Registry Objects and Repositories

This section will introduce you to the important information how to use the objects.

Object sharing among processes is an important feature of the project.

Every shareable object in the project is inherited from RegistrableObject class. These classes are responsible for correct synchronization with remote data stores.

In the first version of the project there is one RegistrableObject class - ZeroRegistrableObject. ‘Zero’ prefix is a generation number. The main idea is that each generation will provide incompatible functionality. It is because objects schemas and objects states will be stored in a storage. Any significant updates will corrupt the system.

Also, there are repositories interfaces that help to sync with specific data stores. A repository interface can be set for each class (at the same time or separately).

In most cases you will use high-level interfaces for setting storage interfaces.

This is basic example of setting repository interface:

from tethys.core.regobjs import ZeroRegistrableObject
from tethys.core.regobjs.repositories.repo_mongo import MongodbRepository
from tethys.core.networks import ZeroNetwork

uri = "mongodb://root:root@127.0.0.1:27017/some_collection?authSource=admin"
repo = MongodbRepository(uri)

# default: ZeroRegistrableObject.REPOSITORY == LocalRepository()
ZeroRegistrableObject.REPOSITORY = repo

ZeroNetwork().save()  # will save to the mongodb

Another example of setting repository interface:

from tethys.core.regobjs.repositories.repo_local import LocalRepository
from tethys.core.regobjs.repositories.repo_mongo import MongodbRepository
from tethys.core.networks import ZeroNetwork

uri = "mongodb://root:root@127.0.0.1:27017/some_collection?authSource=admin"
repo = MongodbRepository(uri)

ZeroNetwork.REPOSITORY = repo

ZeroNetwork().save()  # will save to the mongodb
ZeroNetwork(_repo=LocalRepository()).save()  # will save to the local dict()

Each registry object contains methods for database communication.

Methods load and list allow loading data from storages. Method refresh uses the load method to sync data from a database. Method delete remove the object in a database (but you can continue to use local copy).

Example to understand the concept:

from tethys.core.regobjs import ZeroRegistrableObject
from tethys.core.networks import ZeroNetwork
from tethys.core.pipes import ZeroPipe

class TestPipe(ZeroPipe):
    FIELDS_SCHEMA = {}

    def __init__(self, **_):
        pass

TestPipe(_id="test_pipe")

obj = ZeroNetwork(["test_pipe"], _id="test_net").save(
     save_dependency=True,  # execute save method for related objects (like test_pipe)
     save_dependency_depth=1  # saving recursion depth [will save ZeroNetwork and TestPipe]
)
assert obj.pipes_list == ["test_pipe"]

obj.pipes_list = []
assert obj.pipes_list == []

assert obj.load("test_net") is obj
assert obj.pipes_list == []

assert obj.load("test_net", with_cache=False) is obj
assert obj.pipes_list == ["test_pipe"]  # It will be loaded from the repository

obj.pipes_list = []
assert obj.pipes_list == []

assert obj.refresh() is obj
assert obj.pipes_list == ["test_pipe"]

obj.pipes_list = []
assert obj.pipes_list == []

assert obj.list() == [obj]
assert obj.pipes_list == ["test_pipe"]

obj.pipes_list = []
assert obj.pipes_list == []

assert obj.delete() is obj
assert obj.refresh() is None
assert obj.pipes_list == []

assert obj.save()
assert obj.refresh() is obj
assert obj.pipes_list == []

Also objects provide simple locks. You can lock objects for changes in a database. It’s an example how to use locks in the project:

import time
from tethys.core.networks import ZeroNetwork

start = time.time()
obj = ZeroNetwork().save()

assert obj.lock(lock_ttl=1) is True
assert obj.lock(blocking=True, lock_ttl=5) is True
print(time.time() - start)  # ~ 1s

assert obj.lock(blocking=True, wait_timeout=1) is True
print(time.time() - start)  # ~ 2s

with obj.lock_context(blocking=False, lock_ttl=5) as lock_ready:
    assert lock_ready is False
    print(time.time() - start)  # ~ 2s

assert obj.lock(blocking=True) is True
print(time.time() - start)  # ~ 2s

obj.unlock()

This Lock mechanism doesn’t provide database locks.

If you need to lock an object in a database, you must use specific repository interfaces and databases that provide this functionality.