ball_streamobserver.h

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/// @file ball_streamobserver.h
///
/// The content of this file has been pre-processed for Doxygen.
///
 
 
// ball_streamobserver.h                                              -*-C++-*-
#ifndef INCLUDED_BALL_STREAMOBSERVER
#define INCLUDED_BALL_STREAMOBSERVER
 
/// @defgroup ball_streamobserver ball_streamobserver
/// @brief  Provide an observer that emits log records to a stream.
/// @addtogroup bal
/// @{
/// @addtogroup ball
/// @{
/// @addtogroup ball_streamobserver
/// @{
///
/// <h1> Outline </h1>
/// * <a href="#ball_streamobserver-purpose"> Purpose</a>
/// * <a href="#ball_streamobserver-classes"> Classes </a>
/// * <a href="#ball_streamobserver-description"> Description </a>
///   * <a href="#ball_streamobserver-log-record-formatting"> Log Record Formatting </a>
///     * <a href="#ball_streamobserver-scheme-based-format-specifications"> Scheme-Based Format Specifications (Recommended) </a>
///     * <a href="#ball_streamobserver-legacy-format-specifications"> Legacy Format Specifications </a>
///   * <a href="#ball_streamobserver-thread-safety"> Thread Safety </a>
///   * <a href="#ball_streamobserver-usage"> Usage </a>
///     * <a href="#ball_streamobserver-example-1-basic-usage"> Example 1: Basic Usage </a>
///
/// # Purpose {#ball_streamobserver-purpose}
/// Provide an observer that emits log records to a stream.
///
/// # Classes {#ball_streamobserver-classes}
///
/// -  ball::StreamObserver: observer that emits log records to a stream
///
/// @see  ball_record, ball_context, ball_loggermanager
///
/// # Description {#ball_streamobserver-description}
/// This component provides a concrete implementation of the
/// `ball::Observer` protocol for receiving and processing log records:
/// @code
///                ,--------------------.
///               ( ball::StreamObserver )
///                `--------------------'
///                          |              ctor
///                          |              disablePublishInLocalTime
///                          |              enablePublishInLocalTime
///                          |              setFormat
///                          |              setRecordFormatFunctor
///                          |              getFormat
///                          |              isPublishInLocalTimeEnabled
///                          V
///                   ,--------------.
///                  ( ball::Observer )
///                   `--------------'
///                                         publish
///                                         releaseRecords
///                                         dtor
/// @endcode
/// `ball::StreamObserver` is a concrete class derived from `ball::Observer`
/// that processes the log records it receives through its `publish` method by
/// writing them to an output stream.  Given its minimal functionality,
/// `ball::StreamObserver` should be used with care in a production environment.
/// It is not recommended to construct this observer with file-based streams due
/// to lack of any file rotation functionality.
///
/// ## Log Record Formatting {#ball_streamobserver-log-record-formatting}
///
///
/// By default, the output format of published log records is:
/// @code
/// DATE_TIME PID:THREAD-ID SEVERITY FILE:LINE CATEGORY MESSAGE USER-FIELDS
/// @endcode
/// where `DATE` and `TIME` are of the form `DDMonYYYY` and `HH:MM:SS.mmm`,
/// respectively (`Mon` being the 3-letter abbreviation for the month).  For
/// example, a log record will have the following appearance when the default
/// format is in effect (assuming that no user-defined fields are present):
/// @code
/// 18MAY2005_18:58:12.076 7959:1 WARN ball_streamobserver.t.cpp:404 TEST hello!
/// @endcode
/// For additional flexibility, the `setFormat` method can be called to
/// configure the format of published records to the stream.  The format
/// specifications can be either scheme-tagged (recommended) or legacy
/// `printf`-style format strings that results in a `RecordStringFormatter`
/// being used.
///
/// ### Scheme-Based Format Specifications (Recommended) {#ball_streamobserver-scheme-based-format-specifications}
///
///
/// The recommended way to specify log record formats is using URI-like
/// scheme-tagged format configuration strings.  A scheme-tagged format string
/// begins with a scheme identifier followed by `://` and then a
/// scheme-specific format specification:
/// @code
/// <scheme>://<format-specification>
/// @endcode
/// The scheme determines which formatter will be used and the syntax of the
/// format specification.  The following schemes are currently supported: text,
/// json, qjson.  See [Scheme-Based Formatters](@ref ball-scheme-based-formatters) 
/// for more details of the supported schemes and their accompanying format
/// specification syntaxes.
///
/// For example, to log records to a file in JSON format with printf-style
/// format specification:
/// @code
/// asyncFileObserver.setFormat("qjson://%d %p:%t %s %f:%l %c %m");
/// @endcode
///
/// ### Legacy Format Specifications {#ball_streamobserver-legacy-format-specifications}
///
///
/// For backward compatibility, format specifications that do not begin with a
/// scheme tag are treated as legacy `printf`-style format strings.  Such
/// specifications are implicitly treated as if they had a `text://` prefix
/// and use `ball::RecordStringFormatter`.  For example, the following two
/// calls are equivalent:
/// @code
/// streamObserver.setFormat("%d %p:%t %s %f:%l %c %m %a\n");
/// streamObserver.setFormat("text://%d %p:%t %s %f:%l %c %m %a\n");
/// @endcode
/// These `%`-prefixed conversion specifications are defined in
/// @ref ball_recordstringformatter .
///
/// ## Thread Safety {#ball_streamobserver-thread-safety}
///
///
/// All methods of `ball::StreamObserver` are thread-safe, and can be called
/// concurrently by multiple threads.
///
/// ## Usage {#ball_streamobserver-usage}
///
///
/// This section illustrates intended use of this component.
///
/// ### Example 1: Basic Usage {#ball_streamobserver-example-1-basic-usage}
///
///
/// The following snippets of code illustrate the basic usage of
/// `ball::StreamObserver`.
///
/// First create a `ball::Record` object `record` and a `ball::Context` object
/// `context`.  Note that the default values for these objects (or their
/// contained objects) are perfectly suitable for logging purposes.
/// @code
/// ball::RecordAttributes attributes;
/// ball::UserFields       fieldValues;
/// ball::Context          context;
///
/// bslma::Allocator *ga = bslma::Default::globalAllocator(0);
/// const bsl::shared_ptr<const ball::Record>
///            record(new (*ga) ball::Record(attributes, fieldValues, ga), ga);
/// @endcode
/// Next, create a stream observer `observer` with the `bsl::cout` as the output
/// stream.
/// @code
/// ball::StreamObserver observer(&bsl::cout);
/// @endcode
/// Finally, publish `record` and `context` to `observer`.
/// @code
/// observer.publish(record, context);
/// @endcode
/// This will produce the following output on `stdout`:
/// @code
/// 01JAN0001_24:00:00.000 0 0 OFF  0
/// @endcode
/// @}
/** @} */
/** @} */
 
/** @addtogroup bal
 * @{
 */
/** @addtogroup ball
 * @{
 */
/** @addtogroup ball_streamobserver
 * @{
 */
 
#include <balscm_version.h>
 
#include <ball_observerformatterimp.h>
#include <ball_observer.h>
#include <ball_recordformatterfunctor.h>
#include <ball_recordformattertimezone.h>
 
#include <bsla_deprecated.h>
 
#include <bslma_allocator.h>
#include <bslma_bslallocator.h>
 
#include <bslmt_mutex.h>
 
#include <bsls_assert.h>
#include <bsls_keyword.h>
#include <bsls_review.h>
 
#include <bsl_iosfwd.h>
#include <bsl_functional.h>
 
 
namespace ball {
 
class Context;
class Record;
 
                           // ====================
                           // class StreamObserver
                           // ====================
 
/// This class provides a concrete implementation of the `Observer`
/// protocol.  The `publish` method of this class outputs the log records
/// that it receives to an instance of `bsl::ostream` supplied at
/// construction.
///
/// See @ref ball_streamobserver 
class StreamObserver : public Observer {
  public:
    // TYPES
 
    /// `LogRecordFunctor` is an alias for the type of the functor used for
    /// formatting log records to a stream.
    typedef RecordFormatterFunctor::Type RecordFormatter;
    typedef RecordFormatterFunctor::Type RecordFormatFunctor;
 
    typedef bsl::allocator<char> allocator_type;
 
  private:
    // PRIVATE TYPES
    typedef RecordFormatterTimezone::Enum TimezoneEnum;
 
  private:
    // DATA
    bsl::ostream             *d_stream_p;           // output sink for log
                                                    // records
 
    mutable bslmt::Mutex      d_mutex;              // serializes concurrent
                                                    // calls to 'publish'
 
    ObserverFormatterImp      d_observerFormatterImp;
                                                    // formatter manager that
                                                    // handles all formatting
                                                    // operations
 
  private:
    // NOT IMPLEMENTED
    StreamObserver(const StreamObserver&);
    StreamObserver& operator=(const StreamObserver&);
 
  public:
    // CREATORS
 
    /// Create a stream observer that transmits log records to the specified
    /// `stream`.  Optionally specify an `allocator` (e.g., the address of a
    /// `bslma::Allocator` object) to supply memory; otherwise, the default allocator is used.  
    /// 
    /// \note Note that   a default record format is in effect
    /// for stream logging (see `logRecordDefault`).
    explicit
    StreamObserver(bsl::ostream          *stream,
                   const allocator_type&  allocator = allocator_type());
 
    /// Destroy this stream observer.
    ~StreamObserver() BSLS_KEYWORD_OVERRIDE;
 
    // MANIPULATORS
 
    using Observer::publish;  // Picks up the deprecated `publish` overload.
 
    /// Process the specified log `record` having the specified publishing
    /// `context`.  Print `record` and `context` to the `bsl::ostream` supplied at construction.  
    /// 
    /// \pre The behavior is undefined   if `record` or
    /// `context` is modified during the execution of this method.
    void publish(const bsl::shared_ptr<const Record>& record,
                 const Context&                       context)
                                                         BSLS_KEYWORD_OVERRIDE;
 
    /// Discard any shared reference to a `Record` object that was supplied
    /// to the `publish` method, and is held by this observer.  
    /// 
    /// \note Note that   this operation should be called if resources underlying the
    /// previously provided shared-pointers must be released.  This method
    /// intentionally does nothing as such resources are held, we publish all
    /// records immediately.
    void releaseRecords() BSLS_KEYWORD_OVERRIDE;
 
    /// Disable publishing of the timestamp attribute of records in local
    /// time by this stream observer; henceforth, timestamps will be in UTC
    /// time.  This method has no effect if publishing in local time is not
    /// enabled.
    void disablePublishInLocalTime();
 
    /// Enable publishing of the timestamp attribute of records in local
    /// time by this stream observer.  By default, timestamps are published in UTC time.  
    /// 
    /// \note Note that   this method also affects timestamps for
    /// formatters that use them.
    void enablePublishInLocalTime();
 
    /// Set the formatting functor used when writing records to the stream of
    /// this stream observer to the specified `formatter` functor.  
    /// 
    /// \note Note that   a default format ("\n%d %p %t %s %f %l %c %m %u\n") is in effect until
    /// this method or `setFormat` is called (see
    /// @ref ball_recordstringformatter ).  Also note that the observer emits
    /// newline characters at the beginning and at the end of a log record
    /// by default, so the user needs to add them explicitly to the format string to preserve this behavior.  
    /// 
    /// \note Note that   this method is not
    /// able to communicate the timezone default settings to the
    /// `formatter`, prefer `setFormat`.
    void setRecordFormatFunctor(const RecordFormatter& formatter);
 
    /// Set the formatting functor used when writing records to the stream of
    /// this stream observer to a log file functor created according to the
    /// specified, possibly URI-like scheme tagged, `format`.  Return zero if
    /// the setup with the specified arguments was successful and also save
    /// the `format` to be later retrievable using `getFormat`.  Otherwise (if
    /// no matching scheme could be found or the configuration is invalid)
    /// return a non-zero value and do not change the log record formatter used by this object.  
    /// 
    /// \note Note that   a default format
    /// ("\n%d %p %t %s %f %l %c %m %u\n") is in effect until this method or
    /// `setRecordFormatFunctor` is called.  Also, notice that the observer
    /// emits newline characters at the beginning and at the end of a log
    /// record by (the) default (format), so the user needs to add them
    /// explicitly to (text) format strings to preserve that behavior.
    int setFormat(const bsl::string_view& format);
 
    // ACCESSORS
 
    /// Return `true` if this observer writes the timestamp attribute of
    /// records that it publishes in local time by default, and `false`
    /// otherwise (in which case timestamps are written by default in UTC
    ///  time).
    bool isPublishInLocalTimeEnabled() const;
 
    /// Return the format config of the last successful `setFormat` call.
    const bsl::string& getFormat() const;
};
 
// ============================================================================
//                             INLINE DEFINITIONS
// ============================================================================
 
                           // --------------------
                           // class StreamObserver
                           // --------------------
 
// MANIPULATORS
inline
void StreamObserver::releaseRecords()
{
}
 
}  // close package namespace
 
 
#endif
 
// ----------------------------------------------------------------------------
// Copyright 2017 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 ----------------------------------
 
/** @} */
/** @} */
/** @} */