Add a register instances table

Closes #279 on github.

quicktill/models.py

@@ -810,6 +810,28 @@ class TransactionMeta(Base):
 """)
 
 
+register_seq = Sequence('register_seq')
+
+
+class Register(Base):
+    """A register instance
+
+    An entry is made in this table each time the register starts
+    up. References to this table are then used to ensure a user is
+    only active on at most one register at a time.
+    """
+    __tablename__ = 'registers'
+    id = Column(Integer, register_seq, nullable=False, primary_key=True)
+    version = Column(
+        String(), nullable=False, doc="Software version of the register")
+    startup_time = Column(DateTime(), nullable=False,
+                          server_default=func.current_timestamp())
+    config_name = Column(String(), nullable=False)
+    terminal_name = Column(String(), nullable=False)
+
+    users = relationship('User', back_populates='register')
+
+
 user_seq = Sequence('user_seq')
 
 
@@ -833,8 +855,7 @@ class User(Base, Logged):
                                                      ondelete='SET NULL'),
                       nullable=True, unique=True,
                       doc="Transaction being worked on by this user")
-    register = Column(String(), nullable=True,
-                      doc="Terminal most recently used by this user")
+    register_id = Column(Integer, ForeignKey('registers.id'), nullable=True)
     message = Column(String(), nullable=True,
                      doc="Message to present to user on their next keypress")
     last_seen = Column(DateTime)
@@ -847,6 +868,7 @@ class User(Base, Logged):
         viewonly=True)
     transaction = relationship(Transaction, backref=backref(
         'user', uselist=False))
+    register = relationship(Register)
 
     tillweb_viewname = "tillweb-till-user"
     tillweb_argname = "userid"
@@ -873,7 +895,7 @@ def logtext(self):
 DECLARE
 BEGIN
   IF NEW.transid IS DISTINCT FROM OLD.transid
-    OR NEW.register IS DISTINCT FROM OLD.register THEN
+    OR NEW.register_id IS DISTINCT FROM OLD.register_id THEN
     PERFORM pg_notify('user_register', CAST(NEW.id AS text));
   END IF;
   RETURN NEW;

quicktill/monitor.py

@@ -54,11 +54,17 @@ def notify_user_register(id_str):
         except Exception:
             return
         with td.orm_session():
-            user = td.s.query(User).get(id)
+            user = td.s.query(User)\
+                       .options(joinedload('register'))\
+                       .get(id)
             if not user:
                 return
-            print(f"user_register: {user.fullname} now at register "
-                  f"{user.register} with transaction {user.trans_id}")
+            if user.register:
+                print(f"user_register: {user.fullname} now at register "
+                      f"{user.register_id} ({user.register.terminal_name}) "
+                      f"with transaction {user.trans_id}")
+            else:
+                print(f"user_register: {user.fullname} now not at a register")
 
     @staticmethod
     def notify_group_membership_changed(blank):

quicktill/register.py

@@ -49,7 +49,6 @@
 from sqlalchemy.orm import subqueryload
 from sqlalchemy.orm import joinedload
 from sqlalchemy.orm import undefer
-import uuid
 
 log = logging.getLogger(__name__)
 
@@ -178,12 +177,6 @@
 user.action_descriptions['sell-dept'] = \
     "Sell items using a department key"
 
-# Whenever the register is started it generates a new unique ID for
-# itself.  This is used to distinguish register instances that are
-# running at the same time, so they can coordinate moving transactions
-# and users between registers.
-register_instance = str(uuid.uuid4())
-
 
 class RegisterPlugin(metaclass=plugins.InstancePluginMount):
     """A plugin to add functionality to the register
@@ -798,7 +791,7 @@ def __init__(self, user, hotkeys, autolock=None, timeout=300):
         self.hotkeys = hotkeys
         self.defaultprompt = "Ready"
         # Set user's current register to be us
-        self.user.dbuser.register = register_instance
+        self.user.dbuser.register_id = tillconfig.register_id
         # Save user's current transaction because it is unset by clear()
         candidate_trans = self.user.dbuser.transaction
         self._clear()
@@ -3158,7 +3151,7 @@ def entry(self):
         # repeat it here because it is possible we may not have been
         # entered in response to a keypress - a timer event, for
         # example.
-        if self.user.dbuser.register != register_instance:
+        if self.user.dbuser.register_id != tillconfig.register_id:
             # If the register in the database isn't us, lock immediately
             self.deselect()
             return False
@@ -3204,7 +3197,7 @@ def entry_noninteractive(self):
         call the deselect() method.
         """
         self.user.dbuser = td.s.query(User).get(self.user.userid)
-        if self.user.dbuser.register != register_instance:
+        if self.user.dbuser.register_id != tillconfig.register_id:
             # User has logged in somewhere else
             return False
         if self.transid and not self.user.dbuser.transaction:
@@ -3315,7 +3308,7 @@ def hotkeypress(self, k):
 
         # Check that the user hasn't moved to another terminal.  If
         # they have, lock immediately.
-        if self.user.dbuser.register != register_instance:
+        if self.user.dbuser.register_id != tillconfig.register_id:
             self.deselect()
             return super().hotkeypress(k)
 
@@ -3331,7 +3324,7 @@ def hotkeypress(self, k):
     def select(self, u):
         # Called when the appropriate user token is presented
         self.user = u  # Permissions might have changed!
-        self.user.dbuser.register = register_instance
+        self.user.dbuser.register_id = tillconfig.register_id
         td.s.flush()
         if self.locked:
             self.locked = False

quicktill/till.py

@@ -33,7 +33,7 @@
 from . import listen
 from . import barcode
 from .version import version
-from .models import Session, PayType, Business, zero
+from .models import Session, PayType, Business, Register, zero
 import subprocess
 from sqlalchemy.orm import joinedload
 
@@ -260,10 +260,17 @@ def run(args):
             listen.listener.listen_for("update", runtill.update_notified)
 
         # Load config from database, update database with new config items,
-        # initialise config change listener
+        # initialise config change listener, and generate a new register ID
         with td.orm_session():
             config.ConfigItem.listen_for_changes(listen.listener)
             config.ConfigItem.preload()
+            reg = Register(version=version,
+                           config_name=tillconfig.configname,
+                           terminal_name=tillconfig.terminal_name)
+            td.s.add(reg)
+            td.s.flush()
+            tillconfig.register_id = reg.id
+            td.s.commit()
 
         dbg_kbd = None
         try:

quicktill/tillconfig.py

@@ -17,6 +17,11 @@
 
 terminal_name = "default"
 
+# A new register_id is generated each time the register is started. It
+# is used by the register to ensure each user is only active on one
+# register at a time.
+register_id = None
+
 keyboard = None
 keyboard_right = None
 

release-notes.md

@@ -21,15 +21,21 @@ What's new:
 To upgrade the database:
 
  - run "runtill syncdb" to create the new stocktype metadata table
+   and registers table
 
  - run psql and give the following commands to the database:
 
 ```
 BEGIN;
 
 ALTER TABLE users
+	DROP COLUMN register,
+	ADD COLUMN register_id integer,
         ADD COLUMN last_seen timestamp without time zone;
 
+ALTER TABLE users
+	ADD CONSTRAINT users_register_id_fkey FOREIGN KEY (register_id) REFERENCES public.registers(id);
+
 ALTER TABLE stocklines
         ADD COLUMN note character varying DEFAULT ''::character varying NOT NULL;
 
@@ -39,7 +45,7 @@ CREATE OR REPLACE FUNCTION notify_user_change() RETURNS trigger
 DECLARE
 BEGIN
   IF NEW.transid IS DISTINCT FROM OLD.transid
-    OR NEW.register IS DISTINCT FROM OLD.register THEN
+    OR NEW.register_id IS DISTINCT FROM OLD.register_id THEN
     PERFORM pg_notify('user_register', CAST(NEW.id AS text));
   END IF;
   RETURN NEW;