Docker for WordPress slow - wordpress

Question

Problem:
I have a problem with WordPress & Docker because the slow loading time (+- 7 seconds) of my website. I am not sure why this happends but I think it has something to do with the external database or the shared volumes.
Setup:
I have a custom Dockerfile built on WordPress with XDebug and Mailhog. This Dockerfile is included within my docker-compose.yml, the other services my docker-compose contains are WP-CLI and Mailhog. My Database is hosted on an Amazon RDS so I can share it with my colleagues.
Code:
My Dockerfile looks like this:
FROM wordpress:latest
# Plugins & Media
RUN mkdir -p /var/www/html/wp-content/plugins
RUN mkdir -p /var/www/html/wp-content/uploads
RUN chown -R www-data:www-data /var/www
RUN find /var/www/ -type d -exec chmod 0755 {} \;
RUN find /var/www/ -type f -exec chmod 644 {} \;
# Mailhog
RUN curl --location --output /usr/local/bin/mhsendmail https://github.com/mailhog/mhsendmail/releases/download/v0.2.0/mhsendmail_linux_amd64 && \
chmod +x /usr/local/bin/mhsendmail
RUN echo 'sendmail_path="/usr/local/bin/mhsendmail --smtp-addr=mailhog:1025 --from=noreply#examle.com"' > /usr/local/etc/php/conf.d/mailhog.ini
# Xdebug
ENV XDEBUG_PORT 9000
RUN yes | pecl install xdebug \
&& echo "zend_extension=$(find /usr/local/lib/php/extensions/ -name xdebug.so)" > /usr/local/etc/php/conf.d/xdebug.ini \
&& echo "xdebug.remote_enable=1" >> /usr/local/etc/php/conf.d/xdebug.ini \
&& echo "xdebug.remote_autostart=1" >> /usr/local/etc/php/conf.d/xdebug.ini \
&& echo "xdebug.profiler_enable=1" >> /usr/local/etc/php/conf.d/xdebug.ini \
&& echo "xdebug.profiler_output_name=cachegrind.out.%t" >> /usr/local/etc/php/conf.d/xdebug.ini \
&& echo "xdebug.profiler_output_dir=/tmp" >> /usr/local/etc/php/conf.d/xdebug.ini \
&& echo "max_input_vars=2000" >> /usr/local/etc/php/conf.d/custom.ini \
&& rm -rf /usr/local/etc/php/conf.d/opcache-recommended.ini
EXPOSE 9000
My Docker-compose.yml looks like this:
version: "3.7"
services:
wordpress:
container_name: "${PROJECT_NAME}_wordpress"
restart: always
build:
context: ./
dockerfile: ./Dockerfile
ports:
- "8888:80"
- "443:443"
environment:
WORDPRESS_DB_NAME: "${PROJECT_NAME}"
WORDPRESS_DB_HOST: "${MYSQL_HOST}"
WORDPRESS_DB_USER: "${MYSQL_USER}"
WORDPRESS_DB_PASSWORD: "${MYSQL_PASSWORD}"
WORDPRESS_DEBUG: 1
XDEBUG_CONFIG: remote_host=host.docker.internal
WORDPRESS_CONFIG_EXTRA: |
define('FS_METHOD', 'direct');
volumes:
- "wordpress:/var/www/html"
- "./build/uploads:/var/www/html/wp-content/uploads:cached"
- "./build/plugins:/var/www/html/wp-content/plugins:cached"
- "./build/themes:/var/www/html/wp-content/themes:cached"
cli:
container_name: "${PROJECT_NAME}_cli"
image: "wordpress:cli"
volumes:
- "wordpress:/var/www/html"
- "./build/plugins:/var/www/html/wp-content/plugins:cached"
depends_on:
- wordpress
mailhog:
container_name: "${PROJECT_NAME}_mailhog"
image: mailhog/mailhog
depends_on:
- wordpress
ports:
- "1025:1025"
- "8025:8025"
volumes:
wordpress: null
But I can't find out why it is so slow; I got version 2.1.09.3 of Docker Desktop and working on a fast Mac or Windows.
Can someone help me or point me in the right direction?
Edits
If I look in the docker stats my CPU is around 0.01% and my MEM is around 2.73% so that can't be the problem.
Found out the biggest problem is connecting to the external database. If I move over to a local database the loading time is a lot faster (+- 1 sec).

Answer 1

There some issues for Mac & Windows Volume performance.
Link for more details:
Docker Wordpress super slow
In Mac and Windows there are some volumes performance issues that we should consider.
I made change in my docker-compose.yml
Note as I changed the short syntax to long syntax.
This notation permits add consistency option.
I added wp-content and php-conf (to get php.ini) because they are files directory most frequently called every time when a Wordpress page is loaded in browser.
services:
wordpress:
...
volumes:
- ./data:/data
- ./scripts:/docker-entrypoint-initwp.d
#- ./wp-content:/app/wp-content
- type: bind
source: ./wp-content
target: /app/wp-content
consistency: cached
#- ./php-conf:/usr/local/etc/php
- type: bind
source: ./php-conf
target: /usr/local/etc/php
consistency: cached