DockerのMySQLのdocker-entrypoint.shのメモ

DockerのMySQLのdocker-entrypoint.shについて、解読できた部分をメモに残す。

# コマンドが失敗したら途中で止まる
# -o pipefail でパイプでコマンドをつなげた場合も止まる
set -eo pipefail
# ワイルドカードで該当ファイルがない場合、*自体を対象としない
shopt -s nullglob

# if command starts with an option, prepend mysqld
# 引数の最初の1文字が　'-'　だった場合、mysqldと"$@"を位置パラメータに設定する
# $1 = mysqld, $2 = "$@"
if [ "${1:0:1}" = '-' ]; then
    set -- mysqld "$@"
fi

# skip setup if they want an option that stops mysqld
# for argで引数のループ
# -'?'は引数が-?に一致
wantHelp=
for arg; do
    case "$arg" in
        -'?'|--help|--print-defaults|-V|--version)
            wantHelp=1
            break
            ;;
    esac
done

# 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のスコープは関数内
    local var="$1"
    local fileVar="${var}_FILE"
    # デフォルト値のないパラメータ展開？
    local def="${2:-}"
    # 間接参照で$varや$fileVarの値を変数名とみなす
    if [ "${!var:-}" ] && [ "${!fileVar:-}" ]; then
        echo >&2 "error: both $var and $fileVar are set (but are exclusive)"
        exit 1
    fi
    local val="$def"
    if [ "${!var:-}" ]; then
        val="${!var}"
    elif [ "${!fileVar:-}" ]; then
        val="$(< "${!fileVar}")"
    fi
    export "$var"="$val"
    unset "$fileVar"
}

# usage: process_init_file FILENAME MYSQLCOMMAND...
#    ie: process_init_file foo.sh mysql -uroot
# (process a single initializer file, based on its extension. we define this
# function here, so that initializer scripts (*.sh) can use the same logic,
# potentially recursively, or override the logic used in subsequent calls)
process_init_file() {
    # 引数を1つずらす
    local f="$1"; shift
    # 配列mysqlに残りの引数を代入
    local mysql=( "$@" )

    case "$f" in
        *.sh)     echo "$0: running $f"; . "$f" ;;
        # ${mysql[@]}で配列を展開
        *.sql)    echo "$0: running $f"; "${mysql[@]}" < "$f"; echo ;;
        # gunzip -cで解凍して標準出力へ出力
        *.sql.gz) echo "$0: running $f"; gunzip -c "$f" | "${mysql[@]}"; echo ;;
        *)        echo "$0: ignoring $f" ;;
    esac
    echo
}

_check_config() {
    toRun=( "$@" --verbose --help )
    # 標準出力は捨ててエラーをリダイレクト
    if ! errors="$("${toRun[@]}" 2>&1 >/dev/null)"; then
        cat >&2 <<-EOM
            ERROR: mysqld failed while attempting to check config
            # 配列を展開、${toRun[@]}と同じ　
            command was: "${toRun[*]}"
            $errors
        EOM
        exit 1
    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
_get_config() {
    local conf="$1"; shift
    # mktemp -uはdry-run
    # mysqld --verbose --helpで設定値を表示
    "$@" --verbose --help --log-bin-index="$(mktemp -u)" 2>/dev/null \
        # よく分からない、datadirは/var/lib/mysql/
        | awk '$1 == "'"$conf"'" && /^[^ \t]/ { sub(/^[^ \t]+[ \t]+/, ""); print; exit }'
    # match "datadir      /some/path with/spaces in/it here" but not "--xyz=abc\n     datadir (xyz)"
}

# allow the container to be started with `--user`
# -aはAND、id -uでユーザID表示、0はroot
if [ "$1" = 'mysqld' -a -z "$wantHelp" -a "$(id -u)" = '0' ]; then
    _check_config "$@"
    DATADIR="$(_get_config 'datadir' "$@")"
    mkdir -p "$DATADIR"
    chown -R mysql:mysql "$DATADIR"
    # gosuで指定したユーザで実行、$BASH_SOURCEはファイルの絶対パス
    # つまり、mysqlユーザでdocker-entrypoint.shを再実行する
    exec gosu mysql "$BASH_SOURCE" "$@"
fi

if [ "$1" = 'mysqld' -a -z "$wantHelp" ]; then
    # still need to check config, container may have started with --user
    _check_config "$@"
    # Get config
    DATADIR="$(_get_config 'datadir' "$@")"

    # -dはディレクトリのチェック
    if [ ! -d "$DATADIR/mysql" ]; then
        file_env 'MYSQL_ROOT_PASSWORD'
        if [ -z "$MYSQL_ROOT_PASSWORD" -a -z "$MYSQL_ALLOW_EMPTY_PASSWORD" -a -z "$MYSQL_RANDOM_ROOT_PASSWORD" ]; then
            echo >&2 'error: database is uninitialized and password option is not specified '
            echo >&2 '  You need to specify one of MYSQL_ROOT_PASSWORD, MYSQL_ALLOW_EMPTY_PASSWORD and MYSQL_RANDOM_ROOT_PASSWORD'
            exit 1
        fi

        mkdir -p "$DATADIR"

        echo 'Initializing database'
        # --initialize-insecureでrootのパスワードを生成しない
        "$@" --initialize-insecure
        echo 'Database initialized'

        # command -vでコマンドのパス取得、-eでファイルが存在するとき
        if command -v mysql_ssl_rsa_setup > /dev/null && [ ! -e "$DATADIR/server-key.pem" ]; then
            # https://github.com/mysql/mysql-server/blob/23032807537d8dd8ee4ec1c4d40f0633cd4e12f9/packaging/deb-in/extra/mysql-systemd-start#L81-L84
            echo 'Initializing certificates'
            mysql_ssl_rsa_setup --datadir="$DATADIR"
            echo 'Certificates initialized'
        fi

        SOCKET="$(_get_config 'socket' "$@")"
        # --skip-networkingでネットワーク経由の接続を許可しない
        "$@" --skip-networking --socket="${SOCKET}" &
        pid="$!"

        mysql=( mysql --protocol=socket -uroot -hlocalhost --socket="${SOCKET}" )

        for i in {30..0}; do
            # &> /dev/nullでstdoutとstderrを捨てる（>/dev/null 2>&1）
            if echo 'SELECT 1' | "${mysql[@]}" &> /dev/null; then
                break
            fi
            echo 'MySQL init process in progress...'
            sleep 1
        done
        if [ "$i" = 0 ]; then
            echo >&2 'MySQL init process failed.'
            exit 1
        fi

        if [ -z "$MYSQL_INITDB_SKIP_TZINFO" ]; then
            # sed is for https://bugs.mysql.com/bug.php?id=20545
            # タイムゾーンテーブルをロード
            mysql_tzinfo_to_sql /usr/share/zoneinfo | sed 's/Local time zone must be set--see zic manual page/FCTY/' | "${mysql[@]}" mysql
        fi

        if [ ! -z "$MYSQL_RANDOM_ROOT_PASSWORD" ]; then
            export MYSQL_ROOT_PASSWORD="$(pwgen -1 32)"
            echo "GENERATED ROOT PASSWORD: $MYSQL_ROOT_PASSWORD"
        fi

        rootCreate=
        # default root to listen for connections from anywhere
        file_env 'MYSQL_ROOT_HOST' '%'
        if [ ! -z "$MYSQL_ROOT_HOST" -a "$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
            # <<-はヒアドキュメントでタブを取り除き、標準入力として扱われる
            # readは標準入力から読み込んで変数に格納、-rで\をエスケープ文字としない、-d ''でデリミタなし
            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

        "${mysql[@]}" <<-EOSQL
            -- What's done in this file shouldn't be replicated
            --  or products like mysql-fabric won't work
            SET @@SESSION.SQL_LOG_BIN=0;
            ALTER USER 'root'@'localhost' IDENTIFIED BY '${MYSQL_ROOT_PASSWORD}' ;
            GRANT ALL ON *.* TO 'root'@'localhost' WITH GRANT OPTION ;
            ${rootCreate}
            DROP DATABASE IF EXISTS test ;
            FLUSH PRIVILEGES ;
        EOSQL

        if [ ! -z "$MYSQL_ROOT_PASSWORD" ]; then
            mysql+=( -p"${MYSQL_ROOT_PASSWORD}" )
        fi

        file_env 'MYSQL_DATABASE'
        if [ "$MYSQL_DATABASE" ]; then
            echo "CREATE DATABASE IF NOT EXISTS \`$MYSQL_DATABASE\` ;" | "${mysql[@]}"
            mysql+=( "$MYSQL_DATABASE" )
        fi

        file_env 'MYSQL_USER'
        file_env 'MYSQL_PASSWORD'
        if [ "$MYSQL_USER" -a "$MYSQL_PASSWORD" ]; then
            echo "CREATE USER '$MYSQL_USER'@'%' IDENTIFIED BY '$MYSQL_PASSWORD' ;" | "${mysql[@]}"

            if [ "$MYSQL_DATABASE" ]; then
                echo "GRANT ALL ON \`$MYSQL_DATABASE\`.* TO '$MYSQL_USER'@'%' ;" | "${mysql[@]}"
            fi

            echo 'FLUSH PRIVILEGES ;' | "${mysql[@]}"
        fi

        echo
        ls /docker-entrypoint-initdb.d/ > /dev/null
        for f in /docker-entrypoint-initdb.d/*; do
            process_init_file "$f" "${mysql[@]}"
        done

        if [ ! -z "$MYSQL_ONETIME_PASSWORD" ]; then
            "${mysql[@]}" <<-EOSQL
                ALTER USER 'root'@'%' PASSWORD EXPIRE;
            EOSQL
        fi
        if ! kill -s TERM "$pid" || ! wait "$pid"; then
            echo >&2 'MySQL init process failed.'
            exit 1
        fi

        echo
        echo 'MySQL init process done. Ready for start up.'
        echo
    fi
fi

exec "$@"