diff --git a/apps/emqx_bridge/i18n/emqx_bridge_schema.conf b/apps/emqx_bridge/i18n/emqx_bridge_schema.conf
index 06cc41a91..de9e10e74 100644
--- a/apps/emqx_bridge/i18n/emqx_bridge_schema.conf
+++ b/apps/emqx_bridge/i18n/emqx_bridge_schema.conf
@@ -78,7 +78,7 @@ emqx_bridge_schema {
                           }
                   }
 
-    metric_batched {
+    metric_batching {
                    desc {
                          en: """Count of messages that are currently accumulated in memory waiting for sending in one batch."""
                          zh: """当前积压在内存里，等待批量发送的消息个数"""
@@ -161,9 +161,9 @@ emqx_bridge_schema {
                           }
                   }
 
-     metric_queued {
+     metric_queuing {
                    desc {
-                         en: """Count of messages that are currently queued."""
+                         en: """Count of messages that are currently queuing."""
                          zh: """当前被缓存到磁盘队列的消息个数。"""
                         }
                    label: {
@@ -181,16 +181,6 @@ emqx_bridge_schema {
                            zh: "已发送"
                           }
                   }
-     metric_sent_exception {
-                   desc {
-                         en: """Count of messages that were sent but exceptions occur."""
-                         zh: """发送出现异常的消息个数。"""
-                        }
-                   label: {
-                           en: "Sent Exception"
-                           zh: "发送异常"
-                          }
-                  }
 
      metric_sent_failed {
                    desc {
diff --git a/apps/emqx_bridge/include/emqx_bridge.hrl b/apps/emqx_bridge/include/emqx_bridge.hrl
index bb8ee6e29..2b64dba70 100644
--- a/apps/emqx_bridge/include/emqx_bridge.hrl
+++ b/apps/emqx_bridge/include/emqx_bridge.hrl
@@ -1,6 +1,6 @@
 -define(EMPTY_METRICS,
     ?METRICS(
-        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
+        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
     )
 ).
 
@@ -15,7 +15,6 @@
     Matched,
     Queued,
     Sent,
-    SentExcpt,
     SentFailed,
     SentInflight,
     SentSucc,
@@ -25,7 +24,7 @@
     Rcvd
 ),
     #{
-        'batched' => Batched,
+        'batching' => Batched,
         'dropped' => Dropped,
         'dropped.other' => DroppedOther,
         'dropped.queue_full' => DroppedQueueFull,
@@ -33,9 +32,8 @@
         'dropped.resource_not_found' => DroppedResourceNotFound,
         'dropped.resource_stopped' => DroppedResourceStopped,
         'matched' => Matched,
-        'queued' => Queued,
+        'queuing' => Queued,
         'sent' => Sent,
-        'sent.exception' => SentExcpt,
         'sent.failed' => SentFailed,
         'sent.inflight' => SentInflight,
         'sent.success' => SentSucc,
@@ -57,7 +55,6 @@
     Matched,
     Queued,
     Sent,
-    SentExcpt,
     SentFailed,
     SentInflight,
     SentSucc,
@@ -67,7 +64,7 @@
     Rcvd
 ),
     #{
-        'batched' := Batched,
+        'batching' := Batched,
         'dropped' := Dropped,
         'dropped.other' := DroppedOther,
         'dropped.queue_full' := DroppedQueueFull,
@@ -75,9 +72,8 @@
         'dropped.resource_not_found' := DroppedResourceNotFound,
         'dropped.resource_stopped' := DroppedResourceStopped,
         'matched' := Matched,
-        'queued' := Queued,
+        'queuing' := Queued,
         'sent' := Sent,
-        'sent.exception' := SentExcpt,
         'sent.failed' := SentFailed,
         'sent.inflight' := SentInflight,
         'sent.success' := SentSucc,
diff --git a/apps/emqx_bridge/src/emqx_bridge_api.erl b/apps/emqx_bridge/src/emqx_bridge_api.erl
index bd892edcd..aa6a6af89 100644
--- a/apps/emqx_bridge/src/emqx_bridge_api.erl
+++ b/apps/emqx_bridge/src/emqx_bridge_api.erl
@@ -206,7 +206,7 @@ info_example_basic(webhook) ->
             worker_pool_size => 1,
             health_check_interval => 15000,
             auto_restart_interval => 15000,
-            query_mode => sync,
+            query_mode => async,
             async_inflight_window => 100,
             enable_queue => true,
             max_queue_bytes => 1024 * 1024 * 1024
@@ -624,11 +624,11 @@ aggregate_metrics(AllMetrics) ->
         fun(
             #{
                 metrics := ?metrics(
-                    M1, M2, M3, M4, M5, M6, M7, M8, M9, M10, M11, M12, M13, M14, M15, M16, M17, M18
+                    M1, M2, M3, M4, M5, M6, M7, M8, M9, M10, M11, M12, M13, M14, M15, M16, M17
                 )
             },
             ?metrics(
-                N1, N2, N3, N4, N5, N6, N7, N8, N9, N10, N11, N12, N13, N14, N15, N16, N17, N18
+                N1, N2, N3, N4, N5, N6, N7, N8, N9, N10, N11, N12, N13, N14, N15, N16, N17
             )
         ) ->
             ?METRICS(
@@ -648,8 +648,7 @@ aggregate_metrics(AllMetrics) ->
                 M14 + N14,
                 M15 + N15,
                 M16 + N16,
-                M17 + N17,
-                M18 + N18
+                M17 + N17
             )
         end,
         InitMetrics,
@@ -679,7 +678,7 @@ format_resp(
 
 format_metrics(#{
     counters := #{
-        'batched' := Batched,
+        'batching' := Batched,
         'dropped' := Dropped,
         'dropped.other' := DroppedOther,
         'dropped.queue_full' := DroppedQueueFull,
@@ -687,9 +686,8 @@ format_metrics(#{
         'dropped.resource_not_found' := DroppedResourceNotFound,
         'dropped.resource_stopped' := DroppedResourceStopped,
         'matched' := Matched,
-        'queued' := Queued,
+        'queuing' := Queued,
         'sent' := Sent,
-        'sent.exception' := SentExcpt,
         'sent.failed' := SentFailed,
         'sent.inflight' := SentInflight,
         'sent.success' := SentSucc,
@@ -710,7 +708,6 @@ format_metrics(#{
         Matched,
         Queued,
         Sent,
-        SentExcpt,
         SentFailed,
         SentInflight,
         SentSucc,
diff --git a/apps/emqx_bridge/src/schema/emqx_bridge_schema.erl b/apps/emqx_bridge/src/schema/emqx_bridge_schema.erl
index f55ac840e..1a20da6d6 100644
--- a/apps/emqx_bridge/src/schema/emqx_bridge_schema.erl
+++ b/apps/emqx_bridge/src/schema/emqx_bridge_schema.erl
@@ -102,7 +102,7 @@ fields(bridges) ->
     ] ++ ee_fields_bridges();
 fields("metrics") ->
     [
-        {"batched", mk(integer(), #{desc => ?DESC("metric_batched")})},
+        {"batching", mk(integer(), #{desc => ?DESC("metric_batching")})},
         {"dropped", mk(integer(), #{desc => ?DESC("metric_dropped")})},
         {"dropped.other", mk(integer(), #{desc => ?DESC("metric_dropped_other")})},
         {"dropped.queue_full", mk(integer(), #{desc => ?DESC("metric_dropped_queue_full")})},
@@ -113,9 +113,8 @@ fields("metrics") ->
         {"dropped.resource_stopped",
             mk(integer(), #{desc => ?DESC("metric_dropped_resource_stopped")})},
         {"matched", mk(integer(), #{desc => ?DESC("metric_matched")})},
-        {"queued", mk(integer(), #{desc => ?DESC("metric_queued")})},
+        {"queuing", mk(integer(), #{desc => ?DESC("metric_queuing")})},
         {"sent", mk(integer(), #{desc => ?DESC("metric_sent")})},
-        {"sent.exception", mk(integer(), #{desc => ?DESC("metric_sent_exception")})},
         {"sent.failed", mk(integer(), #{desc => ?DESC("metric_sent_failed")})},
         {"sent.inflight", mk(integer(), #{desc => ?DESC("metric_sent_inflight")})},
         {"sent.success", mk(integer(), #{desc => ?DESC("metric_sent_success")})},
diff --git a/apps/emqx_connector/src/emqx_connector_http.erl b/apps/emqx_connector/src/emqx_connector_http.erl
index 2562bf272..ed5897a59 100644
--- a/apps/emqx_connector/src/emqx_connector_http.erl
+++ b/apps/emqx_connector/src/emqx_connector_http.erl
@@ -31,7 +31,8 @@
     on_stop/2,
     on_query/3,
     on_query_async/4,
-    on_get_status/2
+    on_get_status/2,
+    reply_delegator/2
 ]).
 
 -type url() :: emqx_http_lib:uri_map().
@@ -46,7 +47,7 @@
     namespace/0
 ]).
 
--export([check_ssl_opts/2]).
+-export([check_ssl_opts/2, validate_method/1]).
 
 -type connect_timeout() :: emqx_schema:duration() | infinity.
 -type pool_type() :: random | hash.
@@ -137,8 +138,10 @@ fields(config) ->
 fields("request") ->
     [
         {method,
-            hoconsc:mk(hoconsc:enum([post, put, get, delete]), #{
-                required => false, desc => ?DESC("method")
+            hoconsc:mk(binary(), #{
+                required => false,
+                desc => ?DESC("method"),
+                validator => fun ?MODULE:validate_method/1
             })},
         {path, hoconsc:mk(binary(), #{required => false, desc => ?DESC("path")})},
         {body, hoconsc:mk(binary(), #{required => false, desc => ?DESC("body")})},
@@ -171,6 +174,17 @@ desc(_) ->
 validations() ->
     [{check_ssl_opts, fun check_ssl_opts/1}].
 
+validate_method(M) when M =:= <<"post">>; M =:= <<"put">>; M =:= <<"get">>; M =:= <<"delete">> ->
+    ok;
+validate_method(M) ->
+    case string:find(M, "${") of
+        nomatch ->
+            {error,
+                <<"Invalid method, should be one of 'post', 'put', 'get', 'delete' or variables in ${field} format.">>};
+        _ ->
+            ok
+    end.
+
 sc(Type, Meta) -> hoconsc:mk(Type, Meta).
 ref(Field) -> hoconsc:ref(?MODULE, Field).
 
@@ -286,13 +300,13 @@ on_query(
             Retry
         )
     of
-        {error, econnrefused} ->
+        {error, Reason} when Reason =:= econnrefused; Reason =:= timeout ->
             ?SLOG(warning, #{
                 msg => "http_connector_do_request_failed",
-                reason => econnrefused,
+                reason => Reason,
                 connector => InstId
             }),
-            {recoverable_error, econnrefused};
+            {error, {recoverable_error, Reason}};
         {error, Reason} = Result ->
             ?SLOG(error, #{
                 msg => "http_connector_do_request_failed",
@@ -365,7 +379,7 @@ on_query_async(
         Method,
         NRequest,
         Timeout,
-        ReplyFunAndArgs
+        {fun ?MODULE:reply_delegator/2, [ReplyFunAndArgs]}
     ).
 
 on_get_status(_InstId, #{pool_name := PoolName, connect_timeout := Timeout} = State) ->
@@ -521,3 +535,12 @@ bin(Str) when is_list(Str) ->
     list_to_binary(Str);
 bin(Atom) when is_atom(Atom) ->
     atom_to_binary(Atom, utf8).
+
+reply_delegator(ReplyFunAndArgs, Result) ->
+    case Result of
+        {error, Reason} when Reason =:= econnrefused; Reason =:= timeout ->
+            Result1 = {error, {recoverable_error, Reason}},
+            emqx_resource:apply_reply_fun(ReplyFunAndArgs, Result1);
+        _ ->
+            emqx_resource:apply_reply_fun(ReplyFunAndArgs, Result)
+    end.
diff --git a/apps/emqx_connector/src/emqx_connector_mysql.erl b/apps/emqx_connector/src/emqx_connector_mysql.erl
index b9c200316..802427134 100644
--- a/apps/emqx_connector/src/emqx_connector_mysql.erl
+++ b/apps/emqx_connector/src/emqx_connector_mysql.erl
@@ -420,7 +420,7 @@ on_sql_query(
                 error,
                 LogMeta#{msg => "mysql_connector_do_sql_query_failed", reason => Reason}
             ),
-            {recoverable_error, Reason};
+            {error, {recoverable_error, Reason}};
         {error, Reason} ->
             ?SLOG(
                 error,
diff --git a/apps/emqx_resource/include/emqx_resource.hrl b/apps/emqx_resource/include/emqx_resource.hrl
index 2409a7069..aab0129d1 100644
--- a/apps/emqx_resource/include/emqx_resource.hrl
+++ b/apps/emqx_resource/include/emqx_resource.hrl
@@ -76,8 +76,8 @@
 -type query_result() ::
     ok
     | {ok, term()}
-    | {error, term()}
-    | {recoverable_error, term()}.
+    | {error, {recoverable_error, term()}}
+    | {error, term()}.
 
 -define(WORKER_POOL_SIZE, 16).
 
diff --git a/apps/emqx_resource/src/emqx_resource.erl b/apps/emqx_resource/src/emqx_resource.erl
index c1d500e8b..309c34195 100644
--- a/apps/emqx_resource/src/emqx_resource.erl
+++ b/apps/emqx_resource/src/emqx_resource.erl
@@ -110,7 +110,7 @@
     list_group_instances/1
 ]).
 
--export([inc_received/1]).
+-export([inc_received/1, apply_reply_fun/2]).
 
 -optional_callbacks([
     on_query/3,
@@ -441,6 +441,12 @@ check_and_do(ResourceType, RawConfig, Do) when is_function(Do) ->
         Error -> Error
     end.
 
+apply_reply_fun({F, A}, Result) when is_function(F) ->
+    _ = erlang:apply(F, A ++ [Result]),
+    ok;
+apply_reply_fun(From, Result) ->
+    gen_server:reply(From, Result).
+
 %% =================================================================================
 
 inc_received(ResId) ->
diff --git a/apps/emqx_resource/src/emqx_resource_manager.erl b/apps/emqx_resource/src/emqx_resource_manager.erl
index 2581a3001..c8c097c30 100644
--- a/apps/emqx_resource/src/emqx_resource_manager.erl
+++ b/apps/emqx_resource/src/emqx_resource_manager.erl
@@ -132,11 +132,10 @@ create(MgrId, ResId, Group, ResourceType, Config, Opts) ->
             'matched',
             'sent',
             'dropped',
-            'queued',
-            'batched',
+            'queuing',
+            'batching',
             'sent.success',
             'sent.failed',
-            'sent.exception',
             'sent.inflight',
             'dropped.queue_not_enabled',
             'dropped.queue_full',
diff --git a/apps/emqx_resource/src/emqx_resource_worker.erl b/apps/emqx_resource/src/emqx_resource_worker.erl
index 3a12a6b91..c5841b7ef 100644
--- a/apps/emqx_resource/src/emqx_resource_worker.erl
+++ b/apps/emqx_resource/src/emqx_resource_worker.erl
@@ -131,7 +131,7 @@ init({Id, Index, Opts}) ->
             false ->
                 undefined
         end,
-    emqx_metrics_worker:inc(?RES_METRICS, Id, 'queued', queue_count(Queue)),
+    emqx_metrics_worker:inc(?RES_METRICS, Id, 'queuing', queue_count(Queue)),
     ok = inflight_new(Name),
     St = #{
         id => Id,
@@ -154,12 +154,12 @@ running(enter, _, _St) ->
 running(cast, resume, _St) ->
     keep_state_and_data;
 running(cast, block, St) ->
-    {next_state, block, St};
+    {next_state, blocked, St};
 running(cast, {block, [?QUERY(_, _) | _] = Batch}, #{id := Id, queue := Q} = St) when
     is_list(Batch)
 ->
     Q1 = maybe_append_queue(Id, Q, [?Q_ITEM(Query) || Query <- Batch]),
-    {next_state, block, St#{queue := Q1}};
+    {next_state, blocked, St#{queue := Q1}};
 running({call, From}, {query, Request, _Opts}, St) ->
     query_or_acc(From, Request, St);
 running(cast, {query, Request, Opts}, St) ->
@@ -273,12 +273,12 @@ retry_first_sync(Id, FirstQuery, Name, Ref, Q, #{resume_interval := ResumeT} = S
 drop_head(Id, Q) ->
     {Q1, AckRef, _} = replayq:pop(Q, #{count_limit => 1}),
     ok = replayq:ack(Q1, AckRef),
-    emqx_metrics_worker:inc(?RES_METRICS, Id, 'queued', -1),
+    emqx_metrics_worker:inc(?RES_METRICS, Id, 'queuing', -1),
     Q1.
 
 query_or_acc(From, Request, #{enable_batch := true, acc := Acc, acc_left := Left, id := Id} = St0) ->
     Acc1 = [?QUERY(From, Request) | Acc],
-    emqx_metrics_worker:inc(?RES_METRICS, Id, 'batched'),
+    emqx_metrics_worker:inc(?RES_METRICS, Id, 'batching'),
     St = St0#{acc := Acc1, acc_left := Left - 1},
     case Left =< 1 of
         true -> flush(St);
@@ -303,16 +303,17 @@ flush(#{acc := []} = St) ->
 flush(
     #{
         id := Id,
-        acc := Batch,
+        acc := Batch0,
         batch_size := Size,
         queue := Q0
     } = St
 ) ->
+    Batch = lists:reverse(Batch0),
     QueryOpts = #{
         inflight_name => maps:get(name, St),
         inflight_window => maps:get(async_inflight_window, St)
     },
-    emqx_metrics_worker:inc(?RES_METRICS, Id, 'batched', -length(Batch)),
+    emqx_metrics_worker:inc(?RES_METRICS, Id, 'batching', -length(Batch)),
     Result = call_query(configured, Id, Batch, QueryOpts),
     St1 = cancel_flush_timer(St#{acc_left := Size, acc := []}),
     case batch_reply_caller(Id, Result, Batch) of
@@ -337,13 +338,13 @@ maybe_append_queue(Id, Q, Items) ->
                 {Q1, QAckRef, Items2} = replayq:pop(Q, PopOpts),
                 ok = replayq:ack(Q1, QAckRef),
                 Dropped = length(Items2),
-                emqx_metrics_worker:inc(?RES_METRICS, Id, 'queued', -Dropped),
+                emqx_metrics_worker:inc(?RES_METRICS, Id, 'queuing', -Dropped),
                 emqx_metrics_worker:inc(?RES_METRICS, Id, 'dropped'),
                 emqx_metrics_worker:inc(?RES_METRICS, Id, 'dropped.queue_full'),
                 ?SLOG(error, #{msg => drop_query, reason => queue_full, dropped => Dropped}),
                 Q1
         end,
-    emqx_metrics_worker:inc(?RES_METRICS, Id, 'queued'),
+    emqx_metrics_worker:inc(?RES_METRICS, Id, 'queuing'),
     replayq:append(Q2, Items).
 
 batch_reply_caller(Id, BatchResult, Batch) ->
@@ -365,7 +366,7 @@ reply_caller(Id, ?REPLY(undefined, _, Result), BlockWorker) ->
 reply_caller(Id, ?REPLY({ReplyFun, Args}, _, Result), BlockWorker) when is_function(ReplyFun) ->
     _ =
         case Result of
-            {async_return, _} -> ok;
+            {async_return, _} -> no_reply_for_now;
             _ -> apply(ReplyFun, Args ++ [Result])
         end,
     handle_query_result(Id, Result, BlockWorker);
@@ -374,7 +375,7 @@ reply_caller(Id, ?REPLY(From, _, Result), BlockWorker) ->
     handle_query_result(Id, Result, BlockWorker).
 
 handle_query_result(Id, ?RESOURCE_ERROR_M(exception, _), BlockWorker) ->
-    emqx_metrics_worker:inc(?RES_METRICS, Id, 'sent.exception'),
+    emqx_metrics_worker:inc(?RES_METRICS, Id, 'sent.failed'),
     BlockWorker;
 handle_query_result(_Id, ?RESOURCE_ERROR_M(NotWorking, _), _) when
     NotWorking == not_connected; NotWorking == blocked
@@ -393,12 +394,15 @@ handle_query_result(Id, ?RESOURCE_ERROR_M(Reason, _), BlockWorker) ->
     emqx_metrics_worker:inc(?RES_METRICS, Id, 'dropped'),
     emqx_metrics_worker:inc(?RES_METRICS, Id, 'dropped.other'),
     BlockWorker;
+handle_query_result(Id, {error, {recoverable_error, _}}, _BlockWorker) ->
+    %% the message will be queued in replayq or inflight window,
+    %% i.e. the counter 'queuing' will increase, so we pretend that we have not
+    %% sent this message.
+    emqx_metrics_worker:inc(?RES_METRICS, Id, 'sent', -1),
+    true;
 handle_query_result(Id, {error, _}, BlockWorker) ->
     emqx_metrics_worker:inc(?RES_METRICS, Id, 'sent.failed'),
     BlockWorker;
-handle_query_result(Id, {recoverable_error, _}, _BlockWorker) ->
-    emqx_metrics_worker:inc(?RES_METRICS, Id, 'sent', -1),
-    true;
 handle_query_result(_Id, {async_return, inflight_full}, _BlockWorker) ->
     true;
 handle_query_result(Id, {async_return, {error, _}}, BlockWorker) ->
@@ -433,7 +437,7 @@ call_query(QM0, Id, Query, QueryOpts) ->
     try
         %% if the callback module (connector) wants to return an error that
         %% makes the current resource goes into the `blocked` state, it should
-        %% return `{recoverable_error, Reason}`
+        %% return `{error, {recoverable_error, Reason}}`
         EXPR
     catch
         ERR:REASON:STACKTRACE ->
@@ -449,7 +453,10 @@ call_query(QM0, Id, Query, QueryOpts) ->
 apply_query_fun(sync, Mod, Id, ?QUERY(_, Request) = _Query, ResSt, _QueryOpts) ->
     ?tp(call_query, #{id => Id, mod => Mod, query => _Query, res_st => ResSt}),
     ok = emqx_metrics_worker:inc(?RES_METRICS, Id, 'sent'),
-    ?APPLY_RESOURCE(Mod:on_query(Id, Request, ResSt), Request);
+    ok = emqx_metrics_worker:inc(?RES_METRICS, Id, 'sent.inflight'),
+    Result = ?APPLY_RESOURCE(Mod:on_query(Id, Request, ResSt), Request),
+    ok = emqx_metrics_worker:inc(?RES_METRICS, Id, 'sent.inflight', -1),
+    Result;
 apply_query_fun(async, Mod, Id, ?QUERY(_, Request) = Query, ResSt, QueryOpts) ->
     ?tp(call_query_async, #{id => Id, mod => Mod, query => Query, res_st => ResSt}),
     Name = maps:get(inflight_name, QueryOpts, undefined),
@@ -457,7 +464,7 @@ apply_query_fun(async, Mod, Id, ?QUERY(_, Request) = Query, ResSt, QueryOpts) ->
     ?APPLY_RESOURCE(
         case inflight_is_full(Name, WinSize) of
             true ->
-                ?tp(inflight_full, #{id => Id, wind_size => WinSize}),
+                ?tp(warning, inflight_full, #{id => Id, wind_size => WinSize}),
                 {async_return, inflight_full};
             false ->
                 ok = emqx_metrics_worker:inc(?RES_METRICS, Id, 'sent'),
@@ -474,8 +481,12 @@ apply_query_fun(async, Mod, Id, ?QUERY(_, Request) = Query, ResSt, QueryOpts) ->
 apply_query_fun(sync, Mod, Id, [?QUERY(_, _) | _] = Batch, ResSt, _QueryOpts) ->
     ?tp(call_batch_query, #{id => Id, mod => Mod, batch => Batch, res_st => ResSt}),
     Requests = [Request || ?QUERY(_From, Request) <- Batch],
-    ok = emqx_metrics_worker:inc(?RES_METRICS, Id, 'sent', length(Batch)),
-    ?APPLY_RESOURCE(Mod:on_batch_query(Id, Requests, ResSt), Batch);
+    BatchLen = length(Batch),
+    ok = emqx_metrics_worker:inc(?RES_METRICS, Id, 'sent', BatchLen),
+    ok = emqx_metrics_worker:inc(?RES_METRICS, Id, 'sent.inflight', BatchLen),
+    Result = ?APPLY_RESOURCE(Mod:on_batch_query(Id, Requests, ResSt), Batch),
+    ok = emqx_metrics_worker:inc(?RES_METRICS, Id, 'sent.inflight', -BatchLen),
+    Result;
 apply_query_fun(async, Mod, Id, [?QUERY(_, _) | _] = Batch, ResSt, QueryOpts) ->
     ?tp(call_batch_query_async, #{id => Id, mod => Mod, batch => Batch, res_st => ResSt}),
     Name = maps:get(inflight_name, QueryOpts, undefined),
@@ -483,11 +494,12 @@ apply_query_fun(async, Mod, Id, [?QUERY(_, _) | _] = Batch, ResSt, QueryOpts) ->
     ?APPLY_RESOURCE(
         case inflight_is_full(Name, WinSize) of
             true ->
-                ?tp(inflight_full, #{id => Id, wind_size => WinSize}),
+                ?tp(warning, inflight_full, #{id => Id, wind_size => WinSize}),
                 {async_return, inflight_full};
             false ->
-                ok = emqx_metrics_worker:inc(?RES_METRICS, Id, 'sent', length(Batch)),
-                ok = emqx_metrics_worker:inc(?RES_METRICS, Id, 'sent.inflight'),
+                BatchLen = length(Batch),
+                ok = emqx_metrics_worker:inc(?RES_METRICS, Id, 'sent', BatchLen),
+                ok = emqx_metrics_worker:inc(?RES_METRICS, Id, 'sent.inflight', BatchLen),
                 ReplyFun = fun ?MODULE:batch_reply_after_query/6,
                 Ref = make_message_ref(),
                 Args = {ReplyFun, [self(), Id, Name, Ref, Batch]},
@@ -500,20 +512,29 @@ apply_query_fun(async, Mod, Id, [?QUERY(_, _) | _] = Batch, ResSt, QueryOpts) ->
     ).
 
 reply_after_query(Pid, Id, Name, Ref, ?QUERY(From, Request), Result) ->
+    %% NOTE: 'sent.inflight' is message count that sent but no ACK received,
+    %%        NOT the message number ququed in the inflight window.
+    emqx_metrics_worker:inc(?RES_METRICS, Id, 'sent.inflight', -1),
     case reply_caller(Id, ?REPLY(From, Request, Result)) of
         true ->
+            %% we marked these messages are 'queuing' although they are in inflight window
+            emqx_metrics_worker:inc(?RES_METRICS, Id, 'queuing'),
             ?MODULE:block(Pid);
         false ->
-            emqx_metrics_worker:inc(?RES_METRICS, Id, 'sent.inflight', -1),
             inflight_drop(Name, Ref)
     end.
 
 batch_reply_after_query(Pid, Id, Name, Ref, Batch, Result) ->
+    %% NOTE: 'sent.inflight' is message count that sent but no ACK received,
+    %%        NOT the message number ququed in the inflight window.
+    BatchLen = length(Batch),
+    emqx_metrics_worker:inc(?RES_METRICS, Id, 'sent.inflight', -BatchLen),
     case batch_reply_caller(Id, Result, Batch) of
         true ->
+            %% we marked these messages are 'queuing' although they are in inflight window
+            emqx_metrics_worker:inc(?RES_METRICS, Id, 'queuing', BatchLen),
             ?MODULE:block(Pid);
         false ->
-            emqx_metrics_worker:inc(?RES_METRICS, Id, 'sent.inflight', -length(Batch)),
             inflight_drop(Name, Ref)
     end.
 %%==============================================================================
diff --git a/apps/emqx_resource/src/schema/emqx_resource_schema.erl b/apps/emqx_resource/src/schema/emqx_resource_schema.erl
index 9e54c8a7b..df284bbe8 100644
--- a/apps/emqx_resource/src/schema/emqx_resource_schema.erl
+++ b/apps/emqx_resource/src/schema/emqx_resource_schema.erl
@@ -76,7 +76,7 @@ auto_restart_interval(_) -> undefined.
 
 query_mode(type) -> enum([sync, async]);
 query_mode(desc) -> ?DESC("query_mode");
-query_mode(default) -> sync;
+query_mode(default) -> async;
 query_mode(required) -> false;
 query_mode(_) -> undefined.
 
diff --git a/apps/emqx_resource/test/emqx_connector_demo.erl b/apps/emqx_resource/test/emqx_connector_demo.erl
index 4999b9410..a645af7d8 100644
--- a/apps/emqx_resource/test/emqx_connector_demo.erl
+++ b/apps/emqx_resource/test/emqx_connector_demo.erl
@@ -96,7 +96,7 @@ on_query(_InstId, {inc_counter, N}, #{pid := Pid}) ->
     Pid ! {From, {inc, N}},
     receive
         {ReqRef, ok} -> ok;
-        {ReqRef, incorrect_status} -> {recoverable_error, incorrect_status}
+        {ReqRef, incorrect_status} -> {error, {recoverable_error, incorrect_status}}
     after 1000 ->
         {error, timeout}
     end;
diff --git a/apps/emqx_rule_engine/src/emqx_rule_runtime.erl b/apps/emqx_rule_engine/src/emqx_rule_runtime.erl
index b1d563291..29f2c6bf6 100644
--- a/apps/emqx_rule_engine/src/emqx_rule_runtime.erl
+++ b/apps/emqx_rule_engine/src/emqx_rule_runtime.erl
@@ -510,7 +510,7 @@ nested_put(Alias, Val, Columns0) ->
 -define(IS_RES_DOWN(R), R == stopped; R == not_connected; R == not_found).
 inc_action_metrics(ok, RuleId) ->
     emqx_metrics_worker:inc(rule_metrics, RuleId, 'actions.success');
-inc_action_metrics({recoverable_error, _}, RuleId) ->
+inc_action_metrics({error, {recoverable_error, _}}, RuleId) ->
     emqx_metrics_worker:inc(rule_metrics, RuleId, 'actions.failed.out_of_service');
 inc_action_metrics(?RESOURCE_ERROR_M(R, _), RuleId) when ?IS_RES_DOWN(R) ->
     emqx_metrics_worker:inc(rule_metrics, RuleId, 'actions.failed.out_of_service');
diff --git a/lib-ee/emqx_ee_bridge/src/emqx_ee_bridge_mysql.erl b/lib-ee/emqx_ee_bridge/src/emqx_ee_bridge_mysql.erl
index f76eb388e..616842292 100644
--- a/lib-ee/emqx_ee_bridge/src/emqx_ee_bridge_mysql.erl
+++ b/lib-ee/emqx_ee_bridge/src/emqx_ee_bridge_mysql.erl
@@ -61,7 +61,7 @@ values(post) ->
             enable_batch => false,
             batch_size => ?DEFAULT_BATCH_SIZE,
             batch_time => ?DEFAULT_BATCH_TIME,
-            query_mode => sync,
+            query_mode => async,
             enable_queue => false,
             max_queue_bytes => ?DEFAULT_QUEUE_SIZE
         }