op-node: Fix retrying dialing at startup

I needed to move IsURLAvailable around to break an import cycle.
I have manually tested that the op-node now properly waits for URLs
to be up before erroring.

op-node/client/rpc.go

@@ -3,6 +3,8 @@ package client
 import (
 	"context"
 	"fmt"
+	"net"
+	"net/url"
 	"regexp"
 	"time"
 
@@ -103,17 +105,31 @@ func NewRPC(ctx context.Context, lgr log.Logger, addr string, opts ...RPCOption)
 func dialRPCClientWithBackoff(ctx context.Context, log log.Logger, addr string, attempts int, opts ...rpc.ClientOption) (*rpc.Client, error) {
 	bOff := backoff.Exponential()
 	return backoff.Do(ctx, attempts, bOff, func() (*rpc.Client, error) {
+		if !IsURLAvailable(addr) {
+			log.Warn("failed to dial address, but may connect later", "addr", addr)
+			return nil, fmt.Errorf("address unavailable (%s)", addr)
+		}
 		client, err := rpc.DialOptions(ctx, addr, opts...)
 		if err != nil {
-			if client == nil {
 			return nil, fmt.Errorf("failed to dial address (%s): %w", addr, err)
 		}
-			log.Warn("failed to dial address, but may connect later", "addr", addr, "err", err)
-		}
 		return client, nil
 	})
 }
 
+func IsURLAvailable(address string) bool {
+	u, err := url.Parse(address)
+	if err != nil {
+		return false
+	}
+	conn, err := net.DialTimeout("tcp", u.Host, 5*time.Second)
+	if err != nil {
+		return false
+	}
+	conn.Close()
+	return true
+}
+
 // BaseRPCClient is a wrapper around a concrete *rpc.Client instance to make it compliant
 // with the client.RPC interface.
 // It sets a timeout of 10s on CallContext & 20s on BatchCallContext made through it.

op-service/client/dial.go

@@ -3,8 +3,6 @@ package client
 import (
 	"context"
 	"fmt"
-	"net"
-	"net/url"
 	"time"
 
 	"github.com/ethereum-optimism/optimism/op-node/client"
@@ -53,7 +51,7 @@ func DialRollupClientWithTimeout(timeout time.Duration, log log.Logger, url stri
 func dialRPCClientWithBackoff(ctx context.Context, log log.Logger, addr string) (*rpc.Client, error) {
 	bOff := backoff.Fixed(defaultRetryTime)
 	return backoff.Do(ctx, defaultRetryCount, bOff, func() (*rpc.Client, error) {
-		if !IsURLAvailable(addr) {
+		if !client.IsURLAvailable(addr) {
 			log.Warn("failed to dial address, but may connect later", "addr", addr)
 			return nil, fmt.Errorf("address unavailable (%s)", addr)
 		}
@@ -64,16 +62,3 @@ func dialRPCClientWithBackoff(ctx context.Context, log log.Logger, addr string)
 		return client, nil
 	})
 }
-
-func IsURLAvailable(address string) bool {
-	u, err := url.Parse(address)
-	if err != nil {
-		return false
-	}
-	conn, err := net.DialTimeout("tcp", u.Host, 5*time.Second)
-	if err != nil {
-		return false
-	}
-	conn.Close()
-	return true
-}