Memory Leak Detected
Overview Description
There appears to be a memory leak generated by repeated calls to dates.parse_pattern(dt, format, locale) if the function is called with a wide variety of different formats and locales.
This is because each time a new DateTimePattern is created for a new (format, locale), the object is cached to _pattern_cache (dict), which grows endlessly.
babel/dates.py:1598 (Babel 2.9.1)
def parse_pattern(pattern):
"""Parse date, time, and datetime format patterns."""
...
# here is the problem
_pattern_cache[pattern] = pat = DateTimePattern(pattern, u''.join(result))
Perhaps a better design could be to simply lru_cache the dates.parse_pattern() function ?
from functools import lru_cache
@lru_cache(maxsize=1000)
def parse_pattern(pattern):
"""Parse date, time, and datetime format patterns."""
...
Steps to Reproduce
from datetime import datetime
from babel.localedata import locale_identifiers
from babel.dates import format_datetime
from pympler import tracker # track memory leaks(=> https://github.com/pympler/pympler)
# show initial memory usage
tr = tracker.SummaryTracker()
tr.print_diff()
# create some random datetime
d = datetime(2007, 4, 1, 13, 27, 53)
# create some datetime formats
custom_formats = [ r"M/d/yy, h:mm a" # short
,r"MMM d, y, h:mm:ss a" # medium
,r"MMMM d, y 'at' h:mm:ss a z" # long
,r"EEEE, MMMM d, y 'at' h:mm:ss a zzzz" # full
,r"EEEE, MMMM d, y 'at' hh:mm:ss zzz" # shorter timezone
,r"EEEE, MMMM d, y 'at' hh:mm:ss zzzz" # full, 24hr
,r"EEEE, MMMM d, y 'at' hh:mm:ss"
,r"EEEE, MMMM d, y 'at' h:mm:ss a"
,r"EEEE, d MMM y hh:mm:ss"
,r"EEEE, d MMM y h:mm:ss a"
,r"d MMM y hh:mm:ss"
,r"d MMM y h:mm:ss a"
]
# call format_datetime for all locale/format combinations, about 9.4k combinations
for locale_name in locale_identifiers():
for custom_format in custom_formats:
s = format_datetime(d, locale=locale_name, format=custom_format)
# show difference in memory usage since start
tr.print_diff()
Actual Results
Initial Memory Snapshot
types | # objects | total size
list | 3750 | 318.95 KB
str | 3747 | 260.45 KB
int | 817 | 22.34 KB
Final Memory Snapshot
types | # objects | total size
dict | 272282 | 113.17 MB
str | 21809 | 1.51 MB
list | 12416 | 1.12 MB
babel.dates.DateTimePattern | 9668 | 453.19 KB
tuple | 6829 | 385.02 KB
babel.numbers.NumberPattern | 7550 | 353.91 K