ball_loggerfunctorpayloads.h

Go to the documentation of this file.

/// @file ball_loggerfunctorpayloads.h
///
/// The content of this file has been pre-processed for Doxygen.
///
 
 
// ball_loggerfunctorpayloads.h                                       -*-C++-*-
#ifndef INCLUDED_BALL_LOGGERFUNCTORPAYLOADS
#define INCLUDED_BALL_LOGGERFUNCTORPAYLOADS
 
#include <bsls_ident.h>
BSLS_IDENT("$Id: $")
 
/// @defgroup ball_loggerfunctorpayloads ball_loggerfunctorpayloads
/// @brief  Provide a suite of logger manager singleton functor payloads.
/// @addtogroup bal
/// @{
/// @addtogroup ball
/// @{
/// @addtogroup ball_loggerfunctorpayloads
/// @{
///
/// <h1> Outline </h1>
/// * <a href="#ball_loggerfunctorpayloads-purpose"> Purpose</a>
/// * <a href="#ball_loggerfunctorpayloads-description"> Description </a>
///   * <a href="#ball_loggerfunctorpayloads-support-for-hierarchical-category-names"> Support for Hierarchical Category Names </a>
///   * <a href="#ball_loggerfunctorpayloads-usage"> Usage </a>
///     * <a href="#ball_loggerfunctorpayloads-example-basic-usage"> Example: Basic Usage </a>
///
/// # Purpose {#ball_loggerfunctorpayloads-purpose}
/// Provide a suite of logger manager singleton functor payloads.
///
///@CLASSES
///  ball::LoggerFunctorPayloads: namespace for logger manager functor payloads
///
/// @see  ball_loggermanagerconfiguration, ball_loggermanager
///
/// # Description {#ball_loggerfunctorpayloads-description}
/// This component provides a namespace,
/// `ball::LoggerFunctorPayloads`, containing a suite of functions, each of
/// which may be used as the function body "payload" of one of the various
/// `bsl::function` functors used as callbacks in the @ref ball_loggermanager 
/// component.  Each function provides a specific customization or convenience
/// enhancement to the basic logger functionality.
///
/// **WARNING**: Note that all functions defined in this component are intended
/// for use with the logger manager singleton *only*, and not with any
/// non-singleton instances of `ball::LoggerManager`; in particular, a
/// precondition of each of the functions is that the logger manager singleton
/// must be initialized and not in the process of being shut down.
///
/// The lone function defined in `ball::LoggerFunctorPayloads` at this time,
/// `loadParentCategoryThresholdValues`, has signature:
/// @code
/// (int *, int *, int *, int *, const char *, char)
/// @endcode
/// The initial five types in this signature match the following `typedef` from
/// `ball::LoggerManager` (and `ball::LoggerManagerConfiguration`):
/// @code
/// /// `DefaultThresholdLevelsCallback` is the type of the functor that
/// /// determines default threshold levels for categories added to the
/// /// registry by the `setCategory(const char *)` method.
/// typedef bsl::function<void(int *, int *, int *, int *, const char *)>
///                                             DefaultThresholdLevelsCallback;
/// @endcode
/// The purpose of the trailing `char` argument is discussed in the following
/// section, the Usage example, and the `loadParentCategoryThresholdValues`
/// function-level documentation.
///
/// ## Support for Hierarchical Category Names {#ball_loggerfunctorpayloads-support-for-hierarchical-category-names}
///
///
/// The `ball` logging toolkit does not explicitly support any structure in the
/// registry of category names; each unique sequence of characters defines a
/// unique category that is, from the logger's perspective, a "peer" to all
/// other categories.  The toolkit does, however, provide several callback
/// mechanisms that facilitate customized naming conventions.
///
/// In particular, the `ball::LoggerManager` singleton can be configured with a
/// `DefaultThresholdLevelsCallback` (see the `typedef` definition above) that,
/// if not null, is invoked to populate the four threshold levels whenever the
/// user creates a category having the "default" thresholds.  This component
/// provides the function `loadParentCategoryThresholdValues` that can be used
/// as the payload to `DefaultThresholdLevelsCallback`.
/// `loadParentCategoryThresholdValues` populates its four category threshold
/// level arguments from a specified "child" category name and a `char`
/// delimiter by searching the category registry for a name that is "the most
/// proximate parent category", assuming a hierarchical naming convention that
/// uses the delimiter character.  If such a parent category is found, the
/// "child" category will receive the threshold levels of the parent.  If no
/// such parent exists, the new category will receive the standard "default"
/// thresholds that it would have gotten had the callback been null.
///
/// ## Usage {#ball_loggerfunctorpayloads-usage}
///
///
/// This section illustrates intended use of this component.
///
/// ### Example: Basic Usage {#ball_loggerfunctorpayloads-example-basic-usage}
///
///
/// The following code snippets illustrate how to use this component's
/// `loadParentCategoryThresholdValues` method to allow a newly-created "child"
/// category to inherit the logging threshold levels from its most proximate
/// parent category (if such a category already exists).  Note that the category
/// "hierarchy" is by naming convention only, but that the callback makes it
/// simple for the *user* to impose hierarchical meaning on names that are, from
/// the *logger's* perspective, peers.  In this example, we will choose the dot
/// character (`.`) as the hierarchy delimiter; to the logger itself, `.` is not
/// special.
///
/// To keep this example transparent, we will create and inspect several
/// categories within `main` directly; some categories will be "declared" to be
/// "parent" categories, and we will set the threshold levels explicitly, while
/// other categories will act as "children", which is to say that they will
/// obtain their threshold levels through the callback mechanism.  In a more
/// realistic example, there would be no explicit distinction between "parent"
/// and "child" categories, but rather as categories are dynamically
/// administered by the user, newly created categories would pick up the changes
/// made to existing parents.  As a practical matter, the beginning of the
/// function `main` constitute the "usage" to *install* the callback; the rest
/// of this example merely illustrates the *consequences* of that.
///
/// First, we load the logger manager `configuration` with the desired "payload"
/// function, `ball::LoggerFunctorPayloads::loadParentCategoryThresholdValues`,
/// and use the trailing `char` argument `delimiter`, set to the value `.`,
/// which will be bound into the functor and supplied back to the payload on
/// each invocation.
/// @code
/// // myapp.cpp
/// int main()
/// {
///     using namespace bdlf::PlaceHolders;
///
///     ball::LoggerManagerConfiguration configuration;
///     char delimiter = '.';
///     configuration.setDefaultThresholdLevelsCallback(
///         bdlf::BindUtil::bind(
///            &ball::LoggerFunctorPayloads::loadParentCategoryThresholdValues,
///            _1,
///            _2,
///            _3,
///            _4,
///            _5,
///            delimiter));
/// @endcode
/// Then, we initialize the logger manager, using the configuration defined
/// above:
/// @code
///     ball::LoggerManagerScopedGuard guard(configuration);
/// @endcode
/// The above code is all that the user needs to do to customize the logger to
/// "inherit" thresholds from parents.  The rest of this example illustrates the
/// consequences of having installed `myCallback`.  For convenience in what
/// follows, we define a reference, `manager`, to the singleton logger manager.
/// @code
///     ball::LoggerManager& manager = ball::LoggerManager::singleton();
/// @endcode
/// We now create two "parent" categories named "EQUITY.MARKET" and
/// "EQUITY.GRAPHICS", and give them arbitrary but distinct threshold levels.
/// We also set the default levels to distinct values in order to be able to
/// verify exactly where "child" levels have come from later on.
/// @code
///     manager.setDefaultThresholdLevels(128, 96, 64, 32);
///
///     manager.addCategory("EQUITY.MARKET", 127, 95, 63, 31);
///     manager.addCategory("EQUITY.GRAPHICS", 129, 97, 65, 33);
/// @endcode
/// Note that the call to `addCategory`, which takes the four `int` threshold
/// arguments, does not invoke the callback at all, but rather -- assuming that
/// the named category does not yet exist -- sets the thresholds to the
/// specified values directly.
///
/// We can use the logger manager interface to verify that the levels have been
/// set.  First, we use the `lookupCategory` method to obtain the two parent
/// categories (here assigned `p1` and `p2`).
/// @code
///     const ball::Category *p1 = manager.lookupCategory("EQUITY.MARKET");
///     const ball::Category *p2 = manager.lookupCategory("EQUITY.GRAPHICS");
/// @endcode
/// Next, we can use the appropriate `ball::Category` accessor methods to
/// `assert` the expected results.  Recall that the ordered sequence of levels
/// is "Record", "Pass", "Trigger", and "TriggerAll".
/// @code
///     assert(127 == p1->recordLevel());
///     assert( 95 == p1->passLevel());
///     assert( 63 == p1->triggerLevel());
///     assert( 31 == p1->triggerAllLevel());
///
///     assert(129 == p2->recordLevel());
///     assert( 97 == p2->passLevel());
///     assert( 65 == p2->triggerLevel());
///     assert( 33 == p2->triggerAllLevel());
/// @endcode
/// Now, we will add several "child" categories using the `setCategory` method
/// taking a single argument, the `char*` category name.  This method uses the
/// callback in determining the "default" threshold levels to use.  The six
/// statements are numbered for subsequent discussion.
/// @code
///     manager.setCategory("EQUITY.MARKET.NYSE");                      // (1)
///     manager.setCategory("EQUITY.MARKET.NASDAQ");                    // (2)
///     manager.setCategory("EQUITY.GRAPHICS.MATH.FACTORIAL");          // (3)
///     manager.setCategory("EQUITY.GRAPHICS.MATH.ACKERMANN");          // (4)
///     manager.setCategory("EQUITY.GRAPHICS.MATH");                    // (5)
///     manager.setCategory("EQUITY");                                  // (6)
/// @endcode
/// Note that all six calls to `setCategory` will succeed in adding new
/// categories to the registry.  Calls (1)-(5) will "find" their parent's names
/// and "inherit" the parent's levels.  Call (6), however, will not find a
/// parent category, and so will receive the default threshold levels, just as
/// if there were no callback installed.
///
/// Note also that, although in this "static" (i.e., unadministered) example
/// there is no significance to the order in which the above categories are
/// created, in general (e.g., when categories are being dynamically
/// administered) the order of creation *does* matter.  If line (5) were
/// executed before line (4) then the call on line (4) would find the
/// "EQUITY.GRAPHICS.MATH" category as its "parent" and inherit those threshold
/// levels.  If, before line (4) executed, the thresholds of
/// "EQUITY.GRAPHICS.MATH" were changed, then "EQUITY.GRAPHICS.MATH.FACTORIAL"
/// and "EQUITY.GRAPHICS.MATH.ACKERMANN" would have different threshold levels
/// despite their equivalent standing in the category hierarchy.
///
/// Let us now verify some of the 24 threshold levels that have been set by the
/// above calls.  We will verify the results of lines (1), (3), and (6) above.
/// @code
///     const ball::Category *c1, *c3, *c6;
///
///     c1 =  manager.lookupCategory("EQUITY.MARKET.NYSE");
///     assert(127 == c1->recordLevel());
///     assert( 95 == c1->passLevel());
///     assert( 63 == c1->triggerLevel());
///     assert( 31 == c1->triggerAllLevel());
///
///     c3 =  manager.lookupCategory("EQUITY.GRAPHICS.MATH.FACTORIAL");
///     assert(129 == c3->recordLevel());
///     assert( 97 == c3->passLevel());
///     assert( 65 == c3->triggerLevel());
///     assert( 33 == c3->triggerAllLevel());
///
///     c6 =  manager.lookupCategory("EQUITY");
///     assert(128 == c6->recordLevel());
///     assert( 96 == c6->passLevel());
///     assert( 64 == c6->triggerLevel());
///     assert( 32 == c6->triggerAllLevel());
///
///     return 0;
/// }
/// @endcode
/// @}
/** @} */
/** @} */
 
/** @addtogroup bal
 * @{
 */
/** @addtogroup ball
 * @{
 */
/** @addtogroup ball_loggerfunctorpayloads
 * @{
 */
 
#include <balscm_version.h>
 
 
namespace ball {
 
                    // ============================
                    // struct LoggerFunctorPayloads
                    // ============================
 
/// This `struct` provides a namespace for a suite of utility functions,
/// each of which may be used as the function body for an appropriate
/// `bsl::function` callback functor within @ref ball_loggermanager .
///
/// **WARNING**: Note that all functions are intended for use with the logger
/// manager singleton *only*, and not with any non-singleton instances of
/// `ball::LoggerManager`.
struct LoggerFunctorPayloads {
 
    // CLASS METHODS
 
    /// Load into the specified `recordLevel`, `passLevel`, `triggerLevel`,
    /// and `triggerAllLevel` the respective threshold levels of the
    /// category in the registry of the (singleton) `ball` logger manager
    /// that is the most proximate parent category of the category having
    /// the specified `categoryName` among existing hierarchically named
    /// categories in the registry, if such a parent category exists, or the
    /// default thresholds otherwise; use the specified `delimiter` to
    /// define hierarchical category names.  The behavior is undefined
    /// unless the logger manager singleton has been initialized and is not
    /// in the process of being shut down.
    static
    void loadParentCategoryThresholdValues(int        *recordLevel,
                                           int        *passLevel,
                                           int        *triggerLevel,
                                           int        *triggerAllLevel,
                                           const char *categoryName,
                                           char        delimiter);
};
 
}  // 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 ----------------------------------
 
/** @} */
/** @} */
/** @} */