Add imports location lock to serialize non-atomic operations (#204)

Adding and removing items from the imports location list is currently
implemented in a non-atomic way, by first reading a list of items from the
server, updating it locally, and sending a new list to the server.

Introduce a (per-resource, per-location) lock to all resources that require
modifications of the import list so that those operations are done sequentially.

pkg/translate/imports.go

@@ -10,6 +10,8 @@ func RenderImports(templateTypes ...string) (string, error) {
 
 	for _, templateType := range templateTypes {
 		switch templateType {
+		case "sync":
+			manager.AddStandardImport("sync", "")
 		case "config":
 			//manager.AddStandardImport("fmt", "")
 			manager.AddStandardImport("encoding/xml", "")

templates/sdk/service.tmpl

@@ -2,9 +2,9 @@ package {{packageName .GoSdkPath}}
 {{- if .Entry}}
     {{- if $.Imports}}
         {{- if $.Spec.Params.uuid}}
-            {{renderImports "service" "filtering" "audit" "rule" "version"}}
+            {{renderImports "service" "filtering" "sync" "audit" "rule" "version"}}
         {{- else}}
-            {{renderImports "service" "filtering"}}
+            {{renderImports "service" "filtering" "sync"}}
         {{- end}}
     {{- else}}
         {{- if $.Spec.Params.uuid}}
@@ -22,6 +22,28 @@ package {{packageName .GoSdkPath}}
     {{- end}}
 {{- end}}
 
+{{- if and $.Imports .Entry }}
+var (
+	importsMutexMap     = make(map[string]*sync.Mutex)
+	importsMutexMapLock = sync.Mutex{}
+)
+
+func (s *Service) getImportMutex(xpath string) *sync.Mutex {
+	importsMutexMapLock.Lock()
+	defer importsMutexMapLock.Unlock()
+
+	var importMutex *sync.Mutex
+	var ok bool
+	importMutex, ok = importsMutexMap[xpath]
+	if !ok {
+		importMutex = &sync.Mutex{}
+		importsMutexMap[xpath] = importMutex
+	}
+
+	return importMutex
+}
+{{- end }}
+
 type Service struct {
 client util.PangoClient
 }
@@ -101,8 +123,16 @@ if err != nil {
 
 func (s *Service) importToLocations(ctx context.Context, loc Location, importLocations []ImportLocation, entryName string) error {
 	vn := s.client.Versioning()
-        for _, elt := range importLocations {
-		xpath, err := elt.XpathForLocation(vn, loc)
+
+	importToLocation := func(il ImportLocation) error {
+		xpath, err := il.XpathForLocation(vn, loc)
+                if err != nil {
+			return err
+		}
+
+		mutex := s.getImportMutex(util.AsXpath(xpath))
+                mutex.Lock()
+                defer mutex.Unlock()
 
                 cmd := &xmlapi.Config{
 	                Action:  "get",
@@ -114,7 +144,7 @@ func (s *Service) importToLocations(ctx context.Context, loc Location, importLoc
 			return err
 		}
 
-		existing, err := elt.UnmarshalPangoXML(bytes)
+		existing, err := il.UnmarshalPangoXML(bytes)
                 if err != nil {
                 	return err
 		}
@@ -127,7 +157,7 @@ func (s *Service) importToLocations(ctx context.Context, loc Location, importLoc
 
 		existing = append(existing, entryName)
 
-		element, err := elt.MarshalPangoXML(existing)
+		element, err := il.MarshalPangoXML(existing)
                 if err != nil {
                 	return err
 		}
@@ -142,19 +172,36 @@ func (s *Service) importToLocations(ctx context.Context, loc Location, importLoc
 		if err != nil {
 			return err
 		}
+
+		return err
+	}
+
+        for _, elt := range importLocations {
+		err := importToLocation(elt)
+                if err != nil {
+			return err
+		}
         }
 
 	return nil
 }
 
-func (s *Service) unimportFromLocations(ctx context.Context, updates *xmlapi.MultiConfig, loc Location, importLocations []ImportLocation, values []string) error {
+func (s *Service) unimportFromLocations(ctx context.Context, loc Location, importLocations []ImportLocation, values []string) error {
 	vn := s.client.Versioning()
 	valuesByName := make(map[string]bool)
 	for _, elt := range values {
 		valuesByName[elt] = true
 	}
-        for _, elt := range importLocations {
-		xpath, err := elt.XpathForLocation(vn, loc)
+
+	unimportFromLocation := func(il ImportLocation) error {
+		xpath, err := il.XpathForLocation(vn, loc)
+                if err != nil {
+			return err
+		}
+
+		mutex := s.getImportMutex(util.AsXpath(xpath))
+                mutex.Lock()
+                defer mutex.Unlock()
 
                 cmd := &xmlapi.Config{
 	                Action:  "get",
@@ -166,7 +213,7 @@ func (s *Service) unimportFromLocations(ctx context.Context, updates *xmlapi.Mul
 			return err
 		}
 
-		existing, err := elt.UnmarshalPangoXML(bytes)
+		existing, err := il.UnmarshalPangoXML(bytes)
                 if err != nil {
                 	return err
 		}
@@ -178,7 +225,7 @@ func (s *Service) unimportFromLocations(ctx context.Context, updates *xmlapi.Mul
 			}
 		}
 
-		element, err := elt.MarshalPangoXML(filtered)
+		element, err := il.MarshalPangoXML(filtered)
                 if err != nil {
                 	return err
 		}
@@ -193,6 +240,15 @@ func (s *Service) unimportFromLocations(ctx context.Context, updates *xmlapi.Mul
 		if err != nil {
 			return err
 		}
+
+		return err
+	}
+
+        for _, elt := range importLocations {
+		err := unimportFromLocation(elt)
+                if err != nil {
+			return err
+		}
         }
 
 	return nil
@@ -529,7 +585,7 @@ vn := s.client.Versioning()
     var err error
     deletes := xmlapi.NewMultiConfig(len(values))
   {{- if .Imports }}
-    err = s.unimportFromLocations(ctx, deletes, loc, importLocations, values)
+    err = s.unimportFromLocations(ctx, loc, importLocations, values)
     if err != nil {
         return err
     }