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# Copyright (c) 2018 VMware, Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at:
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
import logging
class MDCFormatter(logging.Formatter):
"""
A custom MDC formatter to prepare Mapped Diagnostic Context
to enrich log message.
"""
def __init__(self, fmt=None, mdcfmt=None, datefmt=None):
"""
:param fmt: build-in format string contains standard
Python %-style mapping keys
:param mdcFmt: mdc format with '{}'-style mapping keys
:param datefmt: Date format to use
"""
super(MDCFormatter, self).__init__(fmt=fmt, datefmt=datefmt)
self._tmpfmt = self._fmt
if mdcfmt:
self._mdcFmt = mdcfmt
else:
self._mdcFmt = '{reqeustID}'
def _mdcfmtKey(self):
"""
maximum barce match algorithm to find the mdc key
:return: key in brace and key not in brace,such as ({key}, key)
"""
left = '{'
right = '}'
target = self._mdcFmt
st = []
keys = []
for index, v in enumerate(target):
if v == left:
st.append(index)
elif v == right:
if len(st) == 0:
continue
elif len(st) == 1:
start = st.pop()
end = index
keys.append(target[start:end + 1])
elif len(st) > 0:
st.pop()
keys = filter(lambda x: x[1:-1].strip('\n \t ') != "", keys)
words = None
if keys:
words = map(lambda x: x[1:-1], keys)
return keys, words
def _replaceStr(self, keys):
fmt = self._mdcFmt
for i in keys:
fmt = fmt.replace(i, i[1:-1] + "=" + i)
return fmt
def format(self, record):
"""
Find mdcs in log record extra field, if key form mdcFmt dosen't
contains mdcs, the values will be empty.
:param record: the logging record instance
:return: string
for example:
the mdcs dict in logging record is
{'key1':'value1','key2':'value2'}
the mdcFmt is" '{key1} {key3}'
the output of mdc message: 'key1=value1 key3='
"""
mdcIndex = self._fmt.find('%(mdc)s')
if mdcIndex == -1:
return super(MDCFormatter, self).format(record)
mdcFmtkeys, mdcFmtWords = self._mdcfmtKey()
if mdcFmtWords is None:
self._fmt = self._fmt.replace("%(mdc)s", "")
return super(MDCFormatter, self).format(record)
mdc = record.__dict__.get('mdc', None)
res = {}
for i in mdcFmtWords:
if mdc and i in mdc:
res[i] = mdc[i]
else:
res[i] = ""
del mdc
try:
mdcstr = self._replaceStr(keys=mdcFmtkeys).format(**res)
self._fmt = self._fmt.replace("%(mdc)s", mdcstr)
s = super(MDCFormatter, self).format(record)
return s
except KeyError as e:
print ("The mdc key %s format is wrong" % e.message)
except Exception:
raise
finally:
# reset fmt format
self._fmt = self._tmpfmt
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