[wildfly-dev] CLI 'module add/remove' Command Discussion

[Edward Wertz]

I discovered that the CLI 'module' command has been in need of a discussion for awhile. There are some issues with the command, and lingering enhancement requests, that can't be cleared up unless a future is clearly established. Since I can't seem to find any existing discussion on the subject, I wanted to throw it out here.

Issues:

 * The main issue is that the current command simply doesn't interact with the server to do anything. It relies on file system access and creates or removes module directories and resources on it's own. The server can then reload and find them. Simple, but effective.

 * Another issue is that the command is disabled for domain mode. Interestingly, since the command can be used in a disconnected state, it can still be used to manipulate domain modules assuming the servers module path remains the default at 'JBOSS_HOME/modules'. A module can be added or removed while the CLI is disconnected, then it can connect and reload the servers to complete the add or remove.

Refactoring Thoughts:

To bring it in-line with most other commands, and allow it to be expanded, the process should probably be happening server-side rather than CLI-side. I'm envisioning something akin to the deploy functionality. For the time being refactoring a simple add/remove, but later expanding it to be far more functional. However I haven't had the chance yet to look into how, or if, the server maintains or manipulates the modules and paths anywhere or if the value is simply passed into the jboss-modules system. I don't believe there's a clear API for the modules system at the moment, so this puts me somewhat in the dark as to whether what I'm thinking about is even possible.

Of course, everything is possible. With enough work.

Concerns:

 * My main concern with needing a connection is that the current functionality would suffer. Right now the module command, being independent from the server, is enabled while the CLI is disconnected. I think that functionality is somewhat valuable since a standalone server reload does not actually remove a module. Once added and the server reloaded, a module is active until a full shutdown and restart. From what I understand it's much easier to add classes to a JVM than remove them, so this is expected. If not fixed a standalone server would have to be started, then the module removed, then shutdown and restarted. While not excessive, it is a little annoying.

 * Also, as pointed out earlier, the command can currently be used on domain servers if certain criteria are met. If a connection is required the command would become completely unusable for domain servers unless the functionality is expanded during the refactoring. 
 ** Note: The first concern doesn't seem to apply to domain servers, since the servers can be completely restarted from the host controller.

Thoughts and input are encouraged. Whether on the technical aspects of a refactor or simply using the command.

Joe Wertz