Add recover middleware for grpc server

Signed-off-by: Madhu Rajanna <madhupr007@gmail.com>

vendor/github.com/grpc-ecosystem/go-grpc-middleware/chain.go

@@ -0,0 +1,183 @@
+// Copyright 2016 Michal Witkowski. All Rights Reserved.
+// See LICENSE for licensing terms.
+
+// gRPC Server Interceptor chaining middleware.
+
+package grpc_middleware
+
+import (
+	"golang.org/x/net/context"
+	"google.golang.org/grpc"
+)
+
+// ChainUnaryServer creates a single interceptor out of a chain of many interceptors.
+//
+// Execution is done in left-to-right order, including passing of context.
+// For example ChainUnaryServer(one, two, three) will execute one before two before three, and three
+// will see context changes of one and two.
+func ChainUnaryServer(interceptors ...grpc.UnaryServerInterceptor) grpc.UnaryServerInterceptor {
+	n := len(interceptors)
+
+	if n > 1 {
+		lastI := n - 1
+		return func(ctx context.Context, req interface{}, info *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (interface{}, error) {
+			var (
+				chainHandler grpc.UnaryHandler
+				curI         int
+			)
+
+			chainHandler = func(currentCtx context.Context, currentReq interface{}) (interface{}, error) {
+				if curI == lastI {
+					return handler(currentCtx, currentReq)
+				}
+				curI++
+				resp, err := interceptors[curI](currentCtx, currentReq, info, chainHandler)
+				curI--
+				return resp, err
+			}
+
+			return interceptors[0](ctx, req, info, chainHandler)
+		}
+	}
+
+	if n == 1 {
+		return interceptors[0]
+	}
+
+	// n == 0; Dummy interceptor maintained for backward compatibility to avoid returning nil.
+	return func(ctx context.Context, req interface{}, _ *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (interface{}, error) {
+		return handler(ctx, req)
+	}
+}
+
+// ChainStreamServer creates a single interceptor out of a chain of many interceptors.
+//
+// Execution is done in left-to-right order, including passing of context.
+// For example ChainUnaryServer(one, two, three) will execute one before two before three.
+// If you want to pass context between interceptors, use WrapServerStream.
+func ChainStreamServer(interceptors ...grpc.StreamServerInterceptor) grpc.StreamServerInterceptor {
+	n := len(interceptors)
+
+	if n > 1 {
+		lastI := n - 1
+		return func(srv interface{}, stream grpc.ServerStream, info *grpc.StreamServerInfo, handler grpc.StreamHandler) error {
+			var (
+				chainHandler grpc.StreamHandler
+				curI         int
+			)
+
+			chainHandler = func(currentSrv interface{}, currentStream grpc.ServerStream) error {
+				if curI == lastI {
+					return handler(currentSrv, currentStream)
+				}
+				curI++
+				err := interceptors[curI](currentSrv, currentStream, info, chainHandler)
+				curI--
+				return err
+			}
+
+			return interceptors[0](srv, stream, info, chainHandler)
+		}
+	}
+
+	if n == 1 {
+		return interceptors[0]
+	}
+
+	// n == 0; Dummy interceptor maintained for backward compatibility to avoid returning nil.
+	return func(srv interface{}, stream grpc.ServerStream, _ *grpc.StreamServerInfo, handler grpc.StreamHandler) error {
+		return handler(srv, stream)
+	}
+}
+
+// ChainUnaryClient creates a single interceptor out of a chain of many interceptors.
+//
+// Execution is done in left-to-right order, including passing of context.
+// For example ChainUnaryClient(one, two, three) will execute one before two before three.
+func ChainUnaryClient(interceptors ...grpc.UnaryClientInterceptor) grpc.UnaryClientInterceptor {
+	n := len(interceptors)
+
+	if n > 1 {
+		lastI := n - 1
+		return func(ctx context.Context, method string, req, reply interface{}, cc *grpc.ClientConn, invoker grpc.UnaryInvoker, opts ...grpc.CallOption) error {
+			var (
+				chainHandler grpc.UnaryInvoker
+				curI         int
+			)
+
+			chainHandler = func(currentCtx context.Context, currentMethod string, currentReq, currentRepl interface{}, currentConn *grpc.ClientConn, currentOpts ...grpc.CallOption) error {
+				if curI == lastI {
+					return invoker(currentCtx, currentMethod, currentReq, currentRepl, currentConn, currentOpts...)
+				}
+				curI++
+				err := interceptors[curI](currentCtx, currentMethod, currentReq, currentRepl, currentConn, chainHandler, currentOpts...)
+				curI--
+				return err
+			}
+
+			return interceptors[0](ctx, method, req, reply, cc, chainHandler, opts...)
+		}
+	}
+
+	if n == 1 {
+		return interceptors[0]
+	}
+
+	// n == 0; Dummy interceptor maintained for backward compatibility to avoid returning nil.
+	return func(ctx context.Context, method string, req, reply interface{}, cc *grpc.ClientConn, invoker grpc.UnaryInvoker, opts ...grpc.CallOption) error {
+		return invoker(ctx, method, req, reply, cc, opts...)
+	}
+}
+
+// ChainStreamClient creates a single interceptor out of a chain of many interceptors.
+//
+// Execution is done in left-to-right order, including passing of context.
+// For example ChainStreamClient(one, two, three) will execute one before two before three.
+func ChainStreamClient(interceptors ...grpc.StreamClientInterceptor) grpc.StreamClientInterceptor {
+	n := len(interceptors)
+
+	if n > 1 {
+		lastI := n - 1
+		return func(ctx context.Context, desc *grpc.StreamDesc, cc *grpc.ClientConn, method string, streamer grpc.Streamer, opts ...grpc.CallOption) (grpc.ClientStream, error) {
+			var (
+				chainHandler grpc.Streamer
+				curI         int
+			)
+
+			chainHandler = func(currentCtx context.Context, currentDesc *grpc.StreamDesc, currentConn *grpc.ClientConn, currentMethod string, currentOpts ...grpc.CallOption) (grpc.ClientStream, error) {
+				if curI == lastI {
+					return streamer(currentCtx, currentDesc, currentConn, currentMethod, currentOpts...)
+				}
+				curI++
+				stream, err := interceptors[curI](currentCtx, currentDesc, currentConn, currentMethod, chainHandler, currentOpts...)
+				curI--
+				return stream, err
+			}
+
+			return interceptors[0](ctx, desc, cc, method, chainHandler, opts...)
+		}
+	}
+
+	if n == 1 {
+		return interceptors[0]
+	}
+
+	// n == 0; Dummy interceptor maintained for backward compatibility to avoid returning nil.
+	return func(ctx context.Context, desc *grpc.StreamDesc, cc *grpc.ClientConn, method string, streamer grpc.Streamer, opts ...grpc.CallOption) (grpc.ClientStream, error) {
+		return streamer(ctx, desc, cc, method, opts...)
+	}
+}
+
+// Chain creates a single interceptor out of a chain of many interceptors.
+//
+// WithUnaryServerChain is a grpc.Server config option that accepts multiple unary interceptors.
+// Basically syntactic sugar.
+func WithUnaryServerChain(interceptors ...grpc.UnaryServerInterceptor) grpc.ServerOption {
+	return grpc.UnaryInterceptor(ChainUnaryServer(interceptors...))
+}
+
+// WithStreamServerChain is a grpc.Server config option that accepts multiple stream interceptors.
+// Basically syntactic sugar.
+func WithStreamServerChain(interceptors ...grpc.StreamServerInterceptor) grpc.ServerOption {
+	return grpc.StreamInterceptor(ChainStreamServer(interceptors...))
+}