[Statsig] Sample noisy events (#4288)

* Sample state:background and state:foreground

* Sample feed events

* Add DEV protection against forgetting to add events to the list

1 files changed, 17 insertions, 3 deletions

diff --git a/src/lib/statsig/statsig.tsx b/src/lib/statsig/statsig.tsx
index 6ffca0ab4..573a123e1 100644
--- a/src/lib/statsig/statsig.tsx
+++ b/src/lib/statsig/statsig.tsx
@@ -87,7 +87,14 @@ export function toClout(n: number | null | undefined): number | undefined {
   }
 }
 
-const DOWNSAMPLED_EVENTS = new Set(['router:navigate:sampled'])
+const DOWNSAMPLED_EVENTS: Set<keyof LogEvents> = new Set([
+  'router:navigate:sampled',
+  'state:background:sampled',
+  'state:foreground:sampled',
+  'home:feedDisplayed:sampled',
+  'feed:endReached:sampled',
+  'feed:refresh:sampled',
+])
 const isDownsampledSession = Math.random() < 0.9 // 90% likely
 
 export function logEvent<E extends keyof LogEvents>(
@@ -98,6 +105,13 @@ export function logEvent<E extends keyof LogEvents>(
     if (isDownsampledSession && DOWNSAMPLED_EVENTS.has(eventName)) {
       return
     }
+    if (process.env.NODE_ENV === 'development') {
+      if (eventName.endsWith(':sampled')) {
+        logger.error(
+          'Did you forget to add ' + eventName + ' to DOWNSAMPLED_EVENTS?',
+        )
+      }
+    }
     const fullMetadata = {
       ...rawMetadata,
     } as Record<string, string> // Statsig typings are unnecessarily strict here.
@@ -199,14 +213,14 @@ AppState.addEventListener('change', (state: AppStateStatus) => {
   lastState = state
   if (state === 'active') {
     lastActive = performance.now()
-    logEvent('state:foreground', {})
+    logEvent('state:foreground:sampled', {})
   } else {
     let secondsActive = 0
     if (lastActive != null) {
       secondsActive = Math.round((performance.now() - lastActive) / 1e3)
     }
     lastActive = null
-    logEvent('state:background', {
+    logEvent('state:background:sampled', {
       secondsActive,
     })
   }