feature(grpc): add grpc exception filter

Author: tychota

integration/microservices/e2e/sum-grpc.spec.ts

@@ -35,6 +35,16 @@ describe('GRPC transport', () => {
       .expect(200, { result: 15 });
   });
 
+  it(`handle exception correctly`, () => {
+    return (
+      request(server)
+        .post('/divide')
+        .send({ first: 42, last: 0 })
+        // TODO: this will change once the grpc client raise the closest HTTP exception to OutOfBound
+        .expect(500, { message: 'Dividing by 0 is Strictly Forbidden' })
+    );
+  });
+
   afterEach(async () => {
     await app.close();
   });

integration/microservices/src/grpc/grpc.controller.ts

@@ -1,8 +1,20 @@
-import { Body, Controller, HttpCode, Post } from '@nestjs/common';
-import { Client, ClientGrpc, GrpcMethod, Transport } from '@nestjs/microservices';
+import { Body, Controller, HttpCode, Post, UseFilters } from '@nestjs/common';
+import {
+  Client,
+  ClientGrpc,
+  GrpcMethod,
+  Transport,
+  GrpcOutOfRangeException,
+  GrpcExceptionFilter,
+} from '@nestjs/microservices';
 import { join } from 'path';
 import { Observable, of } from 'rxjs';
 
+interface DivideParams {
+  first: number;
+  last: number;
+}
+
 @Controller()
 export class GrpcController {
   @Client({
@@ -16,7 +28,7 @@ export class GrpcController {
 
   @Post()
   @HttpCode(200)
-  call(@Body() data: number[]): Observable<number> {
+  sumHttp(@Body() data: number[]): Observable<number> {
     const svc = this.client.getService<any>('Math');
     return svc.sum({ data });
   }
@@ -27,4 +39,21 @@ export class GrpcController {
       result: data.reduce((a, b) => a + b),
     });
   }
+
+  @Post('/divide')
+  @HttpCode(200)
+  divideHttp(@Body() { first, last }: DivideParams): Observable<number> {
+    const svc = this.client.getService<any>('Math');
+    return svc.sum({ first, last });
+  }
+
+  @UseFilters(new GrpcExceptionFilter())
+  @GrpcMethod('Math')
+  async divide({ first, last }: DivideParams): Promise<any> {
+    const result = first / last;
+    if (!isFinite(result)) {
+      throw new GrpcOutOfRangeException('Dividing by 0 is Strictly Forbidden');
+    }
+    return result;
+  }
 }

integration/microservices/src/grpc/math.proto

@@ -3,13 +3,17 @@ syntax = "proto3";
 package math;
 
 service Math {
-  rpc Sum (RequestSum) returns (SumResult) {}
+  rpc Sum(RequestSum) returns (SumResult) {}
+  rpc Divide(RequestDivide) returns (DivideResult) {}
 }
 
-message SumResult {
-  int32 result = 1;
-}
+message SumResult { int32 result = 1; }
+
+message RequestSum { repeated int32 data = 1; }
+
+message DivideResult { int32 result = 1; }
 
-message RequestSum {
-  repeated int32 data = 1;
+message RequestDivide {
+  int32 first = 1;
+  int32 last = 2;
 }

packages/microservices/exceptions/grpc-exception-filter.ts

@@ -0,0 +1,37 @@
+import {
+  Logger,
+  RpcExceptionFilter,
+  ArgumentsHost,
+  Catch,
+} from '@nestjs/common';
+import { isError, isObject } from '@nestjs/common/utils/shared.utils';
+import { MESSAGES } from '@nestjs/core/constants';
+
+import { Observable, throwError } from 'rxjs';
+
+import { GrpcException } from './grpc-exceptions';
+import { GrpcStatus } from 'enums/grpc-status.enum';
+
+@Catch()
+export class GrpcExceptionFilter<T = any, R = any>
+  implements RpcExceptionFilter<T> {
+  private static readonly logger = new Logger('GrpcExceptionsHandler');
+
+  catch(exception: T, host: ArgumentsHost): Observable<R> {
+    if (!(exception instanceof GrpcException)) {
+      const errorMessage = MESSAGES.UNKNOWN_EXCEPTION_MESSAGE;
+      const loggerArgs = isError(exception)
+        ? [exception.message, exception.stack]
+        : [exception];
+
+      const logger = GrpcExceptionFilter.logger;
+      logger.error.apply(logger, loggerArgs as any);
+
+      return throwError({ code: GrpcStatus.UNKNOWN, message: errorMessage });
+    }
+    const code = exception.getCode();
+    const error = exception.getError();
+    const message = isObject(error) ? error : { code, message: error };
+    return throwError(message);
+  }
+}

packages/microservices/exceptions/index.ts

@@ -1,3 +1,4 @@
 export * from './base-rpc-exception-filter';
 export * from './rpc-exception';
 export * from './grpc-exceptions';
+export * from './grpc-exception-filter';