fix(compose): Calculate peer port considering learner nodes differences (#9507)

This PR changes how the compose tool calculates the port for zero1. It
now combines the zeroBasePort (5080) with the opts.PortOffset (default
100) to get the correct peer port (5180). Previously, this calculation
was incorrect, causing learner nodes to try and connect to zero1 on the
wrong port.

Author: matthewmcneely

compose/compose.go

@@ -235,7 +235,8 @@ func getZero(idx int, raft string) service {
 	if idx == 1 {
 		svc.Command += " --bindall"
 	} else {
-		svc.Command += fmt.Sprintf(" --peer=%s:%d", name(basename, 1), basePort)
+		peerPort := zeroBasePort + opts.PortOffset
+		svc.Command += fmt.Sprintf(" --peer=%s:%d", name(basename, 1), peerPort)
 	}
 	if len(opts.MemLimit) > 0 {
 		svc.Deploy.Resources = res{
@@ -258,7 +259,9 @@ func getZero(idx int, raft string) service {
 
 func getAlpha(idx int, raft string) service {
 	basename := "alpha"
+	// internalPort is used for Raft communication between nodes.
 	internalPort := alphaBasePort + opts.PortOffset + getOffset(idx)
+	// grpcPort is the public-facing port for clients. It is offset from the internal port.
 	grpcPort := internalPort + 1000
 	svc := initService(basename, idx, grpcPort)