Docker Volumes: الـ data بتتحفَظ فين

// volumes.js: simulator للـ mounts في Docker: named volumes و anonymous و bind mounts و tmpfs، و lint
import { posix } from "node:path";

export function parseMount(spec) {
  if (typeof spec === "object") return { type: spec.type, source: spec.source ?? null, target: spec.target, readOnly: !!spec.read_only };
  const parts = String(spec).split(":");
  if (parts.length === 1) return { type: "volume", source: null, target: parts[0], readOnly: false }; // anonymous
  const [source, target, mode = "rw"] = parts;
  const bind = /^(\/|\.\/|\.\.\/|~|\.$)/.test(source);
  return { type: bind ? "bind" : "volume", source, target, readOnly: mode.split(",").includes("ro") };
}

export const mountsOf = (svc) => [...(svc.volumes ?? []).map(parseMount), ...(svc.tmpfs ?? []).map((t) => ({ type: "tmpfs", source: null, target: t, readOnly: false }))];

const under = (path, dir) => path === dir || path.startsWith(dir.endsWith("/") ? dir : dir + "/");

export function mountFor(mounts, path) {
  return mounts.filter((m) => under(path, m.target)).sort((a, b) => b.target.length - a.target.length)[0] ?? null;
}

export function createDocker({ images = {}, host = new Map() } = {}) {
  const volumes = new Map(); // الاسم ← Map(path ← content)
  const containers = new Map();
  let anon = 0;
  const hostKey = (m, path) => posix.normalize(posix.join(m.source, posix.relative(m.target, path))).replace(/^\.\//, "");

  function up(name, svc) {
    if (containers.has(name)) return containers.get(name);
    const image = images[svc.image] ?? {};
    const c = { svc, image, layer: new Map(), tmp: new Map(), mounts: mountsOf(svc).map((m) => ({ ...m })) };
    for (const m of c.mounts) {
      if (m.type !== "volume") continue;
      if (!m.source) m.source = `anon-${++anon}`;
      if (!volumes.has(m.source)) {
        // volume جديدة فاضية ← Docker بينسخ فيها اللي في الـ image تحت الـ target ده (copy-up). الـ bind mount لأ
        const v = new Map();
        for (const [p, content] of Object.entries(image)) if (under(p, m.target)) v.set(p, content);
        volumes.set(m.source, v);
      }
    }
    containers.set(name, c);
    return c;
  }

  const get = (name) => { const c = containers.get(name); if (!c) throw new Error(`مفيش container اسمه ${name}`); return c; };

  function write(name, path, content) {
    const c = get(name), m = mountFor(c.mounts, path);
    if (m?.readOnly) throw Object.assign(new Error(`EROFS: ${path} read only`), { code: "EROFS" });
    if (!m) return void c.layer.set(path, content);
    if (m.type === "tmpfs") return void c.tmp.set(path, content);
    if (m.type === "bind") return void host.set(hostKey(m, path), content);
    volumes.get(m.source).set(path, content);
  }

  function read(name, path) {
    const c = get(name), m = mountFor(c.mounts, path);
    if (m?.type === "tmpfs") return c.tmp.get(path) ?? null;
    if (m?.type === "bind") return host.get(hostKey(m, path)) ?? null; // الـ bind بيغطّي اللي في الـ image تحت الـ target
    if (m?.typ
…

$ node lab.js

=== db من غير volume ===
  ERROR DATA-NOT-PERSISTED: /var/lib/postgresql/data مش على volume: الـ data هتروح مع أول down
  بعد restart:     orders "عشرين ألف order" | tmp مش موجود
  بعد down و up:   orders مش موجود
  بعد down -v و up: orders مش موجود | volumes -

=== db على anonymous volume ===
  WARN ANON-DATA: /var/lib/postgresql/data على anonymous volume: up بعد down هيبدأ فاضي
  بعد restart:     orders "عشرين ألف order" | tmp مش موجود
  بعد down و up:   orders مش موجود
  بعد down -v و up: orders مش موجود | volumes anon-3

=== db على named volume ===
  بعد restart:     orders "عشرين ألف order" | tmp مش موجود
  بعد down و up:   orders "عشرين ألف order"
  بعد down -v و up: orders مش موجود | volumes pgdata

=== api في الـ development: bind mount للـ code ===
  -- bind على /app بس
     WARN HIDES-NODE-MODULES: ./ على /app بيغطّي node_modules بتاعة الـ image: ضيف volume على /app/node_modules
     WARN CONFIG-WRITABLE: ./nginx.conf config: اعمله ro
     server.js: "v2 لسه متعدّل" | express: مش موجود
     الـ container غيّر nginx.conf على الـ host: "اتغيّر من جُوّه"
  -- ومعاه volume على node_modules و config ro
     server.js: "v2 لسه متعدّل" | express: "express (Linux b
…

# compose.naive.yaml: كله شغّال... لحد أول docker compose down
services:
  db:
    image: postgres:17
    environment:
      POSTGRES_PASSWORD: dev
    # مفيش volumes: الـ data في الـ writable layer بتاع الـ container

  redis:
    image: redis:7
    volumes:
      - /data            # anonymous volume: كل up بعد down بيبدأ فاضي

  api:
    build: .
    working_dir: /app
    command: node --watch server.js
    volumes:
      - ./:/app          # بيغطّي /app/node_modules اللي اتعمل جُوّه الـ image
      - ./nginx.conf:/etc/nginx/nginx.conf   # الـ container يقدر يعدّل الـ file على الـ host
      - /var/run/docker.sock:/var/run/docker.sock   # root على الـ host

# compose.yaml: الـ data على named volumes، والـ code بـ bind mount للـ development بس
services:
  db:
    image: postgres:17
    environment:
      POSTGRES_PASSWORD_FILE: /run/secrets/pg_password
    volumes:
      - pgdata:/var/lib/postgresql/data
    tmpfs:
      - /tmp

  redis:
    image: redis:7
    command: redis-server --appendonly yes
    volumes:
      - redisdata:/data

  api:
    build: .
    working_dir: /app
    user: "1000:1000"
    command: node --watch server.js
    volumes:
      - ./:/app
      - /app/node_modules          # node_modules بتاعة الـ image (Linux build) تفضل زي ما هي
      - type: bind
        source: ./nginx.conf
        target: /etc/nginx/nginx.conf
        read_only: true
    tmpfs:
      - /tmp

volumes:
  pgdata:       # docker volume ls ← <project>_pgdata
  redisdata:

// lab.js: بنجرّب الـ mounts في الـ simulator: مين بيعيش بعد restart، وبعد down و up، وبعد down -v
import { createDocker, lintMounts } from "./volumes.js";

const images = {
  "postgres:17": {},
  "shop-api:dev": { "/app/server.js": "v1", "/app/node_modules/express/index.js": "express (Linux build)" },
};
const show = (v) => (v === null ? "مش موجود" : JSON.stringify(v));

function story(title, svc) {
  const d = createDocker({ images });
  console.log(`\n=== ${title} ===`);
  for (const f of lintMounts("db", svc)) console.log(`  ${f.severity} ${f.rule}: ${f.msg}`);
  d.up("db", svc);
  d.write("db", "/var/lib/postgresql/data/orders", "عشرين ألف order");
  d.write("db", "/tmp/sort.tmp", "شغل مؤقت");
  d.restart("db");
  console.log(`  بعد restart:     orders ${show(d.read("db", "/var/lib/postgresql/data/orders"))} | tmp ${show(d.read("db", "/tmp/sort.tmp"))}`);
  d.down("db"); d.up("db", svc);
  console.log(`  بعد down و up:   orders ${show(d.read("db", "/var/lib/postgresql/data/orders"))}`);
  d.down("db", { volumes: true }); d.up("db", svc);
  console.log(`  بعد down -v و up: orders ${show(d.read("db", "/var/lib/postgresql/data/orders"))} | volumes ${d.volumes().join(" ") || "-"}`);
}

story("db من غير volume", { image: "postgres:17", tmpfs: ["/tmp"] });
story("db على anonymous volume", { image: "postgres:17", volumes: ["/var/lib/postgresql/data"], tmpfs: ["/tmp"] });
story("db على named volume", { image: "postgres:17", volumes: ["pgdata:/var/lib/postgresql/data"], tmpfs: ["/tmp"] });

console.log("\n=== api في الـ development: bind mount للـ code ===");
const host = new Map([["server.js", "v2 لسه متعدّل"], ["nginx.conf", "server {}"]]);
for (const [title, svc] of [
  ["bind على /app بس", { image: "shop-api:dev", working_dir: "/app", volumes: ["./:/app", "./nginx.conf:/etc/nginx/nginx.conf"] }],
  ["ومعاه volume على node_modules و config ro", { image: "shop-api:dev", working_dir: "/app", volumes: ["./:/app", "/app/node_modules", "./nginx.conf:/etc/nginx/nginx.conf:ro"] }],
]) {
  const d = createDocker({ images, host });
  console.log(`  -- ${title}`);
  for (const f of lintMounts("api", svc)) console.log(`     ${f.severity} ${f.rule}: ${f.msg}`);
  d.up("api", svc);
  console.log(`     server.js: ${show(d.read("api", "/app/server.js"))} | express: ${show(d.read("api", "/app/node_modules/express/index.js"))}`);
  try { d.write("api", "/etc/nginx/nginx.conf", "اتغيّر من جُوّه"); console.log(`     الـ container غيّر nginx.conf على الـ host: ${show(host.get("nginx.conf"))}`); host.set("nginx.conf", "server {}"); }
  catch (e) { console.log(`     الكتابة في nginx.conf: ${e.code}`); }
}