Use less transactions

spinnman/spalloc/spalloc_client.py

@@ -21,7 +21,6 @@
 from packaging.version import Version
 import queue
 import requests
-import sqlite3
 import struct
 import threading
 from typing import Dict, List, Tuple
@@ -98,7 +97,8 @@ def __init__(
         logger.info("established session to {} for {}", service_url, username)
 
     @staticmethod
-    def open_job_from_database(conn: sqlite3.Cursor) -> SpallocJob:
+    def open_job_from_database(
+            service_url, job_url, cookies, headers) -> SpallocJob:
         """
         Create a job from the description in the attached database. This is
         intended to allow for access to the job's allocated resources from
@@ -110,35 +110,16 @@ def open_job_from_database(conn: sqlite3.Cursor) -> SpallocJob:
             credentials may have expired; if so, the job will be unable to
             regenerate them.
 
-        :param ~sqlite3.Cursor conn:
-            The database cursor to retrieve the job details from. Assumes
-            the presence of a ``proxy_configuration`` table with ``kind``,
-            ``name`` and ``value`` columns.
+        :param str service_url:
+        :param str job_url:
+        :param dict(str, str) cookies:
+        :param dict(str, str) headers:
+
         :return:
             The job handle, or ``None`` if the records in the database are
             absent or incomplete.
         :rtype: SpallocJob
         """
-        service_url = None
-        job_url = None
-        cookies = {}
-        headers = {}
-        for row in conn.execute("""
-                SELECT kind, name, value FROM proxy_configuration
-                """):
-            kind, name, value = row
-            if kind == "SPALLOC":
-                if name == "service uri":
-                    service_url = value
-                elif name == "job uri":
-                    job_url = value
-            elif kind == "COOKIE":
-                cookies[name] = value
-            elif kind == "HEADER":
-                headers[name] = value
-        if not service_url or not job_url or not cookies or not headers:
-            # Cannot possibly work without a session or job
-            return None
         session = Session(service_url, session_credentials=(cookies, headers))
         return _SpallocJob(session, job_url)
 
@@ -457,8 +438,8 @@ def __init__(self, session, job_handle):
         self.__proxy_thread = None
         self.__proxy_ping = None
 
-    @overrides(SpallocJob._write_session_credentials_to_db)
-    def _write_session_credentials_to_db(self, cur):
+    @overrides(SpallocJob.get_session_credentials_for_db)
+    def get_session_credentials_for_db(self):
         config = {}
         config["SPALLOC", "service uri"] = self._service_url
         config["SPALLOC", "job uri"] = self._url
@@ -471,10 +452,7 @@ def _write_session_credentials_to_db(self, cur):
             # We never write the auth headers themselves; we just extend the
             # session
             del headers["Authorization"]
-        cur.executemany("""
-            INSERT INTO proxy_configuration(kind, name, value)
-            VALUES(?, ?, ?)
-            """, [(k1, k2, v) for (k1, k2), v in config.items()])
+        return config
 
     @overrides(SpallocJob.get_state)
     def get_state(self):

spinnman/spalloc/spalloc_job.py

@@ -12,7 +12,6 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from sqlite3 import Cursor
 from typing import Dict, Tuple
 from spinn_utilities.abstract_base import AbstractBase, abstractmethod
 from spinn_utilities.abstract_context_manager import AbstractContextManager
@@ -194,17 +193,13 @@ def where_is_machine(self, x: int, y: int) -> Tuple[int, int, int]:
         """
 
     @abstractmethod
-    def _write_session_credentials_to_db(self, cur: Cursor):
+    def get_session_credentials_for_db(self):
         """
-        Write the session credentials for the job to the database accessed by
-        the given cursor.
+        Get the session credentials for the job to be written into a database
 
         .. note::
             May assume that there is a ``proxy_configuration`` table with
             ``kind``, ``name`` and ``value`` columns.
-
-        :param ~sqlite3.Cursor cur:
-            The open cursor to the database.
         """
 
     def __enter__(self):