Merge pull request #3082 from owncloud/thumbnails_refactor_interface

Use decorator pattern and allow more methods to be decorated

thumbnails/pkg/server/grpc/server.go

@@ -6,6 +6,7 @@ import (
 	"github.com/owncloud/ocis/ocis-pkg/version"
 	thumbnailssvc "github.com/owncloud/ocis/protogen/gen/ocis/services/thumbnails/v0"
 	svc "github.com/owncloud/ocis/thumbnails/pkg/service/v0"
+	"github.com/owncloud/ocis/thumbnails/pkg/service/v0/decorators"
 	"github.com/owncloud/ocis/thumbnails/pkg/thumbnail/imgsource"
 	"github.com/owncloud/ocis/thumbnails/pkg/thumbnail/storage"
 )
@@ -30,7 +31,7 @@ func NewService(opts ...Option) grpc.Service {
 		options.Logger.Error().Err(err).Msg("could not get gateway client")
 		return grpc.Service{}
 	}
-	var thumbnail thumbnailssvc.ThumbnailServiceHandler
+	var thumbnail decorators.DecoratedService
 	{
 		thumbnail = svc.NewService(
 			svc.Config(options.Config),
@@ -45,9 +46,9 @@ func NewService(opts ...Option) grpc.Service {
 			svc.CS3Source(imgsource.NewCS3Source(tconf, gc)),
 			svc.CS3Client(gc),
 		)
-		thumbnail = svc.NewInstrument(thumbnail, options.Metrics)
-		thumbnail = svc.NewLogging(thumbnail, options.Logger)
-		thumbnail = svc.NewTracing(thumbnail)
+		thumbnail = decorators.NewInstrument(thumbnail, options.Metrics)
+		thumbnail = decorators.NewLogging(thumbnail, options.Logger)
+		thumbnail = decorators.NewTracing(thumbnail)
 	}
 
 	_ = thumbnailssvc.RegisterThumbnailServiceHandler(

thumbnails/pkg/service/v0/decorators/base.go

@@ -0,0 +1,59 @@
+package decorators
+
+import (
+	"context"
+
+	thumbnailssvc "github.com/owncloud/ocis/protogen/gen/ocis/services/thumbnails/v0"
+)
+
+// Interface acting as facade, holding all the interfaces that this
+// thumbnails microservice is expecting to implement.
+// For now, only the thumbnailssvc.ThumbnailServiceHandler is present,
+// but a future configsvc.ConfigServiceHandler is expected to be added here
+//
+// This interface will also act as the base interface to implement
+// a decorator pattern.
+type DecoratedService interface {
+	thumbnailssvc.ThumbnailServiceHandler
+}
+
+// Base type to implement the decorators. It will provide a basic implementation
+// by delegating to the decoratedService
+//
+// Expected implementations will be like:
+// ```
+// type MyDecorator struct {
+//   Decorator
+//   myCustomOpts *opts
+//   additionalSrv *srv
+// }
+//
+// func NewMyDecorator(next DecoratedService, customOpts *customOpts) DecoratedService {
+//   .....
+//   return MyDecorator{
+//     Decorator: Decorator{next: next},
+//     myCustomOpts: opts,
+//     additionalSrv: srv,
+//   }
+// }
+// ```
+type Decorator struct {
+	next DecoratedService
+}
+
+// Base implementation for the GetThumbnail (for the thumbnailssvc).
+// It will just delegate to the underlying decoratedService
+//
+// Your custom decorator is expected to overwrite this function,
+// but it MUST call the underlying decoratedService at some point
+// ```
+// func (d MyDecorator) GetThumbnail(ctx context.Context, req *thumbnailssvc.GetThumbnailRequest, resp *thumbnailssvc.GetThumbnailResponse) error {
+//   doSomething()
+//   err := d.next.GetThumbnail(ctx, req, resp)
+//   doAnotherThing()
+//   return err
+// }
+// ```
+func (deco Decorator) GetThumbnail(ctx context.Context, req *thumbnailssvc.GetThumbnailRequest, resp *thumbnailssvc.GetThumbnailResponse) error {
+	return deco.next.GetThumbnail(ctx, req, resp)
+}

thumbnails/pkg/service/v0/decorators/instrument.go

@@ -1,4 +1,4 @@
-package svc
+package decorators
 
 import (
 	"context"
@@ -9,15 +9,15 @@ import (
 )
 
 // NewInstrument returns a service that instruments metrics.
-func NewInstrument(next thumbnailssvc.ThumbnailServiceHandler, metrics *metrics.Metrics) thumbnailssvc.ThumbnailServiceHandler {
+func NewInstrument(next DecoratedService, metrics *metrics.Metrics) DecoratedService {
 	return instrument{
-		next:    next,
-		metrics: metrics,
+		Decorator: Decorator{next: next},
+		metrics:   metrics,
 	}
 }
 
 type instrument struct {
-	next    thumbnailssvc.ThumbnailServiceHandler
+	Decorator
 	metrics *metrics.Metrics
 }
 

thumbnails/pkg/service/v0/decorators/logging.go

@@ -1,4 +1,4 @@
-package svc
+package decorators
 
 import (
 	"context"
@@ -9,15 +9,15 @@ import (
 )
 
 // NewLogging returns a service that logs messages.
-func NewLogging(next thumbnailssvc.ThumbnailServiceHandler, logger log.Logger) thumbnailssvc.ThumbnailServiceHandler {
+func NewLogging(next DecoratedService, logger log.Logger) DecoratedService {
 	return logging{
-		next:   next,
-		logger: logger,
+		Decorator: Decorator{next: next},
+		logger:    logger,
 	}
 }
 
 type logging struct {
-	next   thumbnailssvc.ThumbnailServiceHandler
+	Decorator
 	logger log.Logger
 }
 

thumbnails/pkg/service/v0/decorators/tracing.go

@@ -1,4 +1,4 @@
-package svc
+package decorators
 
 import (
 	"context"
@@ -11,14 +11,14 @@ import (
 )
 
 // NewTracing returns a service that instruments traces.
-func NewTracing(next thumbnailssvc.ThumbnailServiceHandler) thumbnailssvc.ThumbnailServiceHandler {
+func NewTracing(next DecoratedService) DecoratedService {
 	return tracing{
-		next: next,
+		Decorator: Decorator{next: next},
 	}
 }
 
 type tracing struct {
-	next thumbnailssvc.ThumbnailServiceHandler
+	Decorator
 }
 
 // GetThumbnail implements the ThumbnailServiceHandler interface.

thumbnails/pkg/service/v0/service.go

@@ -14,6 +14,7 @@ import (
 	"github.com/owncloud/ocis/ocis-pkg/log"
 	thumbnailssvc "github.com/owncloud/ocis/protogen/gen/ocis/services/thumbnails/v0"
 	"github.com/owncloud/ocis/thumbnails/pkg/preprocessor"
+	"github.com/owncloud/ocis/thumbnails/pkg/service/v0/decorators"
 	"github.com/owncloud/ocis/thumbnails/pkg/thumbnail"
 	"github.com/owncloud/ocis/thumbnails/pkg/thumbnail/imgsource"
 	"github.com/pkg/errors"
@@ -22,7 +23,7 @@ import (
 )
 
 // NewService returns a service implementation for Service.
-func NewService(opts ...Option) thumbnailssvc.ThumbnailServiceHandler {
+func NewService(opts ...Option) decorators.DecoratedService {
 	options := newOptions(opts...)
 	logger := options.Logger
 	resolutions, err := thumbnail.ParseResolutions(options.Config.Thumbnail.Resolutions)