Add sample property to Mixpanel events

Change-type: patch
Signed-off-by: Lorenzo Alberto Maria Ambrosi <lorenzoa@balena.io>

lib/gui/app/modules/analytics.js

@@ -31,7 +31,7 @@ const mixpanelToken = settings.get('analyticsMixpanelToken') ||
 
 const configUrl = settings.get('configUrl') || 'http://balena.io/etcher/static/config.json'
 
-const DEFAULT_PROBABILITY = 1
+const DEFAULT_PROBABILITY = 0.1
 
 const services = {
   sentry: sentryToken,
@@ -48,10 +48,16 @@ resinCorvus.install({
   }
 })
 
+let mixpanelSample = DEFAULT_PROBABILITY
+
 getConfig(configUrl)
   .then((config) => {
+    const mixpanel = _.get(config, [ 'analytics', 'mixpanel' ], {})
+    const probability = mixpanel.probability || DEFAULT_PROBABILITY
+    mixpanelSample = probability
+    const validatedConfig = isClientEligible(probability) ? validateMixpanelConfig(mixpanel) : null
     resinCorvus.setConfigs({
-      mixpanel: getMixpanelConfig(config)
+      mixpanel: validatedConfig
     })
   })
 
@@ -70,14 +76,8 @@ function getConfig(url) {
  * @param {Object} - config
  */
 // eslint-disable-next-line
-function getMixpanelConfig(config) {
-  const analytics = config.analytics || {}
-  const mixpanel = analytics.mixpanel || {}
-  const probability = mixpanel.probability || DEFAULT_PROBABILITY
-  if (Math.random() > probability) {
-    return null
-  }
-  return validateMixpanelConfig(mixpanel)
+function isClientEligible(probability) {
+  return Math.random() > probability
 }
 
 /**
@@ -128,7 +128,12 @@ exports.logDebug = resinCorvus.logDebug
  *   image: '/dev/disk2'
  * });
  */
-exports.logEvent = resinCorvus.logEvent
+exports.logEvent = (message, data) => {
+  const sessionData = {
+    mixpanelSample
+  }
+  resinCorvus.logEvent(message, { ...data, sessionData })
+}
 
 /**
  * @summary Log an exception