1 files changed, 71 insertions, 0 deletions
diff --git a/src/core/ext/filters/client_channel/lb_policy/grpclb/grpclb_channel.cc b/src/core/ext/filters/client_channel/lb_policy/grpclb/grpclb_channel.cc
new file mode 100644
index 0000000000..f2967182e2
--- /dev/null
+++ b/src/core/ext/filters/client_channel/lb_policy/grpclb/grpclb_channel.cc
@@ -0,0 +1,71 @@
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/string_util.h>
+
+#include "src/core/ext/filters/client_channel/client_channel.h"
+#include "src/core/ext/filters/client_channel/lb_policy/grpclb/grpclb_channel.h"
+#include "src/core/lib/channel/channel_args.h"
+#include "src/core/lib/iomgr/sockaddr_utils.h"
+#include "src/core/lib/support/string.h"
+
+grpc_channel *grpc_lb_policy_grpclb_create_lb_channel(
+    grpc_exec_ctx *exec_ctx, const char *lb_service_target_addresses,
+    grpc_client_channel_factory *client_channel_factory,
+    grpc_channel_args *args) {
+  grpc_channel *lb_channel = grpc_client_channel_factory_create_channel(
+      exec_ctx, client_channel_factory, lb_service_target_addresses,
+      GRPC_CLIENT_CHANNEL_TYPE_LOAD_BALANCING, args);
+  return lb_channel;
+}
+
+grpc_channel_args *grpc_lb_policy_grpclb_build_lb_channel_args(
+    grpc_exec_ctx *exec_ctx, grpc_slice_hash_table *targets_info,
+    grpc_fake_resolver_response_generator *response_generator,
+    const grpc_channel_args *args) {
+  const grpc_arg to_add[] = {
+      grpc_fake_resolver_response_generator_arg(response_generator)};
+  /* We remove:
+   *
+   * - The channel arg for the LB policy name, since we want to use the default
+   *   (pick_first) in this case.
+   *
+   * - The channel arg for the resolved addresses, since that will be generated
+   *   by the name resolver used in the LB channel.  Note that the LB channel
+   *   will use the fake resolver, so this won't actually generate a query
+   *   to DNS (or some other name service).  However, the addresses returned by
+   *   the fake resolver will have is_balancer=false, whereas our own
+   *   addresses have is_balancer=true.  We need the LB channel to return
+   *   addresses with is_balancer=false so that it does not wind up recursively
+   *   using the grpclb LB policy, as per the special case logic in
+   *   client_channel.c.
+   *
+   * - The channel arg for the server URI, since that will be different for the
+   *   LB channel than for the parent channel (the client channel factory will
+   *   re-add this arg with the right value).
+   *
+   * - The fake resolver generator, because we are replacing it with the one
+   *   from the grpclb policy, used to propagate updates to the LB channel. */
+  static const char *keys_to_remove[] = {
+      GRPC_ARG_LB_POLICY_NAME, GRPC_ARG_LB_ADDRESSES, GRPC_ARG_SERVER_URI,
+      GRPC_ARG_FAKE_RESOLVER_RESPONSE_GENERATOR};
+  return grpc_channel_args_copy_and_add_and_remove(
+      args, keys_to_remove, GPR_ARRAY_SIZE(keys_to_remove), to_add,
+      GPR_ARRAY_SIZE(to_add));
+}