resolver.h

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/*
 *
 * 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.
 *
 */
 
#ifndef GRPC_CORE_EXT_FILTERS_CLIENT_CHANNEL_RESOLVER_H
#define GRPC_CORE_EXT_FILTERS_CLIENT_CHANNEL_RESOLVER_H
 
#include <grpc/support/port_platform.h>
 
#include <grpc/impl/codegen/grpc_types.h>
 
#include "src/core/ext/filters/client_channel/server_address.h"
#include "src/core/ext/filters/client_channel/service_config.h"
#include "src/core/lib/gprpp/orphanable.h"
#include "src/core/lib/gprpp/ref_counted_ptr.h"
#include "src/core/lib/iomgr/combiner.h"
#include "src/core/lib/iomgr/iomgr.h"
 
extern grpc_core::DebugOnlyTraceFlag grpc_trace_resolver_refcount;
 
namespace grpc_core {
 
class Resolver : public InternallyRefCounted<Resolver> {
 public:
  struct Result {
    ServerAddressList addresses;
    RefCountedPtr<ServiceConfig> service_config;
    grpc_error* service_config_error = GRPC_ERROR_NONE;
    const grpc_channel_args* args = nullptr;
 
    // TODO(roth): Remove everything below once grpc_error and
    // grpc_channel_args are convert to copyable and movable C++ objects.
    Result() = default;
    ~Result();
    Result(const Result& other);
    Result(Result&& other);
    Result& operator=(const Result& other);
    Result& operator=(Result&& other);
  };
 
  class ResultHandler {
   public:
    virtual ~ResultHandler() {}
 
    virtual void ReturnResult(Result result) = 0;  // NOLINT
 
    virtual void ReturnError(grpc_error* error) = 0;
 
    // TODO(yashkt): As part of the service config error handling
    // changes, add a method to parse the service config JSON string.
  };
 
  // Not copyable nor movable.
  Resolver(const Resolver&) = delete;
  Resolver& operator=(const Resolver&) = delete;
  virtual ~Resolver();
 
  virtual void StartLocked() = 0;
 
  virtual void RequestReresolutionLocked() {}
 
  virtual void ResetBackoffLocked() {}
 
  // Note: This must be invoked while holding the combiner.
  void Orphan() override {
    ShutdownLocked();
    Unref();
  }
 
 protected:
  // TODO(roth): Once we have a C++-like interface for combiners, this
  // API should change to take a RefCountedPtr<>, so that we always take
  // ownership of a new ref.
  explicit Resolver(Combiner* combiner,
                    std::unique_ptr<ResultHandler> result_handler);
 
  virtual void ShutdownLocked() = 0;
 
  Combiner* combiner() const { return combiner_; }
 
  ResultHandler* result_handler() const { return result_handler_.get(); }
 
 private:
  std::unique_ptr<ResultHandler> result_handler_;
  Combiner* combiner_;
};
 
}  // namespace grpc_core
 
#endif /* GRPC_CORE_EXT_FILTERS_CLIENT_CHANNEL_RESOLVER_H */