Begin optionalizing lb policies: initial code movement

8 files changed, 1601 insertions, 0 deletions

diff --git a/src/core/ext/lb_policy/grpclb/load_balancer_api.c b/src/core/ext/lb_policy/grpclb/load_balancer_api.c
new file mode 100644
index 0000000000..d8af644870
--- /dev/null
+++ b/src/core/ext/lb_policy/grpclb/load_balancer_api.c
@@ -0,0 +1,163 @@
+/*
+ *
+ * Copyright 2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include "src/core/ext/lb_policy/grpclb/load_balancer_api.h"
+#include "third_party/nanopb/pb_decode.h"
+#include "third_party/nanopb/pb_encode.h"
+
+#include <grpc/support/alloc.h>
+
+typedef struct decode_serverlist_arg {
+  int first_pass;
+  int i;
+  size_t num_servers;
+  grpc_grpclb_server **servers;
+} decode_serverlist_arg;
+
+/* invoked once for every Server in ServerList */
+static bool decode_serverlist(pb_istream_t *stream, const pb_field_t *field,
+                              void **arg) {
+  decode_serverlist_arg *dec_arg = *arg;
+  if (dec_arg->first_pass != 0) { /* first pass */
+    grpc_grpclb_server server;
+    if (!pb_decode(stream, grpc_lb_v0_Server_fields, &server)) {
+      return false;
+    }
+    dec_arg->num_servers++;
+  } else { /* second pass */
+    grpc_grpclb_server *server = gpr_malloc(sizeof(grpc_grpclb_server));
+    GPR_ASSERT(dec_arg->num_servers > 0);
+    if (dec_arg->i == 0) { /* first iteration of second pass */
+      dec_arg->servers =
+          gpr_malloc(sizeof(grpc_grpclb_server *) * dec_arg->num_servers);
+    }
+    if (!pb_decode(stream, grpc_lb_v0_Server_fields, server)) {
+      return false;
+    }
+    dec_arg->servers[dec_arg->i++] = server;
+  }
+
+  return true;
+}
+
+grpc_grpclb_request *grpc_grpclb_request_create(const char *lb_service_name) {
+  grpc_grpclb_request *req = gpr_malloc(sizeof(grpc_grpclb_request));
+
+  req->has_client_stats = 0; /* TODO(dgq): add support for stats once defined */
+  req->has_initial_request = 1;
+  req->initial_request.has_name = 1;
+  strncpy(req->initial_request.name, lb_service_name,
+          GRPC_GRPCLB_SERVICE_NAME_MAX_LENGTH);
+  return req;
+}
+
+gpr_slice grpc_grpclb_request_encode(const grpc_grpclb_request *request) {
+  size_t encoded_length;
+  pb_ostream_t sizestream;
+  pb_ostream_t outputstream;
+  gpr_slice slice;
+  memset(&sizestream, 0, sizeof(pb_ostream_t));
+  pb_encode(&sizestream, grpc_lb_v0_LoadBalanceRequest_fields, request);
+  encoded_length = sizestream.bytes_written;
+
+  slice = gpr_slice_malloc(encoded_length);
+  outputstream =
+      pb_ostream_from_buffer(GPR_SLICE_START_PTR(slice), encoded_length);
+  GPR_ASSERT(pb_encode(&outputstream, grpc_lb_v0_LoadBalanceRequest_fields,
+                       request) != 0);
+  return slice;
+}
+
+void grpc_grpclb_request_destroy(grpc_grpclb_request *request) {
+  gpr_free(request);
+}
+
+grpc_grpclb_response *grpc_grpclb_response_parse(gpr_slice encoded_response) {
+  bool status;
+  pb_istream_t stream =
+      pb_istream_from_buffer(GPR_SLICE_START_PTR(encoded_response),
+                             GPR_SLICE_LENGTH(encoded_response));
+  grpc_grpclb_response *res = gpr_malloc(sizeof(grpc_grpclb_response));
+  memset(res, 0, sizeof(*res));
+  status = pb_decode(&stream, grpc_lb_v0_LoadBalanceResponse_fields, res);
+  GPR_ASSERT(status == true);
+  return res;
+}
+
+grpc_grpclb_serverlist *grpc_grpclb_response_parse_serverlist(
+    gpr_slice encoded_response) {
+  grpc_grpclb_serverlist *sl = gpr_malloc(sizeof(grpc_grpclb_serverlist));
+  bool status;
+  decode_serverlist_arg arg;
+  pb_istream_t stream =
+      pb_istream_from_buffer(GPR_SLICE_START_PTR(encoded_response),
+                             GPR_SLICE_LENGTH(encoded_response));
+  pb_istream_t stream_at_start = stream;
+  grpc_grpclb_response *res = gpr_malloc(sizeof(grpc_grpclb_response));
+  memset(res, 0, sizeof(*res));
+  memset(&arg, 0, sizeof(decode_serverlist_arg));
+
+  res->server_list.servers.funcs.decode = decode_serverlist;
+  res->server_list.servers.arg = &arg;
+  arg.first_pass = 1;
+  status = pb_decode(&stream, grpc_lb_v0_LoadBalanceResponse_fields, res);
+  GPR_ASSERT(status == true);
+  GPR_ASSERT(arg.num_servers > 0);
+
+  arg.first_pass = 0;
+  status =
+      pb_decode(&stream_at_start, grpc_lb_v0_LoadBalanceResponse_fields, res);
+  GPR_ASSERT(status == true);
+  GPR_ASSERT(arg.servers != NULL);
+
+  sl->num_servers = arg.num_servers;
+  sl->servers = arg.servers;
+  if (res->server_list.has_expiration_interval) {
+    sl->expiration_interval = res->server_list.expiration_interval;
+  }
+  grpc_grpclb_response_destroy(res);
+  return sl;
+}
+
+void grpc_grpclb_destroy_serverlist(grpc_grpclb_serverlist *serverlist) {
+  size_t i;
+  for (i = 0; i < serverlist->num_servers; i++) {
+    gpr_free(serverlist->servers[i]);
+  }
+  gpr_free(serverlist->servers);
+  gpr_free(serverlist);
+}
+
+void grpc_grpclb_response_destroy(grpc_grpclb_response *response) {
+  gpr_free(response);
+}
diff --git a/src/core/ext/lb_policy/grpclb/load_balancer_api.h b/src/core/ext/lb_policy/grpclb/load_balancer_api.h
new file mode 100644
index 0000000000..c1af304f68
--- /dev/null
+++ b/src/core/ext/lb_policy/grpclb/load_balancer_api.h
@@ -0,0 +1,85 @@
+/*
+ *
+ * Copyright 2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_CLIENT_CONFIG_LB_POLICIES_LOAD_BALANCER_API_H
+#define GRPC_CORE_LIB_CLIENT_CONFIG_LB_POLICIES_LOAD_BALANCER_API_H
+
+#include <grpc/support/slice_buffer.h>
+
+#include "src/core/lib/client_config/lb_policy_factory.h"
+#include "src/core/ext/lb_policy/grpclb/proto/grpc/lb/v0/load_balancer.pb.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#define GRPC_GRPCLB_SERVICE_NAME_MAX_LENGTH 128
+
+typedef grpc_lb_v0_LoadBalanceRequest grpc_grpclb_request;
+typedef grpc_lb_v0_LoadBalanceResponse grpc_grpclb_response;
+typedef grpc_lb_v0_Server grpc_grpclb_server;
+typedef grpc_lb_v0_Duration grpc_grpclb_duration;
+typedef struct grpc_grpclb_serverlist {
+  grpc_grpclb_server **servers;
+  size_t num_servers;
+  grpc_grpclb_duration expiration_interval;
+} grpc_grpclb_serverlist;
+
+/** Create a request for a gRPC LB service under \a lb_service_name */
+grpc_grpclb_request *grpc_grpclb_request_create(const char *lb_service_name);
+
+/** Protocol Buffers v3-encode \a request */
+gpr_slice grpc_grpclb_request_encode(const grpc_grpclb_request *request);
+
+/** Destroy \a request */
+void grpc_grpclb_request_destroy(grpc_grpclb_request *request);
+
+/** Parse (ie, decode) the bytes in \a encoded_response as a \a
+ * grpc_grpclb_response */
+grpc_grpclb_response *grpc_grpclb_response_parse(gpr_slice encoded_response);
+
+/** Destroy \a serverlist */
+void grpc_grpclb_destroy_serverlist(grpc_grpclb_serverlist *serverlist);
+
+/** Parse the list of servers from an encoded \a grpc_grpclb_response */
+grpc_grpclb_serverlist *grpc_grpclb_response_parse_serverlist(
+    gpr_slice encoded_response);
+
+/** Destroy \a response */
+void grpc_grpclb_response_destroy(grpc_grpclb_response *response);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* GRPC_CORE_LIB_CLIENT_CONFIG_LB_POLICIES_LOAD_BALANCER_API_H */
diff --git a/src/core/ext/lb_policy/grpclb/proto/grpc/lb/v0/load_balancer.pb.c b/src/core/ext/lb_policy/grpclb/proto/grpc/lb/v0/load_balancer.pb.c
new file mode 100644
index 0000000000..9719673181
--- /dev/null
+++ b/src/core/ext/lb_policy/grpclb/proto/grpc/lb/v0/load_balancer.pb.c
@@ -0,0 +1,119 @@
+/*
+ *
+ * Copyright 2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+/* Automatically generated nanopb constant definitions */
+/* Generated by nanopb-0.3.5-dev */
+
+#include "src/core/ext/lb_policy/grpclb/proto/grpc/lb/v0/load_balancer.pb.h"
+
+#if PB_PROTO_HEADER_VERSION != 30
+#error Regenerate this file with the current version of nanopb generator.
+#endif
+
+
+
+const pb_field_t grpc_lb_v0_Duration_fields[3] = {
+    PB_FIELD(  1, INT64   , OPTIONAL, STATIC  , FIRST, grpc_lb_v0_Duration, seconds, seconds, 0),
+    PB_FIELD(  2, INT32   , OPTIONAL, STATIC  , OTHER, grpc_lb_v0_Duration, nanos, seconds, 0),
+    PB_LAST_FIELD
+};
+
+const pb_field_t grpc_lb_v0_LoadBalanceRequest_fields[3] = {
+    PB_FIELD(  1, MESSAGE , OPTIONAL, STATIC  , FIRST, grpc_lb_v0_LoadBalanceRequest, initial_request, initial_request, &grpc_lb_v0_InitialLoadBalanceRequest_fields),
+    PB_FIELD(  2, MESSAGE , OPTIONAL, STATIC  , OTHER, grpc_lb_v0_LoadBalanceRequest, client_stats, initial_request, &grpc_lb_v0_ClientStats_fields),
+    PB_LAST_FIELD
+};
+
+const pb_field_t grpc_lb_v0_InitialLoadBalanceRequest_fields[2] = {
+    PB_FIELD(  1, STRING  , OPTIONAL, STATIC  , FIRST, grpc_lb_v0_InitialLoadBalanceRequest, name, name, 0),
+    PB_LAST_FIELD
+};
+
+const pb_field_t grpc_lb_v0_ClientStats_fields[4] = {
+    PB_FIELD(  1, INT64   , OPTIONAL, STATIC  , FIRST, grpc_lb_v0_ClientStats, total_requests, total_requests, 0),
+    PB_FIELD(  2, INT64   , OPTIONAL, STATIC  , OTHER, grpc_lb_v0_ClientStats, client_rpc_errors, total_requests, 0),
+    PB_FIELD(  3, INT64   , OPTIONAL, STATIC  , OTHER, grpc_lb_v0_ClientStats, dropped_requests, client_rpc_errors, 0),
+    PB_LAST_FIELD
+};
+
+const pb_field_t grpc_lb_v0_LoadBalanceResponse_fields[3] = {
+    PB_FIELD(  1, MESSAGE , OPTIONAL, STATIC  , FIRST, grpc_lb_v0_LoadBalanceResponse, initial_response, initial_response, &grpc_lb_v0_InitialLoadBalanceResponse_fields),
+    PB_FIELD(  2, MESSAGE , OPTIONAL, STATIC  , OTHER, grpc_lb_v0_LoadBalanceResponse, server_list, initial_response, &grpc_lb_v0_ServerList_fields),
+    PB_LAST_FIELD
+};
+
+const pb_field_t grpc_lb_v0_InitialLoadBalanceResponse_fields[4] = {
+    PB_FIELD(  1, STRING  , OPTIONAL, STATIC  , FIRST, grpc_lb_v0_InitialLoadBalanceResponse, client_config, client_config, 0),
+    PB_FIELD(  2, STRING  , OPTIONAL, STATIC  , OTHER, grpc_lb_v0_InitialLoadBalanceResponse, load_balancer_delegate, client_config, 0),
+    PB_FIELD(  3, MESSAGE , OPTIONAL, STATIC  , OTHER, grpc_lb_v0_InitialLoadBalanceResponse, client_stats_report_interval, load_balancer_delegate, &grpc_lb_v0_Duration_fields),
+    PB_LAST_FIELD
+};
+
+const pb_field_t grpc_lb_v0_ServerList_fields[3] = {
+    PB_FIELD(  1, MESSAGE , REPEATED, CALLBACK, FIRST, grpc_lb_v0_ServerList, servers, servers, &grpc_lb_v0_Server_fields),
+    PB_FIELD(  3, MESSAGE , OPTIONAL, STATIC  , OTHER, grpc_lb_v0_ServerList, expiration_interval, servers, &grpc_lb_v0_Duration_fields),
+    PB_LAST_FIELD
+};
+
+const pb_field_t grpc_lb_v0_Server_fields[5] = {
+    PB_FIELD(  1, STRING  , OPTIONAL, STATIC  , FIRST, grpc_lb_v0_Server, ip_address, ip_address, 0),
+    PB_FIELD(  2, INT32   , OPTIONAL, STATIC  , OTHER, grpc_lb_v0_Server, port, ip_address, 0),
+    PB_FIELD(  3, BYTES   , OPTIONAL, STATIC  , OTHER, grpc_lb_v0_Server, load_balance_token, port, 0),
+    PB_FIELD(  4, BOOL    , OPTIONAL, STATIC  , OTHER, grpc_lb_v0_Server, drop_request, load_balance_token, 0),
+    PB_LAST_FIELD
+};
+
+
+/* Check that field information fits in pb_field_t */
+#if !defined(PB_FIELD_32BIT)
+/* If you get an error here, it means that you need to define PB_FIELD_32BIT
+ * compile-time option. You can do that in pb.h or on compiler command line.
+ * 
+ * The reason you need to do this is that some of your messages contain tag
+ * numbers or field sizes that are larger than what can fit in 8 or 16 bit
+ * field descriptors.
+ */
+PB_STATIC_ASSERT((pb_membersize(grpc_lb_v0_LoadBalanceRequest, initial_request) < 65536 && pb_membersize(grpc_lb_v0_LoadBalanceRequest, client_stats) < 65536 && pb_membersize(grpc_lb_v0_LoadBalanceResponse, initial_response) < 65536 && pb_membersize(grpc_lb_v0_LoadBalanceResponse, server_list) < 65536 && pb_membersize(grpc_lb_v0_InitialLoadBalanceResponse, client_stats_report_interval) < 65536 && pb_membersize(grpc_lb_v0_ServerList, servers) < 65536 && pb_membersize(grpc_lb_v0_ServerList, expiration_interval) < 65536), YOU_MUST_DEFINE_PB_FIELD_32BIT_FOR_MESSAGES_grpc_lb_v0_Duration_grpc_lb_v0_LoadBalanceRequest_grpc_lb_v0_InitialLoadBalanceRequest_grpc_lb_v0_ClientStats_grpc_lb_v0_LoadBalanceResponse_grpc_lb_v0_InitialLoadBalanceResponse_grpc_lb_v0_ServerList_grpc_lb_v0_Server)
+#endif
+
+#if !defined(PB_FIELD_16BIT) && !defined(PB_FIELD_32BIT)
+/* If you get an error here, it means that you need to define PB_FIELD_16BIT
+ * compile-time option. You can do that in pb.h or on compiler command line.
+ * 
+ * The reason you need to do this is that some of your messages contain tag
+ * numbers or field sizes that are larger than what can fit in the default
+ * 8 bit descriptors.
+ */
+PB_STATIC_ASSERT((pb_membersize(grpc_lb_v0_LoadBalanceRequest, initial_request) < 256 && pb_membersize(grpc_lb_v0_LoadBalanceRequest, client_stats) < 256 && pb_membersize(grpc_lb_v0_LoadBalanceResponse, initial_response) < 256 && pb_membersize(grpc_lb_v0_LoadBalanceResponse, server_list) < 256 && pb_membersize(grpc_lb_v0_InitialLoadBalanceResponse, client_stats_report_interval) < 256 && pb_membersize(grpc_lb_v0_ServerList, servers) < 256 && pb_membersize(grpc_lb_v0_ServerList, expiration_interval) < 256), YOU_MUST_DEFINE_PB_FIELD_16BIT_FOR_MESSAGES_grpc_lb_v0_Duration_grpc_lb_v0_LoadBalanceRequest_grpc_lb_v0_InitialLoadBalanceRequest_grpc_lb_v0_ClientStats_grpc_lb_v0_LoadBalanceResponse_grpc_lb_v0_InitialLoadBalanceResponse_grpc_lb_v0_ServerList_grpc_lb_v0_Server)
+#endif
+
+
diff --git a/src/core/ext/lb_policy/grpclb/proto/grpc/lb/v0/load_balancer.pb.h b/src/core/ext/lb_policy/grpclb/proto/grpc/lb/v0/load_balancer.pb.h
new file mode 100644
index 0000000000..3599f881bb
--- /dev/null
+++ b/src/core/ext/lb_policy/grpclb/proto/grpc/lb/v0/load_balancer.pb.h
@@ -0,0 +1,182 @@
+/*
+ *
+ * Copyright 2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+/* Automatically generated nanopb header */
+/* Generated by nanopb-0.3.5-dev */
+
+#ifndef PB_LOAD_BALANCER_PB_H_INCLUDED
+#define PB_LOAD_BALANCER_PB_H_INCLUDED
+#include "third_party/nanopb/pb.h"
+#if PB_PROTO_HEADER_VERSION != 30
+#error Regenerate this file with the current version of nanopb generator.
+#endif
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* Struct definitions */
+typedef struct _grpc_lb_v0_ClientStats {
+    bool has_total_requests;
+    int64_t total_requests;
+    bool has_client_rpc_errors;
+    int64_t client_rpc_errors;
+    bool has_dropped_requests;
+    int64_t dropped_requests;
+} grpc_lb_v0_ClientStats;
+
+typedef struct _grpc_lb_v0_Duration {
+    bool has_seconds;
+    int64_t seconds;
+    bool has_nanos;
+    int32_t nanos;
+} grpc_lb_v0_Duration;
+
+typedef struct _grpc_lb_v0_InitialLoadBalanceRequest {
+    bool has_name;
+    char name[128];
+} grpc_lb_v0_InitialLoadBalanceRequest;
+
+typedef PB_BYTES_ARRAY_T(64) grpc_lb_v0_Server_load_balance_token_t;
+typedef struct _grpc_lb_v0_Server {
+    bool has_ip_address;
+    char ip_address[46];
+    bool has_port;
+    int32_t port;
+    bool has_load_balance_token;
+    grpc_lb_v0_Server_load_balance_token_t load_balance_token;
+    bool has_drop_request;
+    bool drop_request;
+} grpc_lb_v0_Server;
+
+typedef struct _grpc_lb_v0_InitialLoadBalanceResponse {
+    bool has_client_config;
+    char client_config[64];
+    bool has_load_balancer_delegate;
+    char load_balancer_delegate[64];
+    bool has_client_stats_report_interval;
+    grpc_lb_v0_Duration client_stats_report_interval;
+} grpc_lb_v0_InitialLoadBalanceResponse;
+
+typedef struct _grpc_lb_v0_LoadBalanceRequest {
+    bool has_initial_request;
+    grpc_lb_v0_InitialLoadBalanceRequest initial_request;
+    bool has_client_stats;
+    grpc_lb_v0_ClientStats client_stats;
+} grpc_lb_v0_LoadBalanceRequest;
+
+typedef struct _grpc_lb_v0_ServerList {
+    pb_callback_t servers;
+    bool has_expiration_interval;
+    grpc_lb_v0_Duration expiration_interval;
+} grpc_lb_v0_ServerList;
+
+typedef struct _grpc_lb_v0_LoadBalanceResponse {
+    bool has_initial_response;
+    grpc_lb_v0_InitialLoadBalanceResponse initial_response;
+    bool has_server_list;
+    grpc_lb_v0_ServerList server_list;
+} grpc_lb_v0_LoadBalanceResponse;
+
+/* Default values for struct fields */
+
+/* Initializer values for message structs */
+#define grpc_lb_v0_Duration_init_default         {false, 0, false, 0}
+#define grpc_lb_v0_LoadBalanceRequest_init_default {false, grpc_lb_v0_InitialLoadBalanceRequest_init_default, false, grpc_lb_v0_ClientStats_init_default}
+#define grpc_lb_v0_InitialLoadBalanceRequest_init_default {false, ""}
+#define grpc_lb_v0_ClientStats_init_default      {false, 0, false, 0, false, 0}
+#define grpc_lb_v0_LoadBalanceResponse_init_default {false, grpc_lb_v0_InitialLoadBalanceResponse_init_default, false, grpc_lb_v0_ServerList_init_default}
+#define grpc_lb_v0_InitialLoadBalanceResponse_init_default {false, "", false, "", false, grpc_lb_v0_Duration_init_default}
+#define grpc_lb_v0_ServerList_init_default       {{{NULL}, NULL}, false, grpc_lb_v0_Duration_init_default}
+#define grpc_lb_v0_Server_init_default           {false, "", false, 0, false, {0, {0}}, false, 0}
+#define grpc_lb_v0_Duration_init_zero            {false, 0, false, 0}
+#define grpc_lb_v0_LoadBalanceRequest_init_zero  {false, grpc_lb_v0_InitialLoadBalanceRequest_init_zero, false, grpc_lb_v0_ClientStats_init_zero}
+#define grpc_lb_v0_InitialLoadBalanceRequest_init_zero {false, ""}
+#define grpc_lb_v0_ClientStats_init_zero         {false, 0, false, 0, false, 0}
+#define grpc_lb_v0_LoadBalanceResponse_init_zero {false, grpc_lb_v0_InitialLoadBalanceResponse_init_zero, false, grpc_lb_v0_ServerList_init_zero}
+#define grpc_lb_v0_InitialLoadBalanceResponse_init_zero {false, "", false, "", false, grpc_lb_v0_Duration_init_zero}
+#define grpc_lb_v0_ServerList_init_zero          {{{NULL}, NULL}, false, grpc_lb_v0_Duration_init_zero}
+#define grpc_lb_v0_Server_init_zero              {false, "", false, 0, false, {0, {0}}, false, 0}
+
+/* Field tags (for use in manual encoding/decoding) */
+#define grpc_lb_v0_ClientStats_total_requests_tag 1
+#define grpc_lb_v0_ClientStats_client_rpc_errors_tag 2
+#define grpc_lb_v0_ClientStats_dropped_requests_tag 3
+#define grpc_lb_v0_Duration_seconds_tag          1
+#define grpc_lb_v0_Duration_nanos_tag            2
+#define grpc_lb_v0_InitialLoadBalanceRequest_name_tag 1
+#define grpc_lb_v0_Server_ip_address_tag         1
+#define grpc_lb_v0_Server_port_tag               2
+#define grpc_lb_v0_Server_load_balance_token_tag 3
+#define grpc_lb_v0_Server_drop_request_tag       4
+#define grpc_lb_v0_InitialLoadBalanceResponse_client_config_tag 1
+#define grpc_lb_v0_InitialLoadBalanceResponse_load_balancer_delegate_tag 2
+#define grpc_lb_v0_InitialLoadBalanceResponse_client_stats_report_interval_tag 3
+#define grpc_lb_v0_LoadBalanceRequest_initial_request_tag 1
+#define grpc_lb_v0_LoadBalanceRequest_client_stats_tag 2
+#define grpc_lb_v0_ServerList_servers_tag        1
+#define grpc_lb_v0_ServerList_expiration_interval_tag 3
+#define grpc_lb_v0_LoadBalanceResponse_initial_response_tag 1
+#define grpc_lb_v0_LoadBalanceResponse_server_list_tag 2
+
+/* Struct field encoding specification for nanopb */
+extern const pb_field_t grpc_lb_v0_Duration_fields[3];
+extern const pb_field_t grpc_lb_v0_LoadBalanceRequest_fields[3];
+extern const pb_field_t grpc_lb_v0_InitialLoadBalanceRequest_fields[2];
+extern const pb_field_t grpc_lb_v0_ClientStats_fields[4];
+extern const pb_field_t grpc_lb_v0_LoadBalanceResponse_fields[3];
+extern const pb_field_t grpc_lb_v0_InitialLoadBalanceResponse_fields[4];
+extern const pb_field_t grpc_lb_v0_ServerList_fields[3];
+extern const pb_field_t grpc_lb_v0_Server_fields[5];
+
+/* Maximum encoded size of messages (where known) */
+#define grpc_lb_v0_Duration_size                 22
+#define grpc_lb_v0_LoadBalanceRequest_size       169
+#define grpc_lb_v0_InitialLoadBalanceRequest_size 131
+#define grpc_lb_v0_ClientStats_size              33
+#define grpc_lb_v0_LoadBalanceResponse_size      (165 + grpc_lb_v0_ServerList_size)
+#define grpc_lb_v0_InitialLoadBalanceResponse_size 156
+#define grpc_lb_v0_Server_size                   127
+
+/* Message IDs (where set with "msgid" option) */
+#ifdef PB_MSGID
+
+#define LOAD_BALANCER_MESSAGES \
+
+
+#endif
+
+#ifdef __cplusplus
+} /* extern "C" */
+#endif
+
+#endif
diff --git a/src/core/ext/lb_policy/pick_first/pick_first.c b/src/core/ext/lb_policy/pick_first/pick_first.c
new file mode 100644
index 0000000000..e1dae82c27
--- /dev/null
+++ b/src/core/ext/lb_policy/pick_first/pick_first.c
@@ -0,0 +1,421 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include "src/core/ext/lb_policy/pick_first/pick_first.h"
+#include "src/core/lib/client_config/lb_policy_factory.h"
+
+#include <string.h>
+
+#include <grpc/support/alloc.h>
+#include "src/core/lib/transport/connectivity_state.h"
+
+typedef struct pending_pick {
+  struct pending_pick *next;
+  grpc_pollset *pollset;
+  grpc_connected_subchannel **target;
+  grpc_closure *on_complete;
+} pending_pick;
+
+typedef struct {
+  /** base policy: must be first */
+  grpc_lb_policy base;
+  /** all our subchannels */
+  grpc_subchannel **subchannels;
+  size_t num_subchannels;
+
+  grpc_closure connectivity_changed;
+
+  /** the selected channel (a grpc_connected_subchannel) */
+  gpr_atm selected;
+
+  /** mutex protecting remaining members */
+  gpr_mu mu;
+  /** have we started picking? */
+  int started_picking;
+  /** are we shut down? */
+  int shutdown;
+  /** which subchannel are we watching? */
+  size_t checking_subchannel;
+  /** what is the connectivity of that channel? */
+  grpc_connectivity_state checking_connectivity;
+  /** list of picks that are waiting on connectivity */
+  pending_pick *pending_picks;
+
+  /** our connectivity state tracker */
+  grpc_connectivity_state_tracker state_tracker;
+} pick_first_lb_policy;
+
+#define GET_SELECTED(p) \
+  ((grpc_connected_subchannel *)gpr_atm_acq_load(&(p)->selected))
+
+void pf_destroy(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol) {
+  pick_first_lb_policy *p = (pick_first_lb_policy *)pol;
+  grpc_connected_subchannel *selected = GET_SELECTED(p);
+  size_t i;
+  GPR_ASSERT(p->pending_picks == NULL);
+  for (i = 0; i < p->num_subchannels; i++) {
+    GRPC_SUBCHANNEL_UNREF(exec_ctx, p->subchannels[i], "pick_first");
+  }
+  if (selected != NULL) {
+    GRPC_CONNECTED_SUBCHANNEL_UNREF(exec_ctx, selected, "picked_first");
+  }
+  grpc_connectivity_state_destroy(exec_ctx, &p->state_tracker);
+  gpr_free(p->subchannels);
+  gpr_mu_destroy(&p->mu);
+  gpr_free(p);
+}
+
+void pf_shutdown(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol) {
+  pick_first_lb_policy *p = (pick_first_lb_policy *)pol;
+  pending_pick *pp;
+  grpc_connected_subchannel *selected;
+  gpr_mu_lock(&p->mu);
+  selected = GET_SELECTED(p);
+  p->shutdown = 1;
+  pp = p->pending_picks;
+  p->pending_picks = NULL;
+  grpc_connectivity_state_set(exec_ctx, &p->state_tracker,
+                              GRPC_CHANNEL_FATAL_FAILURE, "shutdown");
+  /* cancel subscription */
+  if (selected != NULL) {
+    grpc_connected_subchannel_notify_on_state_change(
+        exec_ctx, selected, NULL, NULL, &p->connectivity_changed);
+  } else {
+    grpc_subchannel_notify_on_state_change(
+        exec_ctx, p->subchannels[p->checking_subchannel], NULL, NULL,
+        &p->connectivity_changed);
+  }
+  gpr_mu_unlock(&p->mu);
+  while (pp != NULL) {
+    pending_pick *next = pp->next;
+    *pp->target = NULL;
+    grpc_pollset_set_del_pollset(exec_ctx, p->base.interested_parties,
+                                 pp->pollset);
+    grpc_exec_ctx_enqueue(exec_ctx, pp->on_complete, true, NULL);
+    gpr_free(pp);
+    pp = next;
+  }
+}
+
+static void pf_cancel_pick(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol,
+                           grpc_connected_subchannel **target) {
+  pick_first_lb_policy *p = (pick_first_lb_policy *)pol;
+  pending_pick *pp;
+  gpr_mu_lock(&p->mu);
+  pp = p->pending_picks;
+  p->pending_picks = NULL;
+  while (pp != NULL) {
+    pending_pick *next = pp->next;
+    if (pp->target == target) {
+      grpc_pollset_set_del_pollset(exec_ctx, p->base.interested_parties,
+                                   pp->pollset);
+      *target = NULL;
+      grpc_exec_ctx_enqueue(exec_ctx, pp->on_complete, false, NULL);
+      gpr_free(pp);
+    } else {
+      pp->next = p->pending_picks;
+      p->pending_picks = pp;
+    }
+    pp = next;
+  }
+  gpr_mu_unlock(&p->mu);
+}
+
+static void start_picking(grpc_exec_ctx *exec_ctx, pick_first_lb_policy *p) {
+  p->started_picking = 1;
+  p->checking_subchannel = 0;
+  p->checking_connectivity = GRPC_CHANNEL_IDLE;
+  GRPC_LB_POLICY_WEAK_REF(&p->base, "pick_first_connectivity");
+  grpc_subchannel_notify_on_state_change(
+      exec_ctx, p->subchannels[p->checking_subchannel],
+      p->base.interested_parties, &p->checking_connectivity,
+      &p->connectivity_changed);
+}
+
+void pf_exit_idle(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol) {
+  pick_first_lb_policy *p = (pick_first_lb_policy *)pol;
+  gpr_mu_lock(&p->mu);
+  if (!p->started_picking) {
+    start_picking(exec_ctx, p);
+  }
+  gpr_mu_unlock(&p->mu);
+}
+
+int pf_pick(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol, grpc_pollset *pollset,
+            grpc_metadata_batch *initial_metadata,
+            grpc_connected_subchannel **target, grpc_closure *on_complete) {
+  pick_first_lb_policy *p = (pick_first_lb_policy *)pol;
+  pending_pick *pp;
+
+  /* Check atomically for a selected channel */
+  grpc_connected_subchannel *selected = GET_SELECTED(p);
+  if (selected != NULL) {
+    *target = selected;
+    return 1;
+  }
+
+  /* No subchannel selected yet, so acquire lock and then attempt again */
+  gpr_mu_lock(&p->mu);
+  selected = GET_SELECTED(p);
+  if (selected) {
+    gpr_mu_unlock(&p->mu);
+    *target = selected;
+    return 1;
+  } else {
+    if (!p->started_picking) {
+      start_picking(exec_ctx, p);
+    }
+    grpc_pollset_set_add_pollset(exec_ctx, p->base.interested_parties, pollset);
+    pp = gpr_malloc(sizeof(*pp));
+    pp->next = p->pending_picks;
+    pp->pollset = pollset;
+    pp->target = target;
+    pp->on_complete = on_complete;
+    p->pending_picks = pp;
+    gpr_mu_unlock(&p->mu);
+    return 0;
+  }
+}
+
+static void destroy_subchannels(grpc_exec_ctx *exec_ctx, void *arg,
+                                bool iomgr_success) {
+  pick_first_lb_policy *p = arg;
+  size_t i;
+  size_t num_subchannels = p->num_subchannels;
+  grpc_subchannel **subchannels;
+
+  gpr_mu_lock(&p->mu);
+  subchannels = p->subchannels;
+  p->num_subchannels = 0;
+  p->subchannels = NULL;
+  gpr_mu_unlock(&p->mu);
+  GRPC_LB_POLICY_WEAK_UNREF(exec_ctx, &p->base, "destroy_subchannels");
+
+  for (i = 0; i < num_subchannels; i++) {
+    GRPC_SUBCHANNEL_UNREF(exec_ctx, subchannels[i], "pick_first");
+  }
+
+  gpr_free(subchannels);
+}
+
+static void pf_connectivity_changed(grpc_exec_ctx *exec_ctx, void *arg,
+                                    bool iomgr_success) {
+  pick_first_lb_policy *p = arg;
+  grpc_subchannel *selected_subchannel;
+  pending_pick *pp;
+  grpc_connected_subchannel *selected;
+
+  gpr_mu_lock(&p->mu);
+
+  selected = GET_SELECTED(p);
+
+  if (p->shutdown) {
+    gpr_mu_unlock(&p->mu);
+    GRPC_LB_POLICY_WEAK_UNREF(exec_ctx, &p->base, "pick_first_connectivity");
+    return;
+  } else if (selected != NULL) {
+    if (p->checking_connectivity == GRPC_CHANNEL_TRANSIENT_FAILURE) {
+      /* if the selected channel goes bad, we're done */
+      p->checking_connectivity = GRPC_CHANNEL_FATAL_FAILURE;
+    }
+    grpc_connectivity_state_set(exec_ctx, &p->state_tracker,
+                                p->checking_connectivity, "selected_changed");
+    if (p->checking_connectivity != GRPC_CHANNEL_FATAL_FAILURE) {
+      grpc_connected_subchannel_notify_on_state_change(
+          exec_ctx, selected, p->base.interested_parties,
+          &p->checking_connectivity, &p->connectivity_changed);
+    } else {
+      GRPC_LB_POLICY_WEAK_UNREF(exec_ctx, &p->base, "pick_first_connectivity");
+    }
+  } else {
+  loop:
+    switch (p->checking_connectivity) {
+      case GRPC_CHANNEL_READY:
+        grpc_connectivity_state_set(exec_ctx, &p->state_tracker,
+                                    GRPC_CHANNEL_READY, "connecting_ready");
+        selected_subchannel = p->subchannels[p->checking_subchannel];
+        selected =
+            grpc_subchannel_get_connected_subchannel(selected_subchannel);
+        GPR_ASSERT(selected != NULL);
+        GRPC_CONNECTED_SUBCHANNEL_REF(selected, "picked_first");
+        /* drop the pick list: we are connected now */
+        GRPC_LB_POLICY_WEAK_REF(&p->base, "destroy_subchannels");
+        gpr_atm_rel_store(&p->selected, (gpr_atm)selected);
+        grpc_exec_ctx_enqueue(
+            exec_ctx, grpc_closure_create(destroy_subchannels, p), true, NULL);
+        /* update any calls that were waiting for a pick */
+        while ((pp = p->pending_picks)) {
+          p->pending_picks = pp->next;
+          *pp->target = selected;
+          grpc_pollset_set_del_pollset(exec_ctx, p->base.interested_parties,
+                                       pp->pollset);
+          grpc_exec_ctx_enqueue(exec_ctx, pp->on_complete, true, NULL);
+          gpr_free(pp);
+        }
+        grpc_connected_subchannel_notify_on_state_change(
+            exec_ctx, selected, p->base.interested_parties,
+            &p->checking_connectivity, &p->connectivity_changed);
+        break;
+      case GRPC_CHANNEL_TRANSIENT_FAILURE:
+        grpc_connectivity_state_set(exec_ctx, &p->state_tracker,
+                                    GRPC_CHANNEL_TRANSIENT_FAILURE,
+                                    "connecting_transient_failure");
+        p->checking_subchannel =
+            (p->checking_subchannel + 1) % p->num_subchannels;
+        p->checking_connectivity = grpc_subchannel_check_connectivity(
+            p->subchannels[p->checking_subchannel]);
+        if (p->checking_connectivity == GRPC_CHANNEL_TRANSIENT_FAILURE) {
+          grpc_subchannel_notify_on_state_change(
+              exec_ctx, p->subchannels[p->checking_subchannel],
+              p->base.interested_parties, &p->checking_connectivity,
+              &p->connectivity_changed);
+        } else {
+          goto loop;
+        }
+        break;
+      case GRPC_CHANNEL_CONNECTING:
+      case GRPC_CHANNEL_IDLE:
+        grpc_connectivity_state_set(exec_ctx, &p->state_tracker,
+                                    GRPC_CHANNEL_CONNECTING,
+                                    "connecting_changed");
+        grpc_subchannel_notify_on_state_change(
+            exec_ctx, p->subchannels[p->checking_subchannel],
+            p->base.interested_parties, &p->checking_connectivity,
+            &p->connectivity_changed);
+        break;
+      case GRPC_CHANNEL_FATAL_FAILURE:
+        p->num_subchannels--;
+        GPR_SWAP(grpc_subchannel *, p->subchannels[p->checking_subchannel],
+                 p->subchannels[p->num_subchannels]);
+        GRPC_SUBCHANNEL_UNREF(exec_ctx, p->subchannels[p->num_subchannels],
+                              "pick_first");
+        if (p->num_subchannels == 0) {
+          grpc_connectivity_state_set(exec_ctx, &p->state_tracker,
+                                      GRPC_CHANNEL_FATAL_FAILURE,
+                                      "no_more_channels");
+          while ((pp = p->pending_picks)) {
+            p->pending_picks = pp->next;
+            *pp->target = NULL;
+            grpc_exec_ctx_enqueue(exec_ctx, pp->on_complete, true, NULL);
+            gpr_free(pp);
+          }
+          GRPC_LB_POLICY_WEAK_UNREF(exec_ctx, &p->base,
+                                    "pick_first_connectivity");
+        } else {
+          grpc_connectivity_state_set(exec_ctx, &p->state_tracker,
+                                      GRPC_CHANNEL_TRANSIENT_FAILURE,
+                                      "subchannel_failed");
+          p->checking_subchannel %= p->num_subchannels;
+          p->checking_connectivity = grpc_subchannel_check_connectivity(
+              p->subchannels[p->checking_subchannel]);
+          goto loop;
+        }
+    }
+  }
+
+  gpr_mu_unlock(&p->mu);
+}
+
+static grpc_connectivity_state pf_check_connectivity(grpc_exec_ctx *exec_ctx,
+                                                     grpc_lb_policy *pol) {
+  pick_first_lb_policy *p = (pick_first_lb_policy *)pol;
+  grpc_connectivity_state st;
+  gpr_mu_lock(&p->mu);
+  st = grpc_connectivity_state_check(&p->state_tracker);
+  gpr_mu_unlock(&p->mu);
+  return st;
+}
+
+void pf_notify_on_state_change(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol,
+                               grpc_connectivity_state *current,
+                               grpc_closure *notify) {
+  pick_first_lb_policy *p = (pick_first_lb_policy *)pol;
+  gpr_mu_lock(&p->mu);
+  grpc_connectivity_state_notify_on_state_change(exec_ctx, &p->state_tracker,
+                                                 current, notify);
+  gpr_mu_unlock(&p->mu);
+}
+
+void pf_ping_one(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol,
+                 grpc_closure *closure) {
+  pick_first_lb_policy *p = (pick_first_lb_policy *)pol;
+  grpc_connected_subchannel *selected = GET_SELECTED(p);
+  if (selected) {
+    grpc_connected_subchannel_ping(exec_ctx, selected, closure);
+  } else {
+    grpc_exec_ctx_enqueue(exec_ctx, closure, false, NULL);
+  }
+}
+
+static const grpc_lb_policy_vtable pick_first_lb_policy_vtable = {
+    pf_destroy,
+    pf_shutdown,
+    pf_pick,
+    pf_cancel_pick,
+    pf_ping_one,
+    pf_exit_idle,
+    pf_check_connectivity,
+    pf_notify_on_state_change};
+
+static void pick_first_factory_ref(grpc_lb_policy_factory *factory) {}
+
+static void pick_first_factory_unref(grpc_lb_policy_factory *factory) {}
+
+static grpc_lb_policy *create_pick_first(grpc_lb_policy_factory *factory,
+                                         grpc_lb_policy_args *args) {
+  if (args->num_subchannels == 0) return NULL;
+  pick_first_lb_policy *p = gpr_malloc(sizeof(*p));
+  memset(p, 0, sizeof(*p));
+  grpc_lb_policy_init(&p->base, &pick_first_lb_policy_vtable);
+  p->subchannels =
+      gpr_malloc(sizeof(grpc_subchannel *) * args->num_subchannels);
+  p->num_subchannels = args->num_subchannels;
+  grpc_connectivity_state_init(&p->state_tracker, GRPC_CHANNEL_IDLE,
+                               "pick_first");
+  memcpy(p->subchannels, args->subchannels,
+         sizeof(grpc_subchannel *) * args->num_subchannels);
+  grpc_closure_init(&p->connectivity_changed, pf_connectivity_changed, p);
+  gpr_mu_init(&p->mu);
+  return &p->base;
+}
+
+static const grpc_lb_policy_factory_vtable pick_first_factory_vtable = {
+    pick_first_factory_ref, pick_first_factory_unref, create_pick_first,
+    "pick_first"};
+
+static grpc_lb_policy_factory pick_first_lb_policy_factory = {
+    &pick_first_factory_vtable};
+
+grpc_lb_policy_factory *grpc_pick_first_lb_factory_create() {
+  return &pick_first_lb_policy_factory;
+}
diff --git a/src/core/ext/lb_policy/pick_first/pick_first.h b/src/core/ext/lb_policy/pick_first/pick_first.h
new file mode 100644
index 0000000000..dba86ea7ad
--- /dev/null
+++ b/src/core/ext/lb_policy/pick_first/pick_first.h
@@ -0,0 +1,43 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_CLIENT_CONFIG_LB_POLICIES_PICK_FIRST_H
+#define GRPC_CORE_LIB_CLIENT_CONFIG_LB_POLICIES_PICK_FIRST_H
+
+#include "src/core/lib/client_config/lb_policy_factory.h"
+
+/** Returns a load balancing factory for the pick first policy, which picks up
+ * the first subchannel from \a subchannels to succesfully connect */
+grpc_lb_policy_factory *grpc_pick_first_lb_factory_create();
+
+#endif /* GRPC_CORE_LIB_CLIENT_CONFIG_LB_POLICIES_PICK_FIRST_H */
diff --git a/src/core/ext/lb_policy/round_robin/round_robin.c b/src/core/ext/lb_policy/round_robin/round_robin.c
new file mode 100644
index 0000000000..31056ea138
--- /dev/null
+++ b/src/core/ext/lb_policy/round_robin/round_robin.c
@@ -0,0 +1,542 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include "src/core/ext/lb_policy/round_robin/round_robin.h"
+
+#include <string.h>
+
+#include <grpc/support/alloc.h>
+#include "src/core/lib/transport/connectivity_state.h"
+
+typedef struct round_robin_lb_policy round_robin_lb_policy;
+
+int grpc_lb_round_robin_trace = 0;
+
+/** List of entities waiting for a pick.
+ *
+ * Once a pick is available, \a target is updated and \a on_complete called. */
+typedef struct pending_pick {
+  struct pending_pick *next;
+  grpc_pollset *pollset;
+  grpc_connected_subchannel **target;
+  grpc_closure *on_complete;
+} pending_pick;
+
+/** List of subchannels in a connectivity READY state */
+typedef struct ready_list {
+  grpc_subchannel *subchannel;
+  struct ready_list *next;
+  struct ready_list *prev;
+} ready_list;
+
+typedef struct {
+  /** index within policy->subchannels */
+  size_t index;
+  /** backpointer to owning policy */
+  round_robin_lb_policy *policy;
+  /** subchannel itself */
+  grpc_subchannel *subchannel;
+  /** notification that connectivity has changed on subchannel */
+  grpc_closure connectivity_changed_closure;
+  /** this subchannels current position in subchannel->ready_list */
+  ready_list *ready_list_node;
+  /** last observed connectivity */
+  grpc_connectivity_state connectivity_state;
+} subchannel_data;
+
+struct round_robin_lb_policy {
+  /** base policy: must be first */
+  grpc_lb_policy base;
+
+  /** all our subchannels */
+  size_t num_subchannels;
+  subchannel_data **subchannels;
+
+  /** mutex protecting remaining members */
+  gpr_mu mu;
+  /** have we started picking? */
+  int started_picking;
+  /** are we shutting down? */
+  int shutdown;
+  /** List of picks that are waiting on connectivity */
+  pending_pick *pending_picks;
+
+  /** our connectivity state tracker */
+  grpc_connectivity_state_tracker state_tracker;
+
+  /** (Dummy) root of the doubly linked list containing READY subchannels */
+  ready_list ready_list;
+  /** Last pick from the ready list. */
+  ready_list *ready_list_last_pick;
+};
+
+/** Returns the next subchannel from the connected list or NULL if the list is
+ * empty.
+ *
+ * Note that this function does *not* advance p->ready_list_last_pick. Use \a
+ * advance_last_picked_locked() for that. */
+static ready_list *peek_next_connected_locked(const round_robin_lb_policy *p) {
+  ready_list *selected;
+  selected = p->ready_list_last_pick->next;
+
+  while (selected != NULL) {
+    if (selected == &p->ready_list) {
+      GPR_ASSERT(selected->subchannel == NULL);
+      /* skip dummy root */
+      selected = selected->next;
+    } else {
+      GPR_ASSERT(selected->subchannel != NULL);
+      return selected;
+    }
+  }
+  return NULL;
+}
+
+/** Advance the \a ready_list picking head. */
+static void advance_last_picked_locked(round_robin_lb_policy *p) {
+  if (p->ready_list_last_pick->next != NULL) { /* non-empty list */
+    p->ready_list_last_pick = p->ready_list_last_pick->next;
+    if (p->ready_list_last_pick == &p->ready_list) {
+      /* skip dummy root */
+      p->ready_list_last_pick = p->ready_list_last_pick->next;
+    }
+  } else { /* should be an empty list */
+    GPR_ASSERT(p->ready_list_last_pick == &p->ready_list);
+  }
+
+  if (grpc_lb_round_robin_trace) {
+    gpr_log(GPR_DEBUG, "[READYLIST] ADVANCED LAST PICK. NOW AT NODE %p (SC %p)",
+            p->ready_list_last_pick, p->ready_list_last_pick->subchannel);
+  }
+}
+
+/** Prepends (relative to the root at p->ready_list) the connected subchannel \a
+ * csc to the list of ready subchannels. */
+static ready_list *add_connected_sc_locked(round_robin_lb_policy *p,
+                                           grpc_subchannel *sc) {
+  ready_list *new_elem = gpr_malloc(sizeof(ready_list));
+  new_elem->subchannel = sc;
+  if (p->ready_list.prev == NULL) {
+    /* first element */
+    new_elem->next = &p->ready_list;
+    new_elem->prev = &p->ready_list;
+    p->ready_list.next = new_elem;
+    p->ready_list.prev = new_elem;
+  } else {
+    new_elem->next = &p->ready_list;
+    new_elem->prev = p->ready_list.prev;
+    p->ready_list.prev->next = new_elem;
+    p->ready_list.prev = new_elem;
+  }
+  if (grpc_lb_round_robin_trace) {
+    gpr_log(GPR_DEBUG, "[READYLIST] ADDING NODE %p (SC %p)", new_elem, sc);
+  }
+  return new_elem;
+}
+
+/** Removes \a node from the list of connected subchannels */
+static void remove_disconnected_sc_locked(round_robin_lb_policy *p,
+                                          ready_list *node) {
+  if (node == NULL) {
+    return;
+  }
+  if (node == p->ready_list_last_pick) {
+    /* If removing the lastly picked node, reset the last pick pointer to the
+     * dummy root of the list */
+    p->ready_list_last_pick = &p->ready_list;
+  }
+
+  /* removing last item */
+  if (node->next == &p->ready_list && node->prev == &p->ready_list) {
+    GPR_ASSERT(p->ready_list.next == node);
+    GPR_ASSERT(p->ready_list.prev == node);
+    p->ready_list.next = NULL;
+    p->ready_list.prev = NULL;
+  } else {
+    node->prev->next = node->next;
+    node->next->prev = node->prev;
+  }
+
+  if (grpc_lb_round_robin_trace) {
+    gpr_log(GPR_DEBUG, "[READYLIST] REMOVED NODE %p (SC %p)", node,
+            node->subchannel);
+  }
+
+  node->next = NULL;
+  node->prev = NULL;
+  node->subchannel = NULL;
+
+  gpr_free(node);
+}
+
+void rr_destroy(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol) {
+  round_robin_lb_policy *p = (round_robin_lb_policy *)pol;
+  size_t i;
+  ready_list *elem;
+  for (i = 0; i < p->num_subchannels; i++) {
+    subchannel_data *sd = p->subchannels[i];
+    GRPC_SUBCHANNEL_UNREF(exec_ctx, sd->subchannel, "round_robin");
+    gpr_free(sd);
+  }
+
+  grpc_connectivity_state_destroy(exec_ctx, &p->state_tracker);
+  gpr_free(p->subchannels);
+  gpr_mu_destroy(&p->mu);
+
+  elem = p->ready_list.next;
+  while (elem != NULL && elem != &p->ready_list) {
+    ready_list *tmp;
+    tmp = elem->next;
+    elem->next = NULL;
+    elem->prev = NULL;
+    elem->subchannel = NULL;
+    gpr_free(elem);
+    elem = tmp;
+  }
+  gpr_free(p);
+}
+
+void rr_shutdown(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol) {
+  round_robin_lb_policy *p = (round_robin_lb_policy *)pol;
+  pending_pick *pp;
+  size_t i;
+
+  gpr_mu_lock(&p->mu);
+
+  p->shutdown = 1;
+  while ((pp = p->pending_picks)) {
+    p->pending_picks = pp->next;
+    *pp->target = NULL;
+    grpc_exec_ctx_enqueue(exec_ctx, pp->on_complete, false, NULL);
+    gpr_free(pp);
+  }
+  grpc_connectivity_state_set(exec_ctx, &p->state_tracker,
+                              GRPC_CHANNEL_FATAL_FAILURE, "shutdown");
+  for (i = 0; i < p->num_subchannels; i++) {
+    subchannel_data *sd = p->subchannels[i];
+    grpc_subchannel_notify_on_state_change(exec_ctx, sd->subchannel, NULL, NULL,
+                                           &sd->connectivity_changed_closure);
+  }
+  gpr_mu_unlock(&p->mu);
+}
+
+static void rr_cancel_pick(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol,
+                           grpc_connected_subchannel **target) {
+  round_robin_lb_policy *p = (round_robin_lb_policy *)pol;
+  pending_pick *pp;
+  gpr_mu_lock(&p->mu);
+  pp = p->pending_picks;
+  p->pending_picks = NULL;
+  while (pp != NULL) {
+    pending_pick *next = pp->next;
+    if (pp->target == target) {
+      grpc_pollset_set_del_pollset(exec_ctx, p->base.interested_parties,
+                                   pp->pollset);
+      *target = NULL;
+      grpc_exec_ctx_enqueue(exec_ctx, pp->on_complete, false, NULL);
+      gpr_free(pp);
+    } else {
+      pp->next = p->pending_picks;
+      p->pending_picks = pp;
+    }
+    pp = next;
+  }
+  gpr_mu_unlock(&p->mu);
+}
+
+static void start_picking(grpc_exec_ctx *exec_ctx, round_robin_lb_policy *p) {
+  size_t i;
+  p->started_picking = 1;
+
+  gpr_log(GPR_DEBUG, "LB_POLICY: p=%p num_subchannels=%d", p,
+          p->num_subchannels);
+
+  for (i = 0; i < p->num_subchannels; i++) {
+    subchannel_data *sd = p->subchannels[i];
+    sd->connectivity_state = GRPC_CHANNEL_IDLE;
+    grpc_subchannel_notify_on_state_change(
+        exec_ctx, sd->subchannel, p->base.interested_parties,
+        &sd->connectivity_state, &sd->connectivity_changed_closure);
+    GRPC_LB_POLICY_WEAK_REF(&p->base, "round_robin_connectivity");
+  }
+}
+
+void rr_exit_idle(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol) {
+  round_robin_lb_policy *p = (round_robin_lb_policy *)pol;
+  gpr_mu_lock(&p->mu);
+  if (!p->started_picking) {
+    start_picking(exec_ctx, p);
+  }
+  gpr_mu_unlock(&p->mu);
+}
+
+int rr_pick(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol, grpc_pollset *pollset,
+            grpc_metadata_batch *initial_metadata,
+            grpc_connected_subchannel **target, grpc_closure *on_complete) {
+  round_robin_lb_policy *p = (round_robin_lb_policy *)pol;
+  pending_pick *pp;
+  ready_list *selected;
+  gpr_mu_lock(&p->mu);
+  if ((selected = peek_next_connected_locked(p))) {
+    gpr_mu_unlock(&p->mu);
+    *target = grpc_subchannel_get_connected_subchannel(selected->subchannel);
+    if (grpc_lb_round_robin_trace) {
+      gpr_log(GPR_DEBUG,
+              "[RR PICK] TARGET <-- CONNECTED SUBCHANNEL %p (NODE %p)",
+              selected->subchannel, selected);
+    }
+    /* only advance the last picked pointer if the selection was used */
+    advance_last_picked_locked(p);
+    return 1;
+  } else {
+    if (!p->started_picking) {
+      start_picking(exec_ctx, p);
+    }
+    grpc_pollset_set_add_pollset(exec_ctx, p->base.interested_parties, pollset);
+    pp = gpr_malloc(sizeof(*pp));
+    pp->next = p->pending_picks;
+    pp->pollset = pollset;
+    pp->target = target;
+    pp->on_complete = on_complete;
+    p->pending_picks = pp;
+    gpr_mu_unlock(&p->mu);
+    return 0;
+  }
+}
+
+static void rr_connectivity_changed(grpc_exec_ctx *exec_ctx, void *arg,
+                                    bool iomgr_success) {
+  subchannel_data *sd = arg;
+  round_robin_lb_policy *p = sd->policy;
+  pending_pick *pp;
+  ready_list *selected;
+
+  int unref = 0;
+
+  gpr_mu_lock(&p->mu);
+
+  if (p->shutdown) {
+    unref = 1;
+  } else {
+    switch (sd->connectivity_state) {
+      case GRPC_CHANNEL_READY:
+        grpc_connectivity_state_set(exec_ctx, &p->state_tracker,
+                                    GRPC_CHANNEL_READY, "connecting_ready");
+        /* add the newly connected subchannel to the list of connected ones.
+         * Note that it goes to the "end of the line". */
+        sd->ready_list_node = add_connected_sc_locked(p, sd->subchannel);
+        /* at this point we know there's at least one suitable subchannel. Go
+         * ahead and pick one and notify the pending suitors in
+         * p->pending_picks. This preemtively replicates rr_pick()'s actions. */
+        selected = peek_next_connected_locked(p);
+        if (p->pending_picks != NULL) {
+          /* if the selected subchannel is going to be used for the pending
+           * picks, update the last picked pointer */
+          advance_last_picked_locked(p);
+        }
+        while ((pp = p->pending_picks)) {
+          p->pending_picks = pp->next;
+          *pp->target =
+              grpc_subchannel_get_connected_subchannel(selected->subchannel);
+          if (grpc_lb_round_robin_trace) {
+            gpr_log(GPR_DEBUG,
+                    "[RR CONN CHANGED] TARGET <-- SUBCHANNEL %p (NODE %p)",
+                    selected->subchannel, selected);
+          }
+          grpc_pollset_set_del_pollset(exec_ctx, p->base.interested_parties,
+                                       pp->pollset);
+          grpc_exec_ctx_enqueue(exec_ctx, pp->on_complete, true, NULL);
+          gpr_free(pp);
+        }
+        grpc_subchannel_notify_on_state_change(
+            exec_ctx, sd->subchannel, p->base.interested_parties,
+            &sd->connectivity_state, &sd->connectivity_changed_closure);
+        break;
+      case GRPC_CHANNEL_CONNECTING:
+      case GRPC_CHANNEL_IDLE:
+        grpc_connectivity_state_set(exec_ctx, &p->state_tracker,
+                                    sd->connectivity_state,
+                                    "connecting_changed");
+        grpc_subchannel_notify_on_state_change(
+            exec_ctx, sd->subchannel, p->base.interested_parties,
+            &sd->connectivity_state, &sd->connectivity_changed_closure);
+        break;
+      case GRPC_CHANNEL_TRANSIENT_FAILURE:
+        /* renew state notification */
+        grpc_subchannel_notify_on_state_change(
+            exec_ctx, sd->subchannel, p->base.interested_parties,
+            &sd->connectivity_state, &sd->connectivity_changed_closure);
+
+        /* remove from ready list if still present */
+        if (sd->ready_list_node != NULL) {
+          remove_disconnected_sc_locked(p, sd->ready_list_node);
+          sd->ready_list_node = NULL;
+        }
+        grpc_connectivity_state_set(exec_ctx, &p->state_tracker,
+                                    GRPC_CHANNEL_TRANSIENT_FAILURE,
+                                    "connecting_transient_failure");
+        break;
+      case GRPC_CHANNEL_FATAL_FAILURE:
+        if (sd->ready_list_node != NULL) {
+          remove_disconnected_sc_locked(p, sd->ready_list_node);
+          sd->ready_list_node = NULL;
+        }
+
+        p->num_subchannels--;
+        GPR_SWAP(subchannel_data *, p->subchannels[sd->index],
+                 p->subchannels[p->num_subchannels]);
+        GRPC_SUBCHANNEL_UNREF(exec_ctx, sd->subchannel, "round_robin");
+        p->subchannels[sd->index]->index = sd->index;
+        gpr_free(sd);
+
+        unref = 1;
+        if (p->num_subchannels == 0) {
+          grpc_connectivity_state_set(exec_ctx, &p->state_tracker,
+                                      GRPC_CHANNEL_FATAL_FAILURE,
+                                      "no_more_channels");
+          while ((pp = p->pending_picks)) {
+            p->pending_picks = pp->next;
+            *pp->target = NULL;
+            grpc_exec_ctx_enqueue(exec_ctx, pp->on_complete, true, NULL);
+            gpr_free(pp);
+          }
+        } else {
+          grpc_connectivity_state_set(exec_ctx, &p->state_tracker,
+                                      GRPC_CHANNEL_TRANSIENT_FAILURE,
+                                      "subchannel_failed");
+        }
+    } /* switch */
+  }   /* !unref */
+
+  gpr_mu_unlock(&p->mu);
+
+  if (unref) {
+    GRPC_LB_POLICY_WEAK_UNREF(exec_ctx, &p->base, "round_robin_connectivity");
+  }
+}
+
+static grpc_connectivity_state rr_check_connectivity(grpc_exec_ctx *exec_ctx,
+                                                     grpc_lb_policy *pol) {
+  round_robin_lb_policy *p = (round_robin_lb_policy *)pol;
+  grpc_connectivity_state st;
+  gpr_mu_lock(&p->mu);
+  st = grpc_connectivity_state_check(&p->state_tracker);
+  gpr_mu_unlock(&p->mu);
+  return st;
+}
+
+static void rr_notify_on_state_change(grpc_exec_ctx *exec_ctx,
+                                      grpc_lb_policy *pol,
+                                      grpc_connectivity_state *current,
+                                      grpc_closure *notify) {
+  round_robin_lb_policy *p = (round_robin_lb_policy *)pol;
+  gpr_mu_lock(&p->mu);
+  grpc_connectivity_state_notify_on_state_change(exec_ctx, &p->state_tracker,
+                                                 current, notify);
+  gpr_mu_unlock(&p->mu);
+}
+
+static void rr_ping_one(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol,
+                        grpc_closure *closure) {
+  round_robin_lb_policy *p = (round_robin_lb_policy *)pol;
+  ready_list *selected;
+  grpc_connected_subchannel *target;
+  gpr_mu_lock(&p->mu);
+  if ((selected = peek_next_connected_locked(p))) {
+    gpr_mu_unlock(&p->mu);
+    target = grpc_subchannel_get_connected_subchannel(selected->subchannel);
+    grpc_connected_subchannel_ping(exec_ctx, target, closure);
+  } else {
+    gpr_mu_unlock(&p->mu);
+    grpc_exec_ctx_enqueue(exec_ctx, closure, false, NULL);
+  }
+}
+
+static const grpc_lb_policy_vtable round_robin_lb_policy_vtable = {
+    rr_destroy,
+    rr_shutdown,
+    rr_pick,
+    rr_cancel_pick,
+    rr_ping_one,
+    rr_exit_idle,
+    rr_check_connectivity,
+    rr_notify_on_state_change};
+
+static void round_robin_factory_ref(grpc_lb_policy_factory *factory) {}
+
+static void round_robin_factory_unref(grpc_lb_policy_factory *factory) {}
+
+static grpc_lb_policy *create_round_robin(grpc_lb_policy_factory *factory,
+                                          grpc_lb_policy_args *args) {
+  size_t i;
+  round_robin_lb_policy *p = gpr_malloc(sizeof(*p));
+  GPR_ASSERT(args->num_subchannels > 0);
+  memset(p, 0, sizeof(*p));
+  grpc_lb_policy_init(&p->base, &round_robin_lb_policy_vtable);
+  p->num_subchannels = args->num_subchannels;
+  p->subchannels = gpr_malloc(sizeof(*p->subchannels) * p->num_subchannels);
+  memset(p->subchannels, 0, sizeof(*p->subchannels) * p->num_subchannels);
+  grpc_connectivity_state_init(&p->state_tracker, GRPC_CHANNEL_IDLE,
+                               "round_robin");
+
+  gpr_mu_init(&p->mu);
+  for (i = 0; i < args->num_subchannels; i++) {
+    subchannel_data *sd = gpr_malloc(sizeof(*sd));
+    memset(sd, 0, sizeof(*sd));
+    p->subchannels[i] = sd;
+    sd->policy = p;
+    sd->index = i;
+    sd->subchannel = args->subchannels[i];
+    grpc_closure_init(&sd->connectivity_changed_closure,
+                      rr_connectivity_changed, sd);
+  }
+
+  /* The (dummy node) root of the ready list */
+  p->ready_list.subchannel = NULL;
+  p->ready_list.prev = NULL;
+  p->ready_list.next = NULL;
+  p->ready_list_last_pick = &p->ready_list;
+
+  return &p->base;
+}
+
+static const grpc_lb_policy_factory_vtable round_robin_factory_vtable = {
+    round_robin_factory_ref, round_robin_factory_unref, create_round_robin,
+    "round_robin"};
+
+static grpc_lb_policy_factory round_robin_lb_policy_factory = {
+    &round_robin_factory_vtable};
+
+grpc_lb_policy_factory *grpc_round_robin_lb_factory_create() {
+  return &round_robin_lb_policy_factory;
+}
diff --git a/src/core/ext/lb_policy/round_robin/round_robin.h b/src/core/ext/lb_policy/round_robin/round_robin.h
new file mode 100644
index 0000000000..52db1caa0c
--- /dev/null
+++ b/src/core/ext/lb_policy/round_robin/round_robin.h
@@ -0,0 +1,46 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_CLIENT_CONFIG_LB_POLICIES_ROUND_ROBIN_H
+#define GRPC_CORE_LIB_CLIENT_CONFIG_LB_POLICIES_ROUND_ROBIN_H
+
+#include "src/core/lib/client_config/lb_policy.h"
+
+extern int grpc_lb_round_robin_trace;
+
+#include "src/core/lib/client_config/lb_policy_factory.h"
+
+/** Returns a load balancing factory for the round robin policy */
+grpc_lb_policy_factory *grpc_round_robin_lb_factory_create();
+
+#endif /* GRPC_CORE_LIB_CLIENT_CONFIG_LB_POLICIES_ROUND_ROBIN_H */