balm_defaultmetricsmanager.h

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/// @file balm_defaultmetricsmanager.h
///
/// The content of this file has been pre-processed for Doxygen.
///
 
 
// balm_defaultmetricsmanager.h                                       -*-C++-*-
#ifndef INCLUDED_BALM_DEFAULTMETRICSMANAGER
#define INCLUDED_BALM_DEFAULTMETRICSMANAGER
 
#include <bsls_ident.h>
BSLS_IDENT("$Id: $")
 
/// @defgroup balm_defaultmetricsmanager balm_defaultmetricsmanager
/// @brief  Provide for a default instance of the metrics manager.
/// @addtogroup bal
/// @{
/// @addtogroup balm
/// @{
/// @addtogroup balm_defaultmetricsmanager
/// @{
///
/// <h1> Outline </h1>
/// * <a href="#balm_defaultmetricsmanager-purpose"> Purpose</a>
/// * <a href="#balm_defaultmetricsmanager-classes"> Classes </a>
/// * <a href="#balm_defaultmetricsmanager-description"> Description </a>
///   * <a href="#balm_defaultmetricsmanager-alternative-systems-for-telemetry"> Alternative Systems for Telemetry </a>
///   * <a href="#balm_defaultmetricsmanager-thread-safety"> Thread Safety </a>
///   * <a href="#balm_defaultmetricsmanager-usage"> Usage </a>
///     * <a href="#balm_defaultmetricsmanager-example-1-create-and-access-the-default-balm-metricsmanager-instance"> Example 1: Create and Access the Default balm::MetricsManager Instance </a>
///
/// # Purpose {#balm_defaultmetricsmanager-purpose}
/// Provide for a default instance of the metrics manager.
///
/// # Classes {#balm_defaultmetricsmanager-classes}
///
/// -            balm::DefaultMetricsManager: namespace for the default instance
/// - balm::DefaultMetricsManagerScopedGuard: guard for the default instance
///
/// @see  balm_metricsmanager, balm_metric
///
/// # Description {#balm_defaultmetricsmanager-description}
/// This component provides a namespace for a default instance of
/// the `balm::MetricsManager`.  This `balm::DefaultMetricsManager` provides
/// static operations to create, access, and destroy the default instance of the
/// `balm::MetricsManager`.  The `balm::DefaultMetricsManagedScopedGuard`
/// provides a proctor that creates a default metrics manager on construction
/// and destroys it on destruction.
///
/// `balm::DefaultMetricsManagerScopedGuard` is also here.
///
/// ## Alternative Systems for Telemetry {#balm_defaultmetricsmanager-alternative-systems-for-telemetry}
///
///
/// Bloomberg software may alternatively use the GUTS telemetry API, which is
/// integrated into Bloomberg infrastructure.
///
/// ## Thread Safety {#balm_defaultmetricsmanager-thread-safety}
///
///
/// The default `balm::MetricsManager` instance, once initialized, can be safely
/// accessed from multiple threads.  However, the `create` and `destroy`
/// operations supplied by the `balm::DefaultMetricsManager` are *not*
/// *thread-safe*.  Care must be taken, particularly when releasing the
/// instance.  The expected usage is that the instance will be created during
/// the initialization of an application (while the task has a single thread)
/// and that it will be destroyed just prior to termination (when there is
/// similarly just a single thread).
///
/// ## Usage {#balm_defaultmetricsmanager-usage}
///
///
/// The following examples demonstrate how to create, configure, and destroy
/// the default `balm::MetricsManager` instance.
///
/// ### Example 1: Create and Access the Default balm::MetricsManager Instance {#balm_defaultmetricsmanager-example-1-create-and-access-the-default-balm-metricsmanager-instance}
///
///
/// This example demonstrates how to create the default `balm::MetricManager`
/// instance and publish a single metric to the console.  See the documentation
/// of @ref balm_metric  and @ref balm_metricsmanager  for information on how to record
/// metrics.
///
/// First we create a `balm::DefaultMetricsManagerScopedGuard`, which manages
/// the lifetime of the default metrics manager instance.  At construction, we
/// provide the `balm::DefaultMetricsManagerScopedGuard` an output stream
/// (`stdout`) to which it will publish metrics.  Note that the default metrics
/// manager is intended to be created and destroyed by the *owner* of `main`.
/// The instance should be created during the initialization of an application
/// (while the task has a single thread) and destroyed just prior to termination
/// (when there is similarly a single thread).
/// @code
/// int main(int argc, char *argv[])
/// {
///
///     // ...
///
///     balm::DefaultMetricsManagerScopedGuard managerGuard(bsl::cout);
/// @endcode
/// Once the default instance has been created, it can be accessed using the
/// static `instance` method.
/// @code
///    balm::MetricsManager *manager = balm::DefaultMetricsManager::instance();
///    assert(0 != manager);
/// @endcode
/// The default metrics manager, by default, is configured with a
/// `balm::StreamPublisher` object that will publish all recorded metrics to the
/// consoled.  We use the default `manager` instance to update the collector
/// for a single metric, and then publish all metrics.
/// @code
///     balm::Collector *myMetric =
///                     manager->collectorRepository().getDefaultCollector(
///                                                  "MyCategory", "MyMetric");
///     myMetric->update(10);
///     manager->publishAll();
///
///     // ... rest of program elided ...
/// }
/// @endcode
/// The output of this example would look similar to:
/// @code
/// 05FEB2009_19:20:12.697+0000 1 Records
///    Elapsed Time: 0.009311s
///            MyCategory.MyMetric [ count = 1, total = 10, min = 10, max = 10 ]
/// @endcode
/// Note that the default metrics manager will be destroyed when `managerGuard`
/// exits this scope and is destroyed.  Clients that choose to explicitly call
/// `balm::DefaultMetricsManager::create()` must also explicitly call
/// `balm::DefaultMetricsManager::destroy()`.
/// @}
/** @} */
/** @} */
 
/** @addtogroup bal
 * @{
 */
/** @addtogroup balm
 * @{
 */
/** @addtogroup balm_defaultmetricsmanager
 * @{
 */
 
#include <balscm_version.h>
 
#include <bslma_allocator.h>
 
#include <bsl_iosfwd.h>
 
 
 
 
namespace balm {
 
class MetricsManager;
 
                        // ============================
                        // struct DefaultMetricsManager
                        // ============================
 
/// This struct provides a namespace for static functions that create,
/// access, and destroy the default instance of the `MetricsManager`.  The
/// expected usage is that the default instance will be created during the
/// initialization of an application (while the task has a single thread)
/// and that it will be destroyed just prior to termination (when there is
/// similarly a single thread).
struct DefaultMetricsManager {
 
  private:
    // CLASS DATA
    static MetricsManager      *s_singleton_p; // metrics manager default
                                               // instance
 
    static bslma::Allocator    *s_allocator_p; // allocator used to initialize
                                               // the singleton
  public:
    // CLASS METHODS
 
    /// If the optionally specified `manager` is not 0, return `manager`;
    /// otherwise return the address of the default metrics manager
    /// instance, or 0 if the default metrics manager instance has not yet
    /// been created or has already been destroyed.  Note that this
    /// operation is logically equivalent to
    /// `manager ? manager : instance()`.
    static MetricsManager *manager(MetricsManager *manager = 0);
 
    /// Create the default `MetricsManager` instance and return the address
    /// of the modifiable created instance.  Optionally specify a
    /// `basicAllocator` used to supply memory.  If `basicAllocator` is 0,
    /// the currently installed global allocator is used.  The behavior is
    /// undefined unless `0 == MetricsManager::instance()` prior to calling
    /// this method, or if this method is called from one thread while
    /// another thread is attempting to access the default metrics manager
    /// instance (i.e., this method is *not* thread-safe).  Note that the
    /// returned default metrics manager instance is not configured with a
    /// publisher; clients must create a `Publisher` and add it to the
    /// default metrics manager in order to publish metrics.
    static MetricsManager *create(bslma::Allocator *basicAllocator = 0);
 
    /// Create the default `MetricsManager` instance and configure it with
    /// a `StreamPublisher` that will publish recorded metrics to the
    /// specified `stream`, then return the address of the modifiable
    /// created metrics manager instance.  Optionally specify
    /// `basicAllocator` to use to obtain memory.  If `basicAllocator` is 0,
    /// the currently installed global allocator is used.  The behavior is
    /// undefined unless `0 == MetricsManager::instance()` prior to calling
    /// this method, or if this method is called from one thread while
    /// another thread is attempting to access the default metrics manager
    /// instance (i.e., this method is *not* thread-safe).
    static MetricsManager *create(bsl::ostream&     stream,
                                  bslma::Allocator *basicAllocator = 0);
 
    /// Return the default instance of the `MetricsManager` or 0 if the
    /// default instance has not yet been created or has already been
    /// destroyed.
    static MetricsManager *instance();
 
    /// Destroy the default instance of `MetricsManager`.  After this
    /// method returns, `instance()` will return 0.  The behavior is
    /// undefined if `instance()` is 0 or if this method is called from one
    /// thread while another thread is accessing the default metrics
    /// manager instance (i.e., this method is *not* thread-safe).
    static void destroy();
};
 
                   // ======================================
                   // class DefaultMetricsManagerScopedGuard
                   // ======================================
 
/// This class implements a scoped guard that, on construction, creates the
/// default instance of the metrics manager, and, on destruction, destroys
/// that instance.  Note that the behavior is undefined if the default
/// instance of the metrics manager is created before creating this guard,
/// or if the default instance is externally destroyed before destroying
/// this guard.
///
/// See @ref balm_defaultmetricsmanager 
class DefaultMetricsManagerScopedGuard {
 
    // NOT IMPLEMENTED
    DefaultMetricsManagerScopedGuard(const DefaultMetricsManagerScopedGuard&);
    DefaultMetricsManagerScopedGuard& operator=(
                                      const DefaultMetricsManagerScopedGuard&);
 
  public:
    // CREATORS
 
    /// Create a scoped guard which invokes
    /// `DefaultMetricsManager::create()` to create a default metrics
    /// manager instance that is configured with a stream publisher that
    /// will publish collected metrics to the specified `stream`.
    /// Optionally specify a `basicAllocator` used to supply memory.  If
    /// `basicAllocator` is 0, the currently installed global allocator is
    /// used.  The behavior is undefined unless
    /// `DefaultMetricsManager::instance()` is 0 prior to creating the
    /// guard.
    DefaultMetricsManagerScopedGuard(bsl::ostream&     stream,
                                     bslma::Allocator *basicAllocator = 0);
 
    /// Create a scoped guard which invokes the
    /// `DefaultMetricsManager::create` method.  Optionally specify a
    /// `basicAllocator` used to obtain memory.  If `basicAllocator` is 0,
    /// the currently installed global allocator is used.  The behavior is
    /// undefined unless `0 == DefaultMetricsManager::instance()` prior to
    /// creating the guard.  Note that the default metrics manager instance
    /// is not configured with a publisher; clients must create a
    /// `Publisher` object and add it to the default metrics manager in
    /// order to publish metrics.
    DefaultMetricsManagerScopedGuard(bslma::Allocator *basicAllocator = 0);
 
    /// Destroy this scoped guard which invokes
    /// `DefaultMetricsManager::destroy()`.  The behavior is undefined if
    /// the default instance of the metrics manager is externally destroyed
    /// prior to this destructor being invoked.
    ~DefaultMetricsManagerScopedGuard();
 
    // ACCESSORS
 
    /// Return the address of the `MetricsManager` object managed by this
    /// scoped guard.  The behavior is undefined if the default instance of
    /// the metrics manager is externally destroyed, or if the returned
    /// address is retained after this scoped guard is destroyed.
    MetricsManager *instance() const;
};
 
// ============================================================================
//                            INLINE DEFINITIONS
// ============================================================================
 
                        // ---------------------------
                        // class DefaultMetricsManager
                        // ---------------------------
 
// CLASS METHODS
inline
MetricsManager *DefaultMetricsManager::instance()
{
    return s_singleton_p;
}
 
inline
MetricsManager *DefaultMetricsManager::manager(
                                                  MetricsManager *manager)
{
    return manager ? manager : s_singleton_p;
}
 
                   // --------------------------------------
                   // class DefaultMetricsManagerScopedGuard
                   // --------------------------------------
 
// CREATORS
inline
DefaultMetricsManagerScopedGuard::DefaultMetricsManagerScopedGuard(
                                              bsl::ostream&     stream,
                                              bslma::Allocator *basicAllocator)
{
    DefaultMetricsManager::create(stream, basicAllocator);
}
 
inline
DefaultMetricsManagerScopedGuard::DefaultMetricsManagerScopedGuard(
                                              bslma::Allocator *basicAllocator)
{
    DefaultMetricsManager::create(basicAllocator);
}
 
inline
DefaultMetricsManagerScopedGuard::~DefaultMetricsManagerScopedGuard()
{
    DefaultMetricsManager::destroy();
}
 
// ACCESSORS
inline
MetricsManager *DefaultMetricsManagerScopedGuard::instance() const
{
    return DefaultMetricsManager::instance();
}
}  // close package namespace
 
 
 
#endif
 
// ----------------------------------------------------------------------------
// Copyright 2015 Bloomberg Finance L.P.
//
// 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.
// ----------------------------- END-OF-FILE ----------------------------------
 
/** @} */
/** @} */
/** @} */