Since the module command interface was expanded to include a JSON output
parameter, there is no longer a need for an output DCB. As the JSON can be
printed by both maxadmin and the REST API, this allows the removal of
explicit output formatting in module commands.
The module commands can now produce JSON formatted output which is passed
to the caller. The output should conform to the JSON API as closely as
possible.
Currently, the REST API wraps all JSON produced by module commands inside
a meta-object of the following type:
{
"meta": <output of module command>
}
This allows the output to be JSON API conformant without modifying the
modules and allows incremental updates to code.
The module command self links now point to an endpoint that executes the
module command. Depending on the type of the module command, either a GET
or a POST request must be made.
The module commands now support an optional flag for arguments that when
enabled checks that the argument module name matches the registered domain
name. This can be used to enforce argument type validity for arguments
that are given to modules that expect objects of a certain type.
For example, this is used by the cache and dbfwfilter to prevent valid
filters but of the wrong type being given as arguments.
This commit introduces safe session references that can be handled without
holding locks. This allows the safe searching of sessions with the unique
ID of the session.
Remove the use of raw pointers passed as strings. Change the comments of
the argument types and add more details to the parsing function
documentation.
DCBs and SESSIONs can be passed either as raw pointers or as the string
representations of them.
The preferred way to pass them is to use the raw pointer types. This
removes the need to convert the pointer to string form and back.
The modulecmd_foreach function allows commands to be iterated without having
to manage the locking of the system. This allows the commands to be easily
iterated and gathered into filtered lists without having to build it into
the module command system itself.
The modules can now return human-readable error messages to the caller of
the function. The internals of the modulecmd system also use this to
return errors to the users.
The error messages can be retrieved with a common error function which
should make it easy to use in various clients.
A module can register a function to a domain. These function can then be
called by external actors enabling the modules to expand their
functionality beyond the module API. Each module should use its own domain
e.g the library name.
Currently, the functions do not return results. The possible next step
would be to alter the function entry point to return a result set of
sorts. This would allow the modules to convey structured information to
the client information which would handle the formatting of the result.
Although this sounds good, it is not required for the implementation of
MXS-929.
