env.js

/**
 * Internal environment variables manager.
 *
 * Instantiation of EnvManager class will make a global variable `env` available
 * This class is recommended to globally available, as it can be instantiated
 * only once.
 * EnvManager.get() or EnvManager.set() allow manipulation of `env` object.
 * Environment variables of runtime (deno, node, worker) can be loaded via
 * EnvManager.loadEnv().
 *
 * @license
 * Copyright (c) 2021 RethinkDNS and its authors.
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 */

const defaults = {
  // one of deno, nodejs, or cloudflare workers
  RUNTIME: {
    type: "string",
    default: _determineRuntime(),
  },
  // the env stage (production or development) workers is running in
  // development is always "local" (a laptop /a server, for example)
  WORKER_ENV: {
    type: "string",
    default: "development",
  },
  // the env stage deno is running in
  DENO_ENV: {
    type: "string",
    default: "development",
  },
  // the env stage nodejs is running in
  NODE_ENV: {
    type: "string",
    default: "development",
  },
  // the cloud-platform code is deployed on (cloudflare, fly, deno-deploy)
  CLOUD_PLATFORM: {
    type: "string",
    // also ref: EnvManager.mostLikelyCloudPlatform()
    default: "local",
  },
  // path to tls (private) key
  TLS_KEY_PATH: {
    type: "string",
    default: "test/data/tls/dns.rethinkdns.localhost.key",
  },
  // path to tls (public) cert chain
  TLS_CRT_PATH: {
    type: "string",
    default: "test/data/tls/dns.rethinkdns.localhost.crt",
  },
  // global log level (debug, info, warn, error)
  LOG_LEVEL: {
    type: "string",
    default: "debug",
  },
  // url to blocklist files: trie (td), rank-dir (rd), metadata: (filetag)
  CF_BLOCKLIST_URL: {
    type: "string",
    default: "https://dist.rethinkdns.com/blocklists/",
  },
  // blocklist files version
  CF_LATEST_BLOCKLIST_TIMESTAMP: {
    type: "string",
    default: "1646028986510",
  },
  // primary doh upstream
  CF_DNS_RESOLVER_URL: {
    type: "string",
    default: "https://cloudflare-dns.com/dns-query",
  },
  // secondary doh upstream
  CF_DNS_RESOLVER_URL_2: {
    type: "string",
    default: "https://dns.google/dns-query",
  },
  // max doh request processing timeout some requests may have to wait
  // for blocklists to download before being responded to.
  WORKER_TIMEOUT: {
    type: "number",
    default: "10000", // 10s
  },
  // max blocklist files download timeout
  CF_BLOCKLIST_DOWNLOAD_TIMEOUT: {
    type: "number",
    default: "5000", // 5s
  },
  // total nodes in trie (td)
  TD_NODE_COUNT: {
    type: "number",
    default: "36932169",
  },
  // trie (td) split-files to download and concat, as of Jan '22,
  // trie size is ~60MB which is split in to three ~20MBs+ files
  TD_PARTS: {
    type: "number",
    default: "2",
  },
  // ttl for dns answers, overrides ttls in dns answers
  CACHE_TTL: {
    type: "number",
    default: "1800", // 30m
  },
  // disable downloading blocklists altogether
  DISABLE_BLOCKLISTS: {
    type: "boolean",
    default: false,
  },
  // run in profiler mode
  PROFILE_DNS_RESOLVES: {
    type: "boolean",
    default: false,
  },
  // avoid using the (slow) fetch polyfill if on nodejs
  NODE_AVOID_FETCH: {
    type: "boolean",
    default: true,
  },
  // use only doh upstream on nodejs (udp/tcp is the default on nodejs)
  NODE_DOH_ONLY: {
    type: "boolean",
    default: false,
  },
};

// cast string x to type typ
function caststr(x, typ) {
  if (typeof x === typ) return x;

  if (typ === "boolean") return x === "true";
  else if (typ === "number") return Number(x);
  else if (typ === "string") return (x && x + "") || "";
  else throw new Error(`unsupported type: ${typ}`);
}

function _determineRuntime() {
  if (typeof Deno !== "undefined") {
    return Deno.env.get("RUNTIME") || "deno";
  }

  if (globalThis.wenv) return wenv.RUNTIME || "worker";

  if (typeof process !== "undefined") {
    // process also exists in Workers, where wenv is defined
    if (process.env) return process.env.RUNTIME || "node";
  }

  return null;
}

export default class EnvManager {
  /**
   * Initializes the env manager.
   */
  constructor() {
    this.runtime = _determineRuntime();
    this.envMap = new Map();
    this.load();
  }

  /**
   * Loads env variables from runtime env. and is made globally available
   * through `env` namespace. Existing env variables will be overwritten.
   */
  load() {
    this.envMap = this.defaultEnv();

    console.debug("env defaults", this.envMap);
  }

  determineEnvStage() {
    if (this.runtime === "node") return this.get("NODE_ENV");
    if (this.runtime === "worker") return this.get("WORKER_ENV");
    if (this.runtime === "deno") return this.get("DENO_ENV");
    return null;
  }

  // most-likely but not definitive platform this code is running on
  mostLikelyCloudPlatform() {
    const isDev = this.determineEnvStage() === "development";
    // FLY_ALLOC_ID=5778f6b7-3cc2-d011-36b1-dfe057b0dc79 is set on fly-vms
    const hasFlyAllocId = this.get("FLY_ALLOC_ID") != null;
    // github.com/denoland/deploy_feedback/issues/73
    const hasDenoDeployId = this.get("DENO_DEPLOYMENT_ID") !== undefined;

    if (hasFlyAllocId) return "fly";
    if (hasDenoDeployId) return "deno-deploy";
    // if dev, then whatever is running is likely local
    if (isDev) return "local";
    // if prod, then node is likely running on fly
    if (this.runtime === "node") return "fly";
    // if prod, then deno is likely running on deno-deploy
    if (this.runtime === "deno") return "deno-deploy";
    // if prod, then worker is likely running on cloudflare
    if (this.runtime === "worker") return "cloudflare";

    return null;
  }

  /**
   * Makes default env values.
   * @return {Map} Runtime environment defaults.
   */
  defaultEnv() {
    const env = new Map();

    for (const [key, mappedKey] of Object.entries(defaults)) {
      if (typeof mappedKey !== "object") continue;

      const type = mappedKey.type;
      const val = mappedKey.default;

      if (!type || val == null) {
        console.debug(key, "incomplete env val:", mappedKey);
        continue;
      }

      env.set(key, caststr(val, type));
    }

    env.set("CLOUD_PLATFORM", this.mostLikelyCloudPlatform());

    return env;
  }

  /**
   * @param {String} k - env variable name
   * @return {*} - env variable value
   */
  get(k) {
    let v = null;
    if (this.runtime === "node") {
      v = process.env[k];
    } else if (this.runtime === "deno") {
      v = Deno.env.get(k);
    } else if (this.runtime === "worker") {
      v = globalThis.wenv[k];
    }

    if (v == null) {
      v = this.envMap.get(k);
    }

    const m = defaults[k];
    // set default v when env var for k is not set
    if (m && v == null) v = m.default;

    // type-cast v as approp if k is among the defaults
    if (m && v != null) v = caststr(v, m.type);

    return v;
  }

  /**
   * @param {String} k - env name
   * @param {*} v - env value
   * @param {*} typ - env type, one of boolean, string, or number
   */
  set(k, v, typ) {
    typ = typ || "string";
    this.envMap.set(k, caststr(v, typ));
  }
}