Source code for examples.dogpile_caching.environment

"""Establish data / cache file paths, and configurations,
bootstrap fixture data if necessary.

"""
from hashlib import md5
import os
import sys

from dogpile.cache.region import make_region

from sqlalchemy import create_engine
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import scoped_session
from sqlalchemy.orm import sessionmaker
from . import caching_query

py2k = sys.version_info < (3, 0)

if py2k:
    input = raw_input  # noqa

# dogpile cache regions.  A home base for cache configurations.
regions = {}


# scoped_session.  Apply our custom CachingQuery class to it,
# using a callable that will associate the dictionary
# of regions with the Query.
Session = scoped_session(
    sessionmaker(query_cls=caching_query.query_callable(regions))
)

# global declarative base class.
Base = declarative_base()

root = "./dogpile_data/"

if not os.path.exists(root):
    input(
        "Will create datafiles in %r.\n"
        "To reset the cache + database, delete this directory.\n"
        "Press enter to continue.\n" % root
    )
    os.makedirs(root)

dbfile = os.path.join(root, "dogpile_demo.db")
engine = create_engine("sqlite:///%s" % dbfile, echo=True)
Session.configure(bind=engine)


def md5_key_mangler(key):
    """Receive cache keys as long concatenated strings;
    distill them into an md5 hash.

    """
    return md5(key.encode("ascii")).hexdigest()


# configure the "default" cache region.
regions["default"] = make_region(
    # the "dbm" backend needs
    # string-encoded keys
    key_mangler=md5_key_mangler
).configure(
    # using type 'file' to illustrate
    # serialized persistence.  Normally
    # memcached or similar is a better choice
    # for caching.
    "dogpile.cache.dbm",
    expiration_time=3600,
    arguments={"filename": os.path.join(root, "cache.dbm")},
)

# optional; call invalidate() on the region
# once created so that all data is fresh when
# the app is restarted.  Good for development,
# on a production system needs to be used carefully
# regions['default'].invalidate()


installed = False


def bootstrap():
    global installed
    from . import fixture_data

    if not os.path.exists(dbfile):
        fixture_data.install()
        installed = True