Boto3: Make resources pickleable/serializable

[maxrothman]

Boto3 resources (e.g. instances, s3 objects, etc.) are not pickleable and have no to_json() method or similar. Therefore, there's currently no way to cache resources retrieved via boto3. This is problematic when retrieving a large number of resources that change infrequently. Even a cache of 30s or so can greatly increase the performance of certain programs and drastically reduce the number of necessary API calls to AWS.

Would it be possible to have some way to serialize resources?

[jamesls]

In general, I'd like to improve things with regard to pickling/serializing objects. However, this is going to be challenging to implement giving the dynamic nature of resources/instances.

Marking as a feature request. If anyone has any ideas/suggestions they want to share, feel free to chime in.

[maxrothman]

This should be possible by giving the classes a __reduce__ method. See this StackOverflow question and the Python docs for more info.

[maxrothman]

I might be interested in contributing a patch for this issue if someone could help orient me in the codebase so I can find the callable that generates resources. @jamesls do you have thoughts on potential challenges in making said patch?

[maxrothman]

@jamesls ping. Any update on this?

[maxrothman]

@jamesls ping

[maxrothman]

I'm working on a patch for this. Is there any way currently that given a resource object you can get a reference to the ServiceContext that was used to create it? Or alternatively, is there a way to create a resource object from raw response JSON?

[maxrothman]

@jamesls any insight on the above question?

[maxrothman]

Ping. Is there any way I can get some support on this? I've expressed interest in submitting a patch, but I have some questions (above).

[dazza-codes]

Wow, this is old! The factory pattern (as implemented) screws up easy exception handling and pickling. Looks like this one is thrown in the too hard basket.

E       _pickle.PicklingError: Can't pickle <class 'boto3.resources.factory.s3.ObjectSummary'>: attribute lookup s3.ObjectSummary on boto3.resources.factory failed

A work-around that might somehow find it's way into boto3:

# substitute a namedtuple if necessary for py 2.x or earlier 3.x
# https://docs.python.org/3/library/collections.html#collections.namedtuple
@dataclass(frozen=True)
class S3Object:
    """Just the bucket_name and key for an s3.ObjectSummary
    This simple data class should work around problems with Pickle
    for an s3.ObjectSummary, so if obj is an s3.ObjectSummary, then:
    S3Object(bucket=obj.bucket_name, key=obj.key)
    """
    bucket: str
    key: str

bucket_name = 'example'
s3 = boto3.resource('s3')
s3_bucket = s3.Bucket(bucket_name)

objects = (
    S3Object(bucket=obj.bucket_name, key=obj.key)
    for obj in s3_bucket.objects.filter(Prefix='example_prefix')
)

with multiprocessing.Pool() as pool:
    processed_objects = pool.map(YourProcessor, objects)

[dazza-codes]

Symptoms of the factory patterns gone wrong?

>>> type(objects)
<class 'boto3.resources.collection.s3.Bucket.objectsCollection'>
>>> isinstance(objects, boto3.resources.collection.s3.Bucket.objectsCollection)
E       AttributeError: module 'boto3.resources.collection' has no attribute 's3'

[luiscastillocr]

 File "/home/vagrant/home/vagrant/wikirealty/lib/python3.4/site-packages/memoize/__init__.py", line 339, in decorated_function
    timeout=decorated_function.cache_timeout
  File "/home/vagrant/home/vagrant/wikirealty/lib/python3.4/site-packages/memoize/__init__.py", line 82, in set
    self.cache.set(key=key, value=value, timeout=timeout)
  File "/home/vagrant/home/vagrant/wikirealty/lib/python3.4/site-packages/django/core/cache/backends/memcached.py", line 86, in set
    if not self._cache.set(key, value, self.get_backend_timeout(timeout)):
  File "/home/vagrant/home/vagrant/wikirealty/lib/python3.4/site-packages/memcache.py", line 727, in set
    return self._set("set", key, val, time, min_compress_len, noreply)
  File "/home/vagrant/home/vagrant/wikirealty/lib/python3.4/site-packages/memcache.py", line 1055, in _set
    return _unsafe_set()
  File "/home/vagrant/home/vagrant/wikirealty/lib/python3.4/site-packages/memcache.py", line 1030, in _unsafe_set
    store_info = self._val_to_store_info(val, min_compress_len)
  File "/home/vagrant/home/vagrant/wikirealty/lib/python3.4/site-packages/memcache.py", line 994, in _val_to_store_info
    pickler.dump(val)
_pickle.PicklingError: Can't pickle <class 'boto3.resources.factory.s3.Bucket'>: attribute lookup s3.Bucket on boto3.resources.factory failed

I am getting this error using django-memoize with memcached, looks like it is still an issue!

[dazza-codes]

A similar issue was resolved in:

• https://github.com/microsoft/LightGBM/issues/2189
• http://gael-varoquaux.info/programming/decoration-in-python-done-right-decorating-and-pickling.html

It might help to add a test suite with pickle tests like:

import pickle
import boto3.session
import botocore.session

def test_pickle_botocore_session():
    session = botocore.session.get_session()
    assert pickle.loads(pickle.dumps(session))

def test_pickle_boto3_session():
    session = boto3.session.Session()
    assert pickle.loads(pickle.dumps(session))

Unfortunately they fail:

    def test_pickle_botocore_session():
        session = botocore.session.get_session()
>       assert pickle.loads(pickle.dumps(session))
E       AttributeError: Can't pickle local object '_createenviron.<locals>.encode'

tests/test_clients.py:52: AttributeError
___________________________________________________________________________________ test_pickle_boto3_session ____________________________________________________________________________________

    def test_pickle_boto3_session():
        session = boto3.session.Session()
>       assert pickle.loads(pickle.dumps(session))
E       AttributeError: Can't pickle local object 'lazy_call.<locals>._handler'

[SoraDevin]

Any update on this?