This is especially needed in diskless loading, were a short read could have
caused redis to exit. now the module can handle the error and return to the
caller gracefully.
this fixes#5326
when redis appends the blocked client reply list to the real client, it didn't
bother to check if it is in fact the master client. so a slave executing that
module command will send replies to the master, causing the master to send the
slave error responses, which will mess up the replication offset
(slave will advance it's replication offset, and the master does not)
A filter handle is returned and can be used to unregister a filter. In
the future it can also be used to further configure or manipulate the
filter.
Filters are now automatically unregistered when a module unloads.
In some cases processMultibulkBuffer uses sdsMakeRoomFor to
expand the querybuf, but later in some cases it uses that query
buffer as is for an argv element (see "Optimization"), which means
that the sds in argv may have a lot of wasted space, and then in case
modules keep that argv RedisString inside their data structure, this
space waste will remain for long (until restarted from rdb).
It does not make much sense to limit what modules can do: the admin
should instead limit what module commnads an user may call. So
RedisModule_Call() and other module operations should be able to execute
everything they want: the limitation should be posed by the API exported
by the module itself.
Storing the context is useless, because we can't really reuse that
later. For instance in the API RM_DictNext() that returns a
RedisModuleString for the next key iterated, the user should pass the
new context, because we may run the keys of the dictionary in a
different context of the one where the dictionary was created. Also the
dictionary may be created without a context, but we may still demand
automatic memory management for the returned strings while iterating.
