Merge pull request #2621 from cloudflare/milan/replica-routing-compat-flag

Add `replicaRouting` compat flag

Author: MellowYarker

Diff for: src/workerd/api/actor.c++

@@ -53,11 +53,13 @@ public:
   GlobalActorOutgoingFactory(uint channelId,
       jsg::Ref<DurableObjectId> id,
       kj::Maybe<kj::String> locationHint,
-      ActorGetMode mode)
+      ActorGetMode mode,
+      bool enableReplicaRouting)
       : channelId(channelId),
         id(kj::mv(id)),
         locationHint(kj::mv(locationHint)),
-        mode(mode) {}
+        mode(mode),
+        enableReplicaRouting(enableReplicaRouting) {}
 
   kj::Own<WorkerInterface> newSingleUseClient(kj::Maybe<kj::String> cfStr) override {
     auto& context = IoContext::current();
@@ -71,7 +73,7 @@ public:
       // Lazily initialize actorChannel
       if (actorChannel == kj::none) {
         actorChannel = context.getGlobalActorChannel(
-            channelId, id->getInner(), kj::mv(locationHint), mode, span);
+            channelId, id->getInner(), kj::mv(locationHint), mode, enableReplicaRouting, span);
       }
 
       return KJ_REQUIRE_NONNULL(actorChannel)
@@ -87,6 +89,7 @@ private:
   jsg::Ref<DurableObjectId> id;
   kj::Maybe<kj::String> locationHint;
   ActorGetMode mode;
+  bool enableReplicaRouting;
   kj::Maybe<kj::Own<IoChannelFactory::ActorChannel>> actorChannel;
 };
 
@@ -147,8 +150,10 @@ jsg::Ref<DurableObject> DurableObjectNamespace::getImpl(jsg::Lock& js,
     locationHint = kj::mv(o.locationHint);
   }
 
-  auto outgoingFactory = context.addObject<Fetcher::OutgoingFactory>(
-      kj::heap<GlobalActorOutgoingFactory>(channel, id.addRef(), kj::mv(locationHint), mode));
+  bool enableReplicaRouting = FeatureFlags::get(js).getReplicaRouting();
+  auto outgoingFactory =
+      context.addObject<Fetcher::OutgoingFactory>(kj::heap<GlobalActorOutgoingFactory>(
+          channel, id.addRef(), kj::mv(locationHint), mode, enableReplicaRouting));
   auto requiresHost = FeatureFlags::get(js).getDurableObjectFetchRequiresSchemeAuthority()
       ? Fetcher::RequiresHostAndProtocol::YES
       : Fetcher::RequiresHostAndProtocol::NO;

Diff for: src/workerd/io/compatibility-date.capnp

@@ -588,4 +588,10 @@ struct CompatibilityFlags @0x8f8c1b68151b6cef {
   # Enables node:zlib implementation while it is in-development.
   # Once the node:zlib implementation is complete, this will be automatically enabled when
   # nodejs_compat is enabled.
+
+  replicaRouting @60 :Bool
+      $compatEnableFlag("replica_routing")
+      $experimental;
+  # Enables routing to a replica on the client-side.
+  # Doesn't mean requests *will* be routed to a replica, only that they can be.
 }

Diff for: src/workerd/io/io-channels.h

@@ -151,6 +151,7 @@ class IoChannelFactory {
       const ActorIdFactory::ActorId& id,
       kj::Maybe<kj::String> locationHint,
       ActorGetMode mode,
+      bool enableReplicaRouting,
       SpanParent parentSpan) = 0;
 
   // Get an actor stub from the given namespace for the actor with the given name.

Diff for: src/workerd/io/io-context.h

@@ -721,9 +721,10 @@ class IoContext final: public kj::Refcounted, private kj::TaskSet::ErrorHandler
       const ActorIdFactory::ActorId& id,
       kj::Maybe<kj::String> locationHint,
       ActorGetMode mode,
+      bool enableReplicaRouting,
       SpanParent parentSpan) {
     return getIoChannelFactory().getGlobalActor(
-        channel, id, kj::mv(locationHint), mode, kj::mv(parentSpan));
+        channel, id, kj::mv(locationHint), mode, enableReplicaRouting, kj::mv(parentSpan));
   }
   kj::Own<IoChannelFactory::ActorChannel> getColoLocalActorChannel(
       uint channel, kj::StringPtr id, SpanParent parentSpan) {

Diff for: src/workerd/server/server.c++

@@ -2205,9 +2205,11 @@ private:
       const ActorIdFactory::ActorId& id,
       kj::Maybe<kj::String> locationHint,
       ActorGetMode mode,
+      bool enableReplicaRouting,
       SpanParent parentSpan) override {
     JSG_REQUIRE(mode == ActorGetMode::GET_OR_CREATE, Error,
         "workerd only supports GET_OR_CREATE mode for getting actor stubs");
+    JSG_REQUIRE(!enableReplicaRouting, Error, "workerd does not support replica routing.");
     auto& channels =
         KJ_REQUIRE_NONNULL(ioChannels.tryGet<LinkedIoChannels>(), "link() has not been called");
 

Diff for: src/workerd/tests/test-fixture.c++

@@ -99,6 +99,7 @@ struct DummyIoChannelFactory final: public IoChannelFactory {
       const ActorIdFactory::ActorId& id,
       kj::Maybe<kj::String> locationHint,
       ActorGetMode mode,
+      bool enableReplicaRouting,
       SpanParent parentSpan) override {
     KJ_FAIL_REQUIRE("no actor channels");
   }