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Editing: msg.py
# Copyright 2016-2021 The NATS Authors # Licensed under the Apache License, Version 2.0 (the "License"); # you may not use this file except in compliance with the License. # You may obtain a copy of the License at # # http://www.apache.org/licenses/LICENSE-2.0 # # Unless required by applicable law or agreed to in writing, software # distributed under the License is distributed on an "AS IS" BASIS, # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. # See the License for the specific language governing permissions and # limitations under the License. # from __future__ import annotations import datetime import json from dataclasses import dataclass from typing import TYPE_CHECKING, Dict, List, Optional, Union from nats.errors import Error, MsgAlreadyAckdError, NotJSMessageError if TYPE_CHECKING: from nats import NATS # Subject without domain: # $JS.ACK.<stream>.<consumer>.<delivered>.<sseq>.<cseq>.<tm>.<pending> # _V1_TOKEN_COUNT = 9 # Subject with domain: # $JS.ACK.<domain>.<account hash>.<stream>.<consumer>.<delivered>.<sseq>. # <cseq>.<tm>.<pending>.<a token with a random value> # _V2_TOKEN_COUNT = 12 @dataclass class Msg: """ Msg represents a message delivered by NATS. """ _client: NATS subject: str = "" reply: str = "" data: bytes = b"" headers: Optional[Dict[str, str]] = None _metadata: Optional[Metadata] = None _ackd: bool = False _sid: Optional[int] = None class Ack: Ack = b"+ACK" Nak = b"-NAK" Progress = b"+WPI" Term = b"+TERM" # Reply metadata... Prefix0 = "$JS" Prefix1 = "ACK" Domain = 2 AccHash = 3 Stream = 4 Consumer = 5 NumDelivered = 6 StreamSeq = 7 ConsumerSeq = 8 Timestamp = 9 NumPending = 10 @property def header(self) -> Optional[Dict[str, str]]: """ header returns the headers from a message. """ return self.headers @property def is_acked(self) -> bool: """ Have we sent a terminal ack message (not in-progress) in response to this original message? """ return self._ackd @property def sid(self) -> int: """ sid returns the subscription ID from a message. """ if self._sid is None: raise Error("sid not set") return self._sid async def respond(self, data: bytes) -> None: """ respond replies to the inbox of the message if there is one. """ if not self.reply: raise Error("no reply subject available") if not self._client: raise Error("client not set") await self._client.publish(self.reply, data, headers=self.headers) async def ack(self) -> None: """ ack acknowledges a message delivered by JetStream. """ self._check_reply() await self._client.publish(self.reply) self._ackd = True async def ack_sync(self, timeout: float = 1.0) -> "Msg": """ ack_sync waits for the acknowledgement to be processed by the server. """ self._check_reply() resp = await self._client.request(self.reply, timeout=timeout) self._ackd = True return resp async def nak(self, delay: Union[int, float, None] = None) -> None: """ nak negatively acknowledges a message delivered by JetStream triggering a redelivery. if `delay` is provided, redelivery is delayed for `delay` seconds """ self._check_reply() payload = Msg.Ack.Nak json_args = dict() if delay: json_args["delay"] = int(delay * 10**9) # from seconds to ns if json_args: payload += b" " + json.dumps(json_args).encode() await self._client.publish(self.reply, payload) self._ackd = True async def in_progress(self) -> None: """ in_progress acknowledges a message delivered by JetStream is still being worked on. Unlike other types of acks, an in-progress ack (+WPI) can be done multiple times. """ if self.reply is None or self.reply == "": raise NotJSMessageError await self._client.publish(self.reply, Msg.Ack.Progress) async def term(self) -> None: """ term terminates a message delivered by JetStream and disables redeliveries. """ self._check_reply() await self._client.publish(self.reply, Msg.Ack.Term) self._ackd = True # TODO(@orsinium): use a cached_property. Available in functools since 3.8, # as a package (backports.cached-property), or can be just copy-pasted in the project. @property def metadata(self) -> Metadata: """ metadata returns the Metadata of a JetStream message. """ # Memoize the parsed metadata. metadata = self._metadata if metadata is not None: return metadata metadata = Msg.Metadata._from_reply(self.reply) self._metadata = metadata return metadata def _get_metadata_fields(self, reply: Optional[str]) -> List[str]: return Msg.Metadata._get_metadata_fields(reply) def _check_reply(self) -> None: if self.reply is None or self.reply == "": raise NotJSMessageError if self._ackd: raise MsgAlreadyAckdError(self) @dataclass(frozen=True) class Metadata: """ Metadata is the metadata from a JetStream message. - num_pending is the number of available messages in the Stream that have not been consumed yet. - num_delivered is the number of times that this message has been delivered. For example, num_delivered higher than one means that there have been redeliveries. - timestamp is the time at which the message was delivered. - stream is the name of the stream. - consumer is the name of the consumer. """ sequence: SequencePair num_pending: int num_delivered: int timestamp: datetime.datetime stream: str consumer: str domain: Optional[str] = None @dataclass(frozen=True) class SequencePair: """ SequencePair represents a pair of consumer and stream sequence. """ consumer: int stream: int @classmethod def _get_metadata_fields(cls, reply: Optional[str]) -> List[str]: if not reply: raise NotJSMessageError tokens = reply.split(".") if ( (len(tokens) == _V1_TOKEN_COUNT or len(tokens) >= _V2_TOKEN_COUNT - 1) and tokens[0] == Msg.Ack.Prefix0 and tokens[1] == Msg.Ack.Prefix1 ): return tokens raise NotJSMessageError @classmethod def _from_reply(cls, reply: str) -> Msg.Metadata: """Construct the metadata from the reply string""" tokens = cls._get_metadata_fields(reply) if len(tokens) == _V1_TOKEN_COUNT: t = datetime.datetime.fromtimestamp(int(tokens[7]) / 1_000_000_000.0, datetime.timezone.utc) return cls( sequence=Msg.Metadata.SequencePair( stream=int(tokens[5]), consumer=int(tokens[6]), ), num_delivered=int(tokens[4]), num_pending=int(tokens[8]), timestamp=t, stream=tokens[2], consumer=tokens[3], ) else: t = datetime.datetime.fromtimestamp( int(tokens[Msg.Ack.Timestamp]) / 1_000_000_000.0, datetime.timezone.utc ) # Underscore indicate no domain is set. Expose as empty string # to client. domain = tokens[Msg.Ack.Domain] if domain == "_": domain = "" return cls( sequence=Msg.Metadata.SequencePair( stream=int(tokens[Msg.Ack.StreamSeq]), consumer=int(tokens[Msg.Ack.ConsumerSeq]), ), num_delivered=int(tokens[Msg.Ack.NumDelivered]), num_pending=int(tokens[Msg.Ack.NumPending]), timestamp=t, stream=tokens[Msg.Ack.Stream], consumer=tokens[Msg.Ack.Consumer], domain=domain, )
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