[#BloombergLP-ball-FileObserver]
= xref:BloombergLP.adoc[BloombergLP]::xref:BloombergLP/ball.adoc[ball]::FileObserver
:relfileprefix: ../../
:mrdocs:

This class implements the `Observer` protocol. The `publish` method of this class outputs the log records that it receives to `stdout` and optionally to a user‐specified file. This class is thread‐safe; different threads can operate on an object concurrently. This class is exception‐neutral with no guarantee of rollback. In no event is memory leaked.

== Synopsis

Declared in `<ball_fileobserver.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
class FileObserver
    : public xref:BloombergLP/ball/Observer.adoc[Observer]
----

== Base Classes

[cols="1,4"]
|===
| Name| Description
| `xref:BloombergLP/ball/Observer.adoc[Observer]`
| This class provides a protocol for receiving and processing log record output.
|===

== Type Aliases

[cols="1,4"]
|===
| Name| Description
| xref:BloombergLP/ball/FileObserver/OnFileRotationCallback.adoc[`OnFileRotationCallback`] 
| `OnFileRotationCallback` is an alias for a user‐supplied callback function that is invoked after the file observer attempts to rotate its log file. The callback takes two arguments: (1) an integer status value where 0 indicates a new log file was successfully created and a non‐zero value indicates an error occurred during rotation, and (2) a string that provides the name of the rotated log file if the rotation was successful. E.g.: ` void onLogFileRotation(int rotationStatus, const bsl::string& rotatedLogFileName); `
|===


== Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:BloombergLP/ball/FileObserver/2constructor-0f.adoc[`FileObserver`]         [.small]#[constructor]#
| Constructors
| xref:BloombergLP/ball/FileObserver/2destructor.adoc[`~FileObserver`] [.small]#[destructor]# [.small]#[virtual]#
| Close the log file of this file observer if file logging is enabled, and destroy this file observer.
| xref:BloombergLP/ball/FileObserver/allocator.adoc[`allocator`] 
| Return the memory allocator used by this object.
| xref:BloombergLP/ball/FileObserver/disableFileLogging.adoc[`disableFileLogging`] 
| Disable file logging for this file observer. This method has no effect if file logging is not enabled. Note that records subsequently received through the `publish` method of this file observer may still be logged to `stdout` after calling this method.
| xref:BloombergLP/ball/FileObserver/disableLifetimeRotation.adoc[`disableLifetimeRotation`] 
| Disable log file rotation based on a periodic time interval for this file observer. This method has no effect if rotation‐on‐time‐interval is not enabled.
| xref:BloombergLP/ball/FileObserver/disablePublishInLocalTime.adoc[`disablePublishInLocalTime`] 
| Disable publishing of the timestamp attribute of records in local time by this file observer; henceforth, timestamps will be in UTC time. This method has no effect if publishing in local time is not enabled. Note that this method also affects log filenames (see {Log Filename Patterns}).
| xref:BloombergLP/ball/FileObserver/disableSizeRotation.adoc[`disableSizeRotation`] 
| Disable log file rotation based on log file size for this file observer. This method has no effect if rotation‐on‐size is not enabled.
| xref:BloombergLP/ball/FileObserver/disableStdoutLoggingPrefix.adoc[`disableStdoutLoggingPrefix`] 
| Disable this file observer from using the long output format when logging to `stdout`. Henceforth, this file observer will use the default short output format ("n%s %f:%l %c %m %un") when logging to `stdout`. This method has no effect if the long output format for `stdout` logging is not enabled. Note that this method omits the "%d %p:%t " prefix from the default long output format.
| xref:BloombergLP/ball/FileObserver/disableTimeIntervalRotation.adoc[`disableTimeIntervalRotation`] 
| Disable log file rotation based on a periodic time interval for this file observer. This method has no effect if rotation‐on‐time‐interval is not enabled.
| xref:BloombergLP/ball/FileObserver/disableUserFieldsLogging.adoc[`disableUserFieldsLogging`]  [.small]#[deprecated]#
| Disable the logging of user‐defined fields by this file observer. This method has no effect if logging of user‐defined fields is not enabled, or if a format string other than the default one is in effect.
| xref:BloombergLP/ball/FileObserver/enableFileLogging-06.adoc[`enableFileLogging`] 
| `enableFileLogging` overloads
| xref:BloombergLP/ball/FileObserver/enablePublishInLocalTime.adoc[`enablePublishInLocalTime`] 
| Enable publishing of the timestamp attribute of records in local time by this file observer. This method has no effect if publishing in local time is already enabled. Note that this method also affects log filenames (see {Log Filename Patterns}).
| xref:BloombergLP/ball/FileObserver/enableStdoutLoggingPrefix.adoc[`enableStdoutLoggingPrefix`] 
| Enable this file observer to use the long output format when logging to `stdout`. Henceforth, this file observer will use the output format for `stdout` logging that was set by the most recent call to `setLogFormat`, or the default long output format ("n%d %p:%t %s %f:%l %c %m %un") if `setLogFormat` has not yet been called. This method has no effect if the long output format for `stdout` logging is already enabled.
| xref:BloombergLP/ball/FileObserver/enableUserFieldsLogging.adoc[`enableUserFieldsLogging`]  [.small]#[deprecated]#
| Enable the logging of user‐defined fields by this file observer. This method has no effect if logging of user‐defined fields is already enabled, or if a format string other than the default one is in effect.
| xref:BloombergLP/ball/FileObserver/forceRotation.adoc[`forceRotation`] 
| Forcefully perform a log file rotation by this file observer. Close the current log file, rename the log file if necessary, and open a new log file. This method has no effect if file logging is not enabled. See {Rotated File Naming} for details on filenames of rotated log files.
| xref:BloombergLP/ball/FileObserver/getFileLogFormat.adoc[`getFileLogFormat`] 
| Return the format specification for log records written to the log file by this file observer. See {Log Record Formatting} for details on the syntax of format specifications.
| xref:BloombergLP/ball/FileObserver/getLogFormat.adoc[`getLogFormat`] 
| Load the format specification for log records written by this file observer to the log file into the specified `*logFileFormat` address and the format specification for log records written to `stdout` into the specified `*stdoutFormat` address. See {Log Record Formatting} for details on the syntax of format specifications.
| xref:BloombergLP/ball/FileObserver/getStdoutLogFormat.adoc[`getStdoutLogFormat`] 
| Return the format specification for log records written to `stdout` by this file observer. See {Log Record Formatting} for details on the syntax of format specifications.
| xref:BloombergLP/ball/FileObserver/isFileLoggingEnabled-0657.adoc[`isFileLoggingEnabled`] 
| `isFileLoggingEnabled` overloads
| xref:BloombergLP/ball/FileObserver/isPublishInLocalTimeEnabled.adoc[`isPublishInLocalTimeEnabled`] 
| Return `true` if this file observer writes the timestamp attribute of records by default in local time, and `false` otherwise (in which case timestamps are written in UTC time by default). Note that the value returned by this method also affects log filenames (see {Log Filename Patterns}).
| xref:BloombergLP/ball/FileObserver/isStdoutLoggingPrefixEnabled.adoc[`isStdoutLoggingPrefixEnabled`] 
| Return `true` if this file observer uses the long output format when writing to `stdout`, and `false` otherwise (in which case the default short output format is used). See `enableStdoutLoggingPrefix` and `disableStdoutLoggingPrefix`.
| xref:BloombergLP/ball/FileObserver/isSuppressUniqueFileNameOnRotation.adoc[`isSuppressUniqueFileNameOnRotation`] 
| Return `true` if the log filename uniqueness check on rotation is suppressed, and false otherwise.
| xref:BloombergLP/ball/FileObserver/isUserFieldsLoggingEnabled.adoc[`isUserFieldsLoggingEnabled`]  [.small]#[deprecated]#
| Return `true` if the logging of user‐defined fields is enabled for this file observer, and `false` otherwise.
| xref:BloombergLP/ball/FileObserver/localTimeOffset.adoc[`localTimeOffset`] 
| Return the difference between the local time and UTC time in effect when this file observer was constructed. Note that this value remains unchanged during the lifetime of this object and therefore may become incorrect when the difference between the local time and UTC time changes (e.g., when transitioning into or out of daylight savings time).
| xref:BloombergLP/ball/FileObserver/publish-0d.adoc[`publish`] 
| `publish` overloads
| xref:BloombergLP/ball/FileObserver/releaseRecords.adoc[`releaseRecords`]  [.small]#[virtual]#
| Discard any shared references to `Record` objects that were supplied to the `publish` method, and are held by this observer. Note that this operation should be called if resources underlying the previously provided shared pointers must be released.
| xref:BloombergLP/ball/FileObserver/rotateOnLifetime.adoc[`rotateOnLifetime`] 
| Set this file observer to perform a periodic log file rotation at multiples of the specified `timeInterval`. The behavior is undefined unless `0 < timeInterval.totalMilliseconds()`. This rule replaces any rotation‐on‐time‐interval rule currently in effect.
| xref:BloombergLP/ball/FileObserver/rotateOnSize.adoc[`rotateOnSize`] 
| Set this file observer to perform log file rotation when the size of the file exceeds the specified `size` (in kilobytes). This rule replaces any rotation‐on‐size rule currently in effect. The behavior is undefined unless `size > 0`.
| xref:BloombergLP/ball/FileObserver/rotateOnTimeInterval-02.adoc[`rotateOnTimeInterval`] 
| `rotateOnTimeInterval` overloads
| xref:BloombergLP/ball/FileObserver/rotationLifetime.adoc[`rotationLifetime`] 
| Return the lifetime of the log file that will trigger a file rotation by this file observer if rotation‐on‐lifetime is in effect, and a 0 time interval otherwise.
| xref:BloombergLP/ball/FileObserver/rotationSize.adoc[`rotationSize`] 
| Return the size (in kilobytes) of the log file that will trigger a file rotation by this file observer if rotation‐on‐size is in effect, and 0 otherwise.
| xref:BloombergLP/ball/FileObserver/setFileLogFormat.adoc[`setFileLogFormat`] 
| Set the format specifications for log records written to the log file to `logFileFormat`. See {Log Record Formatting} for details on the syntax of format specifications. Return zero if the format is valid and the corresponding formatter has been set. Otherwise, if the format is invalid, return a non‐zero value and do not change the formatter. Note that default format is in effect following construction until a format‐setting method is called ("n%d %p:%t %s %f:%l %c %m %un" for both file and `stdout` logging).
| xref:BloombergLP/ball/FileObserver/setLogFormat.adoc[`setLogFormat`] 
| Same as `setLogFormats`.
| xref:BloombergLP/ball/FileObserver/setLogFormats.adoc[`setLogFormats`] 
| Set the format specifications for log records written to the log file and to `stdout` to the specified `logFileFormat` and `stdoutFormat`, respectively. If the default short output format is currently in effect for logging to `stdout`, this method has the effect of calling `enableStdoutLoggingPrefix` (see that method and `disableStdoutLoggingPrefix`) and setting the format corresponding to enabled `stdout` logging prefix to `stdoutFormat`. See {Log Record Formatting} for details on the syntax of format specifications. Return zero if both formats are valid and have been set. Otherwise, if either format is invalid, return a non‐zero value. If one of the formats is invalid, it will not be set, but the valid format will be set. Note that default formats are in effect following construction until a format‐setting method is called ("n%d %p:%t %s %f:%l %c %m %un" for both file and `stdout` logging). Also note that the default format 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 (text) format strings to preserve that behavior.
| xref:BloombergLP/ball/FileObserver/setOnFileRotationCallback.adoc[`setOnFileRotationCallback`] 
| Set the specified `onRotationCallback` to be invoked after each time this file observer attempts to perform a log file rotation. The behavior is undefined if the supplied function calls either `setOnFileRotationCallback`, `forceRotation`, or `publish` on this file observer (i.e., the supplied callback should _not_ attempt to write to the `ball` log).
| xref:BloombergLP/ball/FileObserver/setStdoutLogFormat.adoc[`setStdoutLogFormat`] 
| Set the format specifications for log records written to `stdout` to `stdoutFormat`. If the default short output format is currently in effect (for logging to `stdout`) this method has the effect of calling `enableStdoutLoggingPrefix` (see that method and `disableStdoutLoggingPrefix`) and setting the format corresponding to enabled `stdout` logging prefix to `stdoutFormat`. See {Log Record Formatting} for details on the syntax of format specifications. Return zero if the format is valid and the corresponding formatter has been set. Otherwise, if the format is invalid, return a non‐zero value and do not change the formatter. Note that default format is in effect following construction until a format‐setting method is called ("n%d %p:%t %s %f:%l %c %m %un" for both file and `stdout` logging).
| xref:BloombergLP/ball/FileObserver/setStdoutThreshold.adoc[`setStdoutThreshold`] 
| Set the minimum severity of records logged to `stdout` by this file observer to the specified `stdoutThreshold` level. Note that if the value of `stdoutThreshold` is `Severity::e_OFF`, logging to `stdout` is disabled.
| xref:BloombergLP/ball/FileObserver/stdoutThreshold.adoc[`stdoutThreshold`] 
| Return the minimum severity of records that will be logged to `stdout` by this file observer. Note that records with a threshold less severe than `stdoutThreshold()` may still be output to the log file if file logging is enabled.
| xref:BloombergLP/ball/FileObserver/suppressUniqueFileNameOnRotation.adoc[`suppressUniqueFileNameOnRotation`] 
| Suppress generating a unique log file name upon rotation if the specified `suppress` is `true`, and generate a unique filename otherwise. See {Rotated File Naming} for details.
| xref:BloombergLP/ball/FileObserver/2conversion.adoc[`operator BloombergLP::bslmf::NestedTraitDeclaration<FileObserver, UsesBslmaAllocator>`] 
| Declare that this type uses a `bslma` allocator.
|===



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