"logging.handlers" --- Logging handlers
***************************************

**Code source :** Lib/logging/handlers.py


Important
^^^^^^^^^

Cette page contient uniquement des informations de référence. Pour des
tutoriels, veuillez consulter

* Tutoriel basique

* Tutoriel avancé

* livre de recettes sur la journalisation

======================================================================

Les gestionnaires suivants, très utiles, sont fournis dans le paquet.
Notez que trois des gestionnaires ("StreamHandler", "FileHandler" et
"NullHandler") sont en réalité définis dans le module "logging" lui-
même, mais qu’ils sont documentés ici avec les autres gestionnaires.


Gestionnaire à flux — *StreamHandler*
=====================================

La classe "StreamHandler", du paquet "logging", envoie les sorties de
journalisation dans des flux tels que *sys.stdout*, *sys.stderr* ou
n’importe quel objet fichier-compatible (ou, plus précisément, tout
objet qui gère les méthodes "write()" et "flush()").

class logging.StreamHandler(stream=None)

   Renvoie une nouvelle instance de la classe "StreamHandler". Si
   *stream* est spécifié, l’instance l’utilise pour les sorties de
   journalisation ; autrement elle utilise *sys.stderr*.

   emit(record)

      Si un formateur est spécifié, il est utilisé pour formater
      l’enregistrement. L’enregistrement est ensuite écrit dans le
      flux, suivi par "terminator". Si une information d’exception est
      présente, elle est formatée en utilisant
      "traceback.print_exception()" puis ajoutée aux flux.

   flush()

      Purge le flux en appelant sa méthode "flush()". Notez que la
      méthode "close()" est héritée de "Handler" donc elle n'écrit
      rien. Par conséquent, un appel explicite à "flush()" peut
      parfois s'avérer nécessaire.

   setStream(stream)

      Définit le flux de l’instance à la valeur spécifiée, si elle est
      différente. L’ancien flux est purgé avant que le nouveau flux ne
      soit établi.

      Paramètres:
         **stream** -- le flux que le gestionnaire doit utiliser.

      Renvoie:
         the old stream, if the stream was changed, or "None" if it
         wasn't.

      Ajouté dans la version 3.7.

   terminator

      Chaine de caractères utilisée comme marqueur de fin lors de
      l’écriture formatée d'un enregistrement dans un flux. La valeur
      par défaut est "'\n'".

      Si vous ne voulez pas marquer de fin de ligne, il faut définir
      l’attribut "terminator" à la chaîne de caractères vide.

      Dans des versions antérieures, le marqueur de fin était codé en
      dur sous la forme "'\n'".

      Ajouté dans la version 3.2.


Gestionnaire à fichier — *FileHandler*
======================================

La classe "FileHandler", du paquet "logging", envoie les sorties de
journalisation dans un fichier. Elle hérite des fonctionnalités de
sortie de "StreamHandler".

class logging.FileHandler(filename, mode='a', encoding=None, delay=False, errors=None)

   Returns a new instance of the "FileHandler" class. The specified
   file is opened and used as the stream for logging. If *mode* is not
   specified, "'a'" is used.  If *encoding* is not "None", it is used
   to open the file with that encoding.  If *delay* is true, then file
   opening is deferred until the first call to "emit()". By default,
   the file grows indefinitely. If *errors* is specified, it's used to
   determine how encoding errors are handled.

   Modifié dans la version 3.6: L'argument *filename* accepte les
   objets "Path" aussi bien que les chaînes de caractères.

   Modifié dans la version 3.9: ajout du paramètre *errors*.

   close()

      Ferme le fichier.

   emit(record)

      Écrit l’enregistrement dans le fichier.

      Note that if the file was closed due to logging shutdown at exit
      and the file mode is 'w', the record will not be emitted (see
      bpo-42378).


Gestionnaire à puits sans fond — *NullHandler*
==============================================

Ajouté dans la version 3.1.

La classe "NullHandler", située dans le paquet principal "logging", ne
produit aucun formatage ni sortie. C’est essentiellement un
gestionnaire « fantôme » destiné aux développeurs de bibliothèques.

class logging.NullHandler

   Renvoie une nouvelle instance de la classe "NullHandler".

   emit(record)

      Cette méthode ne fait rien.

   handle(record)

      Cette méthode ne fait rien.

   createLock()

      Cette méthode renvoie "None" pour le verrou, étant donné qu’il
      n’y a aucun flux d'entrée-sortie sous-jacent dont l’accès doit
      être sérialisé.

Voir Configuration de la journalisation pour une bibliothèque pour
plus d’information sur l'utilisation de "NullHandler".


Gestionnaire à fichier avec surveillance — *WatchedFileHandler*
===============================================================

The "WatchedFileHandler" class, located in the "logging.handlers"
module, is a "FileHandler" which watches the file it is logging to. If
the file changes, it is closed and reopened using the file name.

Le fichier peut être modifié par des programmes tels que *newsyslog*
ou *logrotate* qui assurent le roulement des fichiers de
journalisation. Ce gestionnaire, destiné à une utilisation sous Unix-
Linux, surveille le fichier pour voir s’il a changé depuis la dernière
écriture (un fichier est considéré comme modifié si son nœud d’index
ou le périphérique auquel il est rattaché a changé). Si le fichier a
changé, l’ancien flux vers ce fichier est fermé, et le fichier est
ouvert pour établir un nouveau flux.

Ce gestionnaire n’est pas approprié pour une utilisation sous
*Windows*, car sous *Windows* les fichiers de journalisation ouverts
ne peuvent être ni déplacés, ni renommés — la journalisation ouvre les
fichiers avec des verrous exclusifs — de telle sorte qu’il n’y a pas
besoin d’un tel gestionnaire. En outre, *ST_INO* n’est pas géré par
*Windows* ; "stat()" renvoie toujours zéro pour cette valeur.

class logging.handlers.WatchedFileHandler(filename, mode='a', encoding=None, delay=False, errors=None)

   Returns a new instance of the "WatchedFileHandler" class. The
   specified file is opened and used as the stream for logging. If
   *mode* is not specified, "'a'" is used.  If *encoding* is not
   "None", it is used to open the file with that encoding.  If *delay*
   is true, then file opening is deferred until the first call to
   "emit()".  By default, the file grows indefinitely. If *errors* is
   provided, it determines how encoding errors are handled.

   Modifié dans la version 3.6: L'argument *filename* accepte les
   objets "Path" aussi bien que les chaînes de caractères.

   Modifié dans la version 3.9: ajout du paramètre *errors*.

   reopenIfNeeded()

      Vérifie si le fichier a changé. Si c’est le cas, le flux
      existant est purgé et fermé et le fichier est rouvert,
      généralement avant d'effectuer l’écriture de l'enregistrement
      dans le fichier.

      Ajouté dans la version 3.6.

   emit(record)

      Écrit l’enregistrement dans le fichier, mais appelle d’abord
      "reopenIfNeeded()" pour rouvrir le fichier s’il a changé.


Base des gestionnaires à roulement — *BaseRotatingHandler*
==========================================================

The "BaseRotatingHandler" class, located in the "logging.handlers"
module, is the base class for the rotating file handlers,
"RotatingFileHandler" and "TimedRotatingFileHandler". You should not
need to instantiate this class, but it has attributes and methods you
may need to override.

class logging.handlers.BaseRotatingHandler(filename, mode, encoding=None, delay=False, errors=None)

   Les paramètres sont les mêmes que pour "FileHandler". Les attributs
   sont :

   namer

      Si cet attribut est un qu’appelable, la méthode
      "rotation_filename()" délègue sa logique à cet appelable. Les
      paramètres passés à l’appelable sont ceux passés à
      "rotation_filename()".

      Note:

        la fonction *namer* est appelée de nombreuses fois durant le
        roulement ; elle doit donc être aussi simple et rapide que
        possible. Elle doit aussi renvoyer toujours la même sortie
        pour une entrée donnée, autrement le comportement du roulement
        pourrait être différent de celui attendu.It's also worth
        noting that care should be taken when using a namer to
        preserve certain attributes in the filename which are used
        during rotation. For example, "RotatingFileHandler" expects to
        have a set of log files whose names contain successive
        integers, so that rotation works as expected, and
        "TimedRotatingFileHandler" deletes old log files (based on the
        "backupCount" parameter passed to the handler's initializer)
        by determining the oldest files to delete. For this to happen,
        the filenames should be sortable using the date/time portion
        of the filename, and a namer needs to respect this. (If a
        namer is wanted that doesn't respect this scheme, it will need
        to be used in a subclass of "TimedRotatingFileHandler" which
        overrides the "getFilesToDelete()" method to fit in with the
        custom naming scheme.)

      Ajouté dans la version 3.3.

   rotator

      Si cet attribut est un appelable, il se substitue à la méthode
      "rotate()". Les paramètres passés à l’appelable sont ceux passés
      à "rotate()".

      Ajouté dans la version 3.3.

   rotation_filename(default_name)

      Modifie le nom du fichier d’un fichier de journalisation lors du
      roulement.

      Cette méthode sert à pouvoir produire un nom de fichier
      personnalisé.

      L’implémentation par défaut appelle l’attribut *namer* du
      gestionnaire, si c’est un appelable, lui passant le nom par
      défaut. Si l’attribut n’est pas un appelable (le défaut est
      "None"), le nom est renvoyé tel quel.

      Paramètres:
         **default_name** -- le nom par défaut du fichier de
         journalisation.

      Ajouté dans la version 3.3.

   rotate(source, dest)

      Lors du roulement, effectue le roulement du journal courant.

      L’implémentation par défaut appelle l’attribut *rotator* du
      gestionnaire, si c’est un appelable, lui passant les arguments
      *source* et *dest*. Si l’attribut n’est pas un appelable (le
      défaut est "None"), le nom de la source est simplement renommé
      avec la destination.

      Paramètres:
         * **source** -- le nom du fichier source. Il s’agit
           normalement du nom du fichier, par exemple ""test.log"".

         * **dest** -- le nom du fichier de destination. Il s’agit
           normalement du nom donné à la source après le roulement,
           par exemple ""test.log.1"".

      Ajouté dans la version 3.3.

La raison d’être de ces attributs est de vous épargner la création
d’une sous-classe — vous pouvez utiliser les mêmes appels pour des
instances de "RotatingFileHandler" et "TimedRotatingFileHandler". Si
l'appelable *namer* ou *rotator* lève une exception, elle est gérée de
la même manière que n’importe quelle exception levée lors d'un appel à
"emit()", c'est-à-dire par la méthode "handleError()" du gestionnaire.

Si vous avez besoin de faire d’importantes modifications au processus
de roulement, surchargez les méthodes.

Pour un exemple, voir Utilisation d’un rotateur et d’un nom pour
personnaliser la rotation des journaux.


Gestionnaire à roulement de fichiers — *RotatingFileHandler*
============================================================

The "RotatingFileHandler" class, located in the "logging.handlers"
module, supports rotation of disk log files.

class logging.handlers.RotatingFileHandler(filename, mode='a', maxBytes=0, backupCount=0, encoding=None, delay=False, errors=None)

   Renvoie une nouvelle instance de la classe "RotatingFileHandler".
   Le fichier spécifié est ouvert et utilisé comme flux de sortie pour
   la journalisation. Si *mode* n’est pas spécifié, "'a'" est utilisé.
   Si *encoding* n’est pas à "None", il est utilisé pour ouvrir le
   fichier avec cet encodage. Si *delay* est à *true*, alors
   l’ouverture du fichier est reportée au premier appel de "emit()".
   Par défaut, le fichier croit indéfiniment. Si *errors* est
   spécifié, il détermine comment sont gérées les erreurs d’encodage.

   Utilisez les valeurs *maxBytes* et *backupCount* pour autoriser le
   roulement du fichier (*rollover*) à une taille prédéterminée. Quand
   la taille limite est sur le point d’être dépassée, le fichier est
   fermé et un nouveau fichier est automatiquement ouvert pour le
   remplacer. Un roulement se produit dès que le fichier de
   journalisation actuel atteint une taille proche de *maxBytes* ; si
   *maxBytes* ou *backupCount* est à 0, le roulement ne se produit
   jamais, donc en temps normal il convient de définir *backupCount* à
   au moins 1, et avoir une valeur de *maxBytes* non nulle. Quand
   *backupCount* est non nul, le système sauvegarde les anciens
   fichiers de journalisation en ajoutant à leur nom les suffixes
   "".1"", "".2"" et ainsi de suite. Par exemple, avec un
   *backupCount* de 5 et "app.log" comme radical du fichier, on
   obtient "app.log", "app.log.1", "app.log.2", jusqu’à "app.log.5".
   Le fichier dans lequel on écrit est toujours "app.log". Quand ce
   fichier est rempli, il est fermé et renommé en "app.log.1", et si
   les fichiers "app.log.1", "app.log.2", etc. existent, alors ils
   sont renommés en "app.log.2", "app.log.3" etc. respectivement.

   Modifié dans la version 3.6: L'argument *filename* accepte les
   objets "Path" aussi bien que les chaînes de caractères.

   Modifié dans la version 3.9: ajout du paramètre *errors*.

   doRollover()

      Effectue un roulement, comme décrit ci-dessus.

   emit(record)

      Écrit l'enregistrement dans le fichier, effectuant un roulement
      au besoin comme décrit précédemment.

   shouldRollover(record)

      See if the supplied record would cause the file to exceed the
      configured size limit.


Gestionnaire à roulement de fichiers périodique — *TimedRotatingFileHandler*
============================================================================

The "TimedRotatingFileHandler" class, located in the
"logging.handlers" module, supports rotation of disk log files at
certain timed intervals.

class logging.handlers.TimedRotatingFileHandler(filename, when='h', interval=1, backupCount=0, encoding=None, delay=False, utc=False, atTime=None, errors=None)

   Renvoie une nouvelle instance de la classe
   "TimedRotatingFileHandler". Le fichier spécifié est ouvert et
   utilisé comme flux de sortie pour la journalisation. Au moment du
   roulement, elle met également à jour le suffixe du nom du fichier.
   L'intervalle entre les roulements est déterminé par les valeurs de
   *when* et *interval*.

   Utilisez *when* pour spécifier le type de *interval*. Ses valeurs
   possibles sont décrites ci-dessous. Notez qu'elles ne sont pas
   sensibles à la casse.

   +------------------+------------------------------+---------------------------+
   | Valeur           | Type d’intervalle            | Rôle de *atTime*          |
   |==================|==============================|===========================|
   | "'S'"            | Secondes                     | Ignoré                    |
   +------------------+------------------------------+---------------------------+
   | "'M'"            | Minutes                      | Ignoré                    |
   +------------------+------------------------------+---------------------------+
   | "'H'"            | Heures                       | Ignoré                    |
   +------------------+------------------------------+---------------------------+
   | "'D'"            | Jours                        | Ignoré                    |
   +------------------+------------------------------+---------------------------+
   | "'W0'-'W6'"      | Jour de la semaine (0 =      | Utilisé pour calculer le  |
   |                  | lundi)                       | moment du roulement       |
   +------------------+------------------------------+---------------------------+
   | "'midnight'"     | Roulement du fichier à       | Utilisé pour calculer le  |
   |                  | minuit, si *atTime* n’est    | moment du roulement       |
   |                  | pas spécifié, sinon à        |                           |
   |                  | l’heure *atTime*             |                           |
   +------------------+------------------------------+---------------------------+

   Pour un roulement selon les jours de la semaine, mettez la valeur
   *W0* pour lundi, *W1* pour mardi, et ainsi de suite jusqu’à *W6*
   pour dimanche. Dans ce cas, la valeur indiquée pour *interval*
   n’est pas utilisée.

   Le système sauvegarde les anciens fichiers de journalisation en
   ajoutant une extension au nom du fichier. Les extensions sont
   basées sur la date et l’heure, au format *strftime*
   "%Y-%m-%d_%H-%M-%S" ou le début de celui-ci, selon l’intervalle du
   roulement.

   Le premier calcul de la date du prochain roulement (quand le
   gestionnaire est créé) dépend de la dernière date de modification
   d’un fichier de journalisation existant, ou à défaut de la date
   actuelle.

   Si *utc* est vrai, les temps sont UTC, sinon l'heure locale est
   utilisée.

   Si *backupCount* est non nul, au plus *backupCount* fichiers sont
   sauvegardés. Si des fichiers supplémentaires devaient être créés
   par le jeu du roulement, les plus vieux seraient supprimés. La
   logique de suppression détermine les fichiers à supprimer selon
   l'intervalle, donc changer cette valeur peut conduire à ce que
   certains fichiers anciens restent sur le disque.

   Si *delay* est à *true*, alors l’ouverture du fichier est reportée
   au premier appel de "emit()".

   Si le roulement doit se produire « à minuit » ou « à un jour fixe
   de la semaine » et si *atTime* n'est pas "None", ce doit être une
   instance de "datetime.time" qui définit l'heure de la journée à
   laquelle le roulement se produit. Dans ce cas, la valeur de
   *atTime* ne sert qu'à déterminer la date du roulement *initial*, la
   date des roulements ultérieurs est déterminée par le calcul
   standard de l'intervalle.

   Si *errors* est définit, il définit comment traiter les erreurs
   d'encodage.

   Note:

     la date du premier roulement est déterminée lors de
     l'initialisation du gestionnaire. Ce n'est que lors d'un
     roulement que la date du roulement suivant n'est déterminée, et
     un roulement n'a lieu que si des entrées doivent être
     journalisées. Gardez bien cela à l'esprit pour ne pas avoir de
     surprises. Par exemple, un gestionnaire avec un intervalle «
     d'une minute » ne produira pas nécessairement des fichiers avec
     des dates (dans le nom desdits fichiers) séparées d'une minute.
     Si une application génère des journaux plus fréquemment que
     toutes les minutes au cours de son exécution, alors *dans ce cas*
     vous obtiendrez des fichiers avec des temps séparés d'une minute.
     Si la même application ne produit une entrée de journal que
     toutes les cinq minutes, il y aura des sauts dans les dates des
     fichiers produits qui correspondront aux moments où rien n'a été
     produit (et donc où aucun roulement n'a eu lieu).

   Modifié dans la version 3.4: ajout du paramètre *atTime*.

   Modifié dans la version 3.6: L'argument *filename* accepte les
   objets "Path" aussi bien que les chaînes de caractères.

   Modifié dans la version 3.9: ajout du paramètre *errors*.

   doRollover()

      Effectue un roulement, comme décrit ci-dessus.

   emit(record)

      Écrit l'enregistrement dans le fichier, effectuant un roulement
      au besoin comme décrit précédemment.

   getFilesToDelete()

      Returns a list of filenames which should be deleted as part of
      rollover. These are the absolute paths of the oldest backup log
      files written by the handler.

   shouldRollover(record)

      See if enough time has passed for a rollover to occur and if it
      has, compute the next rollover time.


Gestionnaire à connecteur — *SocketHandler*
===========================================

The "SocketHandler" class, located in the "logging.handlers" module,
sends logging output to a network socket. The base class uses a TCP
socket.

class logging.handlers.SocketHandler(host, port)

   Returns a new instance of the "SocketHandler" class intended to
   communicate with a remote machine whose address is given by *host*
   and *port*.

   Modifié dans la version 3.4: If "port" is specified as "None", a
   Unix domain socket is created using the value in "host" -
   otherwise, a TCP socket is created.

   close()

      Closes the socket.

   emit()

      Pickles the record's attribute dictionary and writes it to the
      socket in binary format. If there is an error with the socket,
      silently drops the packet. If the connection was previously
      lost, re-establishes the connection. To unpickle the record at
      the receiving end into a "LogRecord", use the "makeLogRecord()"
      function.

   handleError()

      Handles an error which has occurred during "emit()". The most
      likely cause is a lost connection. Closes the socket so that we
      can retry on the next event.

   makeSocket()

      This is a factory method which allows subclasses to define the
      precise type of socket they want. The default implementation
      creates a TCP socket ("socket.SOCK_STREAM").

   makePickle(record)

      Pickles the record's attribute dictionary in binary format with
      a length prefix, and returns it ready for transmission across
      the socket. The details of this operation are equivalent to:

         data = pickle.dumps(record_attr_dict, 1)
         datalen = struct.pack('>L', len(data))
         return datalen + data

      Note that pickles aren't completely secure. If you are concerned
      about security, you may want to override this method to
      implement a more secure mechanism. For example, you can sign
      pickles using HMAC and then verify them on the receiving end, or
      alternatively you can disable unpickling of global objects on
      the receiving end.

   send(packet)

      Send a pickled byte-string *packet* to the socket. The format of
      the sent byte-string is as described in the documentation for
      "makePickle()".

      This function allows for partial sends, which can happen when
      the network is busy.

   createSocket()

      Tries to create a socket; on failure, uses an exponential back-
      off algorithm.  On initial failure, the handler will drop the
      message it was trying to send.  When subsequent messages are
      handled by the same instance, it will not try connecting until
      some time has passed.  The default parameters are such that the
      initial delay is one second, and if after that delay the
      connection still can't be made, the handler will double the
      delay each time up to a maximum of 30 seconds.

      This behaviour is controlled by the following handler
      attributes:

      * "retryStart" (initial delay, defaulting to 1.0 seconds).

      * "retryFactor" (multiplier, defaulting to 2.0).

      * "retryMax" (maximum delay, defaulting to 30.0 seconds).

      This means that if the remote listener starts up *after* the
      handler has been used, you could lose messages (since the
      handler won't even attempt a connection until the delay has
      elapsed, but just silently drop messages during the delay
      period).


DatagramHandler
===============

The "DatagramHandler" class, located in the "logging.handlers" module,
inherits from "SocketHandler" to support sending logging messages over
UDP sockets.

class logging.handlers.DatagramHandler(host, port)

   Returns a new instance of the "DatagramHandler" class intended to
   communicate with a remote machine whose address is given by *host*
   and *port*.

   Note:

     As UDP is not a streaming protocol, there is no persistent
     connection between an instance of this handler and *host*. For
     this reason, when using a network socket, a DNS lookup might have
     to be made each time an event is logged, which can introduce some
     latency into the system. If this affects you, you can do a lookup
     yourself and initialize this handler using the looked-up IP
     address rather than the hostname.

   Modifié dans la version 3.4: If "port" is specified as "None", a
   Unix domain socket is created using the value in "host" -
   otherwise, a UDP socket is created.

   emit()

      Pickles the record's attribute dictionary and writes it to the
      socket in binary format. If there is an error with the socket,
      silently drops the packet. To unpickle the record at the
      receiving end into a "LogRecord", use the "makeLogRecord()"
      function.

   makeSocket()

      The factory method of "SocketHandler" is here overridden to
      create a UDP socket ("socket.SOCK_DGRAM").

   send(s)

      Send a pickled byte-string to a socket. The format of the sent
      byte-string is as described in the documentation for
      "SocketHandler.makePickle()".


SysLogHandler
=============

The "SysLogHandler" class, located in the "logging.handlers" module,
supports sending logging messages to a remote or local Unix syslog.

class logging.handlers.SysLogHandler(address=('localhost', SYSLOG_UDP_PORT), facility=LOG_USER, socktype=socket.SOCK_DGRAM, timeout=None)

   Returns a new instance of the "SysLogHandler" class intended to
   communicate with a remote Unix machine whose address is given by
   *address* in the form of a "(host, port)" tuple.  If *address* is
   not specified, "('localhost', 514)" is used.  The address is used
   to open a socket.  An alternative to providing a "(host, port)"
   tuple is providing an address as a string, for example '/dev/log'.
   In this case, a Unix domain socket is used to send the message to
   the syslog. If *facility* is not specified, "LOG_USER" is used. The
   type of socket opened depends on the *socktype* argument, which
   defaults to "socket.SOCK_DGRAM" and thus opens a UDP socket. To
   open a TCP socket (for use with the newer syslog daemons such as
   rsyslog), specify a value of "socket.SOCK_STREAM". If *timeout* is
   specified, it sets a timeout (in seconds) for the socket
   operations. This can help prevent the program from hanging
   indefinitely if the syslog server is unreachable. By default,
   *timeout* is "None", meaning no timeout is applied.

   Note that if your server is not listening on UDP port 514,
   "SysLogHandler" may appear not to work. In that case, check what
   address you should be using for a domain socket - it's system
   dependent. For example, on Linux it's usually '/dev/log' but on
   OS/X it's '/var/run/syslog'. You'll need to check your platform and
   use the appropriate address (you may need to do this check at
   runtime if your application needs to run on several platforms). On
   Windows, you pretty much have to use the UDP option.

   Note:

     On macOS 12.x (Monterey), Apple has changed the behaviour of
     their syslog daemon - it no longer listens on a domain socket.
     Therefore, you cannot expect "SysLogHandler" to work on this
     system.See gh-91070 for more information.

   Modifié dans la version 3.2: *socktype* was added.

   Modifié dans la version 3.14: *timeout* was added.

   close()

      Closes the socket to the remote host.

   createSocket()

      Tries to create a socket and, if it's not a datagram socket,
      connect it to the other end. This method is called during
      handler initialization, but it's not regarded as an error if the
      other end isn't listening at this point - the method will be
      called again when emitting an event, if there is no socket at
      that point.

      Ajouté dans la version 3.11.

   emit(record)

      The record is formatted, and then sent to the syslog server. If
      exception information is present, it is *not* sent to the
      server.

      Modifié dans la version 3.2.1: (See: bpo-12168.) In earlier
      versions, the message sent to the syslog daemons was always
      terminated with a NUL byte, because early versions of these
      daemons expected a NUL terminated message - even though it's not
      in the relevant specification (**RFC 5424**). More recent
      versions of these daemons don't expect the NUL byte but strip it
      off if it's there, and even more recent daemons (which adhere
      more closely to RFC 5424) pass the NUL byte on as part of the
      message.To enable easier handling of syslog messages in the face
      of all these differing daemon behaviours, the appending of the
      NUL byte has been made configurable, through the use of a class-
      level attribute, "append_nul". This defaults to "True"
      (preserving the existing behaviour) but can be set to "False" on
      a "SysLogHandler" instance in order for that instance to *not*
      append the NUL terminator.

      Modifié dans la version 3.3: (See: bpo-12419.) In earlier
      versions, there was no facility for an "ident" or "tag" prefix
      to identify the source of the message. This can now be specified
      using a class-level attribute, defaulting to """" to preserve
      existing behaviour, but which can be overridden on a
      "SysLogHandler" instance in order for that instance to prepend
      the ident to every message handled. Note that the provided ident
      must be text, not bytes, and is prepended to the message exactly
      as is.

   encodePriority(facility, priority)

      Encodes the facility and priority into an integer. You can pass
      in strings or integers - if strings are passed, internal mapping
      dictionaries are used to convert them to integers.

      The symbolic "LOG_" values are defined in "SysLogHandler" and
      mirror the values defined in the "sys/syslog.h" header file.

      **Priorities**

      +----------------------------+-----------------+
      | Name (string)              | Symbolic value  |
      |============================|=================|
      | "alert"                    | LOG_ALERT       |
      +----------------------------+-----------------+
      | "crit" ou "critical"       | LOG_CRIT        |
      +----------------------------+-----------------+
      | "debug"                    | LOG_DEBUG       |
      +----------------------------+-----------------+
      | "emerg" ou "panic"         | LOG_EMERG       |
      +----------------------------+-----------------+
      | "err" ou "error"           | LOG_ERR         |
      +----------------------------+-----------------+
      | "info"                     | LOG_INFO        |
      +----------------------------+-----------------+
      | "notice"                   | LOG_NOTICE      |
      +----------------------------+-----------------+
      | "warn" ou "warning"        | LOG_WARNING     |
      +----------------------------+-----------------+

      **Facilities**

      +-----------------+-----------------+
      | Name (string)   | Symbolic value  |
      |=================|=================|
      | "auth"          | LOG_AUTH        |
      +-----------------+-----------------+
      | "authpriv"      | LOG_AUTHPRIV    |
      +-----------------+-----------------+
      | "cron"          | LOG_CRON        |
      +-----------------+-----------------+
      | "daemon"        | LOG_DAEMON      |
      +-----------------+-----------------+
      | "ftp"           | LOG_FTP         |
      +-----------------+-----------------+
      | "kern"          | LOG_KERN        |
      +-----------------+-----------------+
      | "lpr"           | LOG_LPR         |
      +-----------------+-----------------+
      | "mail"          | LOG_MAIL        |
      +-----------------+-----------------+
      | "news"          | LOG_NEWS        |
      +-----------------+-----------------+
      | "syslog"        | LOG_SYSLOG      |
      +-----------------+-----------------+
      | "user"          | LOG_USER        |
      +-----------------+-----------------+
      | "uucp"          | LOG_UUCP        |
      +-----------------+-----------------+
      | "local0"        | LOG_LOCAL0      |
      +-----------------+-----------------+
      | "local1"        | LOG_LOCAL1      |
      +-----------------+-----------------+
      | "local2"        | LOG_LOCAL2      |
      +-----------------+-----------------+
      | "local3"        | LOG_LOCAL3      |
      +-----------------+-----------------+
      | "local4"        | LOG_LOCAL4      |
      +-----------------+-----------------+
      | "local5"        | LOG_LOCAL5      |
      +-----------------+-----------------+
      | "local6"        | LOG_LOCAL6      |
      +-----------------+-----------------+
      | "local7"        | LOG_LOCAL7      |
      +-----------------+-----------------+

   mapPriority(levelname)

      Maps a logging level name to a syslog priority name. You may
      need to override this if you are using custom levels, or if the
      default algorithm is not suitable for your needs. The default
      algorithm maps "DEBUG", "INFO", "WARNING", "ERROR" and
      "CRITICAL" to the equivalent syslog names, and all other level
      names to 'warning'.


NTEventLogHandler
=================

The "NTEventLogHandler" class, located in the "logging.handlers"
module, supports sending logging messages to a local Windows NT,
Windows 2000 or Windows XP event log. Before you can use it, you need
Mark Hammond's Win32 extensions for Python installed.

class logging.handlers.NTEventLogHandler(appname, dllname=None, logtype='Application')

   Returns a new instance of the "NTEventLogHandler" class. The
   *appname* is used to define the application name as it appears in
   the event log. An appropriate registry entry is created using this
   name. The *dllname* should give the fully qualified pathname of a
   .dll or .exe which contains message definitions to hold in the log
   (if not specified, "'win32service.pyd'" is used - this is installed
   with the Win32 extensions and contains some basic placeholder
   message definitions. Note that use of these placeholders will make
   your event logs big, as the entire message source is held in the
   log. If you want slimmer logs, you have to pass in the name of your
   own .dll or .exe which contains the message definitions you want to
   use in the event log). The *logtype* is one of "'Application'",
   "'System'" or "'Security'", and defaults to "'Application'".

   close()

      At this point, you can remove the application name from the
      registry as a source of event log entries. However, if you do
      this, you will not be able to see the events as you intended in
      the Event Log Viewer - it needs to be able to access the
      registry to get the .dll name. The current version does not do
      this.

   emit(record)

      Determines the message ID, event category and event type, and
      then logs the message in the NT event log.

   getEventCategory(record)

      Returns the event category for the record. Override this if you
      want to specify your own categories. This version returns 0.

   getEventType(record)

      Returns the event type for the record. Override this if you want
      to specify your own types. This version does a mapping using the
      handler's typemap attribute, which is set up in "__init__()" to
      a dictionary which contains mappings for "DEBUG", "INFO",
      "WARNING", "ERROR" and "CRITICAL". If you are using your own
      levels, you will either need to override this method or place a
      suitable dictionary in the handler's *typemap* attribute.

   getMessageID(record)

      Returns the message ID for the record. If you are using your own
      messages, you could do this by having the *msg* passed to the
      logger being an ID rather than a format string. Then, in here,
      you could use a dictionary lookup to get the message ID. This
      version returns 1, which is the base message ID in
      "win32service.pyd".


SMTPHandler
===========

The "SMTPHandler" class, located in the "logging.handlers" module,
supports sending logging messages to an email address via SMTP.

class logging.handlers.SMTPHandler(mailhost, fromaddr, toaddrs, subject, credentials=None, secure=None, timeout=1.0)

   Returns a new instance of the "SMTPHandler" class. The instance is
   initialized with the from and to addresses and subject line of the
   email. The *toaddrs* should be a list of strings. To specify a non-
   standard SMTP port, use the (host, port) tuple format for the
   *mailhost* argument. If you use a string, the standard SMTP port is
   used. If your SMTP server requires authentication, you can specify
   a (username, password) tuple for the *credentials* argument.

   To specify the use of a secure protocol (TLS), pass in a tuple to
   the *secure* argument. This will only be used when authentication
   credentials are supplied. The tuple should be either an empty
   tuple, or a single-value tuple with the name of a keyfile, or a
   2-value tuple with the names of the keyfile and certificate file.
   (This tuple is passed to the "smtplib.SMTP.starttls()" method.)

   A timeout can be specified for communication with the SMTP server
   using the *timeout* argument.

   Modifié dans la version 3.3: Added the *timeout* parameter.

   emit(record)

      Formats the record and sends it to the specified addressees.

   getSubject(record)

      If you want to specify a subject line which is record-dependent,
      override this method.


MemoryHandler
=============

The "MemoryHandler" class, located in the "logging.handlers" module,
supports buffering of logging records in memory, periodically flushing
them to a *target* handler. Flushing occurs whenever the buffer is
full, or when an event of a certain severity or greater is seen.

"MemoryHandler" is a subclass of the more general "BufferingHandler",
which is an abstract class. This buffers logging records in memory.
Whenever each record is added to the buffer, a check is made by
calling "shouldFlush()" to see if the buffer should be flushed.  If it
should, then "flush()" is expected to do the flushing.

class logging.handlers.BufferingHandler(capacity)

   Initializes the handler with a buffer of the specified capacity.
   Here, *capacity* means the number of logging records buffered.

   emit(record)

      Append the record to the buffer. If "shouldFlush()" returns
      true, call "flush()" to process the buffer.

   flush()

      For a "BufferingHandler" instance, flushing means that it sets
      the buffer to an empty list. This method can be overwritten to
      implement more useful flushing behavior.

   shouldFlush(record)

      Return "True" if the buffer is up to capacity. This method can
      be overridden to implement custom flushing strategies.

class logging.handlers.MemoryHandler(capacity, flushLevel=ERROR, target=None, flushOnClose=True)

   Returns a new instance of the "MemoryHandler" class. The instance
   is initialized with a buffer size of *capacity* (number of records
   buffered). If *flushLevel* is not specified, "ERROR" is used. If no
   *target* is specified, the target will need to be set using
   "setTarget()" before this handler does anything useful. If
   *flushOnClose* is specified as "False", then the buffer is *not*
   flushed when the handler is closed. If not specified or specified
   as "True", the previous behaviour of flushing the buffer will occur
   when the handler is closed.

   Modifié dans la version 3.6: The *flushOnClose* parameter was
   added.

   close()

      Calls "flush()", sets the target to "None" and clears the
      buffer.

   flush()

      For a "MemoryHandler" instance, flushing means just sending the
      buffered records to the target, if there is one. The buffer is
      also cleared when buffered records are sent to the target.
      Override if you want different behavior.

   setTarget(target)

      Sets the target handler for this handler.

   shouldFlush(record)

      Checks for buffer full or a record at the *flushLevel* or
      higher.


HTTPHandler
===========

The "HTTPHandler" class, located in the "logging.handlers" module,
supports sending logging messages to a web server, using either "GET"
or "POST" semantics.

class logging.handlers.HTTPHandler(host, url, method='GET', secure=False, credentials=None, context=None)

   Returns a new instance of the "HTTPHandler" class. The *host* can
   be of the form "host:port", should you need to use a specific port
   number.  If no *method* is specified, "GET" is used. If *secure* is
   true, a HTTPS connection will be used. The *context* parameter may
   be set to a "ssl.SSLContext" instance to configure the SSL settings
   used for the HTTPS connection. If *credentials* is specified, it
   should be a 2-tuple consisting of userid and password, which will
   be placed in a HTTP 'Authorization' header using Basic
   authentication. If you specify credentials, you should also specify
   secure=True so that your userid and password are not passed in
   cleartext across the wire.

   Modifié dans la version 3.5: The *context* parameter was added.

   mapLogRecord(record)

      Provides a dictionary, based on "record", which is to be URL-
      encoded and sent to the web server. The default implementation
      just returns "record.__dict__". This method can be overridden if
      e.g. only a subset of "LogRecord" is to be sent to the web
      server, or if more specific customization of what's sent to the
      server is required.

   emit(record)

      Sends the record to the web server as a URL-encoded dictionary.
      The "mapLogRecord()" method is used to convert the record to the
      dictionary to be sent.

   Note:

     Since preparing a record for sending it to a web server is not
     the same as a generic formatting operation, using
     "setFormatter()" to specify a "Formatter" for a "HTTPHandler" has
     no effect. Instead of calling "format()", this handler calls
     "mapLogRecord()" and then "urllib.parse.urlencode()" to encode
     the dictionary in a form suitable for sending to a web server.


QueueHandler
============

Ajouté dans la version 3.2.

The "QueueHandler" class, located in the "logging.handlers" module,
supports sending logging messages to a queue, such as those
implemented in the "queue" or "multiprocessing" modules.

Along with the "QueueListener" class, "QueueHandler" can be used to
let handlers do their work on a separate thread from the one which
does the logging. This is important in web applications and also other
service applications where threads servicing clients need to respond
as quickly as possible, while any potentially slow operations (such as
sending an email via "SMTPHandler") are done on a separate thread.

class logging.handlers.QueueHandler(queue)

   Returns a new instance of the "QueueHandler" class. The instance is
   initialized with the queue to send messages to. The *queue* can be
   any queue-like object; it's used as-is by the "enqueue()" method,
   which needs to know how to send messages to it. The queue is not
   *required* to have the task tracking API, which means that you can
   use "SimpleQueue" instances for *queue*.

   Note:

     If you are using "multiprocessing", you should avoid using
     "SimpleQueue" and instead use "multiprocessing.Queue".

   Avertissement:

     The "multiprocessing" module uses an internal logger created and
     accessed via "get_logger()". "multiprocessing.Queue" will log
     "DEBUG" level messages upon items being queued. If those log
     messages are processed by a "QueueHandler" using the same
     "multiprocessing.Queue" instance, it will cause a deadlock or
     infinite recursion.

   emit(record)

      Enqueues the result of preparing the LogRecord. Should an
      exception occur (e.g. because a bounded queue has filled up),
      the "handleError()" method is called to handle the error. This
      can result in the record silently being dropped (if
      "logging.raiseExceptions" is "False") or a message printed to
      "sys.stderr" (if "logging.raiseExceptions" is "True").

   prepare(record)

      Prepares a record for queuing. The object returned by this
      method is enqueued.

      The base implementation formats the record to merge the message,
      arguments, exception and stack information, if present.  It also
      removes unpickleable items from the record in-place.
      Specifically, it overwrites the record's "msg" and "message"
      attributes with the merged message (obtained by calling the
      handler's "format()" method), and sets the "args", "exc_info"
      and "exc_text" attributes to "None".

      You might want to override this method if you want to convert
      the record to a dict or JSON string, or send a modified copy of
      the record while leaving the original intact.

      Note:

        The base implementation formats the message with arguments,
        sets the "message" and "msg" attributes to the formatted
        message and sets the "args" and "exc_text" attributes to
        "None" to allow pickling and to prevent further attempts at
        formatting. This means that a handler on the "QueueListener"
        side won't have the information to do custom formatting, e.g.
        of exceptions. You may wish to subclass "QueueHandler" and
        override this method to e.g. avoid setting "exc_text" to
        "None". Note that the "message" / "msg" / "args" changes are
        related to ensuring the record is pickleable, and you might or
        might not be able to avoid doing that depending on whether
        your "args" are pickleable. (Note that you may have to
        consider not only your own code but also code in any libraries
        that you use.)

   enqueue(record)

      Enqueues the record on the queue using "put_nowait()"; you may
      want to override this if you want to use blocking behaviour, or
      a timeout, or a customized queue implementation.

   listener

      When created via configuration using "dictConfig()", this
      attribute will contain a "QueueListener" instance for use with
      this handler. Otherwise, it will be "None".

      Ajouté dans la version 3.12.


QueueListener
=============

Ajouté dans la version 3.2.

The "QueueListener" class, located in the "logging.handlers" module,
supports receiving logging messages from a queue, such as those
implemented in the "queue" or "multiprocessing" modules. The messages
are received from a queue in an internal thread and passed, on the
same thread, to one or more handlers for processing. While
"QueueListener" is not itself a handler, it is documented here because
it works hand-in-hand with "QueueHandler".

Along with the "QueueHandler" class, "QueueListener" can be used to
let handlers do their work on a separate thread from the one which
does the logging. This is important in web applications and also other
service applications where threads servicing clients need to respond
as quickly as possible, while any potentially slow operations (such as
sending an email via "SMTPHandler") are done on a separate thread.

class logging.handlers.QueueListener(queue, *handlers, respect_handler_level=False)

   Returns a new instance of the "QueueListener" class. The instance
   is initialized with the queue to send messages to and a list of
   handlers which will handle entries placed on the queue. The queue
   can be any queue-like object; it's passed as-is to the "dequeue()"
   method, which needs to know how to get messages from it. The queue
   is not *required* to have the task tracking API (though it's used
   if available), which means that you can use "SimpleQueue" instances
   for *queue*.

   Note:

     If you are using "multiprocessing", you should avoid using
     "SimpleQueue" and instead use "multiprocessing.Queue".

   If "respect_handler_level" is "True", a handler's level is
   respected (compared with the level for the message) when deciding
   whether to pass messages to that handler; otherwise, the behaviour
   is as in previous Python versions - to always pass each message to
   each handler.

   Modifié dans la version 3.5: The "respect_handler_level" argument
   was added.

   Modifié dans la version 3.14: "QueueListener" can now be used as a
   context manager via "with". When entering the context, the listener
   is started. When exiting the context, the listener is stopped.
   "__enter__()" returns the "QueueListener" object.

   dequeue(block)

      Dequeues a record and return it, optionally blocking.

      The base implementation uses "get()". You may want to override
      this method if you want to use timeouts or work with custom
      queue implementations.

   prepare(record)

      Prepare a record for handling.

      This implementation just returns the passed-in record. You may
      want to override this method if you need to do any custom
      marshalling or manipulation of the record before passing it to
      the handlers.

   handle(record)

      Handle a record.

      This just loops through the handlers offering them the record to
      handle. The actual object passed to the handlers is that which
      is returned from "prepare()".

   start()

      Starts the listener.

      This starts up a background thread to monitor the queue for
      LogRecords to process.

      Modifié dans la version 3.14: Raises "RuntimeError" if called
      and the listener is already running.

   stop()

      Stops the listener.

      This asks the thread to terminate, and then waits for it to do
      so. Note that if you don't call this before your application
      exits, there may be some records still left on the queue, which
      won't be processed.

   enqueue_sentinel()

      Writes a sentinel to the queue to tell the listener to quit.
      This implementation uses "put_nowait()".  You may want to
      override this method if you want to use timeouts or work with
      custom queue implementations.

      Ajouté dans la version 3.3.

Voir aussi:

  Module "logging"
     Référence d'API pour le module de journalisation.

  Module "logging.config"
     API de configuration pour le module de journalisation.
