This commit refactor the query_mode resource detection code according to
a suggestion from @zmstone. This commit should not contain any
functional change except for a change of the Kafka producer bridge
config.
This commit makes it possible to configure if a Kafka bridge should work
in query mode sync or async by setting the resource_opts.query_mode
configuration option.
Fixes:
https://emqx.atlassian.net/browse/EMQX-8631
Using `simple_one_for_one` has a potential race condition issue where
we read the PID of the resource manager before trying to remove a
resource, and then that PID changes because it was either dead at
first, or it crashed and changed, and later we use this stale PID to
try to remove it from the supervisor. Under such circumstances, the
restarting child might linger in the supervisor, leaking resources.
By using the resource ID itself as a child ID (and using `one_for_one`
restart strategy), we ensure the child is truly removed.
Andrew Mayorov