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//
// Copyright 2020 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.
//
#ifndef GRPC_CORE_EXT_FILTERS_CLIENT_CHANNEL_CONFIG_SELECTOR_H
#define GRPC_CORE_EXT_FILTERS_CLIENT_CHANNEL_CONFIG_SELECTOR_H
#include <grpc/support/port_platform.h>
#include <functional>
#include <map>
#include <vector>
#include "absl/strings/string_view.h"
#include <grpc/grpc.h>
#include "src/core/ext/filters/client_channel/service_config.h"
#include "src/core/ext/filters/client_channel/service_config_parser.h"
#include "src/core/lib/channel/channel_stack.h"
#include "src/core/lib/gprpp/arena.h"
#include "src/core/lib/gprpp/ref_counted.h"
#include "src/core/lib/gprpp/ref_counted_ptr.h"
#include "src/core/lib/transport/metadata_batch.h"
// Channel arg key for ConfigSelector.
#define GRPC_ARG_CONFIG_SELECTOR "grpc.internal.config_selector"
namespace grpc_core {
// Internal API used to allow resolver implementations to override
// MethodConfig and provide input to LB policies on a per-call basis.
class ConfigSelector : public RefCounted<ConfigSelector> {
public:
struct GetCallConfigArgs {
grpc_slice* path;
grpc_metadata_batch* initial_metadata;
Arena* arena;
};
struct CallConfig {
// Can be set to indicate the call should be failed.
grpc_error* error = GRPC_ERROR_NONE;
// The per-method parsed configs that will be passed to
// ServiceConfigCallData.
const ServiceConfigParser::ParsedConfigVector* method_configs = nullptr;
// A ref to the service config that contains method_configs, held by
// the call to ensure that method_configs lives long enough.
RefCountedPtr<ServiceConfig> service_config;
// Call attributes that will be accessible to LB policy implementations.
std::map<const char*, absl::string_view> call_attributes;
// A callback that, if set, will be invoked when the call is
// committed (i.e., when we know that we will never again need to
// ask the picker for a subchannel for this call).
std::function<void()> on_call_committed;
};
~ConfigSelector() override = default;
virtual const char* name() const = 0;
// Will be called only if the two objects have the same name, so
// subclasses can be free to safely down-cast the argument.
virtual bool Equals(const ConfigSelector* other) const = 0;
static bool Equals(const ConfigSelector* cs1, const ConfigSelector* cs2) {
if (cs1 == nullptr) return cs2 == nullptr;
if (cs2 == nullptr) return false;
if (strcmp(cs1->name(), cs2->name()) != 0) return false;
return cs1->Equals(cs2);
}
virtual std::vector<const grpc_channel_filter*> GetFilters() { return {}; }
virtual CallConfig GetCallConfig(GetCallConfigArgs args) = 0;
grpc_arg MakeChannelArg() const;
static RefCountedPtr<ConfigSelector> GetFromChannelArgs(
const grpc_channel_args& args);
};
// Default ConfigSelector that gets the MethodConfig from the service config.
class DefaultConfigSelector : public ConfigSelector {
public:
explicit DefaultConfigSelector(RefCountedPtr<ServiceConfig> service_config)
: service_config_(std::move(service_config)) {
// The client channel code ensures that this will never be null.
// If neither the resolver nor the client application provide a
// config, a default empty config will be used.
GPR_DEBUG_ASSERT(service_config_ != nullptr);
}
const char* name() const override { return "default"; }
// Only comparing the ConfigSelector itself, not the underlying
// service config, so we always return true.
bool Equals(const ConfigSelector* other) const override { return true; }
CallConfig GetCallConfig(GetCallConfigArgs args) override {
CallConfig call_config;
call_config.method_configs =
service_config_->GetMethodParsedConfigVector(*args.path);
call_config.service_config = service_config_;
return call_config;
}
private:
RefCountedPtr<ServiceConfig> service_config_;
};
} // namespace grpc_core
#endif /* GRPC_CORE_EXT_FILTERS_CLIENT_CHANNEL_CONFIG_SELECTOR_H */
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