feat: set max number of car cids to resolve

src/bindings.d.ts

@@ -9,6 +9,7 @@ export interface Environment {
   CARPARK: R2Bucket
   DUDEWHERE: R2Bucket
   SATNAV: R2Bucket
+  MAX_CAR_CIDS_TO_RESOLVE: string
 }
 
 export interface CarCidsContext extends Context {

src/middleware.js

@@ -72,6 +72,13 @@ export function withCarCids (handler) {
       throw new HttpError('missing origin CAR CID(s)', { status: 400 })
     }
 
+    // Cloudflare currently sets a limit of 1000 sub-requests within the worker context
+    // If we have a given root CID splitted across hundreds of CARs, freeway will hit
+    // the sub-requests limit and not serve content anyway
+    if (carCids.length > Number(env.MAX_CAR_CIDS_TO_RESOLVE)) {
+      throw new HttpError('number CAR CIDs is too large to resolve', { status: 501 })
+    }
+
     return handler(request, env, { ...ctx, carCids })
   }
 }

wrangler.toml

@@ -27,6 +27,9 @@ r2_buckets = [
 [env.production.build]
 command = "npm run build"
 
+[env.production.vars]
+MAX_CAR_CIDS_TO_RESOLVE = "250"
+
 # Staging!
 [env.staging]
 account_id = "fffa4b4363a7e5250af8357087263b3a"
@@ -40,6 +43,9 @@ r2_buckets = [
 [env.staging.build]
 command = "npm run build"
 
+[env.staging.vars]
+MAX_CAR_CIDS_TO_RESOLVE = "250"
+
 # Test!
 [env.test]
 workers_dev = true
@@ -51,6 +57,7 @@ r2_buckets = [
 
 [env.test.vars]
 DEBUG = "true"
+MAX_CAR_CIDS_TO_RESOLVE = "250"
 
 [env.alanshaw]
 workers_dev = true