From 86825a95ce655383f9eec8b4d7637ccc6ad5a2dd Mon Sep 17 00:00:00 2001
From: Justin Chadwell <me@jedevc.com>
Date: Wed, 27 Jul 2022 11:48:52 +0100
Subject: [PATCH] buildx: rollback configuration if create fails

This builds on the added warnings from initialized builders, now
erroring the command, and additionally attempting to revert to the
previous configuration.

To preserve the previous configuration, we add a deep Copy() function to
the NodeGroup and Node so that we can easily restore it later if we
encounter a failure.

Signed-off-by: Justin Chadwell <me@jedevc.com>
---
 commands/create.go | 37 ++++++++++++++++++++++++++-----------
 store/nodegroup.go | 38 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 64 insertions(+), 11 deletions(-)

diff --git a/commands/create.go b/commands/create.go
index 9238551c..87b53a80 100644
--- a/commands/create.go
+++ b/commands/create.go
@@ -134,6 +134,11 @@ func runCreate(dockerCli command.Cli, in createOptions, args []string) error {
 		}
 	}
 
+	ngOriginal := ng
+	if ngOriginal != nil {
+		ngOriginal = ngOriginal.Copy()
+	}
+
 	if ng == nil {
 		ng = &store.NodeGroup{
 			Name: name,
@@ -224,16 +229,6 @@ func runCreate(dockerCli command.Cli, in createOptions, args []string) error {
 		return err
 	}
 
-	if in.use && ep != "" {
-		current, err := storeutil.GetCurrentEndpoint(dockerCli)
-		if err != nil {
-			return err
-		}
-		if err := txn.SetCurrent(current, ng.Name, false, false); err != nil {
-			return err
-		}
-	}
-
 	ngi := &nginfo{ng: ng}
 
 	timeoutCtx, cancel := context.WithTimeout(ctx, 20*time.Second)
@@ -244,7 +239,27 @@ func runCreate(dockerCli command.Cli, in createOptions, args []string) error {
 	}
 	for _, info := range ngi.drivers {
 		if err := info.di.Err; err != nil {
-			logrus.Errorf("failed to initialize builder %s (%s): %s", ng.Name, info.di.Name, err)
+			err := errors.Errorf("failed to initialize builder %s (%s): %s", ng.Name, info.di.Name, err)
+			var err2 error
+			if ngOriginal == nil {
+				err2 = txn.Remove(ng.Name)
+			} else {
+				err2 = txn.Save(ngOriginal)
+			}
+			if err2 != nil {
+				logrus.Warnf("Could not rollback to previous state: %s", err2)
+			}
+			return err
+		}
+	}
+
+	if in.use && ep != "" {
+		current, err := storeutil.GetCurrentEndpoint(dockerCli)
+		if err != nil {
+			return err
+		}
+		if err := txn.SetCurrent(current, ng.Name, false, false); err != nil {
+			return err
 		}
 	}
 
diff --git a/store/nodegroup.go b/store/nodegroup.go
index c9f97a67..b6288e09 100644
--- a/store/nodegroup.go
+++ b/store/nodegroup.go
@@ -110,6 +110,44 @@ func (ng *NodeGroup) Update(name, endpoint string, platforms []string, endpoints
 	return nil
 }
 
+func (ng *NodeGroup) Copy() *NodeGroup {
+	nodes := make([]Node, len(ng.Nodes))
+	for i, node := range ng.Nodes {
+		nodes[i] = *node.Copy()
+	}
+	return &NodeGroup{
+		Name:    ng.Name,
+		Driver:  ng.Driver,
+		Nodes:   nodes,
+		Dynamic: ng.Dynamic,
+	}
+}
+
+func (n *Node) Copy() *Node {
+	platforms := []specs.Platform{}
+	copy(platforms, n.Platforms)
+	flags := []string{}
+	copy(flags, n.Flags)
+	driverOpts := map[string]string{}
+	for k, v := range n.DriverOpts {
+		driverOpts[k] = v
+	}
+	files := map[string][]byte{}
+	for k, v := range n.Files {
+		vv := []byte{}
+		copy(vv, v)
+		files[k] = vv
+	}
+	return &Node{
+		Name:       n.Name,
+		Endpoint:   n.Endpoint,
+		Platforms:  platforms,
+		Flags:      flags,
+		DriverOpts: driverOpts,
+		Files:      files,
+	}
+}
+
 func (ng *NodeGroup) validateDuplicates(ep string, idx int) error {
 	i := 0
 	for _, n := range ng.Nodes {