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server.go
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server.go
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package server
import (
"context"
"errors"
"github.com/grpc-ecosystem/grpc-gateway/v2/runtime"
"github.com/kirinse/atlas-app-toolkit/gateway"
"github.com/kirinse/atlas-app-toolkit/health"
"google.golang.org/grpc"
"net"
"net/http"
"sync"
"time"
)
var (
// ErrInitializeTimeout is returned when an InitializerFunc takes too long to finish during Server.Serve
ErrInitializeTimeout = errors.New("initialization timed out")
// DefaultInitializerTimeout is the reasonable default amount of time one would expect initialization to take in the
// worst case
DefaultInitializerTimeout = time.Minute
)
// Server is a wrapper struct that will allow you to stand up your GPRC server, API Gateway and health checks within
// the same struct. The recommended way to initialize this is with the NewServer function.
type Server struct {
initializers []InitializerFunc
initializeTimeout time.Duration
registrars []func(mux *http.ServeMux) error
middlewares []Middleware
// GRPCServer will be started whenever this is served
GRPCServer *grpc.Server
// HTTPServer will be started whenever this is served
HTTPServer *http.Server
isAutomaticStop bool
}
//Middleware wrapper
type Middleware func(handler http.Handler) http.Handler
// Option is a functional option for creating a Server
type Option func(*Server) error
// InitializerFunc is a handler that can be passed into WithInitializer to be executed prior to serving
type InitializerFunc func(context.Context) error
// NewServer creates a Server from the given options. All options are processed in the order they are declared.
func NewServer(opts ...Option) (*Server, error) {
s := &Server{
initializeTimeout: DefaultInitializerTimeout,
HTTPServer: &http.Server{},
registrars: []func(mux *http.ServeMux) error{},
isAutomaticStop: true,
}
for _, opt := range opts {
if err := opt(s); err != nil {
return nil, err
}
}
mux := http.NewServeMux()
for _, register := range s.registrars {
if err := register(mux); err != nil {
return nil, err
}
}
s.HTTPServer.Handler = mux
// Revert user input middlewares
for i, j := 0, len(s.middlewares)-1; i < j; i, j = i+1, j-1 {
s.middlewares[i], s.middlewares[j] = s.middlewares[j], s.middlewares[i]
}
for _, m := range s.middlewares {
s.HTTPServer.Handler = m(s.HTTPServer.Handler)
}
return s, nil
}
// WithInitializerTimeout set the duration initialization will wait before halting and returning an error
func WithInitializerTimeout(timeout time.Duration) Option {
return func(s *Server) error {
s.initializeTimeout = timeout
return nil
}
}
// WithInitializer adds an initialization function that will get called prior to serving.
func WithInitializer(initializerFunc InitializerFunc) Option {
return func(s *Server) error {
s.initializers = append(s.initializers, initializerFunc)
return nil
}
}
// WithGrpcServer adds the given GRPC server to this server. There can only be one GRPC server within a given instance,
// so multiple calls with this option will overwrite the previous ones.
func WithGrpcServer(grpcServer *grpc.Server) Option {
return func(s *Server) error {
s.GRPCServer = grpcServer
return nil
}
}
// WithHandler registers the given http handler to this server by registering the pattern at the root of the http server
func WithHandler(pattern string, handler http.Handler) Option {
return func(s *Server) error {
s.registrars = append(s.registrars, func(mux *http.ServeMux) error {
mux.Handle(pattern, handler)
return nil
})
return nil
}
}
// WithHealthChecks registers the given health checker with this server by registering its endpoints at the root of the
// http server.
func WithHealthChecks(checker health.Checker) Option {
return func(s *Server) error {
s.registrars = append(s.registrars, func(mux *http.ServeMux) error {
checker.RegisterHandler(mux)
return nil
})
return nil
}
}
// WithGateway registers the given gateway options with this server
func WithGateway(options ...gateway.Option) Option {
return func(s *Server) error {
s.registrars = append(s.registrars, func(mux *http.ServeMux) error {
_, err := gateway.NewGateway(append(options,
gateway.WithGatewayOptions(
runtime.WithIncomingHeaderMatcher(
gateway.AtlasDefaultHeaderMatcher())),
gateway.WithMux(mux))...)
return err
})
return nil
}
}
// WithMiddlewares add opportunity to add different middleware
func WithMiddlewares(middleware ...Middleware) Option {
return func(s *Server) error {
s.middlewares = append(s.middlewares, middleware...)
return nil
}
}
func WithAutomaticStop(isAutomaticStop bool) Option {
return func(s *Server) error {
s.isAutomaticStop = isAutomaticStop
return nil
}
}
// Serve invokes all initializers then serves on the given listeners.
//
// If a listener is left blank, then that particular part will not be served.
//
// If a listener is specified for a part that doesn't have a corresponding server, then an error will be returned. This
// can happen, for instance, whenever a gRPC listener is provided but no gRPC server was set or no option was passed
// into NewServer.
//
// If both listeners are nil, then an error is returned
func (s *Server) Serve(grpcL, httpL net.Listener) error {
if grpcL == nil && httpL == nil {
return errors.New("both grpcL and httpL are nil")
}
if err := s.initialize(); err != nil {
return err
}
errC := make(chan error)
if httpL != nil {
if s.HTTPServer == nil {
return errors.New("httpL is specified, but no HTTPServer is provided")
}
go func() { errC <- s.HTTPServer.Serve(httpL) }()
} else {
s.HTTPServer = nil
}
if grpcL != nil {
if s.GRPCServer == nil {
return errors.New("grpcL is specified, but no GRPCServer is provided")
}
go func() { errC <- s.GRPCServer.Serve(grpcL) }()
} else {
s.GRPCServer = nil
}
defer func() {
if s.isAutomaticStop {
s.Stop()
}
}()
return <-errC
}
// Stop immediately terminates the grpc and http servers, immediately closing their active listeners
func (s *Server) Stop() error {
return s.shutdown(context.Background(), false)
}
func (s *Server) GracefulShutdown(ctx context.Context) error {
return s.shutdown(ctx, true)
}
func (s Server) shutdown(ctx context.Context, isGraceful bool) error {
wg := sync.WaitGroup{}
wg.Add(2)
doneC := make(chan bool)
errC := make(chan error)
go func() {
defer wg.Done()
if s.GRPCServer != nil {
if isGraceful {
s.GRPCServer.GracefulStop()
} else {
s.GRPCServer.Stop()
}
}
}()
go func() {
defer wg.Done()
if s.HTTPServer != nil {
if isGraceful {
if err := s.HTTPServer.Shutdown(ctx); err != nil {
errC <- err
}
} else {
if err := s.HTTPServer.Close(); err != nil {
errC <- err
}
}
}
}()
go func() {
wg.Wait()
doneC <- true
}()
select {
case err := <-errC:
return err
case <-doneC:
return nil
}
}
func (s Server) initialize() error {
ctx, cancel := context.WithTimeout(context.Background(), s.initializeTimeout)
defer cancel()
errC := make(chan error)
wg := sync.WaitGroup{}
wg.Add(len(s.initializers))
go func() {
wg.Wait()
errC <- nil
}()
for _, initFunc := range s.initializers {
go func(init InitializerFunc) {
defer wg.Done()
if err := init(ctx); err != nil {
errC <- err
}
}(initFunc)
}
select {
case err := <-errC:
return err
case <-time.After(s.initializeTimeout):
return ErrInitializeTimeout
}
}