Added generic persistent table functionality to Session

model_server/base/session.py

@@ -5,6 +5,8 @@ from pathlib import Path
 from time import strftime, localtime
 from typing import Dict
 
+import pandas as pd
+
 import model_server.conf.defaults
 from model_server.base.models import Model
 
@@ -19,6 +21,22 @@ class Singleton(type):
             cls._instances[cls] = super(Singleton, cls).__call__(*args, **kwargs)
         return cls._instances[cls]
 
+class CsvTable(object):
+    def __init__(self, fpath: Path):
+        self.path = fpath
+        self.empty = True
+
+    def append(self, coords: dict, data: pd.DataFrame) -> bool:
+        assert isinstance(data, pd.DataFrame)
+        for c in reversed(coords.keys()):
+            data.insert(0, c, coords[c])
+        if self.empty:
+            data.to_csv(self.path, index=False, mode='w', header=True)
+        else:
+            data.to_csv(self.path, index=False, mode='a', header=False)
+        self.empty = False
+        return True
+
 class Session(object, metaclass=Singleton):
     """
     Singleton class for a server session that persists data between API calls
@@ -35,6 +53,30 @@ class Session(object, metaclass=Singleton):
         logging.basicConfig(filename=self.logfile, level=logging.INFO, force=True, format=self.log_format)
 
         self.log_info('Initialized session')
+        self.tables = {}
+
+    def write_to_table(self, name: str, coords: dict, data: pd.DataFrame):
+        """
+        Write data to a named data table, initializing if it does not yet exist.
+        :param name: name of the table to persist through session
+        :param coords: dictionary of coordinates to associate with all rows in this method call
+        :param data: DataFrame containing data
+        :return: True if successful
+        """
+        try:
+            if name in self.tables.keys():
+                table = self.tables.get(name)
+            else:
+                table = CsvTable(self.paths['tables'] / (name + '.csv'))
+                self.tables[name] = table
+        except Exception:
+            raise CouldNotCreateTable(f'Unable to create table named {name}')
+
+        try:
+            table.append(coords, data)
+            return True
+        except Exception:
+            raise CouldNotAppendToTable(f'Unable to append data to table named {name}')
 
     def get_paths(self):
         return self.paths
@@ -59,7 +101,7 @@ class Session(object, metaclass=Singleton):
             root_path = Path(root)
         sid = Session.create_session_id(root_path)
         paths = {'root': root_path}
-        for pk in ['inbound_images', 'outbound_images', 'logs']:
+        for pk in ['inbound_images', 'outbound_images', 'logs', 'tables']:
             pa = root_path / sid / model_server.conf.defaults.subdirectories[pk]
             paths[pk] = pa
             try:
@@ -162,5 +204,11 @@ class CouldNotInstantiateModelError(Error):
 class CouldNotCreateDirectory(Error):
     pass
 
+class CouldNotCreateTable(Error):
+    pass
+
+class CouldNotAppendToTable(Error):
+    pass
+
 class InvalidPathError(Error):
     pass
\ No newline at end of file

model_server/conf/defaults.py

@@ -6,6 +6,7 @@ subdirectories = {
     'logs': 'logs',
     'inbound_images': 'images/inbound',
     'outbound_images': 'images/outbound',
+    'tables': 'tables',
 }
 
 server_conf = {

tests/test_session.py

@@ -123,4 +123,20 @@ class TestGetSessionObject(unittest.TestCase):
         self.assertIsInstance(pa, pathlib.Path)
         self.sesh.set_data_directory('outbound_images', pa.__str__())
         self.assertEqual(self.sesh.paths['inbound_images'], self.sesh.paths['outbound_images'])
-        self.assertIsInstance(self.sesh.paths['outbound_images'], pathlib.Path)
\ No newline at end of file
+        self.assertIsInstance(self.sesh.paths['outbound_images'], pathlib.Path)
+
+    def test_make_table(self):
+        import pandas as pd
+        data = [{'modulo': i % 2, 'times one hundred': i * 100} for i in range(0, 8)]
+        self.sesh.write_to_table(
+            'test_numbers', {'X': 0, 'Y': 0}, pd.DataFrame(data[0:4])
+        )
+        self.assertTrue(self.sesh.tables['test_numbers'].path.exists())
+        self.sesh.write_to_table(
+            'test_numbers', {'X': 1, 'Y': 1}, pd.DataFrame(data[4:8])
+        )
+
+        dfv = pd.read_csv(self.sesh.tables['test_numbers'].path)
+        self.assertEqual(len(dfv), len(data))
+        self.assertEqual(dfv.columns[0], 'X')
+        self.assertEqual(dfv.columns[1], 'Y')