異常偵測範例

    docs = (
        pipeline
        | "Read from PubSub"
        >> ReadFromPubSub(subscription=cfg.SUBSCRIPTION_ID, with_attributes=True)
        | "Decode PubSubMessage" >> beam.ParDo(Decode())
    )

    normalized_embedding = (
        docs
        | "Tokenize Text" >> beam.Map(tokenize_sentence)

Tokenizer = AutoTokenizer.from_pretrained(cfg.TOKENIZER_NAME)


def tokenize_sentence(input_dict):
  """
    Takes a dictionary with a text and an id, tokenizes the text, and
    returns a tuple of the text and id and the tokenized text

    Args:
      input_dict: a dictionary with the text and id of the sentence

    Returns:
      A tuple of the text and id, and a dictionary of the tokens.
    """
  text, uid = input_dict["text"], input_dict["id"]
  tokens = Tokenizer([text], padding=True, truncation=True, return_tensors="pt")
  tokens = {key: torch.squeeze(val) for key, val in tokens.items()}
  return (text, uid), tokens

    | "Get Embedding" >> RunInference(KeyedModelHandler(embedding_model_handler))

    embedding_model_handler = PytorchNoBatchModelHandler(
        state_dict_path=cfg.MODEL_STATE_DICT_PATH,
        model_class=ModelWrapper,
        model_params={"config": AutoConfig.from_pretrained(cfg.MODEL_CONFIG_PATH)},
        device="cpu",
    )

# Can be removed once: https://github.com/apache/beam/issues/21863 is fixed
class PytorchNoBatchModelHandler(PytorchModelHandlerKeyedTensor):
  """Wrapper to PytorchModelHandler to limit batch size to 1.
    The tokenized strings generated from BertTokenizer may have different
    lengths, which doesn't work with torch.stack() in current RunInference
    implementation since stack() requires tensors to be the same size.
    Restricting max_batch_size to 1 means there is only 1 example per `batch`
    in the run_inference() call.
    """
  def batch_elements_kwargs(self):
    return {"max_batch_size": 1}

class ModelWrapper(DistilBertModel):
  """Wrapper to DistilBertModel to get embeddings when calling
    forward function."""
  def forward(self, **kwargs):
    output = super().forward(**kwargs)
    sentence_embedding = (
        self.mean_pooling(output,
                          kwargs["attention_mask"]).detach().cpu().numpy())
    return sentence_embedding

  # Mean Pooling - Take attention mask into account for correct averaging
  def mean_pooling(self, model_output, attention_mask):
    """
        Calculates the mean of token embeddings

        Args:
          model_output: The output of the model.
          attention_mask: This is a tensor that contains 1s for all input tokens and
          0s for all padding tokens.

        Returns:
          The mean of the token embeddings.
        """
    token_embeddings = model_output[
        0]  # First element of model_output contains all token embeddings
    input_mask_expanded = (
        attention_mask.unsqueeze(-1).expand(token_embeddings.size()).float())
    return torch.sum(token_embeddings * input_mask_expanded, 1) / torch.clamp(
        input_mask_expanded.sum(1), min=1e-9)

    | "Normalize Embedding" >> beam.ParDo(NormalizeEmbedding())

    predictions = (
        normalized_embedding
        | "Get Prediction from Clustering Model"
        >> RunInference(model_handler=clustering_model_handler)
    )

    clustering_model_handler = KeyedModelHandler(
        CustomSklearnModelHandlerNumpy(
            model_uri=cfg.CLUSTERING_MODEL_PATH, model_file_type=ModelFileType.JOBLIB
        )
    )

class CustomSklearnModelHandlerNumpy(SklearnModelHandlerNumpy):
  # limit batch size to 1 can be removed once: https://github.com/apache/beam/issues/21863 is fixed
  def batch_elements_kwargs(self):
    """Limit batch size to 1 for inference"""
    return {"max_batch_size": 1}

  # run_inference can be removed once: https://github.com/apache/beam/issues/22572 is fixed
  def run_inference(self, batch, model, inference_args=None):
    """Runs inferences on a batch of numpy arrays.

        Args:
          batch: A sequence of examples as numpy arrays. They should
            be single examples.
          model: A numpy model or pipeline. Must implement predict(X).
            Where the parameter X is a numpy array.
          inference_args: Any additional arguments for an inference.

        Returns:
          An Iterable of type PredictionResult.
        """
    _validate_inference_args(inference_args)
    vectorized_batch = np.vstack(batch)
    predictions = hdbscan.approximate_predict(model, vectorized_batch)
    return [PredictionResult(x, y) for x, y in zip(batch, predictions)]

    _ = (
        predictions
        | "Decode Prediction" >> beam.ParDo(DecodePrediction())
        | "Write to BQ" >> beam.io.WriteToBigQuery(
            table=cfg.TABLE_URI,
            schema=cfg.TABLE_SCHEMA,
            write_disposition=beam.io.BigQueryDisposition.WRITE_APPEND,
            create_disposition=beam.io.BigQueryDisposition.CREATE_IF_NEEDED,
        ))

    _ = predictions | "Alert by Email" >> beam.ParDo(TriggerEmailAlert())