AWS ECS Fargateにおいて、タスク内でコンテナ間通信ができない

前提・実現したいこと

ECS Fargate上でシンプルなLAMPアプリを動かしたい

発生している問題・エラーメッセージ

PHP（Laravel）コンテナからMariadbコンテナへアクセスができない

（ECS Execでphp artisan migrateでも同じエラー）

こちらの記事では、同じタスク内においてはlocalhostで通信ができるようですが、アクセスができなく困っております。

タスクのIPに直接アクセス

SQLSTATE[HY000] [2002] No such file or directory (SQL: ・・・

該当のインフラ定義

Laravel・MariaDB両者のコンテナはビルドしたDockerfileをECRで管理

*現状、ツッコミどころが色々ありますが、まずは動かすことを目的にしているので、余計な部分もあります。

Laravel-Dockerfile

FROM php:7.4.24-apache

#install all the system dependencies and enable PHP modules 
RUN apt-get update \
  && apt-get install -y zlib1g-dev \
  && apt-get install -y zip unzip \
  && apt-get -y install libzip-dev libonig-dev \
  && docker-php-ext-install pdo_mysql mysqli zip \
  && docker-php-ext-enable mysqli \
  && a2enmod rewrite

# タイムゾーン設定
ENV TZ=Asia/Tokyo

# cronのインストール
RUN apt-get update && apt-get install -y \
  busybox-static \
  && apt-get clean

#install composer
RUN curl -sS https://getcomposer.org/installer | php -- --install-dir=/usr/bin/ --filename=composer
ENV COMPOSER_ALLOW_SUPERUSER 1
ENV COMPOSER_HOME /composer
ENV PATH $PATH:/composer/vendor/bin

#set our application folder as an environment variable
ENV APP_HOME /var/www/html

#change uid and gid of apache to docker user uid/gid
RUN usermod -u 1000 www-data && groupmod -g 1000 www-data

COPY ./php/vhost.conf /etc/apache2/conf-enabled/vhost.conf

# enable apache module rewrite
RUN a2enmod rewrite

#copy source files and run composer
COPY . $APP_HOME

RUN mkdir bootstrap/sessions
#RUN mkdir storage/framework/sessions && \
#    mkdir storage/framework/views && \
#    mkdir storage/framework/cache

# install all PHP dependencies
RUN composer install --no-dev --no-interaction

#change ownership of our applications
RUN chown -R www-data:www-data $APP_HOME
#    chmod -R 0777 bootstrap && \
 #   chmod -R 0777 storage
RUN mv .env.production .env

EXPOSE 80

MariaDB-Dockerfile

FROM mariadb:10.4

ENV MYSQL_USER=dbuser \
    MYSQL_PASSWORD=**** \
    MYSQL_DATABASE=simplememo \
    MYSQL_ROOT_PASSWORD=****

COPY ./init.sql /docker-entrypoint-initdb.d

EXPOSE 3306

タスク定義(ECS)

json
{
  "ipcMode": null,
  "executionRoleArn": "arn:aws:iam::995962138333:role/ecsTaskExecusionRole",
  "containerDefinitions": [
    {
      "dnsSearchDomains": null,
      "environmentFiles": null,
      "logConfiguration": {
        "logDriver": "awslogs",
        "secretOptions": null,
        "options": {
          "awslogs-group": "/ecs/fargate-laravel",
          "awslogs-region": "ap-northeast-1",
          "awslogs-stream-prefix": "ecs"
        }
      },
      "entryPoint": null,
      "portMappings": [
        {
          "hostPort": 80,
          "protocol": "tcp",
          "containerPort": 80
        }
      ],
      "command": null,
      "linuxParameters": null,
      "cpu": 0,
      "environment": [
        {
          "name": "DB_DATABASE",
          "value": "simplememo"
        },
        {
          "name": "DB_HOST",
          "value": "localhost"
        },
        {
          "name": "DB_PASSWORD",
          "value": "simplememodbuse"
        },
        {
          "name": "DB_USER",
          "value": "dbuser"
        }
      ],
      "resourceRequirements": null,
      "ulimits": null,
      "dnsServers": null,
      "mountPoints": [],
      "workingDirectory": null,
      "secrets": null,
      "dockerSecurityOptions": null,
      "memory": null,
      "memoryReservation": 127,
      "volumesFrom": [],
      "stopTimeout": null,
      "image": "995962138333.dkr.ecr.ap-northeast-1.amazonaws.com/laravelecs:latest",
      "startTimeout": null,
      "firelensConfiguration": null,
      "dependsOn": null,
      "disableNetworking": null,
      "interactive": null,
      "healthCheck": null,
      "essential": true,
      "links": null,
      "hostname": null,
      "extraHosts": null,
      "pseudoTerminal": null,
      "user": null,
      "readonlyRootFilesystem": null,
      "dockerLabels": null,
      "systemControls": null,
      "privileged": null,
      "name": "laravel"
    },
    {
      "dnsSearchDomains": null,
      "environmentFiles": null,
      "logConfiguration": {
        "logDriver": "awslogs",
        "secretOptions": null,
        "options": {
          "awslogs-group": "/ecs/fargate-laravel",
          "awslogs-region": "ap-northeast-1",
          "awslogs-stream-prefix": "ecs"
        }
      },
      "entryPoint": null,
      "portMappings": [
        {
          "hostPort": 3306,
          "protocol": "tcp",
          "containerPort": 3306
        }
      ],
      "command": null,
      "linuxParameters": null,
      "cpu": 0,
      "environment": [],
      "resourceRequirements": null,
      "ulimits": null,
      "dnsServers": null,
      "mountPoints": [],
      "workingDirectory": null,
      "secrets": null,
      "dockerSecurityOptions": null,
      "memory": null,
      "memoryReservation": 128,
      "volumesFrom": [],
      "stopTimeout": null,
      "image": "995962138333.dkr.ecr.ap-northeast-1.amazonaws.com/mariadb:latest",
      "startTimeout": null,
      "firelensConfiguration": null,
      "dependsOn": null,
      "disableNetworking": null,
      "interactive": null,
      "healthCheck": null,
      "essential": true,
      "links": null,
      "hostname": null,
      "extraHosts": null,
      "pseudoTerminal": null,
      "user": null,
      "readonlyRootFilesystem": null,
      "dockerLabels": null,
      "systemControls": null,
      "privileged": null,
      "name": "mariadb"
    }
  ],
  "placementConstraints": [],
  "memory": "512",
  "taskRoleArn": "arn:aws:iam::995962138333:role/ecsTaskExecusionRole",
  "compatibilities": [
    "EC2",
    "FARGATE"
  ],
  "taskDefinitionArn": "arn:aws:ecs:ap-northeast-1:995962138333:task-definition/fargate-laravel:4",
  "family": "fargate-laravel",
  "requiresAttributes": [
    {
      "targetId": null,
      "targetType": null,
      "value": null,
      "name": "com.amazonaws.ecs.capability.logging-driver.awslogs"
    },
    {
      "targetId": null,
      "targetType": null,
      "value": null,
      "name": "ecs.capability.execution-role-awslogs"
    },
    {
      "targetId": null,
      "targetType": null,
      "value": null,
      "name": "com.amazonaws.ecs.capability.ecr-auth"
    },
    {
      "targetId": null,
      "targetType": null,
      "value": null,
      "name": "com.amazonaws.ecs.capability.docker-remote-api.1.19"
    },
    {
      "targetId": null,
      "targetType": null,
      "value": null,
      "name": "com.amazonaws.ecs.capability.docker-remote-api.1.21"
    },
    {
      "targetId": null,
      "targetType": null,
      "value": null,
      "name": "com.amazonaws.ecs.capability.task-iam-role"
    },
    {
      "targetId": null,
      "targetType": null,
      "value": null,
      "name": "ecs.capability.execution-role-ecr-pull"
    },
    {
      "targetId": null,
      "targetType": null,
      "value": null,
      "name": "com.amazonaws.ecs.capability.docker-remote-api.1.18"
    },
    {
      "targetId": null,
      "targetType": null,
      "value": null,
      "name": "ecs.capability.task-eni"
    }
  ],
  "pidMode": null,
  "requiresCompatibilities": [
    "FARGATE"
  ],
  "networkMode": "awsvpc",
  "cpu": "256",
  "revision": 4,
  "status": "ACTIVE",
  "inferenceAccelerators": null,
  "proxyConfiguration": null,
  "volumes": []
}