let st = ShardingTest({shards: 2, rs: {nodes: 3}}); assert.commandWorked(st.s.adminCommand({shardCollection: 'test.foo', key: {x: 'hashed'}})); db.getMongo().setWriteConcern({w: 3}) let session = db.getMongo().startSession(); let sessionColl = session.getDatabase('test')['foo']; session.startTransaction(); sessionColl.insertMany([{x: 1}, {x: 3}]); session.commitTransaction(); // Check logs. See that commitTransaction on the participants was sent with w:'majority' instead of w:3 st.stop();