Docker, Nginx e PHP7: ERROR 111 Conexão recusada ao conectar-se ao upstream

Question

Eu executo uma imagem NGINX-PHP7-COMPOSER que funciona bem, mas ao usar o Slim Framework eu tive que alterar a configuração padrão do Nginx para fazer a URL reescrever o trabalho.

E agora ele mostra esse erro nos registros:

2017-01-21 14:38:34,357 INFO success: php-fpm7 entered RUNNING state, process has stayed up for > than 1 seconds (startsecs)

2017-01-21 14:38:34,359 INFO success: nginx entered RUNNING state, process has stayed up for > than 1 seconds (startsecs)

2017/01/21 14:38:37 [error] 15#15: *1 connect() failed (111: Connection refused) while connecting to upstream, client: 172.18.0.1, server: auth-api, request: "GET /hello HTTP/1.1", upstream: "fastcgi://172.18.0.6:9000", host: "localhost:9100"

172.18.0.1 - - [21/Jan/2017:14:38:37 +0000] "GET /hello HTTP/1.1" 502 537 "-" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_2) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/55.0.2883.95 Safari/537.36"

O arquivo de configuração que eu montei está carregado (eu verifiquei o bash com nginx -T):

server {
    listen 80;
    server_name auth-api;
    index index.php;
    root /var/www/html;

    location / {
        try_files $uri /index.php$is_args$args;
    }

    location ~ \.php {
        try_files $uri =404;
        fastcgi_split_path_info ^(.+\.php)(/.+)$;
        include fastcgi_params;
        fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
        fastcgi_param SCRIPT_NAME $fastcgi_script_name;
        fastcgi_index index.php;
        fastcgi_pass auth-api:9000;
    }

    error_page   500 502 503 504  /50x.html;
    location = /50x.html {
        root   /usr/share/nginx/html;
    }
}

Meu Dockerfile (apenas a imagem que estou carregando do repositório):

FROM richarvey/nginx-php-fpm

E meu docker-compose.yml:

version: '2'

services:

#############
## MARIADB ##
#############

    mariadb:
        image: mariadb
        restart: always
        volumes:
            - "./log/mariadb:/var/log/mysql:rw"
            - "./data/mariadb:/var/lib/mysql:rw"
        environment:
            - "MYSQL_ROOT_PASSWORD=pass"
        ports:
            - "3306:3306"

##############
## FRONTEND ##
##############

    frontend:
        image: skiychan/nginx-php7:latest
        volumes:
            - ./services/frontend/src:/data/www
        links:
            - mariadb:mysql
        ports:
            - "9001:80"

##############
## AUTH API ##
##############

    auth-api:
        build: ./services/api/auth/
        volumes:
            - ./services/api/auth/code/:/var/www/html
            - ./services/api/auth/:/etc/nginx/sites-available/
        links:
            - mariadb:mysql
        ports:
            - "9100:80"
            - "9000:9000"

Eu fiz o ping no IP com o telnet ...

ping de telnet

Você tem alguma ideia do que está errado?