Using the setParameter command to set taskExecutorPoolSize reports no error, but ithe value is ignored. The documentation suggests, this value can't be changed using the database command.

This occurs because in task_executor_pool.cpp, we define the parameter as follows:

MONGO_EXPORT_SERVER_PARAMETER(taskExecutorPoolSize, int, 0);

But it should be defined as

MONGO_EXPORT_STARTUP_SERVER_PARAMETER(taskExecutorPoolSize, int, 0);