NestJS Interceptors: Unable to set HTTP Headers on outgoing requests

I am writing APIs in NestJS which have a set of common headers. I decided to use interceptors in order to append headers to outgoing requests. The headers do not get appended to the request and hence the request keeps on failing.

Interceptor

import * as utils from '../utils/utils';
import {
  CallHandler,
  ExecutionContext,
  Injectable,
  NestInterceptor
} from '@nestjs/common';
import { HEADERS } from '../middlewares/headers.constant';
import { Observable } from 'rxjs';
import { Request } from 'express';
import { DATA_PARTITION_ID } from '../app.constants';

@Injectable()
export class HeadersInterceptor implements NestInterceptor {
  intercept(context: ExecutionContext, next: CallHandler): Observable<void> {
    const ctx = context.switchToHttp();
    const request: Request = ctx.getRequest();

    this.setHeaders(request);

    return next.handle();
  }

  private setHeaders(request): void {
    this.updateHeaders(request, HEADERS.ACCEPT, 'application/json');
    this.updateHeaders(request, HEADERS.CONTENT_TYPE, 'application/json');
    this.updateHeaders(request, HEADERS.ACCEPT_ENCODING, 'gzip, deflate, br');
    this.updateHeaders(
      request,
      HEADERS.DATA_PARTITION_ID,
      DATA_PARTITION_ID
    );
    this.updateHeaders(
      request,
      HEADERS.AUTHORIZATION,
      `Bearer ${utils.parseCookies(request).stoken}`
    );
    this.updateHeaders(request, HEADERS.APP_KEY, '');
  }

  private updateHeaders(
    request: Request,
    property: string,
    value: string
  ): void {
    if (!request.headers.hasOwnProperty(property)) {
      request.headers[property] = value;
    } else {
      void 0;
    }
  }
}

This interceptor simply does one thing: Access the request and append the headers and pass the control to next handler.

Enums

export enum HEADERS {
  DATA_PARTITION_ID = 'Data-Partition-Id',
  AUTHORIZATION = 'Authorization',
  CONTENT_TYPE = 'Content-Type',
  APP_KEY = 'appkey',
  ACCEPT = 'accept',
  ACCEPT_ENCODING = 'accept-encoding'
}

Controller

import { Body, Controller, Post, Req, UseInterceptors } from '@nestjs/common';
import { HeadersInterceptor } from '../interceptors/headers.interceptor';
import { SearchData } from './models/search-data.model';
import { SearchResults } from './models/search-results.model';
import { SearchService } from './search.service';

@Controller('')
@UseInterceptors(new HeadersInterceptor())
export class SearchController {
  constructor(private searchService: SearchService) {}

  @Post('api/search')
  async searchDataById(@Body() searchData: SearchData, @Req() req): Promise<SearchResults> {
    console.log(req.headers);
    return await this.searchService.getSearchResultsById(searchData);
  }
}

Service

import { HttpService, HttpStatus, Injectable } from '@nestjs/common';
import { AppConfigService } from '../app-config/app-config.service';
import { DataMappingPayload } from './models/data-mapping-payload.model';
import { SearchData } from './models/search-data.model';
import { SearchModelMapper } from './search.service.modelmapper';
import { SearchResults } from './models/search-results.model';
import { ServiceException } from '../exception/service.exception';

@Injectable()
export class SearchService {
  constructor(
    private searchModelMapper: SearchModelMapper,
    private configService: AppConfigService,
    private readonly httpService: HttpService
  ) {}

  async getSearchResultsById(searchData: SearchData): Promise<SearchResults> {
    if (searchData.filters.collectionId) {
      console.log(this.configService.appConfig.urls.SEARCH_RESULTS_BY_COLLECTION_ID_URL.replace(
          '${collectionId}',
          searchData.filters.collectionId
        )
      );
      const searchResultsAPI = await this.httpService
        .get(
          this.configService.appConfig.urls.SEARCH_RESULTS_BY_COLLECTION_ID_URL.replace(
            '${collectionId}',
            searchData.filters.collectionId
          )
        )
        .toPromise();
      const kinds = this.searchModelMapper.getUniqueKinds(
        searchResultsAPI.data.results
      );
      const mappingPayload = await this.getDataMapping(kinds);
      return this.searchModelMapper.generateSearchResults(
        kinds,
        mappingPayload,
        searchResultsAPI.data.results
      );
    } else {
      this.raiseException();
    }
  }

  async getDataMapping(kinds: string[]): Promise<[]> {
    const entityKindNames: DataMappingPayload = {
      entityKindNames: kinds
    };
    const dataMappingAPI = await this.httpService
      .post(
        this.configService.appConfig.urls.DATA_CATALOG_SERVICE_URL,
        JSON.stringify(entityKindNames)
      )
      .toPromise();

    return dataMappingAPI.data.entityViewData;
  }

  // To be moved to util functions
  private raiseException(): void {
    throw new ServiceException(
      {
        message: 'This does not have a collection id',
        missing: 'Collection Id',
        code: HttpStatus.BAD_REQUEST
      },
      HttpStatus.BAD_REQUEST
    );
  }
}

When I access req.headers in the controller, I do get all the headers that I needed to set via interceptors.

{
[0]   'accept-encoding': 'gzip, deflate, br',
[0]   'accept-language': 'en-US,en;q=0.9',
[0]   cookie: '_ga=GA1.2.1433024000.1564057108; wfx_unq=AL2gejqqEGELJ5FQ; trafficManagerV2Token=eyJ0eXAiOiJKV1QiLCJhbGciOiJSUzI1NiIsImtpZCI6Ik1UVTJOakU0T0RJNE1nP
T0ifQ.eyJwZXJtaXRVcmwiOiJodHRwczovL2V2ZC5kYXRhLmRlbGZpLmNsb3VkLnNsYi1kcy5jb20vIiwiY291bnRyeUNvZGUiOiJJTiIsImlzcyI6ImNmcy10cmFmZmljLW1hbmFnZXIiLCJpYXQiOjE1NjYyNzM3ND
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zI1NiIsImtpZCI6Ik1UVTRORGcxTWpFeU1BPT0ifQ.eyJzdWIiOiJycHJhYmh1N0BzbGIuY29tIiwiaXNzIjoic2F1dGgtcHJldmlldy5zbGIuY29tIiwiYXVkIjoidGVzdC1zbGJkZXYtZGV2cG9ydGFsLnNsYmFwcC
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IiLCJqb2J0aXRsZSI6IiIsInN1YmlkIjoiRjBfSUMxSjl4SHBaSGVUbnVBaWRCYVhtdzI1YmxuOUhYSXIwMnNscW8wTSIsImlkcCI6Im8zNjUiLCJoZCI6InNsYi5jb20iLCJkZXNpZCI6InJwcmFiaHU3LXNsYi1jb2
0tNWZkODc5NzZAZGVzaWQuZGVsZmkuc2xiLmNvbSIsImNvbnRhY3RfZW1haWwiOiJycHJhYmh1N0BzbGIuY29tIiwicnRfaGFzaCI6IlAzUG1yRXd5WExCR1VwTi05TTdybEEifQ.Z61iRRoS7J1IpF_V_rWLcrgeaSf
QyZG3K5vU4jps_LqB3VkPSvjHXLdv7Ga_LLPI_v2J-WFityHVBnYxLEzKmOuNc_jToPwmBqCmLLfSzIFGiJrFKby09ZbVoCCLHxjyUwB_Uc2VmWuYLce7oPpVFxelgRqnRjO3ymlPm65OvrR09fHiOlo52TULwbyyzeg
xzfodkl0eVTM7TURDi1RxGNHvw8Ghxt--AVIcgCT7hBDxA6w11D7Cr6fWBp1VpE2yawTESUWtZJn5tBmMZeZq2QobptNcuFdiAstQpvi_B5MqY1HY5LjVLOb2jAnEoCTl_gmEfyWr_aIKAFioK4YcQQ; _gid=GA1.2.
1341318697.1566283218; account-id=tenant1; _gat=1; traffic-manager-token=eyJ0eXAiOiJKV1QiLCJhbGciOiJSUzI1NiIsImtpZCI6Ik1UVTRORGcxTWpFeU1BPT0ifQ.eyJwZXJtaXRVcmwi
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qC8y8sCjZ8fTw4yZICl5AwPGZ4IOLkAeg',
[0]   'user-agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/76.0.3809.100 Safari/537.36',
[0]   'content-type': 'application/json',
[0]   accept: 'application/json',
[0]   appkey: '',
[0]   'cache-control': 'no-cache',
[0]   'postman-token': 'cb397012-71aa-460a-b66b-28600538faf9',
[0]   host: 'localhost:8080',
[0]   'content-length': '77',
[0]   connection: 'keep-alive',
[0]   'Data-Partition-Id': 'tenant1',
[0]   Authorization: 'Bearer eyJ0eXAiOiJKV1QiLCJhbGciOiJSUzI1NiIsImtpZCI6Ik1UVTRORGcxTWpFeU1BPT0ifQ.eyJzdWIiOiJycHJhYmh1N0BzbGIuY29tIiwiaXNzIjoic2F1dGgtcHJldmlldy5z
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5MqY1HY5LjVLOb2jAnEoCTl_gmEfyWr_aIKAFioK4YcQQ'
[0] }

When I check the logs of the actual request, it says Authorization is null. Which means the request is not intercepted and not being appended with headers.

Has anyone faced similar issue?

Solution 1:

If I'm understanding you properly, you want to have the headers added to your outgoing HTTP call from the HttpService. The interceptor in NestJS works on IncomingMessage (incoming requests in general) and ServerResponse (or outgoing responses in general). It does not see things that are sent from the HttpService or any other HTTP client. Instead, you'd need to set the headers at the method level, or at the module level if they are all common values. The HttpModule has a register and registerAsync method that can be used to pass values to every HttpService call, so if you have common headers you can manage them in that:

@Module({
  imports: [
    HttpModule.register({
      headers: {} // object of headers you want to set
    }),
  ]
})
export class MyModule {}

And now when you use httpService.get(url) you'll send the headers with it.

Solution 2:

I just want to share my experience here how to add custom header base on an ongoing request

import { REQUEST } from '@nestjs/core';
import { Module, HttpModule } from '@nestjs/common';

@Module({
    imports: [HttpModule.registerAsync({
        useFactory: request => {
            let automated = 0;
            if (request.get('host').includes('localhost')) {
                automated = 1;
            }
            return { headers: { automated } };
        },
        inject: [REQUEST],
    })],
})

I've used the custom provider and injecting the request so I could identify what headers I'll be setting base on the request given, this would be helpful since we could dynamically set any headers base on request given without manually setting it per axios request.

and use it base on NestJS Documentation

@Injectable()
export class CatsService {
    constructor(private httpService: HttpService) {}

    findAll(): Observable<AxiosResponse<Cat[]>> {
        return this.httpService.get('http://localhost:3000/cats');
    }
}