Address flaky transaction tests

Resolves #2841

* Fix test that was source of most failures
* Update max transaction lock time for local container entrypoint
* Update max transaction lock time for github action

---

The majority of failures appeared to be attributed with the
`test_exception_in_child_of_a_nested_transaction_rolls_parent_back` unit test.

To resolve this test, I borrowed the approach taken by the test just below it:
`test_exception_in_parent_of_nested_transaction_after_child_completed_only_rolls_parent_back`
which was already creating a function for the work under test and simply
trapping the TransientTractionError.

After resolving this, I found that the max transaction lock request timeout
parameter needed to be modified. After doing so and letting the test suite run
indefinitely unless error, test failures appeared to have ceased.

Author: juannyG

.github/workflows/start_mongo.sh

@@ -6,7 +6,14 @@ mongodb_dir=$(find ${PWD}/ -type d -name "mongodb-linux-x86_64*")
 
 mkdir $mongodb_dir/data
 
-$mongodb_dir/bin/mongod --dbpath $mongodb_dir/data --logpath $mongodb_dir/mongodb.log --fork --replSet mongoengine
+$mongodb_dir/bin/mongod \
+ --dbpath $mongodb_dir/data \
+ --logpath $mongodb_dir/mongodb.log \
+ --fork \
+ --replSet \
+ --setParameter maxTransactionLockRequestTimeoutMillis=1000 \
+ mongoengine
+
 if (( $(echo "$MONGODB < 6.0" | bc -l) )); then
 mongo --verbose --eval "rs.initiate()"
 mongo --quiet --eval "rs.status().ok"

entrypoint.sh

@@ -3,4 +3,4 @@
 mongod --replSet mongoengine --fork --logpath=/var/log/mongodb.log
 mongo db --eval "rs.initiate()"
 mongod --shutdown
-mongod --replSet mongoengine --bind_ip 0.0.0.0
+mongod --replSet mongoengine --bind_ip 0.0.0.0 --setParameter maxTransactionLockRequestTimeoutMillis=1000

tests/test_context_managers.py

@@ -708,20 +708,30 @@ class B(Document):
         B.drop_collection()
         b_doc = B.objects.create(name="b")
 
-        with pytest.raises(TestRollbackError):
-            with run_in_transaction():
-                a_doc.update(name="trx-parent")
-                try:
-                    with run_in_transaction():
-                        b_doc.update(name="trx-child")
-                        raise TestRollbackError()
-                except TestRollbackError as exc:
-                    # at this stage, the parent transaction is still there
-                    assert A.objects.get(id=a_doc.id).name == "trx-parent"
-                    raise exc
+        def run_tx():
+            try:
+                with run_in_transaction():
+                    a_doc.update(name="trx-parent")
+                    try:
+                        with run_in_transaction():
+                            b_doc.update(name="trx-child")
+                            raise TestRollbackError()
+                    except TestRollbackError as exc:
+                        # at this stage, the parent transaction is still there
+                        assert A.objects.get(id=a_doc.id).name == "trx-parent"
+                        raise exc
+            except OperationError as op_failure:
+                """
+                See thread safety test below for more details about TransientTransactionError handling
+                """
+                if "TransientTransactionError" in str(op_failure):
+                    logging.warning("TransientTransactionError - retrying...")
+                    run_tx()
                 else:
-                    # makes sure it enters the except above
-                    assert False
+                    raise op_failure
+
+        with pytest.raises(TestRollbackError):
+            run_tx()
 
         assert A.objects.get(id=a_doc.id).name == "a"
         assert B.objects.get(id=b_doc.id).name == "b"