Update logs sdk and api to follow specification (#1884)

CHANGELOG.md

@@ -15,6 +15,7 @@ Increment the:
 
 ## [Unreleased]
 
+* [LOGS] Add `include_trace_context` and `EventLogger` [#1884](https://github.com/open-telemetry/opentelemetry-cpp/pull/1884)
 * [METRICS] Change BatchLogRecordProcessorFactory::Create to static method
 * [BUILD] Fix OTELCPP_MAINTAINER_MODE [#1844](https://github.com/open-telemetry/opentelemetry-cpp/pull/1844)
 * [BUILD] Fix compatibility when using clang and libc++, upgrade GTest and

api/include/opentelemetry/common/key_value_iterable.h

@@ -32,5 +32,32 @@ class KeyValueIterable
    */
   virtual size_t size() const noexcept = 0;
 };
+
+/**
+ * Supports internal iteration over a collection of key-value pairs.
+ */
+class NoopKeyValueIterable : public KeyValueIterable
+{
+public:
+  ~NoopKeyValueIterable() override = default;
+
+  /**
+   * Iterate over key-value pairs
+   * @param callback a callback to invoke for each key-value. If the callback returns false,
+   * the iteration is aborted.
+   * @return true if every key-value pair was iterated over
+   */
+  bool ForEachKeyValue(
+      nostd::function_ref<bool(nostd::string_view, common::AttributeValue)>) const noexcept override
+  {
+    return true;
+  }
+
+  /**
+   * @return the number of key-value pairs
+   */
+  size_t size() const noexcept override { return 0; }
+};
+
 }  // namespace common
 OPENTELEMETRY_END_NAMESPACE

api/include/opentelemetry/logs/event_logger.h

@@ -0,0 +1,94 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+#pragma once
+#ifdef ENABLE_LOGS_PREVIEW
+
+#  include <chrono>
+#  include <map>
+#  include <vector>
+
+#  include "opentelemetry/common/macros.h"
+#  include "opentelemetry/logs/log_record.h"
+#  include "opentelemetry/logs/logger.h"
+#  include "opentelemetry/logs/logger_type_traits.h"
+#  include "opentelemetry/logs/severity.h"
+#  include "opentelemetry/nostd/shared_ptr.h"
+#  include "opentelemetry/nostd/string_view.h"
+#  include "opentelemetry/nostd/unique_ptr.h"
+#  include "opentelemetry/version.h"
+
+OPENTELEMETRY_BEGIN_NAMESPACE
+namespace logs
+{
+/**
+ * Handles event log record creation.
+ **/
+class EventLogger
+{
+public:
+  virtual ~EventLogger() = default;
+
+  /* Returns the name of the logger */
+  virtual const nostd::string_view GetName() noexcept = 0;
+
+  /* Returns the delegate logger of this event logger */
+  virtual nostd::shared_ptr<Logger> GetDelegateLogger() noexcept = 0;
+
+  /**
+   * Emit a event Log Record object
+   *
+   * @param event_name Event name
+   * @param log_record Log record
+   */
+  virtual void EmitEvent(nostd::string_view event_name,
+                         nostd::unique_ptr<LogRecord> &&log_record) noexcept = 0;
+
+  /**
+   * Emit a event Log Record object with arguments
+   *
+   * @param event_name Event name
+   * @tparam args Arguments which can be used to set data of log record by type.
+   *  Severity                                -> severity, severity_text
+   *  string_view                             -> body
+   *  AttributeValue                          -> body
+   *  SpanContext                             -> span_id,tace_id and trace_flags
+   *  SpanId                                  -> span_id
+   *  TraceId                                 -> tace_id
+   *  TraceFlags                              -> trace_flags
+   *  SystemTimestamp                         -> timestamp
+   *  system_clock::time_point                -> timestamp
+   *  KeyValueIterable                        -> attributes
+   *  Key value iterable container            -> attributes
+   *  span<pair<string_view, AttributeValue>> -> attributes(return type of MakeAttributes)
+   */
+  template <class... ArgumentType>
+  void EmitEvent(nostd::string_view event_name, ArgumentType &&... args)
+  {
+    nostd::shared_ptr<Logger> delegate_logger = GetDelegateLogger();
+    if (!delegate_logger)
+    {
+      return;
+    }
+    nostd::unique_ptr<LogRecord> log_record = delegate_logger->CreateLogRecord();
+    if (!log_record)
+    {
+      return;
+    }
+
+    IgnoreTraitResult(
+        detail::LogRecordSetterTrait<typename std::decay<ArgumentType>::type>::template Set(
+            log_record.get(), std::forward<ArgumentType>(args))...);
+
+    EmitEvent(event_name, std::move(log_record));
+  }
+
+private:
+  template <class... ValueType>
+  void IgnoreTraitResult(ValueType &&...)
+  {}
+};
+}  // namespace logs
+OPENTELEMETRY_END_NAMESPACE
+
+#endif

api/include/opentelemetry/logs/event_logger_provider.h

@@ -0,0 +1,36 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+#pragma once
+#ifdef ENABLE_LOGS_PREVIEW
+
+#  include "opentelemetry/common/key_value_iterable.h"
+#  include "opentelemetry/common/key_value_iterable_view.h"
+#  include "opentelemetry/logs/event_logger.h"
+#  include "opentelemetry/logs/logger.h"
+#  include "opentelemetry/nostd/shared_ptr.h"
+#  include "opentelemetry/nostd/string_view.h"
+
+OPENTELEMETRY_BEGIN_NAMESPACE
+namespace logs
+{
+/**
+ * Creates new EventLogger instances.
+ */
+class EventLoggerProvider
+{
+public:
+  virtual ~EventLoggerProvider() = default;
+
+  /**
+   * Creates a named EventLogger instance.
+   *
+   */
+
+  virtual nostd::shared_ptr<EventLogger> CreateEventLogger(
+      nostd::shared_ptr<Logger> delegate_logger,
+      nostd::string_view event_domain) noexcept = 0;
+};
+}  // namespace logs
+OPENTELEMETRY_END_NAMESPACE
+#endif