShardingClient {
 // Start the sharding client.
 // * Connects to Geth node.
 // * Verifies or deploys the sharding manager contract.
-func (c *ShardingClient) Start() error {
-	log.Info("Starting collator client")
+func (c *ShardingClient) Start() (*rpc.Client, error) {
 	rpcClient, err := dialRPC(c.endpoint)
 	if err != nil {
-		return err
+		return nil, fmt.Errorf("cannot start rpc client. %v", err)
 	}
 	c.client = ethclient.NewClient(rpcClient)
-	defer rpcClient.Close()
 
 	// Check account existence and unlock account before starting collator client
 	accounts := c.keystore.Accounts()
 	if len(accounts) == 0 {
-		return fmt.Errorf("no accounts found")
+		return nil, fmt.Errorf("no accounts found")
 	}
 
 	if err := c.unlockAccount(accounts[0]); err != nil {
-		return fmt.Errorf("cannot unlock account. %v", err)
+		return nil, fmt.Errorf("cannot unlock account. %v", err)
 	}
 
 	if err := initSMC(c); err != nil {
-		return err
+		return nil, err
 	}
 
-	return nil
+	return rpcClient, nil
 }
 
 // Wait until collator client is shutdown.

sharding/collator/collator_client.go

@@ -2,6 +2,7 @@ package collator
 
 import (
 	"github.com/ethereum/go-ethereum/sharding/client"
+	"github.com/ethereum/go-ethereum/log"
 	cli "gopkg.in/urfave/cli.v1"
 )
 
@@ -12,7 +13,12 @@ func NewCollatorClient(ctx *cli.Context) *client.ShardingClient {
 }
 
 func CollatorStart(sclient *client.ShardingClient) error {
-	sclient.Start()
+	log.Info("Starting collator client")
+	rpcClient, err := sclient.Start()
+	defer rpcClient.Close()
+	if err != nil {
+		return err
+	}
 
 	if err := joinCollatorPool(sclient); err != nil {
 		return err

sharding/proposer/proposer_client.go

@@ -2,6 +2,7 @@ package proposer
 
 import (
 	"github.com/ethereum/go-ethereum/sharding/client"
+	"github.com/ethereum/go-ethereum/log"
 	cli "gopkg.in/urfave/cli.v1"
 )
 
@@ -12,6 +13,7 @@ func NewProposerClient(ctx *cli.Context) *client.ShardingClient {
 }
 
 func ProposerStart(sclient *client.ShardingClient) error {
+	log.Info("Starting proposer client")
 	sclient.Start()
 
 	return nil