Docker from scratch for PHP 8.1 Applications in 2022

... with webservers, queues and databases

Posted by Pascal Landau on 2022-03-21 10:00:00

In the fourth part of this tutorial series on developing PHP on Docker we will revisit the previous tutorials and update some things to be up-to-date in 2022. The article will be split in 3 subparts:

  • Part 4.1: Update the code structure (this article)
    • we'll also introduce three new containers (PHP workers, MySQL and redis) and add a small proof of concept to tie all containers together
  • Part 4.2: Add the tools for local development ( PhpStorm, Docker and Xdebug 3 on PHP 8.1 in 2022, available at 2022-03-22)
    • make the setup work with PhpStorm, including the ability to execute phpunit tests and run xdebug for all php containers (application, fpm and php workers)
  • Part4.3: Include Laravel ( Run Laravel 9 on Docker in 2022, available at 2022-03-23)
    • refactor the code to use Commands, Controllers, Queues, etc.

All code samples are publicly available in my Docker PHP Tutorial repository on github.
You find the branch for this tutorial at part-4-1-docker-from-scratch-for-php-applications-in-2022

All published parts of the Docker PHP Tutorial are collected under a dedicated page at Docker PHP Tutorial. The previous part was Structuring the Docker setup for PHP Projects and the following one is PhpStorm, Docker and Xdebug 3 on PHP 8.1 in 2022.

If you want to follow along, please subscribe to the RSS feed or via email to get automatic notifications when the next part comes out :)

Table of contents

Introduction

If you have read the previous tutorial Structuring the Docker setup for PHP Projects you might encounter some significant changes. The tutorial was published over 2 years ago, Docker has evolved and I have learned more about it. Plus, I gathered practical experience (good and bad) with the previous setup. I would now consider most of the points under Fundamentals on building the containers as either "not required" or simply "overengineered / too complex". To be concrete:

Local docker setup

The goal of this part is the introduction of a working local setup without development tools. In other words: We want the bare minimum to have something running locally.

The main components are:

  • the make setup in the Makefile and in the .make/ directory
  • the docker setup in the .docker/ directory
  • some PHP files that act as a POC for the end2end functionality of the docker setup

Check out the code via

git checkout part_4_section_1_docker_from_scratch_for_php_applications_in_2022_code_structure

initialize it via

make make-init
make docker-build

and run it via

make docker-up

Now you can access the web interface via http://127.0.0.1. The following diagram shows how the containers are connected

Docker container connections

See also the PHP POC for a full test of the setup.

Docker

The docker setup consists of

  • an nginx container as a webserver
  • a MySQL database container
  • a Redis container that acts as a queue
  • a php base image that is used by
    • a php worker container that spawns multiple PHP worker processes via supervisor
    • a php-fpm container as a backend for the nginx container
    • an application container that we use to run commands

Docker images

We keep the .docker/ directory from the previous tutorial , though it will be split into docker-compose/ and images/ like so:

.
└── .docker/
    ├── docker-compose/
    |   ├── docker-compose.yml
    |   └── <other docker-compose files>
    ├── images/
    |   ├── nginx/
    |   |   ├── Dockerfile
    |   |   └── <other files for the nginx image>
    |   └── <other folders for docker images>
    ├── .env
    └── .env.example

docker-compose

All images are build via docker-compose because the docker-compose.yml file(s) provide a nice abstraction layer for the build configuration. In addition, we can also use it to orchestrate the containers, i.e. control volumes, port mappings, networking, etc. - as well as start and stop them via docker-compose up and docker-compose down.

FYI: Even though it is convenient to use docker-compose for both things, I found it also to make the setup more complex than it needs to be when running things later in production (when we are not using docker-compose any longer). I believe the problem here is that some modifications are ONLY required for building while others are ONLY required for running - and combining both in the same file yields a certain amount of noise. But: It is what it is.

We use three separate docker-compose.yml files:

  • docker-compose.yml
    • contains all information valid for all environments
  • docker-compose.local.yml
  • docker-compose-php-base.yml
    • contains information for building the php base image, see PHP images

.docker/.env file and required ENV variables

In our docker setup we basically have 3 different types of variables:

  1. variables that depend on the local setup of an individual developer, e.g. the NGINX_HOST_HTTP_PORT on the host machine (because the default one might already be in use)
  2. variables that are used in multiple images, e.g. the location of the codebase within a container's file system
  3. variables that hold information that is "likely to change", e.g. the exact version of a base image

Since - again - we strive to retain a single source of truth, we extract the information as variables and put them in a .docker/.env file. In a perfect world, I would like to separate these different types in different files - but docker-compose only allows a single .env file, see e.g. this comment. If the file does not exist, it is copied from .docker/.env.example.

The variables are then used in the docker-compose.yml file(s). I found it to be "the least painful" to always use the ? modifier on variables so that docker-compose fails immediately if the variable is missing.

Note: Some variables are expected to be passed via environment variables when docker-compose is invoked (i.e. they are required but not defined in the .env file; see also Shared variables: .make/.env

Images

For MySQL and redis we do not use custom-built images but instead use the official ones directly and configure them through environment variables when starting the containers. In production, we won't use docker anyway for these services but instead rely on the managed versions, e.g.

The remaining containers are defined in their respective subdirectories in the .docker/images/ directory, e.g. the image for the nginx container is build via the Dockerfile located in .docker/images/nginx/Dockerfile.

PHP images

We need 3 different PHP images (fpm, workers, application) and use a slightly different approach than in Structuring the Docker setup for PHP Projects:

Instead of using the official PHP base images (i.e. cli or fpm), we use a "plain" alpine base image and install PHP and the required extensions manually in it. This allows us to build a common base image for all PHP images. Benefits:

  • a central place for shared tools and configuration (no more need for a .shared/ directory)
  • reduced image size when pushing the individual images (the base image is recognized as a layer and thus "already exists")
  • installing extensions via apk add is a lot faster than via docker-php-ext-install

This new approach has two major downsides:

  • we depend on the alpine release cycle of PHP (and PHP extensions)
  • the image build process is more complex, because we must build the base image first before we can build the final images

Fortunately, both issues can be solved rather easily:

  • codecasts/php-alpine maintains an apk repository with the latest PHP versions for alpine
  • we use a dedicated make target to build the images instead of invoking docker-compose directly - this enables us to define a "build order" (base first, rest after) while still having to run only a single command as a developer (see Ensuring the build order)

ENV vs ARG

I've noticed that some build arguments are required in multiple PHP containers, e.g. the name of the application user defined in the APP_USER_NAME ENV variable. The username is needed

  • in the base image to create the user
  • in the fpm image to define the user that runs the fpm processes (see php-fpm.d/www.conf)
  • in the worker image to define the user that runs the worker processes ( see supervisor/supervisord.conf)

Instead of passing the name to all images via build argument, i.e.

  • define it explicitly under services.*.build.args in the docker-compose.yml file
  • "retrieve" it in the Dockerfile via ARG APP_USER_NAME

I've opted to make the username available as an ENV variable in the base image via

ARG APP_USER_NAME
ENV APP_USER_NAME=${APP_USER_NAME}

and thus be able to access it in the child images directly, I can now write

RUN echo ${APP_USER_NAME}

instead of

ARG APP_USER_NAME
RUN echo ${APP_USER_NAME}

I'm not 100% certain that I like this approach as I'm more or less "abusing" ENV variables in ways that they are likely not intended ("Why would the username need to be stored as an ENV variable?") - but I also don't see any other practical downside yet.

Image naming convention

Defining a fully qualified name for images will make it much easier to reference the images later, e.g. when pushing them to the registry.

The naming convention for the images is $(DOCKER_REGISTRY)/$(DOCKER_NAMESPACE)/$(DOCKER_SERVICE_NAME)-$(ENV), e.g.

                   docker.io/dofroscra/nginx-local
$(DOCKER_REGISTRY)---^          ^        ^     ^        docker.io
$(DOCKER_NAMESPACE)-------------^        ^     ^        dofroscra
$(DOCKER_SERVICE_NAME)-------------------^     ^        nginx
$(ENV)-----------------------------------------^        local

and it is used as value for services.*.image, e.g. for nginx

services:
  nginx:
    image: ${DOCKER_REGISTRY?}/${DOCKER_NAMESPACE?}/nginx-${ENV?}:${TAG?}

In case you are wondering: dofroscra stems from Docker From Scratch

Environments and build targets

Our final goal is a setup that we can use for

  • local development
  • in a CI/CD pipeline
  • in production

and even though we strive to for a parity between those different environments, there will be differences due to fundamentally different requirements. E.g.

  • on production I want a container including the sourcecode without any test dependencies
  • on CI I want a container including the sourcecode WITH test dependencies
  • on local I want a container that mounts the sourcecode from my host (including dependencies)

This is reflected through the ENV environment variable. We use it in two places:

  1. as part of the image name as a suffix of the service name (see Image naming convention)
  2. to specify the target build stage

See the docker-compose-php-base.yml file for example:

services:
  php-base:
    image: ${DOCKER_REGISTRY?}/${DOCKER_NAMESPACE?}/php-base-${ENV?}:${TAG?}
    build:
      dockerfile: images/php/base/Dockerfile
      target: ${ENV?}

Using multiple targets in the same Dockerfile enables us to keep a common base but also include environment specific instructions. See the Dockerfile of the php-base image for example

ARG ALPINE_VERSION
FROM composer:${COMPOSER_VERSION} as composer
FROM alpine:${ALPINE_VERSION} as base

RUN apk add --update --no-cache \
        bash

WORKDIR $APP_CODE_PATH

FROM base as local

RUN apk add --no-cache --update \
        mysql-client \
  • it first defines a base stage that includes software required in all environments
  • and then defines a local stage that adds additionally a mysql-client that helps us to debug connectivity issues

After the build for local is finished, we end up with an image called php-base-local that used the local build stage as target build stage.

Makefile

In the following section I will introduce a couple of commands, e.g. for building and running containers. And to be honest, I find it kinda challenging to keep them in mind without having to look up the exact options and arguments. I would usually create a helper function or an alias in my local .bashrc file in a situation like that - but that wouldn't be available to other members of the team then and it would be very specific to this one project.

Instead we'll use a self-documenting Makefile that acts as the central entrypoint in the application. Since Makefiles tend to grow over time, I've adopted some strategies to keep them "sane" via includes, shared variables and better error handling.

.make/*.mk includes

Over time the make setup will grow substantially, thus we split it into multiple .mk files in the .make/ directory. The individual files are prefixed with a number to ensure their order when we include them in the main Makefile via

include .make/*.mk
.
└── .make/
    ├── 01-00-application-setup.mk
    ├── 01-01-application-commands.mk
    └── 02-00-docker.mk

Shared variables: .make/.env

We try to make shared variables available here, because we can then pass them on to individual commands as a prefix, e.g.

.PHONY: some-target
some-target: ## Run some target
    ENV_FOO=BAR some_command --baz

This will make the ENV_FOO available as environment variable to some_command.

Shared variables are used by different components, and we always try to maintain only a single source of truth. An example would be the DOCKER_REGISTRY variable that we need to define the image names of our docker images in the docker-compose.yml files but also when pushing/pulling/deploying images via make targets later. In this case, the variable is required by make as well as docker-compose.

To have a clear separation between variables and "code", we use a .env file located at . make/.env. It can be initialized via

make make-init

by copying the .make/.env.example to .make/.env.

.
└── .make/
    ├── .make/.env.example
    └── .make/.env

The file is included in the main Makefile via

-include .make/.env

The - prefix ensures that make doesn't fail if the file does not exist (yet), see GNU make: Including Other Makefiles.

Manual modifications

You can always modify the .make/.env file manually if required. This might be the case when you run docker on Linux and need to match the user id of your host system with the user id of the docker container. It is common that your local user and group have the id 1000. In this case you would add the entries manually to the .make/.env file.

APP_USER_ID=1000
APP_GROUP_ID=1000

See also section Solving permission issues.

Enforce required parameters

We kinda "abuse" make for executing arbitrary commands (instead of building artifacts) and some of those commands require parameters that can be passed as command arguments in the form

make some-target FOO=bar

There is no way to "define" those parameters as we would in a method signature - but we can still ensure to fail as early as possible if a parameter is missing via

@$(if $(FOO),,$(error FOO is empty or undefined))

See also SO: How to abort makefile if variable not set?

We use this technique for example to ensure that all required variables are defined when we execute docker targets via the validate-docker-variables precondition target:

.PHONY: validate-docker-variables
validate-docker-variables: 
    @$(if $(TAG),,$(error TAG is undefined))
    @$(if $(ENV),,$(error ENV is undefined))
    @$(if $(DOCKER_REGISTRY),,$(error DOCKER_REGISTRY is undefined - Did you run make-init?))
    @$(if $(DOCKER_NAMESPACE),,$(error DOCKER_NAMESPACE is undefined - Did you run make-init?))
    @$(if $(APP_USER_NAME),,$(error APP_USER_NAME is undefined - Did you run make-init?))
    @$(if $(APP_GROUP_NAME),,$(error APP_GROUP_NAME is undefined - Did you run make-init?))

.PHONY:docker-build-image
docker-build-image: validate-docker-variables
    $(DOCKER_COMPOSE) build $(DOCKER_SERVICE_NAME)

Make + Docker = <3

We already introduced quite some complexity into our setup:

  • "global" variables (shared between make and docker)
  • multiple docker-compose.yml files
  • build dependencies

Bringing it all together "manually" is quite an effort and prone to errors. But we can nicely tuck the complexity away in .make/02-00-docker.mk by defining the two variables DOCKER_COMPOSE and DOCKER_COMPOSE_PHP_BASE

DOCKER_DIR:=./.docker
DOCKER_ENV_FILE:=$(DOCKER_DIR)/.env
DOCKER_COMPOSE_DIR:=$(DOCKER_DIR)/docker-compose
DOCKER_COMPOSE_FILE:=$(DOCKER_COMPOSE_DIR)/docker-compose.yml
DOCKER_COMPOSE_FILE_LOCAL:=$(DOCKER_COMPOSE_DIR)/docker-compose.local.yml
DOCKER_COMPOSE_FILE_PHP_BASE:=$(DOCKER_COMPOSE_DIR)/docker-compose-php-base.yml
DOCKER_COMPOSE_PROJECT_NAME:=dofroscra_$(ENV)

DOCKER_COMPOSE_COMMAND:=ENV=$(ENV) \
 TAG=$(TAG) \
 DOCKER_REGISTRY=$(DOCKER_REGISTRY) \
 DOCKER_NAMESPACE=$(DOCKER_NAMESPACE) \
 APP_USER_NAME=$(APP_USER_NAME) \
 APP_GROUP_NAME=$(APP_GROUP_NAME) \
 docker-compose -p $(DOCKER_COMPOSE_PROJECT_NAME) --env-file $(DOCKER_ENV_FILE)

DOCKER_COMPOSE:=$(DOCKER_COMPOSE_COMMAND) -f $(DOCKER_COMPOSE_FILE) -f $(DOCKER_COMPOSE_FILE_LOCAL)
DOCKER_COMPOSE_PHP_BASE:=$(DOCKER_COMPOSE_COMMAND) -f $(DOCKER_COMPOSE_FILE_PHP_BASE)
  • DOCKER_COMPOSE uses docker-compose.yml and extends it with docker-compose.local.yml
  • DOCKER_COMPOSE_PHP_BASE uses only docker-compose-php-base.yml

The variables can then be used later in make recipes.

Ensuring the build order

As mentioned under PHP images, we need to build images in a certain order and use the following make targets:

.PHONY: docker-build-image
docker-build-image: ## Build all docker images OR a specific image by providing the service name via: make docker-build DOCKER_SERVICE_NAME=<service>
    $(DOCKER_COMPOSE) build $(DOCKER_SERVICE_NAME)

.PHONY: docker-build-php
docker-build-php: ## Build the php base image
    $(DOCKER_COMPOSE_PHP_BASE) build $(DOCKER_SERVICE_NAME_PHP_BASE)

.PHONY: docker-build
docker-build: docker-build-php docker-build-image ## Build the php image and then all other docker images

As a developer, I can now simply run make docker-build - which will first build the php-base image via docker-build-php and then build all the remaining images via docker-build-image (by not specifying the DOCKER_SERVICE_NAME variable, docker-compose will build all services listed in the docker-compose.yml files).

I would argue that the make recipes themselves are quite readable and easy to understand but when we run them with the -n option to only "Print the recipe that would be executed, but not execute it", we get a feeling for the complexity:

$ make docker-build -n
ENV=local TAG=latest DOCKER_REGISTRY=docker.io DOCKER_NAMESPACE=dofroscra APP_USER_NAME=application APP_GROUP_NAME=application docker-compose -p dofroscra_local --env-file ./.docker/.env -f ./.docker/docker-compose/docker-compose-php-base.yml build php-base
ENV=local TAG=latest DOCKER_REGISTRY=docker.io DOCKER_NAMESPACE=dofroscra APP_USER_NAME=application APP_GROUP_NAME=application docker-compose -p dofroscra_local --env-file ./.docker/.env -f ./.docker/docker-compose/docker-compose.yml -f ./.docker/docker-compose/docker-compose.local.yml build

Run commands in the docker containers

Tooling is an important part in the development workflow. This includes things like linters, static analyzers and testing tools but also "custom" tools geared towards your specific workflow. Those tools usually require a PHP runtime. For now, we only have a single "tool" defined in the file setup.php. It ensures that a table called jobs is created.

To run this tool, we must first start the docker setup via make docker-up and then execute the script in the application container. The corresponding target is defined in .make/01-00-application-setup.mk:

.PHONY: setup-db
setup-db: ## Setup the DB tables
    $(EXECUTE_IN_APPLICATION_CONTAINER) php setup.php $(ARGS);

which essentially translates to

docker-compose exec -T --user application application php setup.php

if we are outside of a container and to

php setup.php

if we are inside a container. That's quite handy, because we can run the tooling directly from the host system without having to log into a container.

The "magic" happens in the EXECUTE_IN_APPLICATION_CONTAINER variable that is defined in .make/02-00-docker.mk as

EXECUTE_IN_WORKER_CONTAINER?=
EXECUTE_IN_APPLICATION_CONTAINER?=

EXECUTE_IN_CONTAINER?=
ifndef EXECUTE_IN_CONTAINER
    # check if 'make' is executed in a docker container, 
    # see https://stackoverflow.com/a/25518538/413531
    # `wildcard $file` checks if $file exists, 
    # see https://www.gnu.org/software/make/manual/html_node/Wildcard-Function.html
    # i.e. if the result is "empty" then $file does NOT exist 
    # => we are NOT in a container
    ifeq ("$(wildcard /.dockerenv)","")
        EXECUTE_IN_CONTAINER=true
    endif
endif
ifeq ($(EXECUTE_IN_CONTAINER),true)
    EXECUTE_IN_APPLICATION_CONTAINER:=$(DOCKER_COMPOSE) exec -T --user $(APP_USER_NAME) $(DOCKER_SERVICE_NAME_APPLICATION)
    EXECUTE_IN_WORKER_CONTAINER:=$(DOCKER_COMPOSE) exec -T --user $(APP_USER_NAME) $(DOCKER_SERVICE_NAME_PHP_WORKER)
endif

We can take a look via -n again to see the resolved recipe on the host system

pascal.landau:/c/_codebase/dofroscra# make setup-db ARGS=--drop -n
ENV=local TAG=latest DOCKER_REGISTRY=docker.io DOCKER_NAMESPACE=dofroscra APP_USER_NAME=application APP_GROUP_NAME=application docker-compose -p dofroscra_local --env-file ./.docker/.env -f ./.docker/docker-compose/docker-compose.yml -f ./.docker/docker-compose/docker-compose.local.yml exec -T --user application application php setup.php --drop

Within a container it looks like this:

root:/var/www/app# make setup-db ARGS=--drop -n
php setup.php --drop;

Solving permission issues

If you are using Linux, you might run into permission issues when modifying files that are shared between the host system and the docker containers when the user id is not the same as explained in section Synchronizing file and folder ownership on shared volumes of the previous tutorial.

In this case, you need to modify the .make/.env manually and add the APP_USER_ID and APP_GROUP_ID variables according to your local setup. This must be done before building the images to ensure that the correct user id is used in the images.

In very rare cases it can lead to problems, because your local ids will already exist in the docker containers. I've personally never run into this problem, but you can read about it in more detail at Docker and the host filesystem owner matching problem. The author even proposes a general solution via the Github project "FooBarWidget/matchhostfsowner".

PHP POC

To ensure that everything works as expected, the repository contains a minimal PHP proof of concept. By default, port 80 from the host ist forwarded to port 80 of the nginx container.

FYI: I would also recommend to add the following entry in the hosts file on the host machine

127.0.0.1 app.local

so that we can access the application via http://app.local instead of http://127.0.0.1.

The files of the POC essentially ensure that the container connections outlined in Local docker setup work as expected:

Docker container connections

  • dependencies.php
    • returns configured Redis and PDO objects to talk to the queue and the database
  • setup.php
    • => ensures that application can talk to mysql
  • public/index.php
  • worker.php
    • is started as daemon process in the php-worker container
    • checks the redis datasbase 0 for the key "queue" every second
    • if a value is found it is stored in the jobs table of the database
      • => ensures that php-worker can talk to redis and mysql

A full test scenario is defined in test.sh and looks like this:

$ bash test.sh

  Building the docker setup

//...

  Starting the docker setup

//...

  Clearing DB

ENV=local TAG=latest DOCKER_REGISTRY=docker.io DOCKER_NAMESPACE=dofroscra APP_USER_NAME=application APP_GROUP_NAME=application docker-compose -p dofroscra_local --env-file ./.docker/.env -f ./.docker/docker-compose/docker-compose.yml -f ./.docker/docker-compose/docker-compose.local.yml exec -T --user application application php setup.php --drop;
Dropping table 'jobs'
Done
Creating table 'jobs'
Done

  Stopping workers

ENV=local TAG=latest DOCKER_REGISTRY=docker.io DOCKER_NAMESPACE=dofroscra APP_USER_NAME=application APP_GROUP_NAME=application docker-compose -p dofroscra_local --env-file ./.docker/.env -f ./.docker/docker-compose/docker-compose.yml -f ./.docker/docker-compose/docker-compose.local.yml exec -T --user application php-worker supervisorctl stop worker:*;
worker:worker_00: stopped
worker:worker_01: stopped
worker:worker_02: stopped
worker:worker_03: stopped

  Ensuring that queue and db are empty

Items in queue
array(0) {
}
Items in db
array(0) {
}

  Dispatching a job 'foo'

Adding item 'foo' to queue

  Asserting the job 'foo' is on the queue

Items in queue
array(1) {
  [0]=>
  string(3) "foo"
}

  Starting the workers

ENV=local TAG=latest DOCKER_REGISTRY=docker.io DOCKER_NAMESPACE=dofroscra APP_USER_NAME=application APP_GROUP_NAME=application docker-compose -p dofroscra_local --env-file ./.docker/.env -f ./.docker/docker-compose/docker-compose.yml -f ./.docker/docker-compose/docker-compose.local.yml exec -T --user application php-worker supervisorctl start worker:*;
worker:worker_00: started
worker:worker_01: started
worker:worker_02: started
worker:worker_03: started

  Asserting the queue is now empty

Items in queue
array(0) {
}

  Asserting the db now contains the job 'foo'

Items in db
array(1) {
  [0]=>
  string(3) "foo"
}

Wrapping up

Congratulations, you made it! If some things are not completely clear by now, don't hesitate to leave a comment. Apart from that, you should now have a running docker setup and the means to "control" it conveniently via make.

In the next part of this tutorial, we will configure PhpStorm as our IDE to use the docker setup.

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