Documentation
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Overview ¶
`grpcweb` implements the gRPC-Web spec as a wrapper around a gRPC-Go Server.
It allows web clients (see companion JS library) to talk to gRPC-Go servers over the gRPC-Web spec. It supports HTTP/1.1 and HTTP2 encoding of a gRPC stream and supports unary and server-side streaming RPCs. Bi-di and client streams are unsupported due to limitations in browser protocol support.
See https://github.com/grpc/grpc/blob/master/doc/PROTOCOL-WEB.md for the protocol specification.
Here's an example of how to use it inside an existing gRPC Go server on a separate http.Server that serves over TLS:
grpcServer := grpc.Server()
wrappedGrpc := grpcweb.WrapServer(grpcServer)
tlsHttpServer.Handler = http.HandlerFunc(func(resp http.ResponseWriter, req *http.Request) {
if wrappedGrpc.IsGrpcWebRequest(req) {
wrappedGrpc.ServeHTTP(resp, req)
return
}
// Fall back to other servers.
http.DefaultServeMux.ServeHTTP(resp, req)
})
If you'd like to have a standalone binary, please take a look at `grpcwebproxy`.
Index ¶
- func ClientHealthCheck(ctx context.Context, backendConn *grpc.ClientConn, service string, ...) error
- func ListGRPCResources(server *grpc.Server) []string
- func WebsocketRequestOrigin(req *http.Request) (string, error)
- type Option
- func WithAllowNonRootResource(allowNonRootResources bool) Option
- func WithAllowedRequestHeaders(headers []string) Option
- func WithCorsForRegisteredEndpointsOnly(onlyRegistered bool) Option
- func WithCorsMaxAge(maxAge time.Duration) Option
- func WithEndpointsFunc(endpointsFunc func() []string) Option
- func WithOriginFunc(originFunc func(origin string) bool) Option
- func WithWebsocketCompressionMode(compressionMode websocket.CompressionMode) Option
- func WithWebsocketOriginFunc(websocketOriginFunc func(req *http.Request) bool) Option
- func WithWebsocketPingInterval(websocketPingInterval time.Duration) Option
- func WithWebsockets(enableWebsockets bool) Option
- func WithWebsocketsMessageReadLimit(websocketReadLimit int64) Option
- type WrappedGrpcServer
- func (w *WrappedGrpcServer) HandleGrpcWebRequest(resp http.ResponseWriter, req *http.Request)
- func (w *WrappedGrpcServer) HandleGrpcWebsocketRequest(resp http.ResponseWriter, req *http.Request)
- func (w *WrappedGrpcServer) IsAcceptableGrpcCorsRequest(req *http.Request) bool
- func (w *WrappedGrpcServer) IsGrpcWebRequest(req *http.Request) bool
- func (w *WrappedGrpcServer) IsGrpcWebSocketRequest(req *http.Request) bool
- func (w *WrappedGrpcServer) ServeHTTP(resp http.ResponseWriter, req *http.Request)
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
func ClientHealthCheck ¶
func ClientHealthCheck(ctx context.Context, backendConn *grpc.ClientConn, service string, setServingStatus func(serving bool)) error
Client health check function is also part of the grpc/internal package The following code is a simplified version of client.go For more details see: https://pkg.go.dev/google.golang.org/grpc/health
func ListGRPCResources ¶
ListGRPCResources is a helper function that lists all URLs that are registered on gRPC server.
This makes it easy to register all the relevant routes in your HTTP router of choice.
Types ¶
type Option ¶
type Option func(*options)
func WithAllowNonRootResource ¶
WithAllowNonRootResource enables the gRPC wrapper to serve requests that have a path prefix added to the URL, before the service name and method placeholders.
This should be set to false when exposing the endpoint as the root resource, to avoid the performance cost of path processing for every request.
The default behaviour is `false`, i.e. always serves requests assuming there is no prefix to the gRPC endpoint.
func WithAllowedRequestHeaders ¶
WithAllowedRequestHeaders allows for customizing what gRPC request headers a browser can add.
This is controlling the CORS pre-flight `Access-Control-Allow-Headers` method and applies to *all* gRPC handlers. However, a special `*` value can be passed in that allows the browser client to provide *any* header, by explicitly whitelisting all `Access-Control-Request-Headers` of the pre-flight request.
The default behaviour is `[]string{'*'}`, allowing all browser client headers. This option overrides that default, while maintaining a whitelist for gRPC-internal headers.
Unfortunately, since the CORS pre-flight happens independently from gRPC handler execution, it is impossible to automatically discover it from the gRPC handler itself.
The relevant CORS pre-flight docs: https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Access-Control-Allow-Headers
func WithCorsForRegisteredEndpointsOnly ¶
WithCorsForRegisteredEndpointsOnly allows for customizing whether OPTIONS requests with the `X-GRPC-WEB` header will only be accepted if they match a registered gRPC endpoint.
This should be set to false to allow handling gRPC requests for unknown endpoints (e.g. for proxying).
The default behaviour is `true`, i.e. only allows CORS requests for registered endpoints.
func WithCorsMaxAge ¶
WithCorsMaxAge customize the `Access-Control-Max-Age: <delta-seconds>` header which controls the cache age for a CORS preflight request that checks to see if the CORS protocol is understood.
The default age is 10 minutes.
func WithEndpointsFunc ¶
WithEndpointsFunc allows for providing a custom function that provides all supported endpoints for use when the when `WithCorsForRegisteredEndpoints` option` is not set to false (i.e. the default state).
When wrapping a http.Handler with `WrapHttpHandler`, failing to specify the `WithEndpointsFunc` option will cause all CORS requests to result in a 403 error for websocket requests (if websockets are enabled) or be passed to the handler http.Handler or grpc.Server backend (i.e. as if it wasn't wrapped).
When wrapping grpc.Server with `WrapGrpcServer`, registered endpoints will be automatically detected, however if this `WithEndpointsFunc` option is specified, the server will not be queried for its endpoints and this function will be called instead.
func WithOriginFunc ¶
WithOriginFunc allows for customizing what CORS Origin requests are allowed.
This is controlling the CORS pre-flight `Access-Control-Allow-Origin`. This mechanism allows you to limit the availability of the APIs based on the domain name of the calling website (Origin). You can provide a function that filters the allowed Origin values.
The default behaviour is to deny all requests from remote origins.
The relevant CORS pre-flight docs: https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Access-Control-Allow-Origin
func WithWebsocketCompressionMode ¶
func WithWebsocketCompressionMode(compressionMode websocket.CompressionMode) Option
WithWebsocketCompressionMode sets compression mode for websocket requests
The default mode is CompressionNoContextTakeover
func WithWebsocketOriginFunc ¶
WithWebsocketOriginFunc allows for customizing the acceptance of Websocket requests - usually to check that the origin is valid.
The default behaviour is to check that the origin of the request matches the host of the request and deny all requests from remote origins.
func WithWebsocketPingInterval ¶
WithWebsocketPingInterval enables websocket keepalive pinging with the configured timeout.
The default behaviour is to disable websocket pinging.
func WithWebsockets ¶
WithWebsockets allows for handling grpc-web requests of websockets - enabling bidirectional requests.
The default behaviour is false, i.e. to disallow websockets
func WithWebsocketsMessageReadLimit ¶
WithWebsocketsMessageReadLimit sets the maximum message read limit on the underlying websocket.
The default message read limit is 32769 bytes
type WrappedGrpcServer ¶
type WrappedGrpcServer struct {
// contains filtered or unexported fields
}
func WrapHandler ¶
func WrapHandler(handler http.Handler, options ...Option) *WrappedGrpcServer
WrapHandler takes a http.Handler (such as a http.Mux) and returns a *WrappedGrpcServer that provides gRPC-Web Compatibility.
This behaves nearly identically to WrapServer except when the WithCorsForRegisteredEndpointsOnly setting is true. Then a WithEndpointsFunc option must be provided or all CORS requests will NOT be handled.
func WrapServer ¶
func WrapServer(server *grpc.Server, options ...Option) *WrappedGrpcServer
WrapServer takes a gRPC Server in Go and returns a *WrappedGrpcServer that provides gRPC-Web Compatibility.
The internal implementation fakes out a http.Request that carries standard gRPC, and performs the remapping inside http.ResponseWriter, i.e. mostly the re-encoding of Trailers (that carry gRPC status).
You can control the behaviour of the wrapper (e.g. modifying CORS behaviour) using `With*` options.
func (*WrappedGrpcServer) HandleGrpcWebRequest ¶
func (w *WrappedGrpcServer) HandleGrpcWebRequest(resp http.ResponseWriter, req *http.Request)
HandleGrpcWebRequest takes a HTTP request that is assumed to be a gRPC-Web request and wraps it with a compatibility layer to transform it to a standard gRPC request for the wrapped gRPC server and transforms the response to comply with the gRPC-Web protocol.
func (*WrappedGrpcServer) HandleGrpcWebsocketRequest ¶
func (w *WrappedGrpcServer) HandleGrpcWebsocketRequest(resp http.ResponseWriter, req *http.Request)
HandleGrpcWebsocketRequest takes a HTTP request that is assumed to be a gRPC-Websocket request and wraps it with a compatibility layer to transform it to a standard gRPC request for the wrapped gRPC server and transforms the response to comply with the gRPC-Web protocol.
func (*WrappedGrpcServer) IsAcceptableGrpcCorsRequest ¶
func (w *WrappedGrpcServer) IsAcceptableGrpcCorsRequest(req *http.Request) bool
IsAcceptableGrpcCorsRequest determines if a request is a CORS pre-flight request for a gRPC-Web request and that this request is acceptable for CORS.
You can control the CORS behaviour using `With*` options in the WrapServer function.
func (*WrappedGrpcServer) IsGrpcWebRequest ¶
func (w *WrappedGrpcServer) IsGrpcWebRequest(req *http.Request) bool
IsGrpcWebRequest determines if a request is a gRPC-Web request by checking that the "content-type" is "application/grpc-web" and that the method is POST.
func (*WrappedGrpcServer) IsGrpcWebSocketRequest ¶
func (w *WrappedGrpcServer) IsGrpcWebSocketRequest(req *http.Request) bool
IsGrpcWebSocketRequest determines if a request is a gRPC-Web request by checking that the "Sec-Websocket-Protocol" header value contains "grpc-websockets"
func (*WrappedGrpcServer) ServeHTTP ¶
func (w *WrappedGrpcServer) ServeHTTP(resp http.ResponseWriter, req *http.Request)
ServeHTTP takes a HTTP request and if it is a gRPC-Web request wraps it with a compatibility layer to transform it to a standard gRPC request for the wrapped gRPC server and transforms the response to comply with the gRPC-Web protocol.
The gRPC-Web compatibility is only invoked if the request is a gRPC-Web request as determined by IsGrpcWebRequest or the request is a pre-flight (CORS) request as determined by IsAcceptableGrpcCorsRequest.
You can control the CORS behaviour using `With*` options in the WrapServer function.
Source Files