json.Decoder memory leak?

Hello,

I’ve got a service written in Python that reads data from ElasticSearch frequently 24/7.

Recently I’ve migrated it from orjson to msgspec.json. Since then, the service runs out of memory pretty quickly.

Following https://docs.python.org/3/library/tracemalloc.html#pretty-top I’m able to capture the top 10 lines that contributes large memory usage, which turns out it’s the decode(...) method from msgspec.json.Decoder

Top 10 lines
#1: /app/elasticsearch_repository.py:69: 26821.3 KiB
    self.__decoder.decode(
#2: /app/prepare_data_service.py:280: 3649.2 KiB
    cache_info_rt = decoder.decode(cache_info_data)
#3: /usr/local/lib/python3.10/multiprocessing/reduction.py:51: 1568.1 KiB
    cls(buf, protocol).dump(obj)
#4: /usr/local/lib/python3.10/linecache.py:137: 628.2 KiB
    lines = fp.readlines()
#5: /usr/local/lib/python3.10/json/decoder.py:353: 82.7 KiB
    obj, end = self.scan_once(s, idx)
#6: /usr/local/lib/python3.10/multiprocessing/queues.py:122: 40.2 KiB
    return _ForkingPickler.loads(res)
#7: /usr/local/lib/python3.10/tracemalloc.py:67: 11.9 KiB
    return (self.size, self.count, self.traceback)
#8: /app/elasticsearch_repository.py:68: 3.7 KiB
    return [
#9: /usr/local/lib/python3.10/http/client.py:1293: 3.6 KiB
    self.putrequest(method, url, **skips)
#10: /app/venv/lib/python3.10/site-packages/elasticsearch/client/utils.py:347: 1.8 KiB
    return func(*args, params=params, headers=headers, **kwargs)
193 other: 70.2 KiB
Total allocated size: 32880.9 KiB

Here are the structs for decoding:

'''
structs for msgspec
'''
from typing import Dict, List, Optional

from msgspec import Struct


class Query(Struct):
    """
    Struct for Query
    """
    date: str
    depAirport: str
    arrAirport: str


class Request(Struct):
    """
    Struct for Request
    """
    supplier: str
    tripType: str
    fareClass: str
    adultAmount: int
    childAmount: int
    infantAmount: int
    queries: List[Query]
    timestamp: int


class Segment(Struct):
    """
    Struct for Segment
    """
    fareClass: str
    depDate: str
    depTime: str
    flightNo: str
    carrier: str
    orgAirport: str
    arriveDate: str
    arriveTime: str
    dstAirport: str


class Flight(Struct):
    """
    Struct for Flight
    """
    segments: List[Segment]


class Price(Struct):
    """
    Struct for Price
    """
    price: float
    tax: float
    totalPrice: float
    seatsStatus: Optional[str] = None
    currencyCode: Optional[str] = None


class Trip(Struct):
    """
    Struct for Trip
    """
    flights: List[Flight]
    prices: Dict[str, Price]
    extended = Dict[str, str]


class Result(Struct):
    """
    Struct of Result
    """
    trips: List[Trip]


class CacheInfo(Struct):
    """
    Struct of CacheInfo
    """
    request: Request
    result: Result

I read from https://jcristharif.com/msgspec/structs.html#struct-nogc that

structs referencing only scalar values (ints, strings, bools, …) won’t contribute to GC load, but structs referencing containers (lists, dicts, structs, …) will.

Is this related? What’s the recommendation to resolve this issue?

Thanks!

[jcrist]

msgspec 0.7.0 has been released. Wheels are available on pypi now, should be up on conda-forge once the conda-forge bots detect the change.

[jcrist]

As mentioned above, we should have a release out before the 21st.