Refactor: Task Executor (#15154)

### What problem does this PR solve?

1. Break huge function into smaller pieces
2. Add unit test for the smaller pieces function
3. Layer-ed design
a. infra layer - task_context.py, recording_context.py,
write_operation_interceptor.py, ...
    b. service layer - *_service.py
    c. business layer - task_handler.py
4. Default behavior: use "refactor-ed version" - can switch to original
version by change env variable

### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)
- [x] Refactoring
- [x] Performance Improvement

---------

Co-authored-by: Liu An <asiro@qq.com>
Co-authored-by: Zhichang Yu <yuzhichang@gmail.com>

test/unit_test/common/test_settings_queue.py

@@ -0,0 +1,208 @@
+#
+#  Copyright 2025 The InfiniFlow Authors. All Rights Reserved.
+#
+#  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.
+#
+"""Test cases for get_svr_queue_name and get_svr_queue_names functions in common.settings."""
+
+from common.settings import get_svr_queue_name, get_svr_queue_names
+
+
+class TestGetSvrQueueName:
+    """Test cases for get_svr_queue_name function."""
+
+    def test_default_suffix(self):
+        """Test that default suffix is 'common'."""
+
+        result = get_svr_queue_name(0)
+        assert result == "te.0.common"
+
+    def test_priority_zero(self):
+        """Test queue name with priority 0 (low)."""
+
+        result = get_svr_queue_name(0)
+        assert result == "te.0.common"
+
+    def test_priority_one(self):
+        """Test queue name with priority 1 (high)."""
+
+        result = get_svr_queue_name(1)
+        assert result == "te.1.common"
+
+    def test_explicit_suffix_common(self):
+        """Test with explicit 'common' suffix."""
+
+        result = get_svr_queue_name(0, "common")
+        assert result == "te.0.common"
+
+    def test_suffix_parameter_ignored(self):
+        """Test that suffix parameter is currently ignored (hardcoded to 'common').
+        
+        Note: The function signature accepts a suffix parameter but currently
+        hardcodes 'common' in the return value. This test documents this behavior.
+        """
+
+        # Even with different suffix values, result should be the same
+        result_default = get_svr_queue_name(0, "common")
+        result_resume = get_svr_queue_name(0, "resume")
+        result_graphrag = get_svr_queue_name(0, "graphrag")
+
+        # All should return the same value since suffix is hardcoded
+        assert result_default == result_resume == result_graphrag == "te.0.common"
+
+    def test_format_structure(self):
+        """Test that queue name follows expected format: {SVR_QUEUE_NAME}.{priority}.common."""
+
+        for priority in [0, 1]:
+            result = get_svr_queue_name(priority)
+            parts = result.split(".")
+            assert len(parts) == 3
+            assert parts[0] == "te"  # SVR_QUEUE_NAME
+            assert parts[1] == str(priority)
+            assert parts[2] == "common"
+
+    def test_different_priorities_produce_different_results(self):
+        """Test that different priorities produce different queue names."""
+
+        result_0 = get_svr_queue_name(0)
+        result_1 = get_svr_queue_name(1)
+
+        assert result_0 != result_1
+        assert result_0 == "te.0.common"
+        assert result_1 == "te.1.common"
+
+    def test_with_various_priority_values(self):
+        """Test with various priority values beyond 0 and 1."""
+
+        # Test with other priority values to ensure format is correct
+        for priority in [2, 5, 10, 100]:
+            result = get_svr_queue_name(priority)
+            expected = f"te.{priority}.common"
+            assert result == expected
+
+    def test_returns_string_type(self):
+        """Test that function returns a string."""
+
+        result = get_svr_queue_name(0)
+        assert isinstance(result, str)
+
+    def test_no_whitespace_issues(self):
+        """Test that queue name has no unexpected whitespace."""
+
+        for priority in [0, 1]:
+            result = get_svr_queue_name(priority)
+            assert " " not in result
+            assert "\t" not in result
+            assert "\n" not in result
+
+
+class TestGetSvrQueueNames:
+    """Test cases for get_svr_queue_names function."""
+
+    def test_returns_list(self):
+        """Test that function returns a list."""
+
+        result = get_svr_queue_names("common")
+        assert isinstance(result, list)
+
+    def test_returns_two_queues(self):
+        """Test that function returns exactly two queue names."""
+
+        result = get_svr_queue_names("common")
+        assert len(result) == 2
+
+    def test_sorted_high_to_low(self):
+        """Test that queue names are sorted from high priority to low priority."""
+
+        result = get_svr_queue_names("common")
+        assert result[0] == "te.1.common"  # High priority first
+        assert result[1] == "te.0.common"  # Low priority second
+
+    def test_expected_values(self):
+        """Test that returned values match expected queue names."""
+
+        result = get_svr_queue_names("common")
+        expected = ["te.1.common", "te.0.common"]
+        assert result == expected
+
+    def test_suffix_parameter_passed_through(self):
+        """Test that suffix parameter is passed to get_svr_queue_name.
+        
+        Note: Since get_svr_queue_name currently hardcodes 'common' as the suffix,
+        different suffix values will still produce the same result.
+        """
+
+        # All suffixes should produce same result due to hardcoded suffix in get_svr_queue_name
+        result_common = get_svr_queue_names("common")
+        result_resume = get_svr_queue_names("resume")
+        result_graphrag = get_svr_queue_names("graphrag")
+
+        expected = ["te.1.common", "te.0.common"]
+        assert result_common == expected
+        assert result_resume == expected  # suffix is currently ignored
+        assert result_graphrag == expected  # suffix is currently ignored
+
+    def test_all_elements_are_strings(self):
+        """Test that all elements in the returned list are strings."""
+
+        result = get_svr_queue_names("common")
+        for item in result:
+            assert isinstance(item, str)
+
+    def test_consistent_results(self):
+        """Test that multiple calls return consistent results."""
+
+        result1 = get_svr_queue_names("common")
+        result2 = get_svr_queue_names("common")
+        result3 = get_svr_queue_names("common")
+
+        assert result1 == result2 == result3
+
+    def test_with_empty_suffix(self):
+        """Test with empty string suffix."""
+
+        result = get_svr_queue_names("")
+        # Should still work since suffix is ignored
+        assert result == ["te.1.common", "te.0.common"]
+
+
+class TestGetSvrQueueNameWithMockedConstant:
+    """Test cases with mocked SVR_QUEUE_NAME constant."""
+
+    def test_with_custom_queue_name(self):
+        """Test with a custom SVR_QUEUE_NAME constant."""
+        # Need to patch where the constant is imported in settings module
+        import common.settings as settings_mod
+
+        original_value = settings_mod.SVR_QUEUE_NAME
+        try:
+            settings_mod.SVR_QUEUE_NAME = "custom_queue"
+            result = settings_mod.get_svr_queue_name(0)
+            assert result == "custom_queue.0.common"
+
+            result = settings_mod.get_svr_queue_name(1)
+            assert result == "custom_queue.1.common"
+        finally:
+            settings_mod.SVR_QUEUE_NAME = original_value
+
+    def test_with_custom_queue_names(self):
+        """Test get_svr_queue_names with a custom SVR_QUEUE_NAME constant."""
+        import common.settings as settings_mod
+
+        original_value = settings_mod.SVR_QUEUE_NAME
+        try:
+            settings_mod.SVR_QUEUE_NAME = "custom_queue"
+            result = settings_mod.get_svr_queue_names("common")
+            assert result == ["custom_queue.1.common", "custom_queue.0.common"]
+        finally:
+            settings_mod.SVR_QUEUE_NAME = original_value