Docker for MySQL

1. Dockerfile

FROM debian:stretch-slim

# add our user and group first to make sure their IDs get assigned consistently, regardless of whatever dependencies get added
RUN groupadd -r mysql && useradd -r -g mysql mysql

RUN apt-get update && apt-get install -y --no-install-recommends gnupg dirmngr && rm -rf /var/lib/apt/lists/*

# add gosu for easy step-down from root
ENV GOSU_VERSION 1.7
RUN set -x \
	&& apt-get update && apt-get install -y --no-install-recommends ca-certificates wget && rm -rf /var/lib/apt/lists/* \
	&& wget -O /usr/local/bin/gosu "https://github.com/tianon/gosu/releases/download/$GOSU_VERSION/gosu-$(dpkg --print-architecture)" \
	&& wget -O /usr/local/bin/gosu.asc "https://github.com/tianon/gosu/releases/download/$GOSU_VERSION/gosu-$(dpkg --print-architecture).asc" \
	&& export GNUPGHOME="$(mktemp -d)" \
	&& gpg --batch --keyserver ha.pool.sks-keyservers.net --recv-keys B42F6819007F00F88E364FD4036A9C25BF357DD4 \
	&& gpg --batch --verify /usr/local/bin/gosu.asc /usr/local/bin/gosu \
	&& gpgconf --kill all \
	&& rm -rf "$GNUPGHOME" /usr/local/bin/gosu.asc \
	&& chmod +x /usr/local/bin/gosu \
	&& gosu nobody true \
	&& apt-get purge -y --auto-remove ca-certificates wget

RUN mkdir /docker-entrypoint-initdb.d

RUN apt-get update && apt-get install -y --no-install-recommends \
# for MYSQL_RANDOM_ROOT_PASSWORD
		pwgen \
# for mysql_ssl_rsa_setup
		openssl \
# FATAL ERROR: please install the following Perl modules before executing /usr/local/mysql/scripts/mysql_install_db:
# File::Basename
# File::Copy
# Sys::Hostname
# Data::Dumper
		perl \
	&& rm -rf /var/lib/apt/lists/*

RUN set -ex; \
# gpg: key 5072E1F5: public key "MySQL Release Engineering " imported
	key='A4A9406876FCBD3C456770C88C718D3B5072E1F5'; \
	export GNUPGHOME="$(mktemp -d)"; \
	gpg --batch --keyserver ha.pool.sks-keyservers.net --recv-keys "$key"; \
	gpg --batch --export "$key" > /etc/apt/trusted.gpg.d/mysql.gpg; \
	gpgconf --kill all; \
	rm -rf "$GNUPGHOME"; \
	apt-key list > /dev/null

ENV MYSQL_MAJOR 5.7
ENV MYSQL_VERSION 5.7.29-1debian9

RUN echo "deb http://repo.mysql.com/apt/debian/ stretch mysql-${MYSQL_MAJOR}" > /etc/apt/sources.list.d/mysql.list

# the "/var/lib/mysql" stuff here is because the mysql-server postinst doesn't have an explicit way to disable the mysql_install_db codepath besides having a database already "configured" (ie, stuff in /var/lib/mysql/mysql)
# also, we set debconf keys to make APT a little quieter
RUN { \
		echo mysql-community-server mysql-community-server/data-dir select ''; \
		echo mysql-community-server mysql-community-server/root-pass password ''; \
		echo mysql-community-server mysql-community-server/re-root-pass password ''; \
		echo mysql-community-server mysql-community-server/remove-test-db select false; \
	} | debconf-set-selections \
	&& apt-get update && apt-get install -y mysql-server="${MYSQL_VERSION}" && rm -rf /var/lib/apt/lists/* \
	&& rm -rf /var/lib/mysql && mkdir -p /var/lib/mysql /var/run/mysqld \
	&& chown -R mysql:mysql /var/lib/mysql /var/run/mysqld \
# ensure that /var/run/mysqld (used for socket and lock files) is writable regardless of the UID our mysqld instance ends up having at runtime
	&& chmod 777 /var/run/mysqld \
# comment out a few problematic configuration values
	&& find /etc/mysql/ -name '*.cnf' -print0 \
		| xargs -0 grep -lZE '^(bind-address|log)' \
		| xargs -rt -0 sed -Ei 's/^(bind-address|log)/#&/' \
# don't reverse lookup hostnames, they are usually another container
	&& echo '[mysqld]\nskip-host-cache\nskip-name-resolve' > /etc/mysql/conf.d/docker.cnf

VOLUME /var/lib/mysql

COPY docker-entrypoint.sh /usr/local/bin/
RUN ln -s usr/local/bin/docker-entrypoint.sh /entrypoint.sh # backwards compat
ENTRYPOINT ["docker-entrypoint.sh"]

EXPOSE 3306 33060
CMD ["mysqld"]

2. docker-entrypoint.sh

#!/bin/bash
set -eo pipefail
shopt -s nullglob

# logging functions
mysql_log() {
	local type="$1"; shift
	printf '%s [%s] [Entrypoint]: %s\n' "$(date --rfc-3339=seconds)" "$type" "$*"
}
mysql_note() {
	mysql_log Note "$@"
}
mysql_warn() {
	mysql_log Warn "$@" >&2
}
mysql_error() {
	mysql_log ERROR "$@" >&2
	exit 1
}

# usage: file_env VAR [DEFAULT]
#    ie: file_env 'XYZ_DB_PASSWORD' 'example'
# (will allow for "$XYZ_DB_PASSWORD_FILE" to fill in the value of
#  "$XYZ_DB_PASSWORD" from a file, especially for Docker's secrets feature)
file_env() {
	local var="$1"
	local fileVar="${var}_FILE"
	local def="${2:-}"
	if [ "${!var:-}" ] && [ "${!fileVar:-}" ]; then
		mysql_error "Both $var and $fileVar are set (but are exclusive)"
	fi
	local val="$def"
	if [ "${!var:-}" ]; then
		val="${!var}"
	elif [ "${!fileVar:-}" ]; then
		val="$(< "${!fileVar}")"
	fi
	export "$var"="$val"
	unset "$fileVar"
}

# check to see if this file is being run or sourced from another script
_is_sourced() {
	# https://unix.stackexchange.com/a/215279
	[ "${#FUNCNAME[@]}" -ge 2 ] \
		&& [ "${FUNCNAME[0]}" = '_is_sourced' ] \
		&& [ "${FUNCNAME[1]}" = 'source' ]
}

# usage: docker_process_init_files [file [file [...]]]
#    ie: docker_process_init_files /always-initdb.d/*
# process initializer files, based on file extensions
docker_process_init_files() {
	# mysql here for backwards compatibility "${mysql[@]}"
	mysql=( docker_process_sql )

	echo
	local f
	for f; do
		case "$f" in
			*.sh)     mysql_note "$0: running $f"; . "$f" ;;
			*.sql)    mysql_note "$0: running $f"; docker_process_sql < "$f"; echo ;;
			*.sql.gz) mysql_note "$0: running $f"; gunzip -c "$f" | docker_process_sql; echo ;;
			*)        mysql_warn "$0: ignoring $f" ;;
		esac
		echo
	done
}

mysql_check_config() {
	local toRun=( "$@" --verbose --help ) errors
	if ! errors="$("${toRun[@]}" 2>&1 >/dev/null)"; then
		mysql_error $'mysqld failed while attempting to check config\n\tcommand was: '"${toRun[*]}"$'\n\t'"$errors"
	fi
}

# Fetch value from server config
# We use mysqld --verbose --help instead of my_print_defaults because the
# latter only show values present in config files, and not server defaults
mysql_get_config() {
	local conf="$1"; shift
	"$@" --verbose --help --log-bin-index="$(mktemp -u)" 2>/dev/null \
		| awk -v conf="$conf" '$1 == conf && /^[^ \t]/ { sub(/^[^ \t]+[ \t]+/, ""); print; exit }'
	# match "datadir      /some/path with/spaces in/it here" but not "--xyz=abc\n     datadir (xyz)"
}

# Do a temporary startup of the MySQL server, for init purposes
docker_temp_server_start() {
	if [ "${MYSQL_MAJOR}" = '5.6' ] || [ "${MYSQL_MAJOR}" = '5.7' ]; then
		"$@" --skip-networking --socket="${SOCKET}" &
		mysql_note "Waiting for server startup"
		local i
		for i in {30..0}; do
			# only use the root password if the database has already been initializaed
			# so that it won't try to fill in a password file when it hasn't been set yet
			extraArgs=()
			if [ -z "$DATABASE_ALREADY_EXISTS" ]; then
				extraArgs+=( '--dont-use-mysql-root-password' )
			fi
			if docker_process_sql "${extraArgs[@]}" --database=mysql <<<'SELECT 1' &> /dev/null; then
				break
			fi
			sleep 1
		done
		if [ "$i" = 0 ]; then
			mysql_error "Unable to start server."
		fi
	else
		# For 5.7+ the server is ready for use as soon as startup command unblocks
		if ! "$@" --daemonize --skip-networking --socket="${SOCKET}"; then
			mysql_error "Unable to start server."
		fi
	fi
}

# Stop the server. When using a local socket file mysqladmin will block until
# the shutdown is complete.
docker_temp_server_stop() {
	if ! mysqladmin --defaults-extra-file=<( _mysql_passfile ) shutdown -uroot --socket="${SOCKET}"; then
		mysql_error "Unable to shut down server."
	fi
}

# Verify that the minimally required password settings are set for new databases.
docker_verify_minimum_env() {
	if [ -z "$MYSQL_ROOT_PASSWORD" -a -z "$MYSQL_ALLOW_EMPTY_PASSWORD" -a -z "$MYSQL_RANDOM_ROOT_PASSWORD" ]; then
		mysql_error $'Database is uninitialized and password option is not specified\n\tYou need to specify one of MYSQL_ROOT_PASSWORD, MYSQL_ALLOW_EMPTY_PASSWORD and MYSQL_RANDOM_ROOT_PASSWORD'
	fi
}

# creates folders for the database
# also ensures permission for user mysql of run as root
docker_create_db_directories() {
	local user; user="$(id -u)"

	# TODO other directories that are used by default? like /var/lib/mysql-files
	# see https://github.com/docker-library/mysql/issues/562
	mkdir -p "$DATADIR"

	if [ "$user" = "0" ]; then
		# this will cause less disk access than `chown -R`
		find "$DATADIR" \! -user mysql -exec chown mysql '{}' +
	fi
}

# initializes the database directory
docker_init_database_dir() {
	mysql_note "Initializing database files"
	if [ "$MYSQL_MAJOR" = '5.6' ]; then
		mysql_install_db --datadir="$DATADIR" --rpm --keep-my-cnf "${@:2}"
	else
		"$@" --initialize-insecure
	fi
	mysql_note "Database files initialized"

	if command -v mysql_ssl_rsa_setup > /dev/null && [ ! -e "$DATADIR/server-key.pem" ]; then
		# https://github.com/mysql/mysql-server/blob/23032807537d8dd8ee4ec1c4d40f0633cd4e12f9/packaging/deb-in/extra/mysql-systemd-start#L81-L84
		mysql_note "Initializing certificates"
		mysql_ssl_rsa_setup --datadir="$DATADIR"
		mysql_note "Certificates initialized"
	fi
}

# Loads various settings that are used elsewhere in the script
# This should be called after mysql_check_config, but before any other functions
docker_setup_env() {
	# Get config
	declare -g DATADIR SOCKET
	DATADIR="$(mysql_get_config 'datadir' "$@")"
	SOCKET="$(mysql_get_config 'socket' "$@")"

	# Initialize values that might be stored in a file
	file_env 'MYSQL_ROOT_HOST' '%'
	file_env 'MYSQL_DATABASE'
	file_env 'MYSQL_USER'
	file_env 'MYSQL_PASSWORD'
	file_env 'MYSQL_ROOT_PASSWORD'

	declare -g DATABASE_ALREADY_EXISTS
	if [ -d "$DATADIR/mysql" ]; then
		DATABASE_ALREADY_EXISTS='true'
	fi
}

# Execute sql script, passed via stdin
# usage: docker_process_sql [--dont-use-mysql-root-password] [mysql-cli-args]
#    ie: docker_process_sql --database=mydb <<<'INSERT ...'
#    ie: docker_process_sql --dont-use-mysql-root-password --database=mydb 
docker_process_sql() {
	passfileArgs=()
	if [ '--dont-use-mysql-root-password' = "$1" ]; then
		passfileArgs+=( "$1" )
		shift
	fi
	# args sent in can override this db, since they will be later in the command
	if [ -n "$MYSQL_DATABASE" ]; then
		set -- --database="$MYSQL_DATABASE" "$@"
	fi

	mysql --defaults-file=<( _mysql_passfile "${passfileArgs[@]}") --protocol=socket -uroot -hlocalhost --socket="${SOCKET}" "$@"
}

# Initializes database with timezone info and root password, plus optional extra db/user
docker_setup_db() {
	# Load timezone info into database
	if [ -z "$MYSQL_INITDB_SKIP_TZINFO" ]; then
		# sed is for https://bugs.mysql.com/bug.php?id=20545
		mysql_tzinfo_to_sql /usr/share/zoneinfo \
			| sed 's/Local time zone must be set--see zic manual page/FCTY/' \
			| docker_process_sql --dont-use-mysql-root-password --database=mysql
			# tell docker_process_sql to not use MYSQL_ROOT_PASSWORD since it is not set yet
	fi
	# Generate random root password
	if [ -n "$MYSQL_RANDOM_ROOT_PASSWORD" ]; then
		export MYSQL_ROOT_PASSWORD="$(pwgen -1 32)"
		mysql_note "GENERATED ROOT PASSWORD: $MYSQL_ROOT_PASSWORD"
	fi
	# Sets root password and creates root users for non-localhost hosts
	local rootCreate=
	# default root to listen for connections from anywhere
	if [ -n "$MYSQL_ROOT_HOST" ] && [ "$MYSQL_ROOT_HOST" != 'localhost' ]; then
		# no, we don't care if read finds a terminating character in this heredoc
		# https://unix.stackexchange.com/questions/265149/why-is-set-o-errexit-breaking-this-read-heredoc-expression/265151#265151
		read -r -d '' rootCreate <<-EOSQL || true
			CREATE USER 'root'@'${MYSQL_ROOT_HOST}' IDENTIFIED BY '${MYSQL_ROOT_PASSWORD}' ;
			GRANT ALL ON *.* TO 'root'@'${MYSQL_ROOT_HOST}' WITH GRANT OPTION ;
		EOSQL
	fi

	local passwordSet=
	if [ "$MYSQL_MAJOR" = '5.6' ]; then
		# no, we don't care if read finds a terminating character in this heredoc (see above)
		read -r -d '' passwordSet <<-EOSQL || true
			DELETE FROM mysql.user WHERE user NOT IN ('mysql.sys', 'mysqlxsys', 'root') OR host NOT IN ('localhost') ;
			SET PASSWORD FOR 'root'@'localhost'=PASSWORD('${MYSQL_ROOT_PASSWORD}') ;
			-- 5.5: https://github.com/mysql/mysql-server/blob/e48d775c6f066add457fa8cfb2ebc4d5ff0c7613/scripts/mysql_secure_installation.sh#L192-L210
			-- 5.6: https://github.com/mysql/mysql-server/blob/06bc670db0c0e45b3ea11409382a5c315961f682/scripts/mysql_secure_installation.sh#L218-L236
			-- 5.7: https://github.com/mysql/mysql-server/blob/913071c0b16cc03e703308250d795bc381627e37/client/mysql_secure_installation.cc#L792-L818
			-- 8.0: https://github.com/mysql/mysql-server/blob/b93c1661d689c8b7decc7563ba15f6ed140a4eb6/client/mysql_secure_installation.cc#L726-L749
			DELETE FROM mysql.db WHERE Db='test' OR Db='test\_%' ;
			-- https://github.com/docker-library/mysql/pull/479#issuecomment-414561272 ("This is only needed for 5.5 and 5.6")
		EOSQL
	else
		# no, we don't care if read finds a terminating character in this heredoc (see above)
		read -r -d '' passwordSet <<-EOSQL || true
			ALTER USER 'root'@'localhost' IDENTIFIED BY '${MYSQL_ROOT_PASSWORD}' ;
		EOSQL
	fi

	# tell docker_process_sql to not use MYSQL_ROOT_PASSWORD since it is just now being set
	docker_process_sql --dont-use-mysql-root-password --database=mysql <<-EOSQL
		-- What's done in this file shouldn't be replicated
		--  or products like mysql-fabric won't work
		SET @@SESSION.SQL_LOG_BIN=0;
		${passwordSet}
		GRANT ALL ON *.* TO 'root'@'localhost' WITH GRANT OPTION ;
		FLUSH PRIVILEGES ;
		${rootCreate}
		DROP DATABASE IF EXISTS test ;
	EOSQL

	# Creates a custom database and user if specified
	if [ -n "$MYSQL_DATABASE" ]; then
		mysql_note "Creating database ${MYSQL_DATABASE}"
		docker_process_sql --database=mysql <<<"CREATE DATABASE IF NOT EXISTS \`$MYSQL_DATABASE\` ;"
	fi

	if [ -n "$MYSQL_USER" ] && [ -n "$MYSQL_PASSWORD" ]; then
		mysql_note "Creating user ${MYSQL_USER}"
		docker_process_sql --database=mysql <<<"CREATE USER '$MYSQL_USER'@'%' IDENTIFIED BY '$MYSQL_PASSWORD' ;"

		if [ -n "$MYSQL_DATABASE" ]; then
			mysql_note "Giving user ${MYSQL_USER} access to schema ${MYSQL_DATABASE}"
			docker_process_sql --database=mysql <<<"GRANT ALL ON \`$MYSQL_DATABASE\`.* TO '$MYSQL_USER'@'%' ;"
		fi

		docker_process_sql --database=mysql <<<"FLUSH PRIVILEGES ;"
	fi
}

_mysql_passfile() {
	# echo the password to the "file" the client uses
	# the client command will use process substitution to create a file on the fly
	# ie: --defaults-file=<( _mysql_passfile )
	if [ '--dont-use-mysql-root-password' != "$1" ] && [ -n "$MYSQL_ROOT_PASSWORD" ]; then
		cat <<-EOF
			[client]
			password="${MYSQL_ROOT_PASSWORD}"
		EOF
	fi
}

# Mark root user as expired so the password must be changed before anything
# else can be done (only supported for 5.6+)
mysql_expire_root_user() {
	if [ -n "$MYSQL_ONETIME_PASSWORD" ]; then
		docker_process_sql --database=mysql <<-EOSQL
			ALTER USER 'root'@'%' PASSWORD EXPIRE;
		EOSQL
	fi
}

# check arguments for an option that would cause mysqld to stop
# return true if there is one
_mysql_want_help() {
	local arg
	for arg; do
		case "$arg" in
			-'?'|--help|--print-defaults|-V|--version)
				return 0
				;;
		esac
	done
	return 1
}

_main() {
	# if command starts with an option, prepend mysqld
	if [ "${1:0:1}" = '-' ]; then
		set -- mysqld "$@"
	fi

	# skip setup if they aren't running mysqld or want an option that stops mysqld
	if [ "$1" = 'mysqld' ] && ! _mysql_want_help "$@"; then
		mysql_note "Entrypoint script for MySQL Server ${MYSQL_VERSION} started."

		mysql_check_config "$@"
		# Load various environment variables
		docker_setup_env "$@"
		docker_create_db_directories

		# If container is started as root user, restart as dedicated mysql user
		if [ "$(id -u)" = "0" ]; then
			mysql_note "Switching to dedicated user 'mysql'"
			exec gosu mysql "$BASH_SOURCE" "$@"
		fi

		# there's no database, so it needs to be initialized
		if [ -z "$DATABASE_ALREADY_EXISTS" ]; then
			docker_verify_minimum_env
			docker_init_database_dir "$@"

			mysql_note "Starting temporary server"
			docker_temp_server_start "$@"
			mysql_note "Temporary server started."

			docker_setup_db
			docker_process_init_files /docker-entrypoint-initdb.d/*

			mysql_expire_root_user

			mysql_note "Stopping temporary server"
			docker_temp_server_stop
			mysql_note "Temporary server stopped"

			echo
			mysql_note "MySQL init process done. Ready for start up."
			echo
		fi
	fi
	exec "$@"
}

# If we are sourced from elsewhere, don't perform any further actions
if ! _is_sourced; then
	_main "$@"
fi