feat: support lookup with timeout

.travis.yml

@@ -1,8 +1,8 @@
 sudo: false
 language: node_js
 node_js:
-  - 6
-  - 4
+  - '6'
+  - '4'
 script:
   - npm run ci
 after_script:

README.md

@@ -23,6 +23,8 @@ failover-dns
 
 Use local cache dns query result when dns query fail.
 
+- Support dns lookup with `options.timeout`.
+
 ## Installation
 
 ```bash
@@ -37,12 +39,26 @@ const dns = require('failover-dns');
 // must listen `error` event to logging by yourself
 dns.on('error', err => console.error(err));
 
-dns.lookup('cnpmjs.org', { family: 4 }, (err, ip, family) => {
+dns.lookup('cnpmjs.org', { family: 4, timeout: 2000 }, (err, ip, family) => {
   if (err) throw err;
   console.log(ip, family);
 });
 ```
 
+## Default dns query timeout
+
+Default is `0`:
+
+```js
+exports.defaultTimeout = 0;
+```
+
+Maybe you want to set global default timeout is `2000ms`:
+
+```js
+exports.defaultTimeout = 2000;
+```
+
 ## License
 
 [MIT](LICENSE)

index.js

@@ -9,19 +9,28 @@ module.exports = exports = new EventEmitter();
 
 exports.DNS_LOOKUP_CACHE = DNS_LOOKUP_CACHE;
 
+// you can set global timeout, default is 0
+exports.defaultTimeout = 0;
+
 exports.lookup = function lookup(hostname, options, callback) {
   if (typeof options === 'function') {
     callback = options;
-    options = {};
+    options = null;
   }
+  options = options || {};
+  options.timeout = options.timeout || exports.defaultTimeout;
+
+  // don't failover on `options.all = true`
   if (options.all) {
-    // don't failover on options.all
     return dns.lookup(hostname, options, callback);
   }
 
   const cacheKey = `${hostname}_${options.family}_${options.hints}`;
-  dns.lookup(hostname, options, (err, ip, family) => {
+  exports._lookupWithTimeout(hostname, options, (err, ip, family) => {
     if (err) {
+      if (err.name === 'Error') {
+        err.name = 'DNSLookupError';
+      }
       const address = DNS_LOOKUP_CACHE[cacheKey];
       if (address) {
         // emit error event for logging
@@ -49,3 +58,28 @@ exports.lookup = function lookup(hostname, options, callback) {
     callback(null, ip, family);
   });
 };
+
+exports._lookupWithTimeout = function lookupWithTimeout(hostname, options, callback) {
+  if (!options.timeout) {
+    return dns.lookup(hostname, options, callback);
+  }
+
+  let timer = setTimeout(() => {
+    timer = null;
+    const cb = callback;
+    callback = null;
+    const err = new Error(`getaddrinfo TIMEOUT ${hostname}`);
+    err.name = 'DNSLookupTimeoutError';
+    err.options = options;
+    err.code = 'TIMEOUT';
+    cb(err);
+  }, options.timeout);
+
+  dns.lookup(hostname, options, (err, ip, family) => {
+    timer && clearTimeout(timer);
+    if (!callback) {
+      return;
+    }
+    callback(err, ip, family);
+  });
+};

package.json

@@ -7,8 +7,8 @@
     "index.js"
   ],
   "scripts": {
-    "test": "npm run lint && mocha -t 5000 -r intelli-espower-loader test/*.test.js",
-    "test-cov": "istanbul cover _mocha -- -t 5000 -r intelli-espower-loader test/*.test.js",
+    "test": "npm run lint && mocha -t 15000 -r intelli-espower-loader test/*.test.js",
+    "test-cov": "istanbul cover _mocha -- -t 15000 -r intelli-espower-loader test/*.test.js",
     "lint": "eslint test *.js",
     "ci": "npm run lint && npm run test-cov",
     "autod": "autod -w --prefix '^'"

test/failover-dns.test.js

@@ -18,6 +18,26 @@ describe('test/failover-dns.test.js', () => {
     });
   });
 
+  it('should lookup with options=null from dns server', done => {
+    dns.lookup('a.alipayobjects.com', null, (err, ip, family) => {
+      console.log(err, ip, family);
+      assert(err == null);
+      assert((/^\d+\.\d+\.\d+\.\d+$/).test(ip));
+      assert(family === 4);
+      done();
+    });
+  });
+
+  it('should lookup with options.timeout', done => {
+    dns.lookup('as.alipayobjects.com', { timeout: 5000 }, (err, ip, family) => {
+      console.log(err, ip, family);
+      assert(err == null);
+      assert((/^\d+\.\d+\.\d+\.\d+$/).test(ip));
+      assert(family === 4);
+      done();
+    });
+  });
+
   it('should lookup with options.family from dns server', done => {
     dns.lookup('cnpmjs.org', { family: 4 }, (err, ip, family) => {
       console.log(err, ip, family);
@@ -66,6 +86,48 @@ describe('test/failover-dns.test.js', () => {
     });
   });
 
+  it('should mock timeout then return address from local cache', done => {
+    done = pedding(2, done);
+    mm(require('dns'), 'lookup', (hostname, options, callback) => {
+      setTimeout(() => {
+        callback(null, '127.0.0.1', 4);
+      }, 600);
+    });
+
+    dns.once('error', err => {
+      console.log(err);
+      assert(err.name === 'DNSLookupTimeoutError');
+      assert(err.message === 'getaddrinfo TIMEOUT a.alipayobjects.com');
+      done();
+    });
+    dns.lookup('a.alipayobjects.com', { family: 4, timeout: 500 }, (err, ip, family) => {
+      console.log('lookup result', err, ip, family);
+      assert(err == null);
+      assert((/^\d+\.\d+\.\d+\.\d+$/).test(ip));
+      assert(family === 4);
+      // wait for dns.lookup() done and ignore callback
+      setTimeout(done, 200);
+    });
+  });
+
+  it('should mock timeout and local cache missing', done => {
+    mm(require('dns'), 'lookup', (hostname, options, callback) => {
+      setTimeout(() => {
+        callback(null, '127.0.0.1', 4);
+      }, 600);
+    });
+
+    dns.lookup('foo.cnpmjs.org', { family: 4, timeout: 500 }, (err, ip, family) => {
+      console.log('lookup result', err, ip, family);
+      assert(err);
+      assert(err.name === 'DNSLookupTimeoutError');
+      assert(err.message === 'getaddrinfo TIMEOUT foo.cnpmjs.org');
+      assert(err.code === 'TIMEOUT');
+      // wait for dns.lookup() done and ignore callback
+      setTimeout(done, 200);
+    });
+  });
+
   it('should lookup with options.all from dns server', done => {
     dns.lookup('a.alipayobjects.com', { all: true }, (err, ips) => {
       console.log(err, ips);
@@ -80,6 +142,8 @@ describe('test/failover-dns.test.js', () => {
     dns.lookup('cnpmjs.org', { family: 6 }, (err, ip, family) => {
       console.log(err, ip, family);
       assert(err);
+      assert(err.name === 'DNSLookupError');
+      assert(err.message === 'getaddrinfo ENOTFOUND cnpmjs.org');
       done();
     });
   });