from hazelcast.errors import IllegalStateError
from hazelcast.protocol.codec import (
queue_add_all_codec,
queue_add_listener_codec,
queue_clear_codec,
queue_compare_and_remove_all_codec,
queue_compare_and_retain_all_codec,
queue_contains_all_codec,
queue_contains_codec,
queue_drain_to_max_size_codec,
queue_is_empty_codec,
queue_iterator_codec,
queue_offer_codec,
queue_peek_codec,
queue_poll_codec,
queue_put_codec,
queue_remaining_capacity_codec,
queue_remove_codec,
queue_remove_listener_codec,
queue_size_codec,
queue_take_codec,
)
from hazelcast.proxy.base import PartitionSpecificProxy, ItemEvent, ItemEventType
from hazelcast.util import check_not_none, to_millis, ImmutableLazyDataList
[docs]class Queue(PartitionSpecificProxy):
"""Concurrent, blocking, distributed, observable queue.
Queue is not a partitioned data-structure. All of the Queue content is stored in
a single machine (and in the backup). Queue will not scale by adding more members in the cluster.
"""
[docs] def add(self, item):
"""Adds the specified item to this queue if there is available space.
Args:
item: The specified item.
Returns:
hazelcast.future.Future[bool]: ``True`` if element is successfully added, ``False`` otherwise.
"""
def result_fnc(f):
if f.result():
return True
raise IllegalStateError("Queue is full!")
return self.offer(item).continue_with(result_fnc)
[docs] def add_all(self, items):
"""Adds the elements in the specified collection to this queue.
Args:
items (list): Collection which includes the items to be added.
Returns:
hazelcast.future.Future[bool]: ``True`` if this queue is changed after call, ``False`` otherwise.
"""
check_not_none(items, "Value can't be None")
data_items = []
for item in items:
check_not_none(item, "Value can't be None")
data_items.append(self._to_data(item))
request = queue_add_all_codec.encode_request(self.name, data_items)
return self._invoke(request, queue_add_all_codec.decode_response)
[docs] def add_listener(self, include_value=False, item_added_func=None, item_removed_func=None):
"""Adds an item listener for this queue. Listener will be notified for all queue add/remove events.
Args:
include_value (bool): Whether received events include the updated item or not.
item_added_func (function): Function to be called when an item is added to this set.
item_removed_func (function): Function to be called when an item is deleted from this set.
Returns:
hazelcast.future.Future[str]: A registration id which is used as a key to remove the listener.
"""
codec = queue_add_listener_codec
request = codec.encode_request(self.name, include_value, self._is_smart)
def handle_event_item(item, uuid, event_type):
item = item if include_value else None
member = self._context.cluster_service.get_member(uuid)
item_event = ItemEvent(self.name, item, event_type, member, self._to_object)
if event_type == ItemEventType.ADDED:
if item_added_func:
item_added_func(item_event)
else:
if item_removed_func:
item_removed_func(item_event)
return self._register_listener(
request,
lambda r: codec.decode_response(r),
lambda reg_id: queue_remove_listener_codec.encode_request(self.name, reg_id),
lambda m: codec.handle(m, handle_event_item),
)
[docs] def clear(self):
"""Clears this queue. Queue will be empty after this call.
Returns:
hazelcast.future.Future[None]:
"""
request = queue_clear_codec.encode_request(self.name)
return self._invoke(request)
[docs] def contains(self, item):
"""Determines whether this queue contains the specified item or not.
Args:
item: The specified item to be searched.
Returns:
hazelcast.future.Future[bool]: ``True`` if the specified item exists in this queue, ``False`` otherwise.
"""
check_not_none(item, "Item can't be None")
item_data = self._to_data(item)
request = queue_contains_codec.encode_request(self.name, item_data)
return self._invoke(request, queue_contains_codec.decode_response)
[docs] def contains_all(self, items):
"""Determines whether this queue contains all of the items in the specified collection or not.
Args:
items (list): The specified collection which includes the items to be searched.
Returns:
hazelcast.future.Future[bool]: ``True`` if all of the items in the specified collection exist
in this queue, ``False`` otherwise.
"""
check_not_none(items, "Items can't be None")
data_items = []
for item in items:
check_not_none(item, "item can't be None")
data_items.append(self._to_data(item))
request = queue_contains_all_codec.encode_request(self.name, data_items)
return self._invoke(request, queue_contains_all_codec.decode_response)
[docs] def drain_to(self, target_list, max_size=-1):
"""Transfers all available items to the given `target_list` and removes these items from this queue.
If a max_size is specified, it transfers at most the given number of items.
In case of a failure, an item can exist in both collections or none of them.
This operation may be more efficient than polling elements repeatedly and putting into collection.
Args:
target_list (list): the list where the items in this queue will be transferred.
max_size (int): The maximum number items to transfer.
Returns:
hazelcast.future.Future[int]: Number of transferred items.
"""
def handler(message):
response = queue_drain_to_max_size_codec.decode_response(message)
target_list.extend(map(self._to_object, response))
return len(response)
request = queue_drain_to_max_size_codec.encode_request(self.name, max_size)
return self._invoke(request, handler)
[docs] def iterator(self):
"""Returns all of the items in this queue.
Returns:
list: Collection of items in this queue.
"""
def handler(message):
return ImmutableLazyDataList(
queue_iterator_codec.decode_response(message), self._to_object
)
request = queue_iterator_codec.encode_request(self.name)
return self._invoke(request, handler)
[docs] def is_empty(self):
"""Determines whether this set is empty or not.
Returns:
hazelcast.future.Future[bool]: ``True`` if this queue is empty, ``False`` otherwise.
"""
request = queue_is_empty_codec.encode_request(self.name)
return self._invoke(request, queue_is_empty_codec.decode_response)
[docs] def offer(self, item, timeout=0):
"""Inserts the specified element into this queue if it is possible to do so immediately
without violating capacity restrictions.
If there is no space currently available:
- If the timeout is provided, it waits until this timeout elapses and returns the result.
- If the timeout is not provided, returns ``False`` immediately.
Args:
item: The item to be added.
timeout (int): Maximum time in seconds to wait for addition.
Returns:
hazelcast.future.Future[bool]: ``True`` if the element was added to this queue, ``False`` otherwise.
"""
check_not_none(item, "Value can't be None")
element_data = self._to_data(item)
request = queue_offer_codec.encode_request(self.name, element_data, to_millis(timeout))
return self._invoke(request, queue_offer_codec.decode_response)
[docs] def peek(self):
"""Retrieves the head of queue without removing it from the queue.
Returns:
hazelcast.future.Future[any]: the head of this queue, or ``None`` if this queue is empty.
"""
def handler(message):
return self._to_object(queue_peek_codec.decode_response(message))
request = queue_peek_codec.encode_request(self.name)
return self._invoke(request, handler)
[docs] def poll(self, timeout=0):
"""Retrieves and removes the head of this queue.
If this queue is empty:
- If the timeout is provided, it waits until this timeout elapses and returns the result.
- If the timeout is not provided, returns ``None``.
Args:
timeout (int): Maximum time in seconds to wait for addition.
Returns:
hazelcast.future.Future[any]: The head of this queue, or ``None`` if this queue is empty
or specified timeout elapses before an item is added to the queue.
"""
def handler(message):
return self._to_object(queue_poll_codec.decode_response(message))
request = queue_poll_codec.encode_request(self.name, to_millis(timeout))
return self._invoke(request, handler)
[docs] def put(self, item):
"""Adds the specified element into this queue.
If there is no space, it waits until necessary space becomes available.
Args:
item: The specified item.
Returns:
hazelcast.future.Future[None]:
"""
check_not_none(item, "Value can't be None")
element_data = self._to_data(item)
request = queue_put_codec.encode_request(self.name, element_data)
return self._invoke(request)
[docs] def remaining_capacity(self):
"""Returns the remaining capacity of this queue.
Returns:
hazelcast.future.Future[int]: Remaining capacity of this queue.
"""
request = queue_remaining_capacity_codec.encode_request(self.name)
return self._invoke(request, queue_remaining_capacity_codec.decode_response)
[docs] def remove(self, item):
"""Removes the specified element from the queue if it exists.
Args:
item: The specified element to be removed.
Returns:
hazelcast.future.Future[bool]: ``True`` if the specified element exists in this queue, ``False`` otherwise.
"""
check_not_none(item, "Value can't be None")
item_data = self._to_data(item)
request = queue_remove_codec.encode_request(self.name, item_data)
return self._invoke(request, queue_remove_codec.decode_response)
[docs] def remove_all(self, items):
"""Removes all of the elements of the specified collection from this queue.
Args:
items (list): The specified collection.
Returns:
hazelcast.future.Future[bool]: ``True`` if the call changed this queue, ``False`` otherwise.
"""
check_not_none(items, "Value can't be None")
data_items = []
for item in items:
check_not_none(item, "Value can't be None")
data_items.append(self._to_data(item))
request = queue_compare_and_remove_all_codec.encode_request(self.name, data_items)
return self._invoke(request, queue_compare_and_remove_all_codec.decode_response)
[docs] def remove_listener(self, registration_id):
"""Removes the specified item listener.
Returns silently if the specified listener was not added before.
Args:
registration_id (str): Id of the listener to be deleted.
Returns:
hazelcast.future.Future[bool]: ``True`` if the item listener is removed, ``False`` otherwise.
"""
return self._deregister_listener(registration_id)
[docs] def retain_all(self, items):
"""Removes the items which are not contained in the specified collection.
In other words, only the items that are contained in the specified collection will be retained.
Args:
items (list): Collection which includes the elements to be retained in this set.
Returns:
hazelcast.future.Future[bool]: ``True`` if this queue changed as a result of the call, ``False`` otherwise.
"""
check_not_none(items, "Value can't be None")
data_items = []
for item in items:
check_not_none(item, "Value can't be None")
data_items.append(self._to_data(item))
request = queue_compare_and_retain_all_codec.encode_request(self.name, data_items)
return self._invoke(request, queue_compare_and_retain_all_codec.decode_response)
[docs] def size(self):
"""Returns the number of elements in this collection.
If the size is greater than ``2**31 - 1``, it returns ``2**31 - 1``
Returns:
hazelcast.future.Future[int]: Size of the queue.
"""
request = queue_size_codec.encode_request(self.name)
return self._invoke(request, queue_size_codec.decode_response)
[docs] def take(self):
"""Retrieves and removes the head of this queue, if necessary, waits until an item becomes available.
Returns:
hazelcast.future.Future[any]: The head of this queue.
"""
def handler(message):
return self._to_object(queue_take_codec.decode_response(message))
request = queue_take_codec.encode_request(self.name)
return self._invoke(request, handler)