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// Copyright The OpenTelemetry Authors
// SPDX-License-Identifier: Apache-2.0
#pragma once
#ifdef ENABLE_METRICS_PREVIEW
# include <iostream>
# include "opentelemetry/common/attribute_value.h"
# include "opentelemetry/common/key_value_iterable_view.h"
# include "opentelemetry/nostd/shared_ptr.h"
# include "opentelemetry/nostd/string_view.h"
OPENTELEMETRY_BEGIN_NAMESPACE
namespace metrics
{
// Enum classes to help determine instrument types in other parts of the API
enum class InstrumentKind
{
Counter = 0,
UpDownCounter = 1,
ValueRecorder = 2,
ValueObserver = 3,
SumObserver = 4,
UpDownSumObserver = 5,
};
class Instrument
{
public:
// Note that Instruments should be created using the Meter class.
// Please refer to meter.h for documentation.
Instrument() = default;
/**
* Base class constructor for all other instrument types. Whether or not
* an instrument is synchronous or bound, it requires a name, description,
* unit, and enabled flag.
*
* @param name is the identifier of the instrumenting library
* @param description explains what the metric captures
* @param unit specifies the data type held in the instrument
* @param enabled determines if the metric is currently capturing data
* @return Instrument type with the specified attributes
*/
Instrument(nostd::string_view name,
nostd::string_view description,
nostd::string_view unit,
bool enabled)
{}
// Returns true if the instrument is enabled and collecting data
virtual bool IsEnabled() = 0;
// Return the instrument name
virtual nostd::string_view GetName() = 0;
// Return the instrument description
virtual nostd::string_view GetDescription() = 0;
// Return the insrument's units of measurement
virtual nostd::string_view GetUnits() = 0;
// Return the intrument's kind
virtual InstrumentKind GetKind() = 0;
virtual ~Instrument() = default;
};
template <class T>
class BoundSynchronousInstrument : virtual public Instrument
{
public:
BoundSynchronousInstrument() = default;
BoundSynchronousInstrument(nostd::string_view name,
nostd::string_view description,
nostd::string_view unit,
bool enabled);
/**
* Frees the resources associated with this Bound Instrument.
* The Metric from which this instrument was created is not impacted.
*
* @param none
* @return void
*/
virtual void unbind() {}
/**
* Incremements the reference count of this bound object when a new instance is
* either created or the same instance is returned as a result of binding
*
* @param none
* @return void
*/
virtual void inc_ref() {}
/**
* Return the object's current reference count. This information is used to remove
* stale objects from instrument registries.
*/
virtual int get_ref() { return 0; }
/**
* Records a single synchronous metric event; a call to the aggregator
* Since this is a bound synchronous instrument, labels are not required in * metric capture
* calls.
*
* @param value is the numerical representation of the metric being captured
* @return void
*/
virtual void update(T value) {}
};
template <class T>
class SynchronousInstrument : virtual public Instrument
{
public:
SynchronousInstrument() = default;
SynchronousInstrument(nostd::string_view name,
nostd::string_view description,
nostd::string_view unit,
bool enabled)
{}
/**
* Returns a Bound Instrument associated with the specified labels. * Multiples requests
* with the same set of labels may return the same Bound Instrument instance.
*
* It is recommended that callers keep a reference to the Bound Instrument
* instead of repeatedly calling this operation.
*
* @param labels the set of labels, as key-value pairs
* @return a Bound Instrument
*/
virtual nostd::shared_ptr<BoundSynchronousInstrument<T>> bind(
const common::KeyValueIterable &labels)
{
return nostd::shared_ptr<BoundSynchronousInstrument<T>>();
}
/**
* Records a single synchronous metric event.
* Since this is an unbound synchronous instrument, labels are required in * metric capture
* calls.
*
* update can be used in instruments with both add or record since it simply
* activated the aggregator
*
* @param labels the set of labels, as key-value pairs
* @param value is the numerical representation of the metric being captured
* @return void
*/
virtual void update(T value, const common::KeyValueIterable &labels) = 0;
};
template <class T>
class ObserverResult;
template <class T>
class AsynchronousInstrument : virtual public Instrument
{
public:
AsynchronousInstrument() = default;
AsynchronousInstrument(nostd::string_view name,
nostd::string_view description,
nostd::string_view unit,
bool enabled,
void(callback)(ObserverResult<T>))
{}
/**
* Captures data through a manual call rather than the automatic collection process instituted
* in the run function. Asynchronous instruments are generally expected to obtain data from
* their callbacks rather than direct calls. This function is used by the callback to store data.
*
* @param value is the numerical representation of the metric being captured
* @param labels is the numerical representation of the metric being captured
* @return none
*/
virtual void observe(T value, const common::KeyValueIterable &labels) = 0;
/**
* Captures data by activating the callback function associated with the
* instrument and storing its return value. Callbacks for asynchronous
* instruments are defined during construction.
*
* @param none
* @return none
*/
virtual void run() = 0;
protected:
// Callback function which takes a pointer to an Asynchronous instrument (this) type which is
// stored in an observer result type and returns nothing. This function calls the instrument's
// observe.
void (*callback_)(ObserverResult<T>);
};
} // namespace metrics
OPENTELEMETRY_END_NAMESPACE
#endif
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