fix(bridge-mqtt): add max_inflight_size option back

For compatibility with versions below 4.2, we still
use the `max_inflight_size` option, but generate it
as the `max_inflight`

Previous PR: https://github.com/emqx/emqx/pull/3938

apps/emqx_bridge_mqtt/etc/emqx_bridge_mqtt.conf

@@ -152,7 +152,7 @@ bridge.mqtt.aws.batch_size = 32
 ## 0 means infinity (no limit on the inflight window)
 ##
 ## Value: Integer
-bridge.mqtt.aws.max_inflight = 32
+bridge.mqtt.aws.max_inflight_size = 32
 
 ## Base directory for replayq to store messages on disk
 ## If this config entry is missing or set to undefined,

apps/emqx_bridge_mqtt/priv/emqx_bridge_mqtt.schema

@@ -103,7 +103,7 @@
   {datatype, {duration, s}}
 ]}.
 
-{mapping, "bridge.mqtt.$name.max_inflight", "emqx_bridge_mqtt.bridges", [
+{mapping, "bridge.mqtt.$name.max_inflight_size", "emqx_bridge_mqtt.bridges", [
    {default, 0},
    {datatype, integer}
  ]}.
@@ -222,6 +222,8 @@
                        mqttv5 -> v5;
                        _ -> v4
                    end};
+            Tr(max_inflight_size, Size, Cfg) ->
+                Cfg#{max_inflight => Size};
             Tr(Key, Value, Cfg) ->
                 Cfg#{Key => Value}
          end,

apps/emqx_bridge_mqtt/src/emqx_bridge_worker.erl

@@ -132,8 +132,8 @@
 %%      and work as message batch transport layer
 %% reconnect_delay_ms: Delay in milli-seconds for the bridge worker to retry
 %%      in case of transportation failure.
-%% max_inflight_batches: Max number of batches allowed to send-ahead before
-%%      receiving confirmation from remote node/cluster
+%% max_inflight: Max number of batches allowed to send-ahead before receiving
+%%       confirmation from remote node/cluster
 %% mountpoint: The topic mount point for messages sent to remote node/cluster
 %%      `undefined', `<<>>' or `""' to disable
 %% forwards: Local topics to subscribe.