[2/3] sdks/python: sink data with Milvus Search I/O connector (#36729)

* sdks/python: add milvus sink integration

* CHANGES.md: update release notes

* sdks/python: fix py docs formatting issues

* sdks/python: fix linting issues

* sdks/python: delegate auto-flushing to milvus backend

* sdks/python: address gemini comments

Author: mohamedawnallah

CHANGES.md

@@ -75,6 +75,8 @@
 * X feature added (Java/Python) ([#X](https://github.com/apache/beam/issues/X)).
 * Python examples added for Milvus search enrichment handler on [Beam Website](https://beam.apache.org/documentation/transforms/python/elementwise/enrichment-milvus/)
   including jupyter notebook example (Python) ([#36176](https://github.com/apache/beam/issues/36176)).
+* Milvus sink I/O connector added (Python) ([#36702](https://github.com/apache/beam/issues/36702)).
+Now Beam has full support for Milvus integration including Milvus enrichment and sink operations.
 
 ## Breaking Changes
 

sdks/python/apache_beam/ml/rag/ingestion/milvus_search.py

@@ -0,0 +1,346 @@
+#
+# Licensed to the Apache Software Foundation (ASF) under one or more
+# contributor license agreements.  See the NOTICE file distributed with
+# this work for additional information regarding copyright ownership.
+# The ASF licenses this file to You 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.
+
+import logging
+from dataclasses import dataclass
+from dataclasses import field
+from typing import Any
+from typing import Callable
+from typing import Dict
+from typing import List
+from typing import Optional
+
+from pymilvus import MilvusClient
+from pymilvus.exceptions import MilvusException
+
+import apache_beam as beam
+from apache_beam.ml.rag.ingestion.base import VectorDatabaseWriteConfig
+from apache_beam.ml.rag.ingestion.jdbc_common import WriteConfig
+from apache_beam.ml.rag.ingestion.postgres_common import ColumnSpec
+from apache_beam.ml.rag.ingestion.postgres_common import ColumnSpecsBuilder
+from apache_beam.ml.rag.types import Chunk
+from apache_beam.ml.rag.utils import DEFAULT_WRITE_BATCH_SIZE
+from apache_beam.ml.rag.utils import MilvusConnectionParameters
+from apache_beam.ml.rag.utils import MilvusHelpers
+from apache_beam.ml.rag.utils import retry_with_backoff
+from apache_beam.ml.rag.utils import unpack_dataclass_with_kwargs
+from apache_beam.transforms import DoFn
+
+_LOGGER = logging.getLogger(__name__)
+
+
+@dataclass
+class MilvusWriteConfig:
+  """Configuration parameters for writing data to Milvus collections.
+
+  This class defines the parameters needed to write data to a Milvus collection,
+  including collection targeting, batching behavior, and operation timeouts.
+
+  Args:
+    collection_name: Name of the target Milvus collection to write data to.
+      Must be a non-empty string.
+    partition_name: Name of the specific partition within the collection to
+      write to. If empty, writes to the default partition.
+    timeout: Maximum time in seconds to wait for write operations to complete.
+      If None, uses the client's default timeout.
+    write_config: Configuration for write operations including batch size and
+      other write-specific settings.
+    kwargs: Additional keyword arguments for write operations. Enables forward
+      compatibility with future Milvus client parameters.
+  """
+  collection_name: str
+  partition_name: str = ""
+  timeout: Optional[float] = None
+  write_config: WriteConfig = field(default_factory=WriteConfig)
+  kwargs: Dict[str, Any] = field(default_factory=dict)
+
+  def __post_init__(self):
+    if not self.collection_name:
+      raise ValueError("Collection name must be provided")
+
+  @property
+  def write_batch_size(self):
+    """Returns the batch size for write operations.
+
+    Returns:
+      The configured batch size, or DEFAULT_WRITE_BATCH_SIZE if not specified.
+    """
+    return self.write_config.write_batch_size or DEFAULT_WRITE_BATCH_SIZE
+
+
+@dataclass
+class MilvusVectorWriterConfig(VectorDatabaseWriteConfig):
+  """Configuration for writing vector data to Milvus collections.
+
+  This class extends VectorDatabaseWriteConfig to provide Milvus-specific
+  configuration for ingesting vector embeddings and associated metadata.
+  It defines how Apache Beam chunks are converted to Milvus records and
+  handles the write operation parameters.
+
+  The configuration includes connection parameters, write settings, and
+  column specifications that determine how chunk data is mapped to Milvus
+  fields.
+
+  Args:
+    connection_params: Configuration for connecting to the Milvus server,
+      including URI, credentials, and connection options.
+    write_config: Configuration for write operations including collection name,
+      partition, batch size, and timeouts.
+    column_specs: List of column specifications defining how chunk fields are
+      mapped to Milvus collection fields. Defaults to standard RAG fields
+      (id, embedding, sparse_embedding, content, metadata).
+
+  Example:
+    config = MilvusVectorWriterConfig(
+      connection_params=MilvusConnectionParameters(
+        uri="http://localhost:19530"),
+      write_config=MilvusWriteConfig(collection_name="my_collection"),
+      column_specs=MilvusVectorWriterConfig.default_column_specs())
+  """
+  connection_params: MilvusConnectionParameters
+  write_config: MilvusWriteConfig
+  column_specs: List[ColumnSpec] = field(
+      default_factory=lambda: MilvusVectorWriterConfig.default_column_specs())
+
+  def create_converter(self) -> Callable[[Chunk], Dict[str, Any]]:
+    """Creates a function to convert Apache Beam Chunks to Milvus records.
+
+    Returns:
+      A function that takes a Chunk and returns a dictionary representing
+      a Milvus record with fields mapped according to column_specs.
+    """
+    def convert(chunk: Chunk) -> Dict[str, Any]:
+      result = {}
+      for col in self.column_specs:
+        result[col.column_name] = col.value_fn(chunk)
+      return result
+
+    return convert
+
+  def create_write_transform(self) -> beam.PTransform:
+    """Creates the Apache Beam transform for writing to Milvus.
+
+    Returns:
+      A PTransform that can be applied to a PCollection of Chunks to write
+      them to the configured Milvus collection.
+    """
+    return _WriteToMilvusVectorDatabase(self)
+
+  @staticmethod
+  def default_column_specs() -> List[ColumnSpec]:
+    """Returns default column specifications for RAG use cases.
+
+    Creates column mappings for standard RAG fields: id, dense embedding,
+    sparse embedding, content text, and metadata. These specifications
+    define how Chunk fields are converted to Milvus-compatible formats.
+
+    Returns:
+      List of ColumnSpec objects defining the default field mappings.
+    """
+    column_specs = ColumnSpecsBuilder()
+    return column_specs\
+      .with_id_spec()\
+      .with_embedding_spec(convert_fn=lambda values: list(values))\
+      .with_sparse_embedding_spec(conv_fn=MilvusHelpers.sparse_embedding)\
+      .with_content_spec()\
+      .with_metadata_spec(convert_fn=lambda values: dict(values))\
+      .build()
+
+
+class _WriteToMilvusVectorDatabase(beam.PTransform):
+  """Apache Beam PTransform for writing vector data to Milvus.
+
+  This transform handles the conversion of Apache Beam Chunks to Milvus records
+  and coordinates the write operations. It applies the configured converter
+  function and uses a DoFn for batched writes to optimize performance.
+
+  Args:
+    config: MilvusVectorWriterConfig containing all necessary parameters for
+      the write operation.
+  """
+  def __init__(self, config: MilvusVectorWriterConfig):
+    self.config = config
+
+  def expand(self, pcoll: beam.PCollection[Chunk]):
+    """Expands the PTransform to convert chunks and write to Milvus.
+
+    Args:
+      pcoll: PCollection of Chunk objects to write to Milvus.
+
+    Returns:
+      PCollection of dictionaries representing the records written to Milvus.
+    """
+    return (
+        pcoll
+        | "Convert to Records" >> beam.Map(self.config.create_converter())
+        | beam.ParDo(
+            _WriteMilvusFn(
+                self.config.connection_params, self.config.write_config)))
+
+
+class _WriteMilvusFn(DoFn):
+  """DoFn that handles batched writes to Milvus.
+
+  This DoFn accumulates records in batches and flushes them to Milvus when
+  the batch size is reached or when the bundle finishes. This approach
+  optimizes performance by reducing the number of individual write operations.
+
+  Args:
+    connection_params: Configuration for connecting to the Milvus server.
+    write_config: Configuration for write operations including batch size
+      and collection details.
+  """
+  def __init__(
+      self,
+      connection_params: MilvusConnectionParameters,
+      write_config: MilvusWriteConfig):
+    self._connection_params = connection_params
+    self._write_config = write_config
+    self.batch = []
+
+  def process(self, element, *args, **kwargs):
+    """Processes individual records, batching them for efficient writes.
+
+    Args:
+      element: A dictionary representing a Milvus record to write.
+      *args: Additional positional arguments.
+      **kwargs: Additional keyword arguments.
+
+    Yields:
+      The original element after adding it to the batch.
+    """
+    _ = args, kwargs  # Unused parameters
+    self.batch.append(element)
+    if len(self.batch) >= self._write_config.write_batch_size:
+      self._flush()
+    yield element
+
+  def finish_bundle(self):
+    """Called when a bundle finishes processing.
+
+    Flushes any remaining records in the batch to ensure all data is written.
+    """
+    self._flush()
+
+  def _flush(self):
+    """Flushes the current batch of records to Milvus.
+
+    Creates a MilvusSink connection and writes all batched records,
+    then clears the batch for the next set of records.
+    """
+    if len(self.batch) == 0:
+      return
+    with _MilvusSink(self._connection_params, self._write_config) as sink:
+      sink.write(self.batch)
+      self.batch = []
+
+  def display_data(self):
+    """Returns display data for monitoring and debugging.
+
+    Returns:
+      Dictionary containing database, collection, and batch size information
+      for display in the Apache Beam monitoring UI.
+    """
+    res = super().display_data()
+    res["database"] = self._connection_params.db_name
+    res["collection"] = self._write_config.collection_name
+    res["batch_size"] = self._write_config.write_batch_size
+    return res
+
+
+class _MilvusSink:
+  """Low-level sink for writing data directly to Milvus.
+
+  This class handles the direct interaction with the Milvus client for
+  upsert operations. It manages the connection lifecycle and provides
+  context manager support for proper resource cleanup.
+
+  Args:
+    connection_params: Configuration for connecting to the Milvus server.
+    write_config: Configuration for write operations including collection
+      and partition targeting.
+  """
+  def __init__(
+      self,
+      connection_params: MilvusConnectionParameters,
+      write_config: MilvusWriteConfig):
+    self._connection_params = connection_params
+    self._write_config = write_config
+    self._client = None
+
+  def write(self, documents):
+    """Writes a batch of documents to the Milvus collection.
+
+    Performs an upsert operation to insert new documents or update existing
+    ones based on primary key. After the upsert, flushes the collection to
+    ensure data persistence.
+
+    Args:
+      documents: List of dictionaries representing Milvus records to write.
+        Each dictionary should contain fields matching the collection schema.
+    """
+    self._client = MilvusClient(
+        **unpack_dataclass_with_kwargs(self._connection_params))
+
+    resp = self._client.upsert(
+        collection_name=self._write_config.collection_name,
+        partition_name=self._write_config.partition_name,
+        data=documents,
+        timeout=self._write_config.timeout,
+        **self._write_config.kwargs)
+
+    _LOGGER.debug(
+        "Upserted into Milvus: upsert_count=%d, cost=%d",
+        resp.get("upsert_count", 0),
+        resp.get("cost", 0))
+
+  def __enter__(self):
+    """Enters the context manager and establishes Milvus connection.
+
+    Returns:
+      Self, enabling use in 'with' statements.
+    """
+    if not self._client:
+      connection_params = unpack_dataclass_with_kwargs(self._connection_params)
+
+      # Extract retry parameters from connection_params.
+      max_retries = connection_params.pop('max_retries', 3)
+      retry_delay = connection_params.pop('retry_delay', 1.0)
+      retry_backoff_factor = connection_params.pop('retry_backoff_factor', 2.0)
+
+      def create_client():
+        return MilvusClient(**connection_params)
+
+      self._client = retry_with_backoff(
+          create_client,
+          max_retries=max_retries,
+          retry_delay=retry_delay,
+          retry_backoff_factor=retry_backoff_factor,
+          operation_name="Milvus connection",
+          exception_types=(MilvusException, ))
+    return self
+
+  def __exit__(self, exc_type, exc_val, exc_tb):
+    """Exits the context manager and closes the Milvus connection.
+
+    Args:
+      exc_type: Exception type if an exception was raised.
+      exc_val: Exception value if an exception was raised.
+      exc_tb: Exception traceback if an exception was raised.
+    """
+    _ = exc_type, exc_val, exc_tb  # Unused parameters
+    if self._client:
+      self._client.close()