tracing/span.h

// Copyright 2026 Google LLC
//
// 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
//
//    https://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 THIRD_PARTY_CREDENTIO_TRACING_SPAN_H_
#define THIRD_PARTY_CREDENTIO_TRACING_SPAN_H_

#include <cstdint>
#include <string>
#include <variant>

#include "absl/status/status.h"
#include "absl/strings/string_view.h"

namespace credentio_tracing {

// Represents supported primitive attribute values that can be attached to a
// tracing span.
using AttributeValue =
    std::variant<std::string, uint64_t, int64_t, double, bool>;

// Abstract interface for a tracing span representing an operation duration.
//
// Implementations of Span record information about execution status, timed
// events, and key-value attributes.
//
// Thread safety: a span may be started on one thread and ended on another --
// the asynchronous encoding pipeline routinely does this, for example a span
// that ends inside an RPC callback while its siblings end on the calling
// thread. Implementations must therefore synchronize any state they share
// between spans, such as a destination shared by all spans of an operation.
// A single span instance must not be used concurrently from multiple threads;
// callers hand a span off to at most one thread at a time, which establishes
// the happens-before edge that makes its own state safe to access unguarded.
class Span {
 public:
  virtual ~Span() = default;

  // Sets a key-value attribute on the span.
  virtual void SetAttribute(absl::string_view key, AttributeValue value) = 0;

  // Records a point-in-time event with the specified name within the span.
  virtual void AddEvent(absl::string_view name) = 0;

  // Sets the execution status for the operation tracked by the span.
  virtual void SetStatus(const absl::Status& status) = 0;

  // Completes execution of the span and records its end time.
  virtual void End() = 0;

  // Sets the execution status and completes execution of the span.
  void EndWithStatus(const absl::Status& status) {
    SetStatus(status);
    End();
  }
};

}  // namespace credentio_tracing

#endif  // THIRD_PARTY_CREDENTIO_TRACING_SPAN_H_