Prepare for chaining autogenerated conversion methods

cmd/kube-conversion/conversion.go

@@ -20,7 +20,6 @@ import (
 	"io"
 	"os"
 	"runtime"
-	"strings"
 
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/api"
 	_ "github.com/GoogleCloudPlatform/kubernetes/pkg/api/v1beta1"
@@ -33,39 +32,51 @@ import (
 )
 
 var (
-	outputDest = flag.StringP("output", "o", "-", "Output destination; '-' means stdout")
-	versions   = flag.StringP("versions", "v", "v1beta3", "Comma separated list of versions for conversion.")
+	functionDest = flag.StringP("funcDest", "f", "-", "Output for conversion functions; '-' means stdout")
+	namesDest    = flag.StringP("nameDest", "n", "-", "Output for function names; '-' means stdout")
+	version      = flag.StringP("version", "v", "v1beta3", "Version for conversion.")
 )
 
 func main() {
 	runtime.GOMAXPROCS(runtime.NumCPU())
 	flag.Parse()
 
-	var out io.Writer
-	if *outputDest == "-" {
-		out = os.Stdout
+	var funcOut io.Writer
+	if *functionDest == "-" {
+		funcOut = os.Stdout
 	} else {
-		file, err := os.Create(*outputDest)
+		file, err := os.Create(*functionDest)
 		if err != nil {
-			glog.Fatalf("Couldn't open %v: %v", *outputDest, err)
+			glog.Fatalf("Couldn't open %v: %v", *functionDest, err)
 		}
 		defer file.Close()
-		out = file
+		funcOut = file
 	}
-
-	versionsForConversion := strings.Split(*versions, ",")
-	for _, version := range versionsForConversion {
-		generator := conversion.NewGenerator(api.Scheme.Raw())
-		// TODO(wojtek-t): Change the overwrites to a flag.
-		generator.OverwritePackage(version, "")
-		generator.OverwritePackage("api", "newer")
-		for _, knownType := range api.Scheme.KnownTypes(version) {
-			if err := generator.GenerateConversionsForType(version, knownType); err != nil {
-				glog.Errorf("error while generating conversion functions for %v: %v", knownType, err)
-			}
+	var nameOut io.Writer
+	if *namesDest == "-" {
+		nameOut = os.Stdout
+	} else {
+		file, err := os.Create(*namesDest)
+		if err != nil {
+			glog.Fatalf("Couldn't open %v: %v", *functionDest, err)
 		}
-		if err := generator.WriteConversionFunctions(out); err != nil {
-			glog.Fatalf("Error while writing conversion functions: %v", err)
+		defer file.Close()
+		nameOut = file
+	}
+
+	generator := conversion.NewGenerator(api.Scheme.Raw())
+	// TODO(wojtek-t): Change the overwrites to a flag.
+	generator.OverwritePackage(*version, "")
+	generator.OverwritePackage("api", "newer")
+	for _, knownType := range api.Scheme.KnownTypes(*version) {
+		if err := generator.GenerateConversionsForType(*version, knownType); err != nil {
+			glog.Errorf("error while generating conversion functions for %v: %v", knownType, err)
 		}
 	}
+	if err := generator.WriteConversionFunctions(funcOut); err != nil {
+		glog.Fatalf("Error while writing conversion functions: %v", err)
+	}
+	if err := generator.WriteConversionFunctionNames(nameOut); err != nil {
+		glog.Fatalf("Error while writing conversion functions: %v", err)
+	}
 }

docs/devel/api_changes.md

@@ -222,9 +222,24 @@ types, structural change in particular - you must add some logic to convert
 versioned APIs to and from the internal representation.  If you see errors from
 the `serialization_test`, it may indicate the need for explicit conversions.
 
+Performance of conversions very heavily influence performance of apiserver.
+Thus, we are auto-generating conversion functions that are much more efficient
+than the generic ones (which are based on reflections and thus are highly
+inefficient).
+
 The conversion code resides with each versioned API -
-`pkg/api/<version>/conversion.go`.  Unsurprisingly, this also requires you to
-add tests to `pkg/api/<version>/conversion_test.go`.
+`pkg/api/<version>/conversion.go`.  To regenerate conversion functions:
+   - run
+```
+   $ go run cmd/kube-conversion/conversion.go -v <version> -f <file1.txt> -n <file2.txt>
+```
+   - replace all conversion functions (convert\* functions) in the above file
+     with the contents of \<file1.txt\>
+   - replace arguments of `newer.Scheme.AddGeneratedConversionFuncs`
+     with the contents of \<file2.txt\>
+
+Unsurprisingly, this also requires you to add tests to
+`pkg/api/<version>/conversion_test.go`.
 
 ## Update the fuzzer