feat(indexer): probabilistic feature flag

src/middleware/withLocator.js

@@ -21,9 +21,7 @@ import { Client } from '@storacha/indexing-service-client'
  */
 export function withLocator (handler) {
   return async (request, env, ctx) => {
-    const useIndexingService = new URL(request.url).searchParams
-      .getAll('ff')
-      .includes('indexing-service')
+    const useIndexingService = isIndexingServiceEnabled(request, env)
 
     const locator = useIndexingService
       ? new IndexingServiceLocator({
@@ -46,3 +44,22 @@ export function withLocator (handler) {
     return handler(request, env, { ...ctx, locator })
   }
 }
+
+/**
+ * Determines if the indexing service is enabled. It is enabled if the request
+ * contains the `ff=indexing-service` query parameter or if a random chance
+ * falls within the ramp-up probability. If `FF_RAMP_UP_PROBABILITY` is not set,
+ * it defaults to 0%.
+ *
+ * @param {Request} request
+ * @param {LocatorEnvironment} env
+ * @returns {boolean}
+ */
+function isIndexingServiceEnabled (request, env) {
+  const withIndexingServicesArg = new URL(request.url).searchParams
+    .getAll('ff')
+    .includes('indexing-service')
+  const probability = env.FF_RAMP_UP_PROBABILITY ? Number(env.FF_RAMP_UP_PROBABILITY) : 0
+  const withIndexerEnabled = Math.random() * 100 <= probability
+  return withIndexingServicesArg || withIndexerEnabled
+}

src/middleware/withLocator.types.ts

@@ -10,6 +10,7 @@ export interface LocatorEnvironment extends MiddlewareEnvironment {
   CARPARK: R2Bucket
   CARPARK_PUBLIC_BUCKET_URL?: string
   INDEXING_SERVICE_URL?: string
+  FF_RAMP_UP_PROBABILITY?: string
 }
 
 export interface LocatorContext extends MiddlewareContext {

wrangler.toml

@@ -53,6 +53,7 @@ MAX_SHARDS = "825"
 FF_RATE_LIMITER_ENABLED = "false"
 FF_EGRESS_TRACKER_ENABLED = "false"
 FF_TELEMETRY_ENABLED = "true"
+FF_RAMP_UP_PROBABILITY = "10"
 GATEWAY_SERVICE_DID = "did:web:w3s.link"
 UPLOAD_SERVICE_DID = "did:web:web3.storage"
 CONTENT_CLAIMS_SERVICE_URL = "https://claims.web3.storage"
@@ -80,6 +81,7 @@ FF_RATE_LIMITER_ENABLED = "false"
 FF_EGRESS_TRACKER_ENABLED = "true"
 FF_TELEMETRY_ENABLED = "true"
 FF_DELEGATIONS_STORAGE_ENABLED = "true"
+FF_RAMP_UP_PROBABILITY = "100"
 GATEWAY_SERVICE_DID = "did:web:staging.w3s.link"
 UPLOAD_SERVICE_DID = "did:web:staging.web3.storage"
 CONTENT_CLAIMS_SERVICE_URL = "https://staging.claims.web3.storage"
@@ -100,6 +102,7 @@ DEBUG = "true"
 FF_RATE_LIMITER_ENABLED = "false"
 FF_EGRESS_TRACKER_ENABLED = "false"
 FF_TELEMETRY_ENABLED = "true"
+FF_RAMP_UP_PROBABILITY = "100"
 MAX_SHARDS = "120"
 GATEWAY_SERVICE_DID = "did:web:staging.w3s.link"
 UPLOAD_SERVICE_DID = "did:web:staging.web3.storage"
@@ -145,6 +148,7 @@ FF_RATE_LIMITER_ENABLED = "false"
 FF_EGRESS_TRACKER_ENABLED = "true"
 FF_TELEMETRY_ENABLED = "true"
 FF_DELEGATIONS_STORAGE_ENABLED = "true"
+FF_RAMP_UP_PROBABILITY = "100"
 GATEWAY_SERVICE_DID = "did:web:staging.w3s.link"
 UPLOAD_SERVICE_DID = "did:web:staging.web3.storage"
 CONTENT_CLAIMS_SERVICE_URL = "https://staging.claims.web3.storage"