grpc_validator

Documentation

Overview

`grpc_validator` is a generic request contents validator server-side middleware for gRPC.

Request Validator Middleware

Validating input is important, and hard. It also causes a lot of boilerplate code. This middleware checks for the existence of a `Validate` method on each of the messages of a gRPC request. This includes the single request of the `Unary` calls, as well as each message of the inbound Stream calls. In case of a validation failure, an `InvalidArgument` gRPC status is returned, along with a description of the validation failure.

While it is generic, it was intended to be used with https://github.com/mwitkow/go-proto-validators, a Go protocol buffers codegen plugin that creates the `Validate` methods (including nested messages) based on declarative options in the `.proto` files themselves. For example:

syntax = "proto3";
package validator.examples;
import "github.com/mwitkow/go-proto-validators/validator.proto";

message InnerMessage {
  // some_integer can only be in range (1, 100).
  int32 some_integer = 1 [(validator.field) = {int_gt: 0, int_lt: 100}];
  // some_float can only be in range (0;1).
  double some_float = 2 [(validator.field) = {float_gte: 0, float_lte: 1}];
}

message OuterMessage {
  // important_string must be a lowercase alpha-numeric of 5 to 30 characters (RE2 syntax).
  string important_string = 1 [(validator.field) = {regex: "^[a-z]{2,5}$"}];
  // proto3 doesn't have `required`, the `msg_exist` enforces presence of InnerMessage.
  InnerMessage inner = 2 [(validator.field) = {msg_exists : true}];
}

The `OuterMessage.Validate` would include validation of regexes, existence of the InnerMessage and the range values within it. The `grpc_validator` middleware would then automatically use that to check all messages processed by the server.

Please consult https://github.com/mwitkow/go-proto-validators for details on `protoc` invocation and other parameters of customization.

Index

• func StreamServerInterceptor() grpc.StreamServerInterceptor
• func UnaryClientInterceptor() grpc.UnaryClientInterceptor
• func UnaryServerInterceptor() grpc.UnaryServerInterceptor

Functions

func StreamServerInterceptor

func StreamServerInterceptor() grpc.StreamServerInterceptor

StreamServerInterceptor returns a new streaming server interceptor that validates incoming messages.

The stage at which invalid messages will be rejected with `InvalidArgument` varies based on the type of the RPC. For `ServerStream` (1:m) requests, it will happen before reaching any userspace handlers. For `ClientStream` (n:1) or `BidiStream` (n:m) RPCs, the messages will be rejected on calls to `stream.Recv()`.

func UnaryClientInterceptor

func UnaryClientInterceptor() grpc.UnaryClientInterceptor

UnaryClientInterceptor returns a new unary client interceptor that validates outgoing messages.

Invalid messages will be rejected with `InvalidArgument` before sending the request to server.

func UnaryServerInterceptor

func UnaryServerInterceptor() grpc.UnaryServerInterceptor

UnaryServerInterceptor returns a new unary server interceptor that validates incoming messages.

Invalid messages will be rejected with `InvalidArgument` before reaching any userspace handlers.