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from pvl.syslog.filter import SyslogFilter

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import re

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import logging; log = logging.getLogger('pvl.syslog.rule')

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class SyslogRule (object) :

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    """

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        A rule matches syslog lines, and formats them.

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            tag         - apply given tag to matches

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    """

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    def __init__ (self, tag, program=None, pattern=None, format=None, flags=0) :

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        pattern = re.compile(pattern, flags)

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        self.filter = SyslogFilter(prog=program)

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        self.tag = tag

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        self.format = format

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        self.pattern = pattern

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    def apply (self, item) :

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        """

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            Apply rule against given item.

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        """

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        # filter

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        match = self.filter.filter(item)

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        log.debug("filter: %s", match)

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        if not match :

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            # ignore

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            return None

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        if self.pattern :

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            match = self.pattern.match(item['msg'])

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            if not match :

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                # ignore

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                return None

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            # apply

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            item.update(match.groupdict())

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        if self.tag is False :

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            # drop

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            return False

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        if self.format :

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            # return

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            return self.tag, self.format.format(**item)

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