From a4be45186d49e20989b2415cf5572fc2379c31c3 Mon Sep 17 00:00:00 2001
From: Pavel Sviderski <me@psviderski.name>
Date: Thu, 14 Nov 2024 09:12:25 +1000
Subject: [PATCH] find first available machine for running a service

---
 internal/cli/client/service.go | 42 ++++++++++++++++++++++++++++++----
 1 file changed, 37 insertions(+), 5 deletions(-)

diff --git a/internal/cli/client/service.go b/internal/cli/client/service.go
index d3304b51..05b4863e 100644
--- a/internal/cli/client/service.go
+++ b/internal/cli/client/service.go
@@ -2,10 +2,13 @@ package client
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"github.com/docker/docker/api/types/container"
 	"google.golang.org/grpc/metadata"
 	"google.golang.org/protobuf/types/known/emptypb"
+	"slices"
+	"uncloud/internal/machine/api/pb"
 )
 
 // ServiceOptions contains all the options for creating a service.
@@ -30,18 +33,28 @@ func (c *Client) RunService(ctx context.Context, opts *ServiceOptions) (RunServi
 		return resp, fmt.Errorf("list machines: %w", err)
 	}
 
-	// TODO: find the first available machine (state UP).
-	machineIP, _ := listResp.Machines[0].Machine.Network.ManagementIp.ToAddr()
-	resp.MachineName = listResp.Machines[0].Machine.Name
+	var machine *pb.MachineMember
 	if opts.Machine != "" {
+		// Check if the machine ID or name exists if it's explicitly specified.
 		for _, m := range listResp.Machines {
 			if m.Machine.Name == opts.Machine || m.Machine.Id == opts.Machine {
-				machineIP, _ = m.Machine.Network.ManagementIp.ToAddr()
-				resp.MachineName = m.Machine.Name
+				machine = m
 				break
 			}
+			return resp, fmt.Errorf("machine %q not found", opts.Machine)
+		}
+	} else {
+		machine, err = firstAvailableMachine(listResp.Machines)
+		if err != nil {
+			return resp, err
 		}
 	}
+	if machine == nil { // This should never happen.
+		return resp, errors.New("no available machine to run the service")
+	}
+
+	machineIP, _ := machine.Machine.Network.ManagementIp.ToAddr()
+	resp.MachineName = machine.Machine.Name
 
 	md := metadata.Pairs("machines", machineIP.String())
 	ctx = metadata.NewOutgoingContext(ctx, md)
@@ -66,3 +79,22 @@ func (c *Client) RunService(ctx context.Context, opts *ServiceOptions) (RunServi
 
 	return resp, nil
 }
+
+func firstAvailableMachine(machines []*pb.MachineMember) (*pb.MachineMember, error) {
+	// Find the first UP machine.
+	upIdx := slices.IndexFunc(machines, func(m *pb.MachineMember) bool {
+		return m.State == pb.MachineMember_UP
+	})
+	if upIdx != -1 {
+		return machines[upIdx], nil
+	}
+	// There is no UP machine, try to find the first SUSPECT machine.
+	suspectIdx := slices.IndexFunc(machines, func(m *pb.MachineMember) bool {
+		return m.State == pb.MachineMember_SUSPECT
+	})
+	if suspectIdx != -1 {
+		return machines[suspectIdx], nil
+	}
+
+	return nil, errors.New("no available machine to run the service")
+}