feat: support add plugin function

Author: vicanso

lib/client.js

@@ -965,6 +965,17 @@ class Client extends EventEmitter {
   addAlgorithm(type, fn) {
     return internal(this).influx.addAlgorithm(type, fn);
   }
+  /**
+   * Add plugin function
+   * @param {Function} fn - plugin function
+   * @since 2.11.0
+   * @example
+   * const noCache = require('superagent-no-cache')
+   * client.addPlugin(noCache);
+  */
+  addPlugin(fn) {
+    return internal(this).influx.addPlugin(fn);
+  }
 }
 
 module.exports = Client;

lib/influx.js

@@ -200,6 +200,14 @@ class Influx {
   addAlgorithm(type, fn) {
     return internal(this).client.addAlgorithm(type, fn);
   }
+
+  /**
+   * Add plugin function
+   * @param {Function} fn plugin function
+   */
+  addPlugin(fn) {
+    return internal(this).client.addPlugin(fn);
+  }
 }
 
 module.exports = Influx;

test/client.js

@@ -506,6 +506,26 @@ describe('Client', () => {
     }).catch(done);
   });
 
+  it('get measurement', done => {
+    let called = false;
+    client.addPlugin((req) => {
+      if (called) {
+        return;
+      }
+      if (!req.backendServer) {
+        done(new Error('the backend field is null'));
+      }
+      called = true;
+    });
+    client.query('http')
+      .then(() => {
+        if (!called) {
+          done(new Error('not called'));
+        }
+      })
+      .catch(done);
+  });
+
   it('drop database', function(done) {
     this.timeout(5000);
     client.stopHealthCheck();