Add parquet support to write_to_file_stage.py (#1937)

Add support for writing DataFrames to parquet files in `write_to_file_stage.py`.

Closes #980 

## By Submitting this PR I confirm:
- I am familiar with the [Contributing Guidelines](https://github.com/nv-morpheus/Morpheus/blob/main/docs/source/developer_guide/contributing.md).
- When the PR is ready for review, new or existing tests cover these changes.
- When the PR is ready for review, the documentation is up to date with these changes.

Authors:
  - Yuchen Zhang (https://github.com/yczhang-nv)

Approvers:
  - Michael Demoret (https://github.com/mdemoret-nv)

URL: #1937

python/morpheus/morpheus/controllers/write_to_file_controller.py

@@ -119,18 +119,32 @@ def _convert_to_strings(self, df: DataFrameType):
 
     def node_fn(self, obs: mrc.Observable, sub: mrc.Subscriber):
 
-        # Open up the file handle
-        with open(self._output_file, "a", encoding='UTF-8') as out_file:
+        # When writing to a parquet file, we need to open the file in binary mode
+        if self._file_type == FileTypes.PARQUET:
+            with open(self._output_file, "wb") as out_file:
 
-            def write_to_file(x: MessageMeta):
+                def write_to_file(x: MessageMeta):
 
-                lines = self._convert_to_strings(x.df)
+                    x.df.to_parquet(out_file)
 
-                out_file.writelines(lines)
+                    if self._flush:
+                        out_file.flush()
 
-                if self._flush:
-                    out_file.flush()
-
-                return x
+                    return x
 
             obs.pipe(ops.map(write_to_file)).subscribe(sub)
+
+        else:
+            with open(self._output_file, "a", encoding='UTF-8') as out_file:
+
+                def write_to_file(x: MessageMeta):
+
+                    lines = self._convert_to_strings(x.df)
+                    out_file.writelines(lines)
+
+                    if self._flush:
+                        out_file.flush()
+
+                    return x
+
+                obs.pipe(ops.map(write_to_file)).subscribe(sub)

tests/morpheus/stages/test_write_to_file_stage_pipe.py

@@ -0,0 +1,65 @@
+#!/usr/bin/env python
+# SPDX-FileCopyrightText: Copyright (c) 2024, NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+#
+# 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.
+
+import types
+
+import pandas as pd
+import pytest
+
+from _utils.dataset_manager import DatasetManager
+from morpheus.common import FileTypes
+from morpheus.io.deserializers import read_file_to_df
+from morpheus.pipeline.linear_pipeline import LinearPipeline
+from morpheus.stages.input.in_memory_source_stage import InMemorySourceStage
+from morpheus.stages.output.write_to_file_stage import WriteToFileStage
+from morpheus.stages.postprocess.serialize_stage import SerializeStage
+from morpheus.stages.preprocess.deserialize_stage import DeserializeStage
+
+
+@pytest.mark.parametrize("output_file", ["/tmp/output.json", "/tmp/output.csv", "/tmp/output.parquet"])
+@pytest.mark.gpu_and_cpu_mode
+def test_write_to_file_stage_pipe(config,
+                                  df_pkg: types.ModuleType,
+                                  dataset: DatasetManager,
+                                  output_file: str,
+                                  execution_mode: str) -> None:
+    """
+    Test WriteToFileStage with different output formats (JSON, CSV, Parquet)
+    """
+
+    filter_probs_df = dataset['filter_probs.csv']
+    pipe = LinearPipeline(config)
+    pipe.set_source(InMemorySourceStage(config, [filter_probs_df]))
+    pipe.add_stage(DeserializeStage(config))
+    pipe.add_stage(SerializeStage(config))
+    pipe.add_stage(WriteToFileStage(config, filename=output_file, overwrite=True))
+    pipe.run()
+
+    if output_file.endswith(".json"):
+        output_df = pd.read_json(output_file, lines=True)
+        dataset.assert_compare_df(filter_probs_df, output_df)
+
+    elif output_file.endswith(".csv"):
+        # The output data will contain an additional id column that we will need to slice off
+        output_df = df_pkg.read_csv(output_file).iloc[:, 1:]
+        dataset.assert_compare_df(filter_probs_df, output_df)
+
+    elif output_file.endswith(".parquet"):
+        output_df = read_file_to_df(file_name=output_file, file_type=FileTypes.PARQUET)
+        # The c++ WriteToFileStage will add an additional index column to the output
+        if execution_mode == "GPU":
+            output_df = output_df.iloc[:, 1:]
+        assert output_df.values.tolist() == filter_probs_df.values.tolist()