[issue-3] Implemented Sumologic Api throttling

.gitignore

@@ -1,2 +1,3 @@
 coverage/
 .nyc_output/
+node_modules/

lib/job.js

@@ -3,6 +3,9 @@
 const events = require('events');
 const http = require('got');
 const qs = require('querystring');
+const throttledQueue = require('throttled-queue');
+
+const throttle = throttledQueue(4, 1000); // At most make 240 request every minute.
 
 class Job extends events.EventEmitter {
   constructor(auth, query, from, to, timeZone) {
@@ -35,7 +38,7 @@ class Job extends events.EventEmitter {
       body: JSON.stringify({ query, from, to, timeZone })
     }, this.options);
 
-    http.post('https://api.sumologic.com/api/v1/search/jobs', options)
+    this.throttleReq(http.post('https://api.sumologic.com/api/v1/search/jobs', options))
       .then((response) => {
         this.searchJobId = response.headers.location;
         this.options.headers.cookie = response.headers['set-cookie'];
@@ -56,6 +59,10 @@ class Job extends events.EventEmitter {
     });
   }
 
+  throttleReq(req) {
+    return new Promise(resolve => { throttle(() => { resolve(req) }); });
+  }
+
   onceCreated() {
     if (this.searchJobId) return Promise.resolve();
     return new Promise((resolve) => this.once('created', () => setTimeout(resolve, 1000)));
@@ -96,7 +103,7 @@ class Job extends events.EventEmitter {
     attempts++;
 
     return this.onceCreated()
-      .then(() => http.get(this.searchJobId, this.options))
+      .then(() => this.throttleReq(http.get(this.searchJobId, this.options)))
       .then((response) => Object.assign(this.status, response.body))
       .then((status) => {
         if (status.messageCount > 0) this.emit('messages');
@@ -117,7 +124,7 @@ class Job extends events.EventEmitter {
       attempts++;
 
       return this.waitForResults(type)
-        .then(() => http.get(url, this.options))
+        .then(() => this.throttleReq(http.get(url, this.options)))
         .then((response) => {
           this[`${type}Fields`] = response.body.fields;
           this[`${type}Offset`] = this[`${type}Offset`] + response.body[`${type}s`].length;