chore(gatsby-telemetry): Migrate flush to TypeScript (#25886)

packages/gatsby-telemetry/src/create-flush.ts

@@ -0,0 +1,19 @@
+const { join } = require(`path`)
+const { fork } = require(`child_process`)
+
+export function createFlush(isTrackingEnabled: boolean): () => Promise<void> {
+  return async function flush(): Promise<void> {
+    if (!isTrackingEnabled) {
+      return
+    }
+
+    // Submit events on background w/o blocking the main process
+    // nor relying on it's lifecycle
+    const forked = fork(join(__dirname, `send.js`), {
+      detached: true,
+      stdio: `ignore`,
+      execArgv: [],
+    })
+    forked.unref()
+  }
+}

packages/gatsby-telemetry/src/index.ts

@@ -1,9 +1,10 @@
 import { AnalyticsTracker, IAggregateStats } from "./telemetry"
 import * as express from "express"
+import { createFlush } from "./create-flush"
 
 const instance = new AnalyticsTracker()
 
-const flush = require(`./flush`)(instance.isTrackingEnabled())
+const flush = createFlush(instance.isTrackingEnabled())
 
 process.on(`exit`, flush)