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 *
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 * in the documentation and/or other materials provided with the
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#ifndef GRPC_CORE_EXT_LOAD_REPORTING_LOAD_REPORTING_H
#define GRPC_CORE_EXT_LOAD_REPORTING_LOAD_REPORTING_H

#include <grpc/impl/codegen/grpc_types.h>
#include "src/core/lib/channel/channel_stack.h"

/** Metadata key for the gRPC LB load balancer token.
 *
 * The value corresponding to this key is an opaque token that is given to the
 * frontend as part of each pick; the frontend sends this token to the backend
 * in each request it sends when using that pick. The token is used by the
 * backend to verify the request and to allow the backend to report load to the
 * gRPC LB system. */
#define GRPC_LB_TOKEN_MD_KEY "lb-token"

/** Metadata key for gRPC LB cost reporting.
 *
 * The value corresponding to this key is an opaque binary blob reported by the
 * backend as part of its trailing metadata containing cost information for the
 * call. */
#define GRPC_LB_COST_MD_KEY "lb-cost-bin"

/** Identifiers for the invocation point of the users LR callback */
typedef enum grpc_load_reporting_source {
  GRPC_LR_POINT_UNKNOWN = 0,
  GRPC_LR_POINT_CHANNEL_CREATION,
  GRPC_LR_POINT_CHANNEL_DESTRUCTION,
  GRPC_LR_POINT_CALL_CREATION,
  GRPC_LR_POINT_CALL_DESTRUCTION
} grpc_load_reporting_source;

/** Call information to be passed to the provided LR callback. */
typedef struct grpc_load_reporting_call_data {
  const grpc_load_reporting_source source; /**< point of last data update. */

  /** Unique identifier for the channel associated with the data */
  intptr_t channel_id;

  /** Unique identifier for the call associated with the data. If the call
   * hasn't been created yet, it'll have a value of zero. */
  intptr_t call_id;

  /** Only valid when \a source is \a GRPC_LR_POINT_CALL_DESTRUCTION, that is,
   * once the call has completed */
  const grpc_call_final_info *final_info;

  const char *initial_md_string;  /**< value string for LR's initial md key */
  const char *trailing_md_string; /**< value string for LR's trailing md key */
  const char *method_name;        /**< Corresponds to :path header */
} grpc_load_reporting_call_data;

/** Return a \a grpc_arg enabling load reporting */
grpc_arg grpc_load_reporting_enable_arg();

#endif /* GRPC_CORE_EXT_LOAD_REPORTING_LOAD_REPORTING_H */
