src/core/lib/surface/channel.cc - platform/external/grpc-grpc - Git at Google

 /*
  *
  * Copyright 2015 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/port_platform.h>

 #include "src/core/lib/surface/channel.h"

 #include <inttypes.h>
 #include <string.h>

 #include <algorithm>
 #include <atomic>
 #include <functional>
 #include <memory>

 #include "absl/status/status.h"

 #include <grpc/compression.h>
 #include <grpc/grpc.h>
 #include <grpc/impl/codegen/gpr_types.h>
 #include <grpc/support/alloc.h>
 #include <grpc/support/log.h>

 #include "src/core/lib/channel/channel_args.h"
 #include "src/core/lib/channel/channel_stack.h"
 #include "src/core/lib/channel/channel_stack_builder_impl.h"
 #include "src/core/lib/channel/channel_trace.h"
 #include "src/core/lib/channel/channelz.h"
 #include "src/core/lib/config/core_configuration.h"
 #include "src/core/lib/debug/stats.h"
 #include "src/core/lib/debug/stats_data.h"
 #include "src/core/lib/debug/trace.h"
 #include "src/core/lib/gpr/useful.h"
 #include "src/core/lib/gprpp/manual_constructor.h"
 #include "src/core/lib/gprpp/ref_counted_ptr.h"
 #include "src/core/lib/iomgr/error.h"
 #include "src/core/lib/iomgr/exec_ctx.h"
 #include "src/core/lib/resource_quota/memory_quota.h"
 #include "src/core/lib/resource_quota/resource_quota.h"
 #include "src/core/lib/surface/api_trace.h"
 #include "src/core/lib/surface/call.h"
 #include "src/core/lib/surface/channel_init.h"
 #include "src/core/lib/surface/channel_stack_type.h"
 #include "src/core/lib/surface/init_internally.h"
 #include "src/core/lib/transport/transport.h"

 // IWYU pragma: no_include <type_traits>

 namespace grpc_core {

 Channel::Channel(bool is_client, bool is_promising, std::string target,
                  const ChannelArgs& channel_args,
                  grpc_compression_options compression_options,
                  RefCountedPtr<grpc_channel_stack> channel_stack)
     : is_client_(is_client),
       is_promising_(is_promising),
       compression_options_(compression_options),
       call_size_estimate_(channel_stack->call_stack_size +
                           grpc_call_get_initial_size_estimate()),
       channelz_node_(channel_args.GetObjectRef<channelz::ChannelNode>()),
       allocator_(channel_args.GetObject<ResourceQuota>()
                      ->memory_quota()
                      ->CreateMemoryOwner(target)),
       target_(std::move(target)),
       channel_stack_(std::move(channel_stack)) {
   // We need to make sure that grpc_shutdown() does not shut things down
   // until after the channel is destroyed.  However, the channel may not
   // actually be destroyed by the time grpc_channel_destroy() returns,
   // since there may be other existing refs to the channel.  If those
   // refs are held by things that are visible to the wrapped language
   // (such as outstanding calls on the channel), then the wrapped
   // language can be responsible for making sure that grpc_shutdown()
   // does not run until after those refs are released.  However, the
   // channel may also have refs to itself held internally for various
   // things that need to be cleaned up at channel destruction (e.g.,
   // LB policies, subchannels, etc), and because these refs are not
   // visible to the wrapped language, it cannot be responsible for
   // deferring grpc_shutdown() until after they are released.  To
   // accommodate that, we call grpc_init() here and then call
   // grpc_shutdown() when the channel is actually destroyed, thus
   // ensuring that shutdown is deferred until that point.
   InitInternally();
   auto channelz_node = channelz_node_;
   *channel_stack_->on_destroy = [channelz_node]() {
     if (channelz_node != nullptr) {
       channelz_node->AddTraceEvent(
           channelz::ChannelTrace::Severity::Info,
           grpc_slice_from_static_string("Channel destroyed"));
     }
     ShutdownInternally();
   };
 }

 absl::StatusOr<RefCountedPtr<Channel>> Channel::CreateWithBuilder(
     ChannelStackBuilder* builder) {
   auto channel_args = builder->channel_args();
   if (builder->channel_stack_type() == GRPC_SERVER_CHANNEL) {
     global_stats().IncrementServerChannelsCreated();
   } else {
     global_stats().IncrementClientChannelsCreated();
   }
   absl::StatusOr<RefCountedPtr<grpc_channel_stack>> r = builder->Build();
   if (!r.ok()) {
     auto status = r.status();
     gpr_log(GPR_ERROR, "channel stack builder failed: %s",
             status.ToString().c_str());
     return status;
   }

   grpc_compression_options compression_options;
   grpc_compression_options_init(&compression_options);
   auto default_level =
       channel_args.GetInt(GRPC_COMPRESSION_CHANNEL_DEFAULT_LEVEL);
   if (default_level.has_value()) {
     compression_options.default_level.is_set = true;
     compression_options.default_level.level = Clamp(
         static_cast<grpc_compression_level>(*default_level),
         GRPC_COMPRESS_LEVEL_NONE,
         static_cast<grpc_compression_level>(GRPC_COMPRESS_LEVEL_COUNT - 1));
   }
   auto default_algorithm =
       channel_args.GetInt(GRPC_COMPRESSION_CHANNEL_DEFAULT_ALGORITHM);
   if (default_algorithm.has_value()) {
     compression_options.default_algorithm.is_set = true;
     compression_options.default_algorithm.algorithm =
         Clamp(static_cast<grpc_compression_algorithm>(*default_algorithm),
               GRPC_COMPRESS_NONE,
               static_cast<grpc_compression_algorithm>(
                   GRPC_COMPRESS_ALGORITHMS_COUNT - 1));
   }
   auto enabled_algorithms_bitset =
       channel_args.GetInt(GRPC_COMPRESSION_CHANNEL_ENABLED_ALGORITHMS_BITSET);
   if (enabled_algorithms_bitset.has_value()) {
     compression_options.enabled_algorithms_bitset =
         *enabled_algorithms_bitset | 1 /* always support no compression */;
   }

   return RefCountedPtr<Channel>(new Channel(
       grpc_channel_stack_type_is_client(builder->channel_stack_type()),
       builder->IsPromising(), std::string(builder->target()), channel_args,
       compression_options, std::move(*r)));
 }

 namespace {

 void* channelz_node_copy(void* p) {
   channelz::ChannelNode* node = static_cast<channelz::ChannelNode*>(p);
   node->Ref().release();
   return p;
 }
 void channelz_node_destroy(void* p) {
   channelz::ChannelNode* node = static_cast<channelz::ChannelNode*>(p);
   node->Unref();
 }
 int channelz_node_cmp(void* p1, void* p2) { return QsortCompare(p1, p2); }
 const grpc_arg_pointer_vtable channelz_node_arg_vtable = {
     channelz_node_copy, channelz_node_destroy, channelz_node_cmp};

 void CreateChannelzNode(ChannelStackBuilder* builder) {
   auto args = builder->channel_args();
   // Check whether channelz is enabled.
   const bool channelz_enabled = args.GetBool(GRPC_ARG_ENABLE_CHANNELZ)
                                     .value_or(GRPC_ENABLE_CHANNELZ_DEFAULT);
   if (!channelz_enabled) return;
   // Get parameters needed to create the channelz node.
   const size_t channel_tracer_max_memory = std::max(
       0, args.GetInt(GRPC_ARG_MAX_CHANNEL_TRACE_EVENT_MEMORY_PER_NODE)
              .value_or(GRPC_MAX_CHANNEL_TRACE_EVENT_MEMORY_PER_NODE_DEFAULT));
   const bool is_internal_channel =
       args.GetBool(GRPC_ARG_CHANNELZ_IS_INTERNAL_CHANNEL).value_or(false);
   // Create the channelz node.
   std::string target(builder->target());
   RefCountedPtr<channelz::ChannelNode> channelz_node =
       MakeRefCounted<channelz::ChannelNode>(
           target.c_str(), channel_tracer_max_memory, is_internal_channel);
   channelz_node->AddTraceEvent(
       channelz::ChannelTrace::Severity::Info,
       grpc_slice_from_static_string("Channel created"));
   // Add channelz node to channel args.
   // We remove the is_internal_channel arg, since we no longer need it.
   builder->SetChannelArgs(
       args.Remove(GRPC_ARG_CHANNELZ_IS_INTERNAL_CHANNEL)
           .Set(GRPC_ARG_CHANNELZ_CHANNEL_NODE,
                ChannelArgs::Pointer(channelz_node.release(),
                                     &channelz_node_arg_vtable)));
 }

 }  // namespace

 absl::StatusOr<RefCountedPtr<Channel>> Channel::Create(
     const char* target, ChannelArgs args,
     grpc_channel_stack_type channel_stack_type,
     grpc_transport* optional_transport) {
   ChannelStackBuilderImpl builder(
       grpc_channel_stack_type_string(channel_stack_type), channel_stack_type);
   if (!args.GetString(GRPC_ARG_DEFAULT_AUTHORITY).has_value()) {
     auto ssl_override = args.GetString(GRPC_SSL_TARGET_NAME_OVERRIDE_ARG);
     if (ssl_override.has_value()) {
       args = args.Set(GRPC_ARG_DEFAULT_AUTHORITY,
                       std::string(ssl_override.value()));
     }
   }
   if (grpc_channel_stack_type_is_client(channel_stack_type)) {
     auto channel_args_mutator =
         grpc_channel_args_get_client_channel_creation_mutator();
     if (channel_args_mutator != nullptr) {
       args = channel_args_mutator(target, args, channel_stack_type);
     }
   }
   builder.SetChannelArgs(args).SetTarget(target).SetTransport(
       optional_transport);
   if (!CoreConfiguration::Get().channel_init().CreateStack(&builder)) {
     return nullptr;
   }
   // We only need to do this for clients here. For servers, this will be
   // done in src/core/lib/surface/server.cc.
   if (grpc_channel_stack_type_is_client(channel_stack_type)) {
     CreateChannelzNode(&builder);
   }
   return CreateWithBuilder(&builder);
 }

 void Channel::UpdateCallSizeEstimate(size_t size) {
   size_t cur = call_size_estimate_.load(std::memory_order_relaxed);
   if (cur < size) {
     // size grew: update estimate
     call_size_estimate_.compare_exchange_weak(
         cur, size, std::memory_order_relaxed, std::memory_order_relaxed);
     // if we lose: never mind, something else will likely update soon enough
   } else if (cur == size) {
     // no change: holding pattern
   } else if (cur > 0) {
     // size shrank: decrease estimate
     call_size_estimate_.compare_exchange_weak(
         cur, std::min(cur - 1, (255 * cur + size) / 256),
         std::memory_order_relaxed, std::memory_order_relaxed);
     // if we lose: never mind, something else will likely update soon enough
   }
 }

 }  // namespace grpc_core

 char* grpc_channel_get_target(grpc_channel* channel) {
   GRPC_API_TRACE("grpc_channel_get_target(channel=%p)", 1, (channel));
   auto target = grpc_core::Channel::FromC(channel)->target();
   char* buffer = static_cast<char*>(gpr_zalloc(target.size() + 1));
   memcpy(buffer, target.data(), target.size());
   return buffer;
 }

 void grpc_channel_get_info(grpc_channel* channel,
                            const grpc_channel_info* channel_info) {
   grpc_core::ApplicationCallbackExecCtx callback_exec_ctx;
   grpc_core::ExecCtx exec_ctx;
   grpc_channel_element* elem = grpc_channel_stack_element(
       grpc_core::Channel::FromC(channel)->channel_stack(), 0);
   elem->filter->get_channel_info(elem, channel_info);
 }

 void grpc_channel_reset_connect_backoff(grpc_channel* channel) {
   grpc_core::ApplicationCallbackExecCtx callback_exec_ctx;
   grpc_core::ExecCtx exec_ctx;
   GRPC_API_TRACE("grpc_channel_reset_connect_backoff(channel=%p)", 1,
                  (channel));
   grpc_transport_op* op = grpc_make_transport_op(nullptr);
   op->reset_connect_backoff = true;
   grpc_channel_element* elem = grpc_channel_stack_element(
       grpc_core::Channel::FromC(channel)->channel_stack(), 0);
   elem->filter->start_transport_op(elem, op);
 }

 static grpc_call* grpc_channel_create_call_internal(
     grpc_channel* c_channel, grpc_call* parent_call, uint32_t propagation_mask,
     grpc_completion_queue* cq, grpc_pollset_set* pollset_set_alternative,
     grpc_core::Slice path, absl::optional<grpc_core::Slice> authority,
     grpc_core::Timestamp deadline) {
   auto channel = grpc_core::Channel::FromC(c_channel)->Ref();
   GPR_ASSERT(channel->is_client());
   GPR_ASSERT(!(cq != nullptr && pollset_set_alternative != nullptr));

   grpc_call_create_args args;
   args.channel = std::move(channel);
   args.server = nullptr;
   args.parent = parent_call;
   args.propagation_mask = propagation_mask;
   args.cq = cq;
   args.pollset_set_alternative = pollset_set_alternative;
   args.server_transport_data = nullptr;
   args.path = std::move(path);
   args.authority = std::move(authority);
   args.send_deadline = deadline;

   grpc_call* call;
   GRPC_LOG_IF_ERROR("call_create", grpc_call_create(&args, &call));
   return call;
 }

 grpc_call* grpc_channel_create_call(grpc_channel* channel,
                                     grpc_call* parent_call,
                                     uint32_t propagation_mask,
                                     grpc_completion_queue* completion_queue,
                                     grpc_slice method, const grpc_slice* host,
                                     gpr_timespec deadline, void* reserved) {
   GPR_ASSERT(!reserved);
   grpc_core::ApplicationCallbackExecCtx callback_exec_ctx;
   grpc_core::ExecCtx exec_ctx;
   grpc_call* call = grpc_channel_create_call_internal(
       channel, parent_call, propagation_mask, completion_queue, nullptr,
       grpc_core::Slice(grpc_core::CSliceRef(method)),
       host != nullptr
           ? absl::optional<grpc_core::Slice>(grpc_core::CSliceRef(*host))
           : absl::nullopt,
       grpc_core::Timestamp::FromTimespecRoundUp(deadline));

   return call;
 }

 grpc_call* grpc_channel_create_pollset_set_call(
     grpc_channel* channel, grpc_call* parent_call, uint32_t propagation_mask,
     grpc_pollset_set* pollset_set, const grpc_slice& method,
     const grpc_slice* host, grpc_core::Timestamp deadline, void* reserved) {
   GPR_ASSERT(!reserved);
   return grpc_channel_create_call_internal(
       channel, parent_call, propagation_mask, nullptr, pollset_set,
       grpc_core::Slice(method),
       host != nullptr
           ? absl::optional<grpc_core::Slice>(grpc_core::CSliceRef(*host))
           : absl::nullopt,
       deadline);
 }

 namespace grpc_core {

 RegisteredCall::RegisteredCall(const char* method_arg, const char* host_arg) {
   path = Slice::FromCopiedString(method_arg);
   if (host_arg != nullptr && host_arg[0] != 0) {
     authority = Slice::FromCopiedString(host_arg);
   }
 }

 RegisteredCall::RegisteredCall(const RegisteredCall& other)
     : path(other.path.Ref()) {
   if (other.authority.has_value()) {
     authority = other.authority->Ref();
   }
 }

 RegisteredCall::~RegisteredCall() {}

 }  // namespace grpc_core

 void* grpc_channel_register_call(grpc_channel* channel, const char* method,
                                  const char* host, void* reserved) {
   GRPC_API_TRACE(
       "grpc_channel_register_call(channel=%p, method=%s, host=%s, reserved=%p)",
       4, (channel, method, host, reserved));
   GPR_ASSERT(!reserved);
   grpc_core::ApplicationCallbackExecCtx callback_exec_ctx;
   grpc_core::ExecCtx exec_ctx;
   return grpc_core::Channel::FromC(channel)->RegisterCall(method, host);
 }

 namespace grpc_core {

 RegisteredCall* Channel::RegisterCall(const char* method, const char* host) {
   MutexLock lock(&registration_table_.mu);
   registration_table_.method_registration_attempts++;
   auto key = std::make_pair(std::string(host != nullptr ? host : ""),
                             std::string(method != nullptr ? method : ""));
   auto rc_posn = registration_table_.map.find(key);
   if (rc_posn != registration_table_.map.end()) {
     return &rc_posn->second;
   }
   auto insertion_result = registration_table_.map.insert(
       {std::move(key), RegisteredCall(method, host)});
   return &insertion_result.first->second;
 }

 }  // namespace grpc_core

 grpc_call* grpc_channel_create_registered_call(
     grpc_channel* channel, grpc_call* parent_call, uint32_t propagation_mask,
     grpc_completion_queue* completion_queue, void* registered_call_handle,
     gpr_timespec deadline, void* reserved) {
   grpc_core::RegisteredCall* rc =
       static_cast<grpc_core::RegisteredCall*>(registered_call_handle);
   GRPC_API_TRACE(
       "grpc_channel_create_registered_call("
       "channel=%p, parent_call=%p, propagation_mask=%x, completion_queue=%p, "
       "registered_call_handle=%p, "
       "deadline=gpr_timespec { tv_sec: %" PRId64
       ", tv_nsec: %d, clock_type: %d }, "
       "reserved=%p)",
       9,
       (channel, parent_call, (unsigned)propagation_mask, completion_queue,
        registered_call_handle, deadline.tv_sec, deadline.tv_nsec,
        (int)deadline.clock_type, reserved));
   GPR_ASSERT(!reserved);
   grpc_core::ApplicationCallbackExecCtx callback_exec_ctx;
   grpc_core::ExecCtx exec_ctx;
   grpc_call* call = grpc_channel_create_call_internal(
       channel, parent_call, propagation_mask, completion_queue, nullptr,
       rc->path.Ref(),
       rc->authority.has_value()
           ? absl::optional<grpc_core::Slice>(rc->authority->Ref())
           : absl::nullopt,
       grpc_core::Timestamp::FromTimespecRoundUp(deadline));

   return call;
 }

 void grpc_channel_destroy_internal(grpc_channel* c_channel) {
   grpc_core::RefCountedPtr<grpc_core::Channel> channel(
       grpc_core::Channel::FromC(c_channel));
   grpc_transport_op* op = grpc_make_transport_op(nullptr);
   grpc_channel_element* elem;
   GRPC_API_TRACE("grpc_channel_destroy(channel=%p)", 1, (c_channel));
   op->disconnect_with_error = GRPC_ERROR_CREATE("Channel Destroyed");
   elem = grpc_channel_stack_element(channel->channel_stack(), 0);
   elem->filter->start_transport_op(elem, op);
 }

 void grpc_channel_destroy(grpc_channel* channel) {
   grpc_core::ApplicationCallbackExecCtx callback_exec_ctx;
   grpc_core::ExecCtx exec_ctx;
   grpc_channel_destroy_internal(channel);
 }
	/*
	*
	* Copyright 2015 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/port_platform.h>

	#include "src/core/lib/surface/channel.h"

	#include <inttypes.h>
	#include <string.h>

	#include <algorithm>
	#include <atomic>
	#include <functional>
	#include <memory>

	#include "absl/status/status.h"

	#include <grpc/compression.h>
	#include <grpc/grpc.h>
	#include <grpc/impl/codegen/gpr_types.h>
	#include <grpc/support/alloc.h>
	#include <grpc/support/log.h>

	#include "src/core/lib/channel/channel_args.h"
	#include "src/core/lib/channel/channel_stack.h"
	#include "src/core/lib/channel/channel_stack_builder_impl.h"
	#include "src/core/lib/channel/channel_trace.h"
	#include "src/core/lib/channel/channelz.h"
	#include "src/core/lib/config/core_configuration.h"
	#include "src/core/lib/debug/stats.h"
	#include "src/core/lib/debug/stats_data.h"
	#include "src/core/lib/debug/trace.h"
	#include "src/core/lib/gpr/useful.h"
	#include "src/core/lib/gprpp/manual_constructor.h"
	#include "src/core/lib/gprpp/ref_counted_ptr.h"
	#include "src/core/lib/iomgr/error.h"
	#include "src/core/lib/iomgr/exec_ctx.h"
	#include "src/core/lib/resource_quota/memory_quota.h"
	#include "src/core/lib/resource_quota/resource_quota.h"
	#include "src/core/lib/surface/api_trace.h"
	#include "src/core/lib/surface/call.h"
	#include "src/core/lib/surface/channel_init.h"
	#include "src/core/lib/surface/channel_stack_type.h"
	#include "src/core/lib/surface/init_internally.h"
	#include "src/core/lib/transport/transport.h"

	// IWYU pragma: no_include <type_traits>

	namespace grpc_core {

	Channel::Channel(bool is_client, bool is_promising, std::string target,
	const ChannelArgs& channel_args,
	grpc_compression_options compression_options,
	RefCountedPtr<grpc_channel_stack> channel_stack)
	: is_client_(is_client),
	is_promising_(is_promising),
	compression_options_(compression_options),
	call_size_estimate_(channel_stack->call_stack_size +
	grpc_call_get_initial_size_estimate()),
	channelz_node_(channel_args.GetObjectRef<channelz::ChannelNode>()),
	allocator_(channel_args.GetObject<ResourceQuota>()
	->memory_quota()
	->CreateMemoryOwner(target)),
	target_(std::move(target)),
	channel_stack_(std::move(channel_stack)) {
	// We need to make sure that grpc_shutdown() does not shut things down
	// until after the channel is destroyed. However, the channel may not
	// actually be destroyed by the time grpc_channel_destroy() returns,
	// since there may be other existing refs to the channel. If those
	// refs are held by things that are visible to the wrapped language
	// (such as outstanding calls on the channel), then the wrapped
	// language can be responsible for making sure that grpc_shutdown()
	// does not run until after those refs are released. However, the
	// channel may also have refs to itself held internally for various
	// things that need to be cleaned up at channel destruction (e.g.,
	// LB policies, subchannels, etc), and because these refs are not
	// visible to the wrapped language, it cannot be responsible for
	// deferring grpc_shutdown() until after they are released. To
	// accommodate that, we call grpc_init() here and then call
	// grpc_shutdown() when the channel is actually destroyed, thus
	// ensuring that shutdown is deferred until that point.
	InitInternally();
	auto channelz_node = channelz_node_;
	*channel_stack_->on_destroy = [channelz_node]() {
	if (channelz_node != nullptr) {
	channelz_node->AddTraceEvent(
	channelz::ChannelTrace::Severity::Info,
	grpc_slice_from_static_string("Channel destroyed"));
	}
	ShutdownInternally();
	};
	}

	absl::StatusOr<RefCountedPtr<Channel>> Channel::CreateWithBuilder(
	ChannelStackBuilder* builder) {
	auto channel_args = builder->channel_args();
	if (builder->channel_stack_type() == GRPC_SERVER_CHANNEL) {
	global_stats().IncrementServerChannelsCreated();
	} else {
	global_stats().IncrementClientChannelsCreated();
	}
	absl::StatusOr<RefCountedPtr<grpc_channel_stack>> r = builder->Build();
	if (!r.ok()) {
	auto status = r.status();
	gpr_log(GPR_ERROR, "channel stack builder failed: %s",
	status.ToString().c_str());
	return status;
	}

	grpc_compression_options compression_options;
	grpc_compression_options_init(&compression_options);
	auto default_level =
	channel_args.GetInt(GRPC_COMPRESSION_CHANNEL_DEFAULT_LEVEL);
	if (default_level.has_value()) {
	compression_options.default_level.is_set = true;
	compression_options.default_level.level = Clamp(
	static_cast<grpc_compression_level>(*default_level),
	GRPC_COMPRESS_LEVEL_NONE,
	static_cast<grpc_compression_level>(GRPC_COMPRESS_LEVEL_COUNT - 1));
	}
	auto default_algorithm =
	channel_args.GetInt(GRPC_COMPRESSION_CHANNEL_DEFAULT_ALGORITHM);
	if (default_algorithm.has_value()) {
	compression_options.default_algorithm.is_set = true;
	compression_options.default_algorithm.algorithm =
	Clamp(static_cast<grpc_compression_algorithm>(*default_algorithm),
	GRPC_COMPRESS_NONE,
	static_cast<grpc_compression_algorithm>(
	GRPC_COMPRESS_ALGORITHMS_COUNT - 1));
	}
	auto enabled_algorithms_bitset =
	channel_args.GetInt(GRPC_COMPRESSION_CHANNEL_ENABLED_ALGORITHMS_BITSET);
	if (enabled_algorithms_bitset.has_value()) {
	compression_options.enabled_algorithms_bitset =
	enabled_algorithms_bitset \| 1 / always support no compression */;
	}

	return RefCountedPtr<Channel>(new Channel(
	grpc_channel_stack_type_is_client(builder->channel_stack_type()),
	builder->IsPromising(), std::string(builder->target()), channel_args,
	compression_options, std::move(*r)));
	}

	namespace {

	void* channelz_node_copy(void* p) {
	channelz::ChannelNode* node = static_cast<channelz::ChannelNode*>(p);
	node->Ref().release();
	return p;
	}
	void channelz_node_destroy(void* p) {
	channelz::ChannelNode* node = static_cast<channelz::ChannelNode*>(p);
	node->Unref();
	}
	int channelz_node_cmp(void* p1, void* p2) { return QsortCompare(p1, p2); }
	const grpc_arg_pointer_vtable channelz_node_arg_vtable = {
	channelz_node_copy, channelz_node_destroy, channelz_node_cmp};

	void CreateChannelzNode(ChannelStackBuilder* builder) {
	auto args = builder->channel_args();
	// Check whether channelz is enabled.
	const bool channelz_enabled = args.GetBool(GRPC_ARG_ENABLE_CHANNELZ)
	.value_or(GRPC_ENABLE_CHANNELZ_DEFAULT);
	if (!channelz_enabled) return;
	// Get parameters needed to create the channelz node.
	const size_t channel_tracer_max_memory = std::max(
	0, args.GetInt(GRPC_ARG_MAX_CHANNEL_TRACE_EVENT_MEMORY_PER_NODE)
	.value_or(GRPC_MAX_CHANNEL_TRACE_EVENT_MEMORY_PER_NODE_DEFAULT));
	const bool is_internal_channel =
	args.GetBool(GRPC_ARG_CHANNELZ_IS_INTERNAL_CHANNEL).value_or(false);
	// Create the channelz node.
	std::string target(builder->target());
	RefCountedPtr<channelz::ChannelNode> channelz_node =
	MakeRefCounted<channelz::ChannelNode>(
	target.c_str(), channel_tracer_max_memory, is_internal_channel);
	channelz_node->AddTraceEvent(
	channelz::ChannelTrace::Severity::Info,
	grpc_slice_from_static_string("Channel created"));
	// Add channelz node to channel args.
	// We remove the is_internal_channel arg, since we no longer need it.
	builder->SetChannelArgs(
	args.Remove(GRPC_ARG_CHANNELZ_IS_INTERNAL_CHANNEL)
	.Set(GRPC_ARG_CHANNELZ_CHANNEL_NODE,
	ChannelArgs::Pointer(channelz_node.release(),
	&channelz_node_arg_vtable)));
	}

	} // namespace

	absl::StatusOr<RefCountedPtr<Channel>> Channel::Create(
	const char* target, ChannelArgs args,
	grpc_channel_stack_type channel_stack_type,
	grpc_transport* optional_transport) {
	ChannelStackBuilderImpl builder(
	grpc_channel_stack_type_string(channel_stack_type), channel_stack_type);
	if (!args.GetString(GRPC_ARG_DEFAULT_AUTHORITY).has_value()) {
	auto ssl_override = args.GetString(GRPC_SSL_TARGET_NAME_OVERRIDE_ARG);
	if (ssl_override.has_value()) {
	args = args.Set(GRPC_ARG_DEFAULT_AUTHORITY,
	std::string(ssl_override.value()));
	}
	}
	if (grpc_channel_stack_type_is_client(channel_stack_type)) {
	auto channel_args_mutator =
	grpc_channel_args_get_client_channel_creation_mutator();
	if (channel_args_mutator != nullptr) {
	args = channel_args_mutator(target, args, channel_stack_type);
	}
	}
	builder.SetChannelArgs(args).SetTarget(target).SetTransport(
	optional_transport);
	if (!CoreConfiguration::Get().channel_init().CreateStack(&builder)) {
	return nullptr;
	}
	// We only need to do this for clients here. For servers, this will be
	// done in src/core/lib/surface/server.cc.
	if (grpc_channel_stack_type_is_client(channel_stack_type)) {
	CreateChannelzNode(&builder);
	}
	return CreateWithBuilder(&builder);
	}

	void Channel::UpdateCallSizeEstimate(size_t size) {
	size_t cur = call_size_estimate_.load(std::memory_order_relaxed);
	if (cur < size) {
	// size grew: update estimate
	call_size_estimate_.compare_exchange_weak(
	cur, size, std::memory_order_relaxed, std::memory_order_relaxed);
	// if we lose: never mind, something else will likely update soon enough
	} else if (cur == size) {
	// no change: holding pattern
	} else if (cur > 0) {
	// size shrank: decrease estimate
	call_size_estimate_.compare_exchange_weak(
	cur, std::min(cur - 1, (255 * cur + size) / 256),
	std::memory_order_relaxed, std::memory_order_relaxed);
	// if we lose: never mind, something else will likely update soon enough
	}
	}

	} // namespace grpc_core

	char* grpc_channel_get_target(grpc_channel* channel) {
	GRPC_API_TRACE("grpc_channel_get_target(channel=%p)", 1, (channel));
	auto target = grpc_core::Channel::FromC(channel)->target();
	char* buffer = static_cast<char*>(gpr_zalloc(target.size() + 1));
	memcpy(buffer, target.data(), target.size());
	return buffer;
	}

	void grpc_channel_get_info(grpc_channel* channel,
	const grpc_channel_info* channel_info) {
	grpc_core::ApplicationCallbackExecCtx callback_exec_ctx;
	grpc_core::ExecCtx exec_ctx;
	grpc_channel_element* elem = grpc_channel_stack_element(
	grpc_core::Channel::FromC(channel)->channel_stack(), 0);
	elem->filter->get_channel_info(elem, channel_info);
	}

	void grpc_channel_reset_connect_backoff(grpc_channel* channel) {
	grpc_core::ApplicationCallbackExecCtx callback_exec_ctx;
	grpc_core::ExecCtx exec_ctx;
	GRPC_API_TRACE("grpc_channel_reset_connect_backoff(channel=%p)", 1,
	(channel));
	grpc_transport_op* op = grpc_make_transport_op(nullptr);
	op->reset_connect_backoff = true;
	grpc_channel_element* elem = grpc_channel_stack_element(
	grpc_core::Channel::FromC(channel)->channel_stack(), 0);
	elem->filter->start_transport_op(elem, op);
	}

	static grpc_call* grpc_channel_create_call_internal(
	grpc_channel* c_channel, grpc_call* parent_call, uint32_t propagation_mask,
	grpc_completion_queue* cq, grpc_pollset_set* pollset_set_alternative,
	grpc_core::Slice path, absl::optional<grpc_core::Slice> authority,
	grpc_core::Timestamp deadline) {
	auto channel = grpc_core::Channel::FromC(c_channel)->Ref();
	GPR_ASSERT(channel->is_client());
	GPR_ASSERT(!(cq != nullptr && pollset_set_alternative != nullptr));

	grpc_call_create_args args;
	args.channel = std::move(channel);
	args.server = nullptr;
	args.parent = parent_call;
	args.propagation_mask = propagation_mask;
	args.cq = cq;
	args.pollset_set_alternative = pollset_set_alternative;
	args.server_transport_data = nullptr;
	args.path = std::move(path);
	args.authority = std::move(authority);
	args.send_deadline = deadline;

	grpc_call* call;
	GRPC_LOG_IF_ERROR("call_create", grpc_call_create(&args, &call));
	return call;
	}

	grpc_call* grpc_channel_create_call(grpc_channel* channel,
	grpc_call* parent_call,
	uint32_t propagation_mask,
	grpc_completion_queue* completion_queue,
	grpc_slice method, const grpc_slice* host,
	gpr_timespec deadline, void* reserved) {
	GPR_ASSERT(!reserved);
	grpc_core::ApplicationCallbackExecCtx callback_exec_ctx;
	grpc_core::ExecCtx exec_ctx;
	grpc_call* call = grpc_channel_create_call_internal(
	channel, parent_call, propagation_mask, completion_queue, nullptr,
	grpc_core::Slice(grpc_core::CSliceRef(method)),
	host != nullptr
	? absl::optional<grpc_core::Slice>(grpc_core::CSliceRef(*host))
	: absl::nullopt,
	grpc_core::Timestamp::FromTimespecRoundUp(deadline));

	return call;
	}

	grpc_call* grpc_channel_create_pollset_set_call(
	grpc_channel* channel, grpc_call* parent_call, uint32_t propagation_mask,
	grpc_pollset_set* pollset_set, const grpc_slice& method,
	const grpc_slice* host, grpc_core::Timestamp deadline, void* reserved) {
	GPR_ASSERT(!reserved);
	return grpc_channel_create_call_internal(
	channel, parent_call, propagation_mask, nullptr, pollset_set,
	grpc_core::Slice(method),
	host != nullptr
	? absl::optional<grpc_core::Slice>(grpc_core::CSliceRef(*host))
	: absl::nullopt,
	deadline);
	}

	namespace grpc_core {

	RegisteredCall::RegisteredCall(const char* method_arg, const char* host_arg) {
	path = Slice::FromCopiedString(method_arg);
	if (host_arg != nullptr && host_arg[0] != 0) {
	authority = Slice::FromCopiedString(host_arg);
	}
	}

	RegisteredCall::RegisteredCall(const RegisteredCall& other)
	: path(other.path.Ref()) {
	if (other.authority.has_value()) {
	authority = other.authority->Ref();
	}
	}

	RegisteredCall::~RegisteredCall() {}

	} // namespace grpc_core

	void* grpc_channel_register_call(grpc_channel* channel, const char* method,
	const char* host, void* reserved) {
	GRPC_API_TRACE(
	"grpc_channel_register_call(channel=%p, method=%s, host=%s, reserved=%p)",
	4, (channel, method, host, reserved));
	GPR_ASSERT(!reserved);
	grpc_core::ApplicationCallbackExecCtx callback_exec_ctx;
	grpc_core::ExecCtx exec_ctx;
	return grpc_core::Channel::FromC(channel)->RegisterCall(method, host);
	}

	namespace grpc_core {

	RegisteredCall* Channel::RegisterCall(const char* method, const char* host) {
	MutexLock lock(&registration_table_.mu);
	registration_table_.method_registration_attempts++;
	auto key = std::make_pair(std::string(host != nullptr ? host : ""),
	std::string(method != nullptr ? method : ""));
	auto rc_posn = registration_table_.map.find(key);
	if (rc_posn != registration_table_.map.end()) {
	return &rc_posn->second;
	}
	auto insertion_result = registration_table_.map.insert(
	{std::move(key), RegisteredCall(method, host)});
	return &insertion_result.first->second;
	}

	} // namespace grpc_core

	grpc_call* grpc_channel_create_registered_call(
	grpc_channel* channel, grpc_call* parent_call, uint32_t propagation_mask,
	grpc_completion_queue* completion_queue, void* registered_call_handle,
	gpr_timespec deadline, void* reserved) {
	grpc_core::RegisteredCall* rc =
	static_cast<grpc_core::RegisteredCall*>(registered_call_handle);
	GRPC_API_TRACE(
	"grpc_channel_create_registered_call("
	"channel=%p, parent_call=%p, propagation_mask=%x, completion_queue=%p, "
	"registered_call_handle=%p, "
	"deadline=gpr_timespec { tv_sec: %" PRId64
	", tv_nsec: %d, clock_type: %d }, "
	"reserved=%p)",
	9,
	(channel, parent_call, (unsigned)propagation_mask, completion_queue,
	registered_call_handle, deadline.tv_sec, deadline.tv_nsec,
	(int)deadline.clock_type, reserved));
	GPR_ASSERT(!reserved);
	grpc_core::ApplicationCallbackExecCtx callback_exec_ctx;
	grpc_core::ExecCtx exec_ctx;
	grpc_call* call = grpc_channel_create_call_internal(
	channel, parent_call, propagation_mask, completion_queue, nullptr,
	rc->path.Ref(),
	rc->authority.has_value()
	? absl::optional<grpc_core::Slice>(rc->authority->Ref())
	: absl::nullopt,
	grpc_core::Timestamp::FromTimespecRoundUp(deadline));

	return call;
	}

	void grpc_channel_destroy_internal(grpc_channel* c_channel) {
	grpc_core::RefCountedPtr<grpc_core::Channel> channel(
	grpc_core::Channel::FromC(c_channel));
	grpc_transport_op* op = grpc_make_transport_op(nullptr);
	grpc_channel_element* elem;
	GRPC_API_TRACE("grpc_channel_destroy(channel=%p)", 1, (c_channel));
	op->disconnect_with_error = GRPC_ERROR_CREATE("Channel Destroyed");
	elem = grpc_channel_stack_element(channel->channel_stack(), 0);
	elem->filter->start_transport_op(elem, op);
	}

	void grpc_channel_destroy(grpc_channel* channel) {
	grpc_core::ApplicationCallbackExecCtx callback_exec_ctx;
	grpc_core::ExecCtx exec_ctx;
	grpc_channel_destroy_internal(channel);
	}