grpc/src/core/ext/filters/client_channel/service_config_parser.h

//
// Copyright 2016 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_SERVICE_CONFIG_PARSER_H
#define GRPC_CORE_EXT_FILTERS_CLIENT_CHANNEL_SERVICE_CONFIG_PARSER_H

#include <grpc/support/port_platform.h>

#include <memory>

#include "absl/container/inlined_vector.h"

#include <grpc/impl/codegen/grpc_types.h>

#include "src/core/lib/iomgr/error.h"
#include "src/core/lib/json/json.h"

namespace grpc_core {

// Service config parser registry.
// See service_config.h for more information.
class ServiceConfigParser {
 public:
  /// This is the base class that all service config parsers MUST use to store
  /// parsed service config data.
  class ParsedConfig {
   public:
    virtual ~ParsedConfig() = default;
  };

  /// This is the base class that all service config parsers should derive from.
  class Parser {
   public:
    virtual ~Parser() = default;

    virtual std::unique_ptr<ParsedConfig> ParseGlobalParams(
        const grpc_channel_args*, const Json& /* json */,
        grpc_error_handle* error) {
      // Avoid unused parameter warning on debug-only parameter
      (void)error;
      GPR_DEBUG_ASSERT(error != nullptr);
      return nullptr;
    }

    virtual std::unique_ptr<ParsedConfig> ParsePerMethodParams(
        const grpc_channel_args*, const Json& /* json */,
        grpc_error_handle* error) {
      // Avoid unused parameter warning on debug-only parameter
      (void)error;
      GPR_DEBUG_ASSERT(error != nullptr);
      return nullptr;
    }
  };

  static constexpr int kNumPreallocatedParsers = 4;
  typedef absl::InlinedVector<std::unique_ptr<ParsedConfig>,
                              kNumPreallocatedParsers>
      ParsedConfigVector;

  static void Init();
  static void Shutdown();

  /// Globally register a service config parser. On successful registration, it
  /// returns the index at which the parser was registered. On failure, -1 is
  /// returned. Each new service config update will go through all the
  /// registered parser. Each parser is responsible for reading the service
  /// config json and returning a parsed config. This parsed config can later be
  /// retrieved using the same index that was returned at registration time.
  static size_t RegisterParser(std::unique_ptr<Parser> parser);

  static ParsedConfigVector ParseGlobalParameters(const grpc_channel_args* args,
                                                  const Json& json,
                                                  grpc_error_handle* error);

  static ParsedConfigVector ParsePerMethodParameters(
      const grpc_channel_args* args, const Json& json,
      grpc_error_handle* error);
};

}  // namespace grpc_core

#endif /* GRPC_CORE_EXT_FILTERS_CLIENT_CHANNEL_SERVICE_CONFIG_PARSER_H */