logging.handlers
— 日志处理程序
¶
The following useful handlers are provided in the package. Note that three of the handlers (
StreamHandler
,
FileHandler
and
NullHandler
) are actually defined in the
logging
module itself, but have been documented here along with the other handlers.
StreamHandler
class, located in the core
logging
package, sends logging output to streams such as
sys.stdout
,
sys.stderr
or any file-like object (or, more precisely, any object which supports
write()
and
flush()
methods).
logging.
StreamHandler
(
stream=None
)
¶
Returns a new instance of the
StreamHandler
class. If
stream
is specified, the instance will use it for logging output; otherwise,
sys.stderr
will be used.
emit
(
record
)
¶
If a formatter is specified, it is used to format the record. The record is then written to the stream with a terminator. If exception information is present, it is formatted using
traceback.print_exception()
and appended to the stream.
3.2 版改变：
StreamHandler
class now has a
terminator
attribute, default value
'\n'
, which is used as the terminator when writing a formatted record to a stream. If you don’t want this newline termination, you can set the handler instance’s
terminator
attribute to the empty string. In earlier versions, the terminator was hardcoded as
'\n'
.
FileHandler
class, located in the core
logging
package, sends logging output to a disk file. It inherits the output functionality from
StreamHandler
.
logging.
FileHandler
(
filename
,
mode='a'
,
encoding=None
,
delay=False
)
¶
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
不是
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.
3.6 版改变：
As well as string values,
Path
objects are also accepted for the
filename
自变量。
close
(
)
¶
Closes the file.
emit
(
record
)
¶
Outputs the record to the file.
3.1 版新增。
NullHandler
class, located in the core
logging
package, does not do any formatting or output. It is essentially a ‘no-op’ handler for use by library developers.
logging.
NullHandler
¶
Returns a new instance of the
NullHandler
类。
emit
(
record
)
¶
This method does nothing.
handle
(
record
)
¶
This method does nothing.
createLock
(
)
¶
This method returns
None
for the lock, since there is no underlying I/O to which access needs to be serialized.
见
Configuring Logging for a Library
for more information on how to use
NullHandler
.
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.
A file change can happen because of usage of programs such as newsyslog and logrotate which perform log file rotation. This handler, intended for use under Unix/Linux, watches the file to see if it has changed since the last emit. (A file is deemed to have changed if its device or inode have changed.) If the file has changed, the old file stream is closed, and the file opened to get a new stream.
This handler is not appropriate for use under Windows, because under Windows open log files cannot be moved or renamed - logging opens the files with exclusive locks - and so there is no need for such a handler. Furthermore,
ST_INO
is not supported under Windows;
stat()
always returns zero for this value.
logging.handlers.
WatchedFileHandler
(
filename
,
mode='a'
,
encoding=None
,
delay=False
)
¶
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
不是
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.
3.6 版改变：
As well as string values,
Path
objects are also accepted for the
filename
自变量。
reopenIfNeeded
(
)
¶
Checks to see if the file has changed. If it has, the existing stream is flushed and closed and the file opened again, typically as a precursor to outputting the record to the file.
3.6 版新增。
emit
(
record
)
¶
Outputs the record to the file, but first calls
reopenIfNeeded()
to reopen the file if it has changed.
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.
logging.handlers.
BaseRotatingHandler
(
filename
,
mode
,
encoding=None
,
delay=False
)
¶
The parameters are as for
FileHandler
. The attributes are:
namer
¶
If this attribute is set to a callable, the
rotation_filename()
method delegates to this callable. The parameters passed to the callable are those passed to
rotation_filename()
.
注意
The namer function is called quite a few times during rollover, so it should be as simple and as fast as possible. It should also return the same output every time for a given input, otherwise the rollover behaviour may not work as expected.
3.3 版新增。
rotator
¶
If this attribute is set to a callable, the
rotate()
method delegates to this callable. The parameters passed to the callable are those passed to
rotate()
.
3.3 版新增。
rotation_filename
(
default_name
)
¶
Modify the filename of a log file when rotating.
This is provided so that a custom filename can be provided.
The default implementation calls the ‘namer’ attribute of the handler, if it’s callable, passing the default name to it. If the attribute isn’t callable (the default is
None
), the name is returned unchanged.
| 参数： | default_name – The default name for the log file. |
|---|
3.3 版新增。
rotate
(
source
,
dest
)
¶
When rotating, rotate the current log.
The default implementation calls the ‘rotator’ attribute of the handler, if it’s callable, passing the source and dest arguments to it. If the attribute isn’t callable (the default is
None
), the source is simply renamed to the destination.
| 参数： |
|
|---|
3.3 版新增。
The reason the attributes exist is to save you having to subclass - you can use the same callables for instances of
RotatingFileHandler
and
TimedRotatingFileHandler
. If either the namer or rotator callable raises an exception, this will be handled in the same way as any other exception during an
emit()
call, i.e. via the
handleError()
method of the handler.
If you need to make more significant changes to rotation processing, you can override the methods.
For an example, see Using a rotator and namer to customize log rotation processing .
RotatingFileHandler
class, located in the
logging.handlers
module, supports rotation of disk log files.
logging.handlers.
RotatingFileHandler
(
filename
,
mode='a'
,
maxBytes=0
,
backupCount=0
,
encoding=None
,
delay=False
)
¶
Returns a new instance of the
RotatingFileHandler
class. The specified file is opened and used as the stream for logging. If
mode
is not specified,
'a'
is used. If
encoding
不是
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.
可以使用
maxBytes
and
backupCount
values to allow the file to
rollover
at a predetermined size. When the size is about to be exceeded, the file is closed and a new file is silently opened for output. Rollover occurs whenever the current log file is nearly
maxBytes
in length; but if either of
maxBytes
or
backupCount
is zero, rollover never occurs, so you generally want to set
backupCount
to at least 1, and have a non-zero
maxBytes
。当
backupCount
is non-zero, the system will save old log files by appending the extensions ‘.1’, ‘.2’ etc., to the filename. For example, with a
backupCount
of 5 and a base file name of
app.log
, you would get
app.log
,
app.log.1
,
app.log.2
, up to
app.log.5
. The file being written to is always
app.log
. When this file is filled, it is closed and renamed to
app.log.1
, and if files
app.log.1
,
app.log.2
, etc. exist, then they are renamed to
app.log.2
,
app.log.3
etc. respectively.
3.6 版改变：
As well as string values,
Path
objects are also accepted for the
filename
自变量。
doRollover
(
)
¶
Does a rollover, as described above.
emit
(
record
)
¶
Outputs the record to the file, catering for rollover as described previously.
TimedRotatingFileHandler
class, located in the
logging.handlers
module, supports rotation of disk log files at certain timed intervals.
logging.handlers.
TimedRotatingFileHandler
(
filename
,
when='h'
,
interval=1
,
backupCount=0
,
encoding=None
,
delay=False
,
utc=False
,
atTime=None
)
¶
Returns a new instance of the
TimedRotatingFileHandler
class. The specified file is opened and used as the stream for logging. On rotating it also sets the filename suffix. Rotating happens based on the product of
when
and
interval
.
可以使用 when to specify the type of interval . The list of possible values is below. Note that they are not case sensitive.
| Value | Type of interval | If/how atTime is used |
|---|---|---|
'S'
|
Seconds | Ignored |
'M'
|
Minutes | Ignored |
'H'
|
Hours | Ignored |
'D'
|
Days | Ignored |
'W0'-'W6'
|
Weekday (0=Monday) | Used to compute initial rollover time |
'midnight'
|
Roll over at midnight, if atTime not specified, else at time atTime | Used to compute initial rollover time |
When using weekday-based rotation, specify ‘W0’ for Monday, ‘W1’ for Tuesday, and so on up to ‘W6’ for Sunday. In this case, the value passed for interval isn’t used.
The system will save old log files by appending extensions to the filename. The extensions are date-and-time based, using the strftime format
%Y-%m-%d_%H-%M-%S
or a leading portion thereof, depending on the rollover interval.
When computing the next rollover time for the first time (when the handler is created), the last modification time of an existing log file, or else the current time, is used to compute when the next rotation will occur.
若 utc argument is true, times in UTC will be used; otherwise local time is used.
若 backupCount is nonzero, at most backupCount files will be kept, and if more would be created when rollover occurs, the oldest one is deleted. The deletion logic uses the interval to determine which files to delete, so changing the interval may leave old files lying around.
若
delay
is true, then file opening is deferred until the first call to
emit()
.
若
atTime
不是
None
, it must be a
datetime.time
instance which specifies the time of day when rollover occurs, for the cases where rollover is set to happen “at midnight” or “on a particular weekday”. Note that in these cases, the
atTime
value is effectively used to compute the
initial
rollover, and subsequent rollovers would be calculated via the normal interval calculation.
注意
Calculation of the initial rollover time is done when the handler is initialised. Calculation of subsequent rollover times is done only when rollover occurs, and rollover occurs only when emitting output. If this is not kept in mind, it might lead to some confusion. For example, if an interval of “every minute” is set, that does not mean you will always see log files with times (in the filename) separated by a minute; if, during application execution, logging output is generated more frequently than once a minute, then you can expect to see log files with times separated by a minute. If, on the other hand, logging messages are only output once every five minutes (say), then there will be gaps in the file times corresponding to the minutes where no output (and hence no rollover) occurred.
3.4 版改变： atTime 参数被添加。
3.6 版改变：
As well as string values,
Path
objects are also accepted for the
filename
自变量。
doRollover
(
)
¶
Does a rollover, as described above.
emit
(
record
)
¶
Outputs the record to the file, catering for rollover as described above.
SocketHandler
class, located in the
logging.handlers
module, sends logging output to a network socket. The base class uses a TCP socket.
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
.
3.4 版改变：
若
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()
函数。
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.
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 string packet to the socket. 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
class, located in the
logging.handlers
module, inherits from
SocketHandler
to support sending logging messages over UDP sockets.
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
.
3.4 版改变：
若
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()
函数。
makeSocket
(
)
¶
The factory method of
SocketHandler
is here overridden to create a UDP socket (
socket.SOCK_DGRAM
).
send
(
s
)
¶
Send a pickled string to a socket.
SysLogHandler
class, located in the
logging.handlers
module, supports sending logging messages to a remote or local Unix syslog.
logging.handlers.
SysLogHandler
(
address=('localhost'
,
SYSLOG_UDP_PORT)
,
facility=LOG_USER
,
socktype=socket.SOCK_DGRAM
)
¶
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
.
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.
3.2 版改变： socktype 被添加。
close
(
)
¶
Closes the socket to the remote host.
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.
Changed in 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
在
SysLogHandler
instance in order for that instance to
not
append the NUL terminator.
3.3 版改变：
(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
or
critical
|
LOG_CRIT |
debug
|
LOG_DEBUG |
emerg
or
panic
|
LOG_EMERG |
err
or
error
|
LOG_ERR |
info
|
LOG_INFO |
notice
|
LOG_NOTICE |
warn
or
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
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.
logging.handlers.
NTEventLogHandler
(
appname
,
dllname=None
,
logtype='Application'
)
¶
Returns a new instance of the
NTEventLogHandler
类。
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
属性。
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
class, located in the
logging.handlers
module, supports sending logging messages to an email address via SMTP.
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
自变量。
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 自变量。
3.3 版新增： timeout argument was added.
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
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.
logging.handlers.
BufferingHandler
(
capacity
)
¶
Initializes the handler with a buffer of the specified capacity.
emit
(
record
)
¶
Appends the record to the buffer. If
shouldFlush()
returns true, calls
flush()
to process the buffer.
flush
(
)
¶
You can override this to implement custom flushing behavior. This version just zaps the buffer to empty.
shouldFlush
(
record
)
¶
Returns true if the buffer is up to capacity. This method can be overridden to implement custom flushing strategies.
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
。若
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.
3.6 版改变： flushOnClose 参数被添加。
flush
(
)
¶
For a
MemoryHandler
, flushing means just sending the buffered records to the target, if there is one. The buffer is also cleared when this happens. 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
class, located in the
logging.handlers
module, supports sending logging messages to a Web server, using either
GET
or
POST
semantics.
logging.handlers.
HTTPHandler
(
host
,
url
,
method='GET'
,
secure=False
,
credentials=None
,
context=None
)
¶
Returns a new instance of the
HTTPHandler
类。
host
can be of the form
host:port
, should you need to use a specific port number. If no
方法
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.
3.5 版改变： context 参数被添加。
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.
注意
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.
3.2 版新增。
QueueHandler
class, located in the
logging.handlers
module, supports sending logging messages to a queue, such as those implemented in the
queue
or
multiprocessing
模块。
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.
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.
emit
(
record
)
¶
Enqueues the result of preparing the LogRecord.
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 and arguments, and removes unpickleable items from the record in-place.
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.
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.
3.2 版新增。
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.
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. 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.
3.5 版改变：
respect_handler_levels
argument was added.
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.
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.
3.3 版新增。
另请参阅
logging
logging.config
logging.handlers
— 日志处理程序