test restoring and deleting spawners while the Hub is down

- set ONDELETE='set null' on spawner->server relation (fixes error when deleting servers that stopped)
- set `spawner.server = None`, which is not triggered when deleting orm_spawner.server

jupyterhub/app.py

@@ -1219,7 +1219,7 @@ class JupyterHub(Application):
                         status = yield spawner.poll()
                     except Exception:
                         self.log.exception("Failed to poll spawner for %s, assuming the spawner is not running.",
-                            user.name if name else '%s|%s' % (user.name, name))
+                            spawner._log_name)
                         status = -1
 
                 if status is None:
@@ -1230,11 +1230,13 @@ class JupyterHub(Application):
                     # user not running. This is expected if server is None,
                     # but indicates the user's server died while the Hub wasn't running
                     # if spawner.server is defined.
-                    log = self.log.warning if spawner.server else self.log.debug
-                    log("%s not running.", user.name)
-                    # remove all server or servers entry from db related to the user
                     if spawner.server:
+                        self.log.warning("%s appears to have stopped while the Hub was down", spawner._log_name)
+                        # remove server entry from db
                         db.delete(spawner.orm_spawner.server)
+                        spawner.server = None
+                    else:
+                        self.log.debug("%s not running", spawner._log_name)
             db.commit()
 
             user_summaries.append(_user_summary(user))

jupyterhub/orm.py

@@ -177,7 +177,7 @@ class Spawner(Base):
     id = Column(Integer, primary_key=True, autoincrement=True)
     user_id = Column(Integer, ForeignKey('users.id', ondelete='CASCADE'))
 
-    server_id = Column(Integer, ForeignKey('servers.id'))
+    server_id = Column(Integer, ForeignKey('servers.id', ondelete='SET NULL'))
     server = relationship(Server)
 
     state = Column(JSONDict)

jupyterhub/tests/test_app.py

@@ -8,9 +8,11 @@ from subprocess import check_output, Popen, PIPE
 from tempfile import NamedTemporaryFile, TemporaryDirectory
 from unittest.mock import patch
 
+from tornado import gen
 import pytest
 
 from .mocking import MockHub
+from .test_api import add_user
 from .. import orm
 from ..app import COOKIE_SECRET_BYTES
 
@@ -161,3 +163,57 @@ def test_load_groups():
     assert gold is not None
     assert sorted([ u.name for u in gold.users ]) == sorted(to_load['gold'])
 
+
+@pytest.mark.gen_test
+def test_resume_spawners(tmpdir, request):
+    if not os.getenv('JUPYTERHUB_TEST_DB_URL'):
+        p = patch.dict(os.environ, {
+            'JUPYTERHUB_TEST_DB_URL': 'sqlite:///%s' % tmpdir.join('jupyterhub.sqlite'),
+        })
+        p.start()
+        request.addfinalizer(p.stop)
+    @gen.coroutine
+    def new_hub():
+        app = MockHub()
+        app.config.ConfigurableHTTPProxy.should_start = False
+        yield app.initialize([])
+        return app
+    app = yield new_hub()
+    db = app.db
+    # spawn a user's server
+    name = 'kurt'
+    user = add_user(db, app, name=name)
+    yield user.spawn()
+    proc = user.spawner.proc
+    assert proc is not None
+
+    # stop the Hub without cleaning up servers
+    app.cleanup_servers = False
+    yield app.stop()
+
+    # proc is still running
+    assert proc.poll() is None
+
+    # resume Hub, should still be running
+    app = yield new_hub()
+    db = app.db
+    user = app.users[name]
+    assert user.running
+    assert user.spawner.server is not None
+
+    # stop the Hub without cleaning up servers
+    app.cleanup_servers = False
+    yield app.stop()
+
+    # stop the server while the Hub is down. BAMF!
+    proc.terminate()
+    proc.wait(timeout=10)
+    assert proc.poll() is not None
+
+    # resume Hub, should be stopped
+    app = yield new_hub()
+    db = app.db
+    user = app.users[name]
+    assert not user.running
+    assert user.spawner.server is None
+    assert list(db.query(orm.Server)) == []

jupyterhub/tests/test_db.py

@@ -46,4 +46,3 @@ def test_upgrade_entrypoint(tmpdir):
 
     # run tokenapp again, it should work
     tokenapp.start()
-    

jupyterhub/tests/test_spawner.py

@@ -299,7 +299,7 @@ def test_spawner_reuse_api_token(db, app):
 
 
 @pytest.mark.gen_test
-def test_spawner_insert_api_token(db, app):
+def test_spawner_insert_api_token(app):
     """Token provided by spawner is not in the db
     
     Insert token into db as a user-provided token.
@@ -326,7 +326,7 @@ def test_spawner_insert_api_token(db, app):
 
 
 @pytest.mark.gen_test
-def test_spawner_bad_api_token(db, app):
+def test_spawner_bad_api_token(app):
     """Tokens are revoked when a Spawner gets another user's token"""
     # we need two users for this one
     user = add_user(app.db, app, name='antimone')
@@ -346,3 +346,37 @@ def test_spawner_bad_api_token(db, app):
         yield user.spawn()
     assert orm.APIToken.find(app.db, other_token) is None
     assert other_user.api_tokens == []
+
+
+@pytest.mark.gen_test
+def test_spawner_delete_server(app):
+    """Test deleting spawner.server
+
+    This can occur during app startup if their server has been deleted.
+    """
+    db = app.db
+    user = add_user(app.db, app, name='gaston')
+    spawner = user.spawner
+    orm_server = orm.Server()
+    db.add(orm_server)
+    db.commit()
+    server_id = orm_server.id
+    spawner.server = Server.from_orm(orm_server)
+    db.commit()
+
+    assert spawner.server is not None
+    assert spawner.orm_spawner.server is not None
+
+    # trigger delete via db
+    db.delete(spawner.orm_spawner.server)
+    db.commit()
+    assert spawner.orm_spawner.server is None
+
+    # setting server = None also triggers delete
+    spawner.server = None
+    db.commit()
+    # verify that the server was actually deleted from the db
+    assert db.query(orm.Server).filter(orm.Server.id == server_id).first() is None
+    # verify that both ORM and top-level references are None
+    assert spawner.orm_spawner.server is None
+    assert spawner.server is None