Apache Log Parsing with Python
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import re from collections import defaultdict, named tuple format_pat= re.compile( r"(?P<host>[\d\.]+)\s" r"(?P<identity>\S*)\s" r"(?P<user>\S*)\s" r"\[(?P<time>.*?)\]\s" r'"(?P<request>.*?)"\s' r"(?P<status>\d+)\s" r"(?P<bytes>\S*)\s" r'"(?P<referer>.*?)"\s' # [SIC] r'"(?P<user_agent>.*?)"\s*' ) Access = namedtuple('Access', ['host', 'identity', 'user', 'time', 'request', 'status', 'bytes', 'referer', 'user_agent'] ) def access_iter( source_iter ): for log in source_iter: for line in (l.rstrip() for l in log): match= format_pat.match(line) if match: yield Access( **match.groupdict() )
That's about it. The access log rows are now first-class Access-class objects that can be processed pleasantly by high-level Python applications.
- The adjacent string concatenation means that the regular expression can be broken up into bits to make it readable.
- When the named tuple attributes match the regular expression names, we can trivially turn the match.groupdict() into a named tuple.
- By using a generator, the other parts of the application can simply loop through the results without tying up memory to create vast intermediate structures.
A couple of years back, a sysadmin was trying to justify spending money on a log analyzer product. I suggested they (at the very least) get an open source log analyzer.
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