ReactPHP and docker: could not resolve hosts from php to nginx container

Question

I work with docker and microservices. Imagine we have 3 services:

          user API
        /
gateway API
        \
          hotel API

Requests go through the gateway to services. I have container with php and nginx, where volumes is the same. Next I give list of configs:

server {
    server_name gateway.api.loc;

    root /var/www/der-ibe/ibe-gateway-api/web;
    client_max_body_size 32m;

    location / {
        try_files $uri @rewriteapp;
    }

    location @rewriteapp {
        rewrite ^(.*)$ /app.php/$1 last;
    }

    location ~ ^/(app|app_dev|config)\.php(/|$) {
       ...
    }
}
server {
    server_name hotel.api.loc;
    root /var/www/der-ibe/ibe-hotel-api/web;
    client_max_body_size 32m;

    location / {
        try_files $uri @rewriteapp;
    }

    location @rewriteapp {
        rewrite ^(.*)$ /app.php/$1 last;
    }

    location ~ ^/(app|app_dev|config)\.php(/|$) {
        ...
    }
}

...

docker-compose.yml

version: "3.1" 
services:

    tphp:
        build: docker/php
        restart: always
        container_name: my_tphp
        extra_hosts:
            - gateway.api.loc:172.14.10.10
            - user.api.loc:172.14.10.10
            - hotel.api.loc:172.14.10.10
        networks:
            - test
        volumes:
            - ../user-api:/var/www/user-api
            - ../hotel-api:/var/www/hotel-api
            - ./:/var/www/gateway-api

    tnginx:
        build: docker/nginx
        restart: always
        container_name: my_tnginx
        ports:
            - 80:80
        networks:
            test:
                 ipv4_address: 172.14.10.10
        volumes:
            - ../user-api:/var/www/user-api
            - ../hotel-api:/var/www/hotel-api
            - ./:/var/www/gateway-api

networks:
    ibe:
      driver: bridge
      ipam:
        driver: default
        config:
          - subnet: 172.14.10.0/24

If I use simple cURL I can reach to hotel and user api, and I can get response from them, but if I try to do it with reactPHP - I can't! My peace of code:

 public function asyncGetRequest(Route $route, $params, $token)
{
    $url = $this->buildURL($route, $params);

    $loop = React\EventLoop\Factory::create();

    $dns = '172.14.10.10';
    $sender = Clue\React\Buzz\Io\Sender::createFromLoopDns($loop, $dns);

    //$url = 'http://172.14.10.10:3000/api/quota/list';

    $client = new Clue\React\Buzz\Browser($loop, $sender);
    //$client = new Clue\React\Buzz\Browser($loop);

    $promise = $client->get($url,
        [
            'Authorization' => $token,
        ]
    );

    /** @var Response $response */
    $response = new Response();

    try {
        $response = Clue\React\Block\await($promise, $loop);
    } catch (ResponseException $e) {
        $this->logger->error($e->getMessage());
    }

    dump($response->getBody()->getContents()); // I work on symfony 3.2
    die;
}

Clue library is just wrapper for react. So the error which I get is: DNS query for hotel.api.loc timed out and the last error An error occurred in the underlying stream.

So I have a question: what I do wrong? Why I have access to nginx container by curl, but can't access by reactPHP? Even If point dns!

But if I use bare ip with port I can reach it. I'm not pro in dns, just basic knowledge.

UPDATE

I use Linux Debian (in container). Work on Mac.

A little about logic: when request URI is gateway.api.loc/api/hotel/list inside gateway we send request to hotel.api.loc to the same URL(/api/hotel/list), accept response and return it.

I repeat that I have access to domains by cURL from, but can't do it with reactPHP and don't understand why...

Answer 1

Your issue is that there is no DNS resolution for gateway.api.loc or hotel.api.loc, they are defined in your Nginx config for routing but no anywhere else for DNS resolution. You need to change your compose to below so they also get resolved in docker DNS resolution

version: "3.1" 
services:

    tphp:
        build: docker/php
        restart: always
        container_name: my_tphp
        extra_hosts:
            - gateway.api.ibe.lazy-ants.loc:172.14.10.10
            - user.api.ibe.lazy-ants.loc:172.14.10.10
            - hotel.api.ibe.lazy-ants.loc:172.14.10.10
        networks:
            - test
        volumes:
            - ../user-api:/var/www/user-api
            - ../hotel-api:/var/www/hotel-api
            - ./:/var/www/gateway-api

    tnginx:
        build: docker/nginx
        restart: always
        container_name: my_tnginx
        ports:
            - 80:80
        networks:
            test:
                 ipv4_address: 172.14.10.10
                 aliases:
                     - hotel.api.loc
                     - gateway.api.loc
        volumes:
            - ../user-api:/var/www/user-api
            - ../hotel-api:/var/www/hotel-api
            - ./:/var/www/gateway-api

networks:
    ibe:
      driver: bridge
      ipam:
        driver: default
        config:
          - subnet: 172.14.10.0/24

This DNS resolution will only work inside the compose and not outside. So if you use it outside then you will have to make host entries

Edit-1

It seems your issue may be code only. You are trying to use gateway IP as DNS when it is not a DNS server.

Change

$loop = React\EventLoop\Factory::create();

$dns = '172.14.10.10';
$sender = Clue\React\Buzz\Io\Sender::createFromLoopDns($loop, $dns);

//$url = 'http://172.14.10.10:3000/api/quota/list';

$client = new Clue\React\Buzz\Browser($loop, $sender);

to

$loop = React\EventLoop\Factory::create();

$dns = '172.14.10.10';
//$sender = Clue\React\Buzz\Io\Sender::createFromLoopDns($loop, $dns);
//$url = 'http://172.14.10.10:3000/api/quota/list';

$client = new Clue\React\Buzz\Browser($loop);

And see if it helps

Answer 2

The issue you're seeing is ReactPHP's incomplete DNS implementation. It doesn't respect /etc/resolv.conf and only added support for /etc/hosts recently. If you're not using react/dns v0.4.11 or later then that's probably the issue and you should try upgrading.

I'm not sure how Docker resolves DNS these days for linked containers. Years ago that worked with a hooked /etc/hosts that provides the hostnames and corresponding IPs. But I think these days Docker is using an internal DNS server. As ReactPHP doesn't pick that up automatically, you have to explicitly set it when creating a DNS resolver.

Try setting 127.0.0.11 as nameserver, which is Docker's internal DNS.