fix: memory pressure in ingest

packages/stats/server/src/router.ts

@@ -1,11 +1,14 @@
 import { Buffer } from "node:buffer"
 import { timingSafeEqual } from "node:crypto"
 import { Effect, Schema } from "effect"
+import * as Semaphore from "effect/Semaphore"
 import { HttpRouter, HttpServerRequest, HttpServerResponse } from "effect/unstable/http"
 import { Resource } from "sst/resource"
 import { Ingest } from "./ingest"
 import { isShuttingDown } from "./shutdown"
 
+const MAX_CONCURRENT_INGEST_REQUESTS = 8
+
 const IngestPayload = Schema.Struct({
   events: Schema.optional(Schema.Unknown),
 })
@@ -13,12 +16,13 @@ const IngestPayload = Schema.Struct({
 export const Routes = HttpRouter.use((router) =>
   Effect.gen(function* () {
     const ingestService = yield* Ingest
+    const ingestRequests = yield* Semaphore.make(MAX_CONCURRENT_INGEST_REQUESTS)
 
     yield* Effect.all(
       [
         router.add("GET", "/health", () => json(200, { ok: true })),
         router.add("GET", "/ready", () => json(isShuttingDown() ? 503 : 200, { ok: !isShuttingDown() })),
-        router.add("POST", "/", ingest(ingestService)),
+        router.add("POST", "/", ingestRequests.withPermit(ingest(ingestService))),
       ],
       { discard: true },
     )
@@ -38,12 +42,14 @@ const ingest = (ingestService: Ingest.Service) =>
     )
     if (!payload) return yield* json(400, { ok: false, error: "Invalid JSON body" })
 
-    const events = Array.isArray(payload.events) ? payload.events.filter(isRecord) : []
+    const events = Array.isArray(payload.events) ? payload.events : []
     if (events.length === 0) return yield* json(202, { ok: true, records: 0 })
 
     return yield* ingestService.write(events).pipe(
       Effect.flatMap((result) => json(202, { ok: true, records: result.records })),
-      Effect.catchTag("IngestError", (error) => json(502, { ok: false, records: events.length, failed: error.failed })),
+      Effect.catchTag("IngestError", (error) =>
+        json(502, { ok: false, records: countRecords(events), failed: error.failed }),
+      ),
     )
   })
 
@@ -54,8 +60,12 @@ function isAuthorized(headers: Record<string, string | undefined>) {
   return timingSafeEqual(actual, expected)
 }
 
-function isRecord(item: unknown): item is Record<string, unknown> {
-  return Boolean(item) && typeof item === "object" && !Array.isArray(item)
+function countRecords(items: unknown[]) {
+  let records = 0
+  for (const item of items) {
+    if (Boolean(item) && typeof item === "object" && !Array.isArray(item)) records++
+  }
+  return records
 }
 
 function json(status: number, body: Record<string, unknown>) {