Merge pull request #1426 from cloudflare/dominik/autogates

Implements autogate framework.

src/workerd/server/BUILD.bazel

@@ -47,6 +47,7 @@ wd_cc_binary(
     tags = ["no-arm64"],
     visibility = ["//visibility:public"],
     deps = [
+        ":autogate",
         ":server",
         ":workerd-meta_capnp",
         ":workerd_capnp",
@@ -118,6 +119,14 @@ wd_cc_capnp_library(
     ],
 )
 
+wd_cc_library(
+    name = "autogate",
+    srcs = ["autogate.c++"],
+    hdrs = ["autogate.h"],
+    visibility = ["//visibility:public"],
+    deps = ["@capnp-cpp//src/kj:kj", ":workerd_capnp"],
+)
+
 [kj_test(
     src = f,
     deps = [

src/workerd/server/autogate.c++

@@ -0,0 +1,55 @@
+// Copyright (c) 2017-2023 Cloudflare, Inc.
+// Licensed under the Apache 2.0 license found in the LICENSE file or at:
+//     https://opensource.org/licenses/Apache-2.0
+#include "autogate.h"
+
+namespace workerd::server {
+
+kj::StringPtr KJ_STRINGIFY(AutogateKey key) {
+  switch (key) {
+    case AutogateKey::TEST_WORKERD:
+      return "test-workerd"_kj;
+    case AutogateKey::NumOfKeys:
+      KJ_FAIL_ASSERT("NumOfKeys should not be used in getName");
+  }
+}
+
+Autogate::Autogate(capnp::List<config::Config::Autogate, capnp::Kind::STRUCT>::Reader autogates) {
+  for (auto autogate : autogates) {
+    if (!autogate.hasName()) {
+      continue;
+    }
+    auto name = autogate.getName();
+    if (!name.startsWith("workerd-autogate-")) {
+      continue;
+    }
+    auto sliced = name.slice(17);
+
+    // Parse the gate name into a AutogateKey.
+    for (AutogateKey i = AutogateKey(0); i < AutogateKey::NumOfKeys; i = AutogateKey((int)i + 1)) {
+      if (kj::str(i) == sliced) {
+        gates.insert(i, autogate.getEnabled());
+        break;
+      }
+    }
+  }
+}
+
+bool Autogate::isEnabled(AutogateKey key) const {
+  return gates.find(key).orDefault(false);
+}
+
+kj::Maybe<Autogate> globalAutogate;
+void initAutogate(config::Config::Reader config) {
+  if (!config.hasAutogates()) {
+    return;
+  }
+
+  globalAutogate = Autogate(config.getAutogates());
+}
+
+void initAutogate(capnp::List<config::Config::Autogate, capnp::Kind::STRUCT>::Reader autogates) {
+  globalAutogate = Autogate(autogates);
+}
+
+}  // namespace workerd::server

src/workerd/server/autogate.h

@@ -0,0 +1,51 @@
+// Copyright (c) 2017-2023 Cloudflare, Inc.
+// Licensed under the Apache 2.0 license found in the LICENSE file or at:
+//     https://opensource.org/licenses/Apache-2.0
+#pragma once
+
+#include "kj/debug.h"
+#include <kj/map.h>
+#include <workerd/server/workerd.capnp.h>
+
+namespace workerd::server {
+
+// Workerd-specific list of autogate keys (can also be used in internal repo).
+enum class AutogateKey {
+  TEST_WORKERD,
+  NumOfKeys // Reserved for iteration.
+};
+
+// This class allows code changes to be rolled out independent of full binary releases. It enables
+// specific code paths to be gradually rolled out via our internal tooling.
+// See the equivalent file in our internal repo for more details.
+//
+// Workerd-specific gates can be added here.
+//
+// Usage:
+//
+//     #include <workerd/server/autogate.h>
+//     Autogate::isEnabled(AutogateKey::YOUR_FEATURE_KEY)
+//
+// When making structural changes here, ensure you align them with autogate.h in workerd.
+class Autogate {
+
+public:
+  Autogate(capnp::List<config::Config::Autogate, capnp::Kind::STRUCT>::Reader autogates);
+
+  bool isEnabled(AutogateKey key) const;
+
+private:
+  kj::HashMap<AutogateKey, bool> gates;
+};
+
+// Retrieves the name of the gate.
+//
+// When adding a new gate, add it into this method as well.
+kj::StringPtr KJ_STRINGIFY(AutogateKey key);
+
+extern kj::Maybe<Autogate> globalAutogate;
+
+void initAutogate(config::Config::Reader config);
+void initAutogate(capnp::List<config::Config::Autogate, capnp::Kind::STRUCT>::Reader autogates);
+
+}  // namespace workerd::server

src/workerd/server/workerd.c++

@@ -20,6 +20,7 @@
 #include <openssl/rand.h>
 #include <workerd/io/compatibility-date.capnp.h>
 #include <workerd/io/supported-compatibility-date.capnp.h>
+#include <workerd/server/autogate.h>
 
 #ifdef WORKERD_EXPERIMENTAL_ENABLE_WEBGPU
 #include <workerd/api/gpu/gpu.h>
@@ -846,6 +847,10 @@ public:
         }
       }
     }
+
+    KJ_IF_SOME(c, config) {
+      initAutogate(c);
+    }
   }
 
   void setConstName(kj::StringPtr name) {

src/workerd/server/workerd.capnp

@@ -76,6 +76,15 @@ struct Config {
   extensions @3 :List(Extension);
   # Extensions provide capabilities to all workers. Extensions are usually prepared separately
   # and are late-linked with the app using this config field.
+
+  autogates @4 :List(Autogate);
+  # A list of gates and a corresponding value of whether they are enabled.
+  # These are used to gate features/changes in workerd and in our internal repo. See the equivalent
+  # config definition in our internal repo for more details.
+  struct Autogate {
+    enabled @0 :Bool;
+    name @1 :Text;
+  }
 }
 
 # ========================================================================================