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dynamo-store is designed to make multi-sharded data storage in DynamoDB seamless

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dynamo-store

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dynamo-store is designed to make multi-sharded data storage in DynamoDB seamless.

Out of the box it supports:

  • Automatic sharding of child dictionaries into other tables (useful for getting around 400KB limit of DyanmoDB)
  • Encryption of data at rest using 128bit AES_CBC
  • Automagic serialization of objects to tables

Documentation

DyStore

DyStore represents a DynamoDB table. The structure of your tables should be represented with DyStore objects, including paths to shards in each table. The DyStore object stores enough information in the tables when serialized to allow recreation of DyStore objects to make life easier in some cases. This means once a object is written to a DyStore, it can be reconstructed from stored metadata in the table.

DyObject

DyObject represents an object in a DyStore. It relies on jsonmodels to control how your object will serialize to JSON which will ultimately end up in your DynamoDB table.

The root and shard DyObjects should implement the following class variables when inheriting DyObject:

  • TABLE_NAME = 'Shard1' # Table to save this shard to in AWS
  • REGION_NAME = 'us-east-2' # Region to sav eto in AWS
  • PRIMARY_KEY_NAME = 'IDX' # Primary key name to use
  • IGNORE_LIST = [] # Variables names to ignore during serialisation
  • CONFIG_LOADER = config_loader() # Class level config loader to prevent having to pass into save() and load() Otherwise the above class variables are all optional.

Config Loading

The config_loader(config, **kwargs) is a callback that is used in DyStore and DyObject calls to control certain operations of dynamo-store. The first parameter config specifies which configuration item is being queried, and the rest of the keyword arguments are context sensitive data for the call.

The config parameter will be one of the CONFIG_LOADER_* class variables defined in DyStore or DyObject, they are documented in the API documentation below.

DyObject supports both config_loader passed into save() and load() as well as a class level config loader using the CONFIG_LOADER class variable. The passed in config loader takes precendence over class variable instance.

Example DyStore usage

from dynamo_store.store import DyStore

def root_store():
    shards = [DyStore('Shard1', 'IDX', path='$.birth_details'),
              DyStore('Shard2', 'IDX', path='$.location')]
    return DyStore('Root', 'ID', shards=shards)

def loader(config, **kwargs):
    if config == DyStore.CONFIG_LOADER_LOAD_KEY:
        encrypted_paths = ['birth_details.hospital', 'birth_details.dob', 'location.city', 'location.country', 'firstname', 'lastname']
        path = kwargs['path']
        if path in encrypted_paths:
            return 'somekey'
    elif config == DyStore.CONFIG_LOADER_KEEP_METADATA:
        return False

    return None

d = {'firstname': 'john',
     'lastname': 'smith',
     'location': {'city': 'Osaka',
                  'country': 'Japan'},
     'birth_details': {'hospital': 'Kosei Nenkin',
                       'dob': '12/2/1995'}}

# Write object to store
key = root_store().write(d)

# Update individual path
root_store().write_path(key, "location.city", "New York")

# Read back object from store
success, obj = root_store().read(key)

# Read individual path
path = root_store().read_path(key, "location.country")

# Delete object from store
root_store().delete(key)

Example DyObject usage

from dynamo_store.object import DyObject
from dynamo_store.store import DyStore
from jsonmodels import fields

class BirthDetails(DyObject):
    TABLE_NAME = 'Shard1'       # Table to save this shard to in AWS
    REGION_NAME = 'us-east-2'   # Region to sav eto in AWS
    PRIMARY_KEY_NAME = 'IDX'    # Primary key name to use

    hospital = fields.StringField()
    dob = fields.StringField()

class Location(DyObject):
    TABLE_NAME = 'Shard2'       # Table to save this shard to in AWS
    REGION_NAME = 'us-east-2'   # Region to save to in AWS
    PRIMARY_KEY_NAME = 'IDX'    # Primary key name to use

    city = fields.StringField()
    country = fields.StringField()
    geolocation = fields.EmbeddedField(GeoLocation)

class Root(DyObject):
    TABLE_NAME = 'Root'         # Table to save to in AWS
    REGION_NAME = 'us-east-2'   # Region to save to in AWS
    PRIMARY_KEY_NAME = 'ID'     # Primary key name to use

    firstname = fields.StringField()
    lastname = fields.StringField()
    location = fields.EmbeddedField(Location)
    birth_details = fields.EmbeddedField(BirthDetails)

def loader(config, **kwargs):
    if config == DyStore.CONFIG_LOADER_LOAD_KEY:
        encrypted_paths = ['birth_details.hospital.value', 'birth_details.dob.value', 'location.city.value', 'location.country.value', 'firstname.value', 'lastname.value']
        path = kwargs['path']
        if path in encrypted_paths:
            return 'somekey'
    elif config == DyStore.CONFIG_LOADER_KEEP_METADATA:
        return False
    elif config == DyObject.CONFIG_LOADER_DICT_TO_CLASS:
        # In this case we can just use the dict key to determine what kind of object it is
        # other cases might require examining the value
        key = kwargs['key']
        if key == 'location':
            return Location
        elif key == 'birth_details':
            return BirthDetails
        elif key == 'geolocation':
            return GeoLocation

    return None

# Setup and save object 
orig = Root()
orig.firstname = 'john'
orig.lastname = 'smith'
orig.location.city = 'Osaka'
orig.location.country = 'Kewpie'
orig.birth_details.dob = '15/03/1980'
orig.birth_details.hospital = 'Good one'
key = orig.save(config_loader=loader)

# Load object using key obtained from save() call
o = Root.load(key, config_loader=loader)
print(o.firstname)
print(o.lastname)
print(o.location.city)
print(o.location.country)
print(o.birth_details.dob)
print(o.birth_details.hospital)

DyStore API

class DyStore(object):
    """
    Invoked on writes to allow control of primary key.
    config_loader(DyStore.CONFIG_LOADER_GENERATE_PK, data=item)
    :param config: DyStore.CONFIG_LOADER_GENERATE_PK
    :param data: item being written
    :returns: string containing primary key to use, None to use uuid4()
    """
    CONFIG_LOADER_GENERATE_PK = 'pk'

    """
    Invoked on decryption/encryption to control key used.
    config_loader(DyStore.CONFIG_LOADER_LOAD_KEY, path=path, data=root)
    :param config: DyStore.CONFIG_LOADER_LOAD_KEY
    :param path: json path of item being encrypted/decrypted
    :param data: root object being encrypted/decrypted
    :returns: string containing key to use, None to ignore decryption/encryption
    """
    CONFIG_LOADER_LOAD_KEY = 'key'

    """
    Invoked on read/write to control if DyStore metadata should be kept in object.
    config_loader(DyStore.CONFIG_LOADER_KEEP_METADATA, data=item)
    :param config: DyStore.CONFIG_LOADER_KEEP_METADATA
    :param data: item being read/written
    :returns: bool controlling if metadata should be kept or not
    """
    CONFIG_LOADER_KEEP_METADATA = 'meta'

    def __init__(self, table_name=None, primary_key_name=None, path=None, shards=[], region='us-east-2'):
        """
        :param table_name: Name of DynamoDB table this object will access
        :param primary_key_name: Primary key name in DynamoDB
        :param path: JSON Path of this object when it is used in a shard, note: see jsonpath-ng for documentation on jsonpath.
        :param shards: Items to shard out to other tables in this object.
        :param region: AWS region for table.
        :param ignore_paths: Paths to ignore during encryption/decryption, can be regexes
        """

    def read_path(self, primary_key, path, config_loader=None):
        """
        Reads a path from an object from this store.
        :param primary_key: Primary key of object to read.
        :param path: JSON path of object to read (can reside in a shard).
        :param config_loader: Config loader to be used: config_loader(config, data) returns setting
        :returns: list of values on success, None otherwise
        """

    def read(self, primary_key, resolve_shards=True, config_loader=None):
        """
        Reads an object from this store.
        :param primary_key: Primary key of object to read.
        :param resolve_shards: Boolean to control whether shards are read.
        :param config_loader: Config loader to be used: config_loader(config, data) returns setting
        :returns: success, value
        """

    def write_path(self, primary_key, path, value, config_loader=None):
        """
        Writes a path in an object to this store.
        :param primary_key: Primary key of object to read.
        :param path: JSON path of object to read (can reside in a shard).
        :param value: Value to write at the JSON path.
        :param config_loader: Config loader to be used: config_loader(config, data) returns setting
        :param root_object: Internal parameter used for proper path resolution in config load calls.
        :returns: True if successful, False otherwise
        """

    def write(self, data, primary_key=None, save_shards=True, config_loader=None):
        """
        Writes an object to this store.
        :param primary_key: Primary key of object to write.
        :param save_shards: Boolean to control whether shards are saved.
        :param config_loader: Config loader to be used: config_loader(config, data) returns setting
        :returns: primary_key used/generated
        """

    def delete(self, primary_key, delete_shards=True, config_loader=None):
        """
        Deletes an object from this store.
        :param primary_key: Primary key of object to delete.
        :param delete_shards: Boolean to control whether shards are deleted.
        :param config_loader: Config loader to be used: config_loader(config, data) returns setting
        :returns: True if successful, False otherwise
        """

DyObject API

class DyObject(object):
    """
    Name of table in AWS to save this object to.
    """
    TABLE_NAME = None

    """
    Region in AWS to save this object to.
    """
    REGION_NAME = None

    """
    Name of primary key to use for this object.
    """
    PRIMARY_KEY_NAME = None

    """
    Config loader callable to use when config queries are made
    """
    CONFIG_LOADER = None

    """
    Variable names to ignore during serialization
    """
    IGNORE_LIST = []

    """
    Variable names to ignore during encryption/decryption
    """
    CRYPTO_IGNORE_PATHS = []

    """
    Invoked on object load when class cant be determined.
    config_loader(DyObject.CONFIG_LOADER_DICT_TO_KEY, key=key, value=value)
    :param config: DyObject.CONFIG_LOADER_DICT_TO_CLASS
    :param key: key in parent object
    :param value: value of dict in object
    :returns: Class to instantiate, None if to keep as dict
    """
    CONFIG_LOADER_DICT_TO_CLASS = 'dict'

    def delete(self, primary_key=None, config_loader=None):
        """
        Delete an object from the store.
        :param primary_key: Primary key to use, (optional: value passed in will be stored in instance for future use).
        :param config_loader: Config loader to be used: config_loader(config, data) returns setting
        :returns: True if successful, False otherwise
        """

    def save(self, primary_key=None, config_loader=None):
        """
        Saves this object to the store.
        :param primary_key: Primary key to use.
        :param config_loader: Config loader to be used: config_loader(config, data) returns setting
        A class wide config loader can also be set, however the passed in config loader takes preference.
        :returns: key of object written
        """

    @classmethod
    def load(cls, primary_key, config_loader=None):
        """
        Loads an object from the store.
        :param cls: Class to instantiate
        :param primary_key: Primary key of object to load.
        :param config_loader: Config loader to be used: config_loader(config, data) returns setting
        :param validate: Enable JSON Models field validation
        A class wide config loader can also be set, however the passed in config loader takes preference.
        :returns: cls object
        """

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