Source code for hazelcast.proxy.cp.atomic_reference

from hazelcast.protocol.codec import (
    atomic_ref_compare_and_set_codec,
    atomic_ref_get_codec,
    atomic_ref_set_codec,
    atomic_ref_contains_codec,
    atomic_ref_apply_codec,
)
from hazelcast.proxy.cp import BaseCPProxy
from hazelcast.util import check_true, check_not_none


[docs]class AtomicReference(BaseCPProxy): """A distributed, highly available object reference with atomic operations. AtomicReference offers linearizability during crash failures and network partitions. It is CP with respect to the CAP principle. If a network partition occurs, it remains available on at most one side of the partition. The following are some considerations you need to know when you use AtomicReference: - AtomicReference works based on the byte-content and not on the object-reference. If you use the ``compare_and_set()`` method, do not change to the original value because its serialized content will then be different. - All methods returning an object return a private copy. You can modify the private copy, but the rest of the world is shielded from your changes. If you want these changes to be visible to the rest of the world, you need to write the change back to the AtomicReference; but be careful about introducing a data-race. - The in-memory format of an AtomicReference is ``binary``. The receiving side does not need to have the class definition available unless it needs to be deserialized on the other side., e.g., because a method like `alter()` is executed. This deserialization is done for every call that needs to have the object instead of the binary content, so be careful with expensive object graphs that need to be deserialized. - If you have an object with many fields or an object graph and you only need to calculate some information or need a subset of fields, you can use the `apply()` method. With the `apply()` method, the whole object does not need to be sent over the line; only the information that is relevant is sent. IAtomicReference does not offer exactly-once / effectively-once execution semantics. It goes with at-least-once execution semantics by default and can cause an API call to be committed multiple times in case of CP member failures. It can be tuned to offer at-most-once execution semantics. Please see `fail-on-indeterminate-operation-state` server-side setting. """
[docs] def compare_and_set(self, expect, update): """Atomically sets the value to the given updated value only if the current value is equal to the expected value. Args: expect: The expected value. update: The new value. Returns: hazelcast.future.Future[bool]: ``True`` if successful, or ``False`` if the actual value was not equal to the expected value. """ expected_data = self._to_data(expect) new_data = self._to_data(update) codec = atomic_ref_compare_and_set_codec request = codec.encode_request(self._group_id, self._object_name, expected_data, new_data) return self._invoke(request, codec.decode_response)
[docs] def get(self): """Gets the current value. Returns: hazelcast.future.Future[any]: The current value. """ codec = atomic_ref_get_codec request = codec.encode_request(self._group_id, self._object_name) def handler(response): return self._to_object(codec.decode_response(response)) return self._invoke(request, handler)
[docs] def set(self, new_value): """Atomically sets the given value. Args: new_value: The new value. Returns: hazelcast.future.Future[None]: """ new_value_data = self._to_data(new_value) codec = atomic_ref_set_codec request = codec.encode_request(self._group_id, self._object_name, new_value_data, False) return self._invoke(request)
[docs] def get_and_set(self, new_value): """Gets the old value and sets the new value. Args: new_value: The new value. Returns: hazelcast.future.Future[any]: The old value. """ new_value_data = self._to_data(new_value) codec = atomic_ref_set_codec request = codec.encode_request(self._group_id, self._object_name, new_value_data, True) def handler(response): return self._to_object(codec.decode_response(response)) return self._invoke(request, handler)
[docs] def is_none(self): """Checks if the stored reference is ``None``. Returns: hazelcast.future.Future[bool]: ``True`` if the stored reference is ``None``, ``False`` otherwise. """ return self.contains(None)
[docs] def clear(self): """Clears the current stored reference, so it becomes ``None``. Returns: hazelcast.future.Future[None]: """ return self.set(None)
[docs] def contains(self, value): """Checks if the reference contains the value. Args: value: The value to check (is allowed to be ``None``). Returns: hazelcast.future.Future[bool]: ``True`` if the value is found, ``False`` otherwise. """ value_data = self._to_data(value) codec = atomic_ref_contains_codec request = codec.encode_request(self._group_id, self._object_name, value_data) return self._invoke(request, codec.decode_response)
[docs] def alter(self, function): """Alters the currently stored reference by applying a function on it. Notes: ``function`` must be an instance of ``IdentifiedDataSerializable`` or ``Portable`` that has a counterpart that implements the `com.hazelcast.core.IFunction` interface registered on the server-side with the actual implementation of the function to be applied. Args: function (hazelcast.serialization.api.Portable or hazelcast.serialization.api.IdentifiedDataSerializable): The function that alters the currently stored reference. Returns: hazelcast.future.Future[None]: """ check_not_none(function, "Function cannot be None") function_data = self._to_data(function) codec = atomic_ref_apply_codec # 0 means don't return the value request = codec.encode_request(self._group_id, self._object_name, function_data, 0, True) return self._invoke(request)
[docs] def alter_and_get(self, function): """Alters the currently stored reference by applying a function on it and gets the result. Notes: ``function`` must be an instance of ``IdentifiedDataSerializable`` or ``Portable`` that has a counterpart that implements the `com.hazelcast.core.IFunction` interface registered on the server-side with the actual implementation of the function to be applied. Args: function (hazelcast.serialization.api.Portable or hazelcast.serialization.api.IdentifiedDataSerializable): The function that alters the currently stored reference. Returns: hazelcast.future.Future[any]: The new value, the result of the applied function. """ check_not_none(function, "Function cannot be None") function_data = self._to_data(function) codec = atomic_ref_apply_codec # 2 means return the new value request = codec.encode_request(self._group_id, self._object_name, function_data, 2, True) def handler(response): return self._to_object(codec.decode_response(response)) return self._invoke(request, handler)
[docs] def get_and_alter(self, function): """Alters the currently stored reference by applying a function on it on and gets the old value. Notes: ``function`` must be an instance of ``IdentifiedDataSerializable`` or ``Portable`` that has a counterpart that implements the `com.hazelcast.core.IFunction` interface registered on the server-side with the actual implementation of the function to be applied. Args: function (hazelcast.serialization.api.Portable or hazelcast.serialization.api.IdentifiedDataSerializable): The function that alters the currently stored reference. Returns: hazelcast.future.Future[any]: The old value, the value before the function is applied. """ check_not_none(function, "Function cannot be None") function_data = self._to_data(function) codec = atomic_ref_apply_codec # 1 means return the old value request = codec.encode_request(self._group_id, self._object_name, function_data, 1, True) def handler(response): return self._to_object(codec.decode_response(response)) return self._invoke(request, handler)
[docs] def apply(self, function): """Applies a function on the value, the actual stored value will not change. Notes: ``function`` must be an instance of ``IdentifiedDataSerializable`` or ``Portable`` that has a counterpart that implements the `com.hazelcast.core.IFunction` interface registered on the server-side with the actual implementation of the function to be applied. Args: function (hazelcast.serialization.api.Portable or hazelcast.serialization.api.IdentifiedDataSerializable): The function applied on the currently stored reference. Returns: hazelcast.future.Future[any]: The result of the function application. """ check_not_none(function, "Function cannot be None") function_data = self._to_data(function) codec = atomic_ref_apply_codec # 2 means return the new value request = codec.encode_request(self._group_id, self._object_name, function_data, 2, False) def handler(response): return self._to_object(codec.decode_response(response)) return self._invoke(request, handler)