roachprod: use 'lb' to denote load balancer

Previously, `L` was used in the `roachprod` expanders and other place to select
load balancers. This change updates it to `LB` or `lb` to be more explicit. The
help for commands have also been updated to inform the user that an option
exists to select a load balancer.

Epic: None
Release Note: None

pkg/cmd/roachprod/main.go

@@ -1021,7 +1021,14 @@ var pgurlCmd = &cobra.Command{
 	Short: "generate pgurls for the nodes in a cluster",
 	Long: `Generate pgurls for the nodes in a cluster.
 
---auth-mode specifies the method of authentication unless --insecure is passed.
+The command generates postgres urls for the specified nodes in a cluster.
+Both the nodes or a load balancer can be specified as the target of the pgurl.
+
+Examples of <cluster>:
+	cluster-name:1-3
+	cluster-name:lb
+
+--auth-mode specifies the method of authentication if --secure is passed.
 Defaults to root if not passed. Available auth-modes are:
 
 	root: authenticates with the root user and root certificates

pkg/roachprod/install/expander.go

@@ -23,8 +23,8 @@ import (
 )
 
 var parameterRe = regexp.MustCompile(`{[^{}]*}`)
-var pgURLRe = regexp.MustCompile(`{pgurl(:[-,0-9]+|:L)?(:[a-z0-9\-]+)?(:[0-9]+)?}`)
-var pgHostRe = regexp.MustCompile(`{pghost(:[-,0-9]+|:L)?(:[a-z0-9\-]+)?(:[0-9]+)?}`)
+var pgURLRe = regexp.MustCompile(`{pgurl(:[-,0-9]+|:(?i)lb)?(:[a-z0-9\-]+)?(:[0-9]+)?}`)
+var pgHostRe = regexp.MustCompile(`{pghost(:[-,0-9]+|:(?i)lb)?(:[a-z0-9\-]+)?(:[0-9]+)?}`)
 var pgPortRe = regexp.MustCompile(`{pgport(:[-,0-9]+)?(:[a-z0-9\-]+)?(:[0-9]+)?}`)
 var uiPortRe = regexp.MustCompile(`{uiport(:[-,0-9]+)}`)
 var storeDirRe = regexp.MustCompile(`{store-dir(:[0-9]+)?}`)
@@ -158,8 +158,8 @@ func (e *expander) maybeExpandPgURL(
 	if err != nil {
 		return "", false, err
 	}
-	switch m[1] {
-	case ":L":
+	switch strings.ToLower(m[1]) {
+	case ":lb":
 		url, err := c.loadBalancerURL(ctx, l, virtualClusterName, sqlInstance, DefaultAuthMode)
 		return url, url != "", err
 	default:
@@ -187,8 +187,8 @@ func (e *expander) maybeExpandPgHost(
 		return "", false, err
 	}
 
-	switch m[1] {
-	case ":L":
+	switch strings.ToLower(m[1]) {
+	case ":lb":
 		services, err := c.DiscoverServices(ctx, virtualClusterName, ServiceTypeSQL, ServiceInstancePredicate(sqlInstance))
 		if err != nil {
 			return "", false, err

pkg/roachprod/install/nodes.go

@@ -44,9 +44,9 @@ func ListNodes(s string, numNodesInCluster int) (Nodes, error) {
 		return nil, errors.AssertionFailedf("invalid number of nodes %d", numNodesInCluster)
 	}
 
-	// "L" is a special value that also returns all nodes, but implies a load
+	// "lb" is a special value that also returns all nodes, but implies a load
 	// balancer should be used when applicable.
-	if s == "all" || s == "L" {
+	if s == "all" || strings.ToLower(s) == "lb" {
 		return allNodes(numNodesInCluster), nil
 	}
 

pkg/roachprod/roachprod.go

@@ -189,7 +189,7 @@ func newCluster(
 // name is set to select a load balancer.
 func preferLoadBalancer(name string) bool {
 	parts := strings.Split(name, ":")
-	return len(parts) == 2 && parts[1] == "L"
+	return len(parts) == 2 && strings.ToLower(parts[1]) == "lb"
 }
 
 // userClusterNameRegexp returns a regexp that matches all clusters owned by the