'pid' is a logging metadata for the log issuer process,
if 'pid' is used as a structured log field, it will be overwritten
by the logging handler module
When multiple clients try to connect concurrently using the same
client ID, they all call `emqx_channel:ensure_connected`, increasing
the live connection count, but only one will successfully acquire the
lock for that client ID. This means that all other clients that
increased the live connection count will not get to call neither
`emqx_channel:ensure_disconnected` nor be monitored for `DOWN`
messages, effectively causing a count leak.
By moving the increment to `emqx_cm:register_channel`, which is only
called inside the lock, we can remove this leakage.
Also, during the handling of `DOWN` messages, we now iterate over all
channel PIDs returned by `eqmx_misc:drain_down`, since it could be
that one or more PIDs are not contained in the `pmon` state.
In order to correctly display the number of connected clients in our
monitor dashboard, we need to track those connections that are
actually connected to clients, not considering connections from
persistent sessions that are disconnected. Today, the
`connections.count` that is displayed in the dashboards considers
those disconnected persistent sessions as well.
Prior to this fix, 'kick' and 'discard' calls may timeout (or
fail for other reason), failures lead to only a log, then
continue to allow the new session to get registered.
As a result, in case a client is stuck, there is no way to
force it to step down, end up with multiple connections (sessions)
for the client ID in dashboard.
After this fix, the stale pids are notified to shutdown
via a gen_server:call, and forced with a exit(Pid, kill) for any
exception happend to the gen_server:call
- Add dialyzer for code analysis
- Correct all the module type declarations
- Use `-type()` to declaration a type instead of `-opaque`
(It is advantageous to the code dialyzer)
BROKEN CHANGES:
- Add a ?DEFAULT_SUBOPTS for emqx_broker:subscribe/1,2,3
- Remove the needless internal function `emqx_vm:port_info(PortTerm, Keys)`
Shawn