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proxystore.endpoint.protocol

Client-endpoint wire protocol.

Clients communicate with their local endpoint over a TCP connection using length-prefixed binary messages. This module only contains the encoding and decoding logic, and it only depends on the standard library so the client does not require any of the endpoints extra dependencies.

A connection starts with a handshake:

  1. The client sends a preamble (MAGIC and PROTOCOL_VERSION) followed by a HELLO message with a random nonce and the client's versions.
  2. The endpoint replies with its preamble and a message with its own nonce and a proof that it knows the endpoint's token.
  3. The client verifies the endpoint's proof then sends an AUTH message with its own proof.
  4. The endpoint verifies the client's proof and replies with its information (UUID, name, and versions).

The preamble format must never change so that clients and endpoints using different protocol versions can detect the mismatch. If the protocol versions differ, the endpoint replies with only its preamble and closes the connection.

After the handshake, each request and response is a message consisting of a fixed-size header, JSON-encoded metadata (e.g., the key), and a raw data payload.

MAGIC module-attribute 

MAGIC = b'PSEP'

Bytes that start every connection.

PROTOCOL_VERSION module-attribute 

PROTOCOL_VERSION = 1

Version of the protocol.

Increment on any incompatible change to the handshake or message formats.

NONCE_SIZE module-attribute 

NONCE_SIZE = 32

Size in bytes of the random nonces exchanged in the handshake.

MAX_META_SIZE module-attribute 

MAX_META_SIZE = 64 * 1024

Maximum size in bytes of the metadata in a message.

VERSION_DOCS_URL module-attribute 

VERSION_DOCS_URL = "https://docs.proxystore.dev/latest/guides/endpoints/#version-compatibility"

Documentation on version compatibility between clients and endpoints.

Op

Bases: IntEnum

Operation codes of messages sent by a client.

HELLO class-attribute instance-attribute 

HELLO = 1

First message of the handshake.

AUTH class-attribute instance-attribute 

AUTH = 2

Second message of the handshake with the client's proof.

GET class-attribute instance-attribute 

GET = 3

Get the object associated with a key.

SET class-attribute instance-attribute 

SET = 4

Set the object associated with a key.

EXISTS class-attribute instance-attribute 

EXISTS = 5

Check if an object associated with a key exists.

EVICT class-attribute instance-attribute 

EVICT = 6

Evict the object associated with a key.

Status

Bases: IntEnum

Status codes of messages sent by an endpoint.

OK class-attribute instance-attribute 

OK = 0

Request succeeded.

NOT_FOUND class-attribute instance-attribute 

NOT_FOUND = 1

No object is associated with the key.

ERROR class-attribute instance-attribute 

ERROR = 2

Request failed. The metadata contains the error message.

UNAUTHORIZED class-attribute instance-attribute 

UNAUTHORIZED = 3

Client failed authentication.

BAD_REQUEST class-attribute instance-attribute 

BAD_REQUEST = 4

Request was malformed.

TOO_LARGE class-attribute instance-attribute 

TOO_LARGE = 5

Request data exceeds the maximum object size of the endpoint.

Preamble dataclass 

Preamble(version: int = PROTOCOL_VERSION)

Preamble that starts every connection.

The format of the preamble must never change so that clients and endpoints using different protocol versions can detect the mismatch.

Attributes:

  • version (int) –

    Protocol version of the sender.

FORMAT class-attribute 

FORMAT: Struct = struct.Struct('!4sH')

Format of the magic bytes and protocol version.

SIZE class-attribute 

SIZE: int = FORMAT.size

Size in bytes of the preamble.

pack 

pack() -> bytes

Pack the preamble.

Source code in proxystore/endpoint/protocol.py 
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def pack(self) -> bytes:
    """Pack the preamble."""
    return self.FORMAT.pack(MAGIC, self.version)

unpack classmethod 

unpack(buffer: BytesLike) -> Self

Unpack a preamble.

Raises:

Source code in proxystore/endpoint/protocol.py 
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@classmethod
def unpack(cls, buffer: BytesLike) -> Self:
    """Unpack a preamble.

    Raises:
        EndpointProtocolError: If the preamble does not start with
            [`MAGIC`][proxystore.endpoint.protocol.MAGIC].
    """
    magic, version = cls.FORMAT.unpack(buffer)
    if magic != MAGIC:
        raise EndpointProtocolError(
            f'Expected connection to start with {MAGIC!r} but got '
            f'{magic!r}.',
        )
    return cls(version)

Header dataclass 

Header(code: int, flags: int, meta_len: int, data_len: int)

Message header.

Attributes:

  • code (int) –

    Op of a request or Status of a response.

  • flags (int) –

    Reserved for future use.

  • meta_len (int) –

    Length in bytes of the metadata.

  • data_len (int) –

    Length in bytes of the data.

FORMAT class-attribute 

FORMAT: Struct = struct.Struct('!BBIQ')

Format of the code, flags, metadata length, and data length.

SIZE class-attribute 

SIZE: int = FORMAT.size

Size in bytes of the header.

pack 

pack() -> bytes

Pack the header.

Source code in proxystore/endpoint/protocol.py 
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def pack(self) -> bytes:
    """Pack the header."""
    return self.FORMAT.pack(
        self.code,
        self.flags,
        self.meta_len,
        self.data_len,
    )

unpack classmethod 

unpack(buffer: BytesLike) -> Self

Unpack a header.

Raises:

Source code in proxystore/endpoint/protocol.py 
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@classmethod
def unpack(cls, buffer: BytesLike) -> Self:
    """Unpack a header.

    Raises:
        EndpointProtocolError: If the metadata length exceeds
            [`MAX_META_SIZE`][proxystore.endpoint.protocol.MAX_META_SIZE].
    """
    header = cls(*cls.FORMAT.unpack(buffer))
    if header.meta_len > MAX_META_SIZE:
        raise EndpointProtocolError(
            f'Message metadata length ({header.meta_len} bytes) exceeds '
            f'the maximum of {MAX_META_SIZE} bytes.',
        )
    return header

Versions

Bases: NamedTuple

ProxyStore and Python versions of a client or endpoint.

Attributes:

  • proxystore (str) –

    ProxyStore version.

  • python (str) –

    Python version.

current classmethod 

current() -> Self

Get the ProxyStore and Python versions of this process.

Source code in proxystore/endpoint/protocol.py 
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@classmethod
def current(cls) -> Self:
    """Get the ProxyStore and Python versions of this process."""
    return cls(proxystore.__version__, platform.python_version())

mismatches 

mismatches(endpoint: Versions) -> list[str]

Find differences between this client's and the endpoint's versions.

The ProxyStore versions must match exactly. The Python versions must have the same major and minor version because objects pickled by one Python version may not unpickle with another, but patch releases are compatible.

Parameters:

  • endpoint (Versions) –

    Versions of the endpoint.

Returns:

  • list[str] –

    Human-readable descriptions of each mismatch. Empty if the versions are compatible.

Source code in proxystore/endpoint/protocol.py 
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def mismatches(self, endpoint: Versions) -> list[str]:
    """Find differences between this client's and the endpoint's versions.

    The ProxyStore versions must match exactly. The Python versions must
    have the same major and minor version because objects pickled by one
    Python version may not unpickle with another, but patch releases are
    compatible.

    Args:
        endpoint: Versions of the endpoint.

    Returns:
        Human-readable descriptions of each mismatch. Empty if the \
        versions are compatible.
    """
    mismatches = []
    if self.proxystore != endpoint.proxystore:
        mismatches.append(
            f'ProxyStore {self.proxystore} (client) vs. '
            f'{endpoint.proxystore} (endpoint)',
        )
    if self.python.split('.')[:2] != endpoint.python.split('.')[:2]:
        mismatches.append(
            f'Python {self.python} (client) vs. {endpoint.python} '
            '(endpoint)',
        )
    return mismatches

Hello dataclass 

Hello(nonce: bytes, versions: Versions)

First message of the handshake sent by the client.

Attributes:

  • nonce (bytes) –

    Random nonce chosen by the client.

  • versions (Versions) –

    Versions of the client.

to_meta 

to_meta() -> dict[str, Any]

Encode as message metadata.

Source code in proxystore/endpoint/protocol.py 
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def to_meta(self) -> dict[str, Any]:
    """Encode as message metadata."""
    return {'nonce': self.nonce.hex(), **self.versions._asdict()}

from_meta classmethod 

from_meta(meta: dict[str, Any]) -> Self

Decode from message metadata.

Raises:

Source code in proxystore/endpoint/protocol.py 
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@classmethod
def from_meta(cls, meta: dict[str, Any]) -> Self:
    """Decode from message metadata.

    Raises:
        EndpointProtocolError: If the metadata is malformed.
    """
    return cls(
        nonce=_get_hex(meta, 'nonce', cls, size=NONCE_SIZE),
        versions=_get_versions(meta, cls),
    )

Challenge dataclass 

Challenge(nonce: bytes, proof: bytes)

Reply of the endpoint to Hello.

Attributes:

  • nonce (bytes) –

    Random nonce chosen by the endpoint.

  • proof (bytes) –

    Proof that the endpoint knows the token.

to_meta 

to_meta() -> dict[str, Any]

Encode as message metadata.

Source code in proxystore/endpoint/protocol.py 
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def to_meta(self) -> dict[str, Any]:
    """Encode as message metadata."""
    return {'nonce': self.nonce.hex(), 'proof': self.proof.hex()}

from_meta classmethod 

from_meta(meta: dict[str, Any]) -> Self

Decode from message metadata.

Raises:

Source code in proxystore/endpoint/protocol.py 
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@classmethod
def from_meta(cls, meta: dict[str, Any]) -> Self:
    """Decode from message metadata.

    Raises:
        EndpointProtocolError: If the metadata is malformed.
    """
    return cls(
        nonce=_get_hex(meta, 'nonce', cls, size=NONCE_SIZE),
        proof=_get_hex(meta, 'proof', cls),
    )

Auth dataclass 

Auth(proof: bytes)

Second message of the handshake with the proof of the client.

Attributes:

  • proof (bytes) –

    Proof that the client knows the token.

to_meta 

to_meta() -> dict[str, Any]

Encode as message metadata.

Source code in proxystore/endpoint/protocol.py 
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def to_meta(self) -> dict[str, Any]:
    """Encode as message metadata."""
    return {'proof': self.proof.hex()}

from_meta classmethod 

from_meta(meta: dict[str, Any]) -> Self

Decode from message metadata.

Raises:

Source code in proxystore/endpoint/protocol.py 
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@classmethod
def from_meta(cls, meta: dict[str, Any]) -> Self:
    """Decode from message metadata.

    Raises:
        EndpointProtocolError: If the metadata is malformed.
    """
    return cls(proof=_get_hex(meta, 'proof', cls))

EndpointInfo dataclass 

EndpointInfo(
    uuid: UUID,
    name: str,
    versions: Versions,
    max_object_size: int | None,
)

Information about an endpoint sent at the end of the handshake.

Attributes:

  • uuid (UUID) –

    UUID of the endpoint.

  • name (str) –

    Name of the endpoint.

  • versions (Versions) –

    Versions of the endpoint.

  • max_object_size (int | None) –

    Maximum size in bytes of objects that can be set on the endpoint or None if there is no limit.

to_meta 

to_meta() -> dict[str, Any]

Encode as message metadata.

Source code in proxystore/endpoint/protocol.py 
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def to_meta(self) -> dict[str, Any]:
    """Encode as message metadata."""
    return {
        'uuid': str(self.uuid),
        'name': self.name,
        'max_object_size': self.max_object_size,
        **self.versions._asdict(),
    }

from_meta classmethod 

from_meta(meta: dict[str, Any]) -> Self

Decode from message metadata.

Raises:

Source code in proxystore/endpoint/protocol.py 
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@classmethod
def from_meta(cls, meta: dict[str, Any]) -> Self:
    """Decode from message metadata.

    Raises:
        EndpointProtocolError: If the metadata is malformed.
    """
    return cls(
        uuid=_parse_uuid(_get(meta, 'uuid', str, cls), 'uuid', cls),
        name=_get(meta, 'name', str, cls),
        versions=_get_versions(meta, cls),
        max_object_size=_get(
            meta,
            'max_object_size',
            (int, type(None)),
            cls,
        ),
    )

Request dataclass 

Request(key: str, endpoint: UUID | None = None)

Metadata of a request sent by a client after the handshake.

Attributes:

  • key (str) –

    Key of the object.

  • endpoint (UUID | None) –

    UUID of the endpoint to forward the request to or None for the local endpoint.

to_meta 

to_meta() -> dict[str, Any]

Encode as message metadata.

Source code in proxystore/endpoint/protocol.py 
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def to_meta(self) -> dict[str, Any]:
    """Encode as message metadata."""
    endpoint = None if self.endpoint is None else str(self.endpoint)
    return {'key': self.key, 'endpoint': endpoint}

from_meta classmethod 

from_meta(meta: dict[str, Any]) -> Self

Decode from message metadata.

Raises:

Source code in proxystore/endpoint/protocol.py 
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@classmethod
def from_meta(cls, meta: dict[str, Any]) -> Self:
    """Decode from message metadata.

    Raises:
        EndpointProtocolError: If the metadata is malformed.
    """
    key = _get(meta, 'key', str, cls)
    if len(key) == 0:
        raise _malformed(cls, 'key')
    endpoint = _get(meta, 'endpoint', (str, type(None)), cls)
    return cls(
        key=key,
        endpoint=None
        if endpoint is None
        else _parse_uuid(endpoint, 'endpoint', cls),
    )

pack_message 

pack_message(
    code: int,
    meta: dict[str, Any] | None = None,
    data_len: int = 0,
) -> bytes

Pack the header and metadata of a message.

The data (if any) is not included so it can be sent separately without being copied.

Parameters:

  • code (int) –

    Op or status code.

  • meta (dict[str, Any] | None, default: None ) –

    Metadata to include in the message.

  • data_len (int, default: 0 ) –

    Length in bytes of the data that will follow.

Source code in proxystore/endpoint/protocol.py 
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def pack_message(
    code: int,
    meta: dict[str, Any] | None = None,
    data_len: int = 0,
) -> bytes:
    """Pack the header and metadata of a message.

    The data (if any) is not included so it can be sent separately without
    being copied.

    Args:
        code: Op or status code.
        meta: Metadata to include in the message.
        data_len: Length in bytes of the data that will follow.
    """
    meta_bytes = b'' if meta is None else encode_meta(meta)
    return Header(code, 0, len(meta_bytes), data_len).pack() + meta_bytes

encode_meta 

encode_meta(meta: dict[str, Any]) -> bytes

Encode message metadata.

Source code in proxystore/endpoint/protocol.py 
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def encode_meta(meta: dict[str, Any]) -> bytes:
    """Encode message metadata."""
    return json.dumps(meta, separators=(',', ':')).encode()

decode_meta 

decode_meta(buffer: bytes | bytearray) -> dict[str, Any]

Decode message metadata.

Raises:

Source code in proxystore/endpoint/protocol.py 
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def decode_meta(buffer: bytes | bytearray) -> dict[str, Any]:
    """Decode message metadata.

    Raises:
        EndpointProtocolError: If the metadata is not a JSON object.
    """
    if len(buffer) == 0:
        return {}
    try:
        meta = json.loads(buffer)
    except (UnicodeDecodeError, json.JSONDecodeError) as e:
        raise EndpointProtocolError(
            f'Failed to decode message metadata: {e}',
        ) from e
    if not isinstance(meta, dict):
        raise EndpointProtocolError(
            f'Expected message metadata to be a JSON object but got '
            f'{type(meta).__name__}.',
        )
    return meta