fix(samplerate): initial sample rate can be overwritten from env

Author: gergelyke

lib/config.js

@@ -2,6 +2,7 @@ var config = {};
 
 config.collectInterval = process.env.TRACE_COLLECT_INTERVAL || 2 * 60 * 1000;
 config.sampleSize = 60;
+config.initialSampleRate = process.env.TRACE_INITIAL_SAMPLE_RATE || 50;
 
 config.collectorApi = process.env.TRACE_COLLECTOR_API_URL ||
   'https://trace-collector-api.risingstack.com';

lib/providers/httpTransaction/index.js

@@ -7,6 +7,7 @@ var microtime = require('microtime');
 
 var getNamespace = require('continuation-local-storage').getNamespace;
 var wraps = require('./wraps');
+var config = require('../../config');
 
 /*
  * @class HttpTransaction
@@ -21,7 +22,7 @@ function HttpTransaction(eventBus, options) {
 
   this.apiKey = options.apiKey;
   this.collectInterval = options.collectInterval;
-  this.sampleRate = 50;
+  this.sampleRate = config.initialSampleRate;
   this.sampleSize = options.sampleSize;
   this.partials = {};
   this.traces = [];