Merge pull request #43657 from thaJeztah/default_builder_version

api: set default "Builder-Version" to "2" (BuildKit) on Linux

2 files changed, 30 insertions, 11 deletions

diff --git a/api/server/router/build/build.go b/api/server/router/build/build.go
index 8ad89ac2b7..75ae8f0ada 100644
--- a/api/server/router/build/build.go
+++ b/api/server/router/build/build.go
@@ -1,6 +1,8 @@
 package build // import "github.com/docker/docker/api/server/router/build"
 
 import (
+	"runtime"
+
 	"github.com/docker/docker/api/server/router"
 	"github.com/docker/docker/api/types"
 )
@@ -37,17 +39,24 @@ func (r *buildRouter) initRoutes() {
 	}
 }
 
-// BuilderVersion derives the default docker builder version from the config
-// Note: it is valid to have BuilderVersion unset which means it is up to the
-// client to choose which builder to use.
+// BuilderVersion derives the default docker builder version from the config.
+//
+// The default on Linux is version "2" (BuildKit), but the daemon can be
+// configured to recommend version "1" (classic Builder). Windows does not
+// yet support BuildKit for native Windows images, and uses "1" (classic builder)
+// as a default.
+//
+// This value is only a recommendation as advertised by the daemon, and it is
+// up to the client to choose which builder to use.
 func BuilderVersion(features map[string]bool) types.BuilderVersion {
-	var bv types.BuilderVersion
-	if v, ok := features["buildkit"]; ok {
-		if v {
-			bv = types.BuilderBuildKit
-		} else {
-			bv = types.BuilderV1
-		}
+	// TODO(thaJeztah) move the default to daemon/config
+	if runtime.GOOS == "windows" {
+		return types.BuilderV1
+	}
+
+	bv := types.BuilderBuildKit
+	if v, ok := features["buildkit"]; ok && !v {
+		bv = types.BuilderV1
 	}
 	return bv
 }
diff --git a/api/swagger.yaml b/api/swagger.yaml
index a53130a92a..181c80a418 100644
--- a/api/swagger.yaml
+++ b/api/swagger.yaml
@@ -8786,7 +8786,17 @@ paths:
               description: "Max API Version the server supports"
             Builder-Version:
               type: "string"
-              description: "Default version of docker image builder"
+              description: |
+                Default version of docker image builder
+
+                The default on Linux is version "2" (BuildKit), but the daemon
+                can be configured to recommend version "1" (classic Builder).
+                Windows does not yet support BuildKit for native Windows images,
+                and uses "1" (classic builder) as a default.
+
+                This value is a recommendation as advertised by the daemon, and
+                it is up to the client to choose which builder to use.
+              default: "2"
             Docker-Experimental:
               type: "boolean"
               description: "If the server is running with experimental mode enabled"