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Concurrency Error

concurrency_error

Error raised when an optimistic concurrency check detects a version conflict.

Indicates that an expected version does not match the current stored version
for an aggregate, meaning another writer committed a change between the
read and write phases of an operation.

ConcurrencyError

Bases: EventStoreError[MetadataValueType]

Raised when an optimistic concurrency check fails.

Captures the conflicting aggregate identity and the expected
versus actual version numbers so callers can decide whether to
retry, reconcile, or fail the operation.

Attributes:

Name Type Description
aggregate_id

The aggregate that experienced the conflict.
expected_version

The version the caller expected.
actual_version

The version currently stored.
Example 
error = ConcurrencyError(
    aggregate_id=UUID("12345678-1234-5678-1234-567812345678"),
    expected_version=1,
    actual_version=2,
)
raise error
Source code in src/forging_blocks/application/errors/concurrency_error.py 
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class ConcurrencyError[MetadataValueType = object](EventStoreError[MetadataValueType]):
    """Raised when an optimistic concurrency check fails.

    Captures the conflicting aggregate identity and the expected
    versus actual version numbers so callers can decide whether to
    retry, reconcile, or fail the operation.

    Attributes:
        aggregate_id: The aggregate that experienced the conflict.
        expected_version: The version the caller expected.
        actual_version: The version currently stored.


    Example:
        ```python
        error = ConcurrencyError(
            aggregate_id=UUID("12345678-1234-5678-1234-567812345678"),
            expected_version=1,
            actual_version=2,
        )
        raise error
        ```
    """

    def __init__(self, aggregate_id: UUID, expected_version: int, actual_version: int) -> None:
        """Initialise with the conflicting aggregate and version details.

        Args:
            aggregate_id: The identifier of the aggregate with the conflict.
            expected_version: The version number the caller expected to find.
            actual_version: The version number actually stored.

        """
        self.aggregate_id = aggregate_id
        self.expected_version = expected_version
        self.actual_version = actual_version
        super().__init__(
            f"Concurrency conflict for aggregate {aggregate_id}: "
            f"expected version {expected_version}, actual {actual_version}"
        )

__init__(aggregate_id: UUID, expected_version: int, actual_version: int) -> None

Initialise with the conflicting aggregate and version details.

Parameters:

Name Type Description Default
aggregate_id UUID

The identifier of the aggregate with the conflict.

 required
expected_version int

The version number the caller expected to find.

 required
actual_version int

The version number actually stored.

 required
Source code in src/forging_blocks/application/errors/concurrency_error.py 
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def __init__(self, aggregate_id: UUID, expected_version: int, actual_version: int) -> None:
    """Initialise with the conflicting aggregate and version details.

    Args:
        aggregate_id: The identifier of the aggregate with the conflict.
        expected_version: The version number the caller expected to find.
        actual_version: The version number actually stored.

    """
    self.aggregate_id = aggregate_id
    self.expected_version = expected_version
    self.actual_version = actual_version
    super().__init__(
        f"Concurrency conflict for aggregate {aggregate_id}: "
        f"expected version {expected_version}, actual {actual_version}"
    )