diff --git a/.github/workflows/build_slim_packages.yaml b/.github/workflows/build_slim_packages.yaml
index f369525e7..640f1298d 100644
--- a/.github/workflows/build_slim_packages.yaml
+++ b/.github/workflows/build_slim_packages.yaml
@@ -11,7 +11,7 @@ on:
 
 jobs:
   build:
-    runs-on: ubuntu-20.04
+    runs-on: ${{ matrix.runs-on }}
 
     strategy:
       fail-fast: false
@@ -21,6 +21,16 @@ jobs:
         os:
         - ubuntu20.04
         - el8
+        runs-on:
+          - aws-amd64
+          - ubuntu-20.04
+        use-self-hosted:
+          - ${{ github.repository_owner == 'emqx' }}
+        exclude:
+          - runs-on: ubuntu-20.04
+            use-self-hosted: true
+          - runs-on: aws-amd64
+            use-self-hosted: false
 
     container: ghcr.io/emqx/emqx-builder/4.4-19:${{ matrix.erl_otp }}-${{ matrix.os }}
 
@@ -38,8 +48,20 @@ jobs:
         fi
     - name: fix-git-unsafe-repository
       run: git config --global --add safe.directory /__w/emqx/emqx
+    - uses: actions/cache@v2
+      with:
+        # dialyzer PLTs
+        path: ~/.cache/rebar3/
+        key: dialyer-${{ matrix.erl_otp }}
     - name: make xref
       run: make xref
+    - name: make dialyzer
+      run: |
+        # TODO: once dialyzer warnings are fixed in 4.4+, we may
+        # enforce this.
+        if [[ "$(./pkg-vsn.sh)" =~ 4.3.* ]]; then
+          make dialyzer
+        fi
     - name: build zip packages
       run: make ${EMQX_NAME}-zip
     - name: build deb/rpm packages
diff --git a/.github/workflows/run_test_cases.yaml b/.github/workflows/run_test_cases.yaml
index 138b07993..4e9a5fc37 100644
--- a/.github/workflows/run_test_cases.yaml
+++ b/.github/workflows/run_test_cases.yaml
@@ -24,8 +24,19 @@ jobs:
           run: make proper
 
     run_common_test:
-        runs-on: ubuntu-20.04
-
+        runs-on: ${{ matrix.runs-on }}
+        strategy:
+          matrix:
+            runs-on:
+              - aws-amd64
+              - ubuntu-20.04
+            use-self-hosted:
+              - ${{ github.repository_owner == 'emqx' }}
+            exclude:
+              - runs-on: ubuntu-20.04
+                use-self-hosted: true
+              - runs-on: aws-amd64
+                use-self-hosted: false
         steps:
         - uses: actions/checkout@v2
         - name: set edition
diff --git a/apps/emqx_auth_mnesia/include/emqx_auth_mnesia.hrl b/apps/emqx_auth_mnesia/include/emqx_auth_mnesia.hrl
index f8569ef8a..1c1798918 100644
--- a/apps/emqx_auth_mnesia/include/emqx_auth_mnesia.hrl
+++ b/apps/emqx_auth_mnesia/include/emqx_auth_mnesia.hrl
@@ -13,6 +13,12 @@
 -type(created_at():: integer()).
 
 -record(emqx_user, {
+          login,
+          password,
+          created_at
+        }).
+
+-type(emqx_user() :: #emqx_user{
           login :: login(),
           password :: binary(),
           created_at :: created_at()
diff --git a/apps/emqx_exproto/src/emqx_exproto_channel.erl b/apps/emqx_exproto/src/emqx_exproto_channel.erl
index cf6229be3..4b354183e 100644
--- a/apps/emqx_exproto/src/emqx_exproto_channel.erl
+++ b/apps/emqx_exproto/src/emqx_exproto_channel.erl
@@ -159,7 +159,7 @@ init(ConnInfo = #{socktype := Socktype,
     Channel = #channel{gcli = #{channel => GRpcChann},
                        conninfo = NConnInfo1,
                        clientinfo = ClientInfo,
-                       conn_state = accepted,
+                       conn_state = idle,
                        timers = #{}
                       },
     case emqx_hooks:run_fold('client.connect', [NConnInfo], #{}) of
diff --git a/apps/emqx_lua_hook/test/emqx_lua_hook_SUITE.erl b/apps/emqx_lua_hook/test/emqx_lua_hook_SUITE.erl
index bb9247464..5b2ed75e7 100644
--- a/apps/emqx_lua_hook/test/emqx_lua_hook_SUITE.erl
+++ b/apps/emqx_lua_hook/test/emqx_lua_hook_SUITE.erl
@@ -75,7 +75,7 @@ case01(_Config) ->
             "\nend",
     ok = file:write_file(ScriptName, Code), ok = emqx_lua_hook:load_scripts(),
 
-    Msg = #message{from = <<"myclient">>, qos = 2, flags = #{retain => true}, topic = <<"a/b/c">>, payload = <<"123">>, headers = #{username => <<"tester">>}},
+    Msg = #message{id = emqx_guid:gen(), from = <<"myclient">>, qos = 2, flags = #{retain => true}, topic = <<"a/b/c">>, payload = <<"123">>, headers = #{username => <<"tester">>}},
     Ret = emqx_hooks:run_fold('message.publish',[], Msg),
     ?assertEqual(Msg#message{payload = <<"hello">>}, Ret).
 
@@ -90,7 +90,7 @@ case02(_Config) ->
             "\nend",
     ok = file:write_file(ScriptName, Code), ok = emqx_lua_hook:load_scripts(),
 
-    Msg = #message{from = <<"myclient">>, qos = 2, flags = #{retain => true}, topic = <<"a/b/c">>, payload = <<"123">>, headers = #{username => <<"tester">>}},
+    Msg = #message{id = emqx_guid:gen(), from = <<"myclient">>, qos = 2, flags = #{retain => true}, topic = <<"a/b/c">>, payload = <<"123">>, headers = #{username => <<"tester">>}},
     Ret = emqx_hooks:run_fold('message.publish',[], Msg),
     ?assertEqual(Msg#message{headers = #{username => <<"tester">>, allow_publish => false}}, Ret).
 
@@ -124,7 +124,7 @@ case04(_Config) ->
             "\nend",
     ok = file:write_file(ScriptName, Code), ok = emqx_lua_hook:load_scripts(),
 
-    Msg = #message{from = <<"broker">>, qos = 2, flags = #{retain => true}, topic = <<"a/b/c">>, payload = <<"123">>, headers = #{username => <<"tester">>}},
+    Msg = #message{id = emqx_guid:gen(), from = <<"broker">>, qos = 2, flags = #{retain => true}, topic = <<"a/b/c">>, payload = <<"123">>, headers = #{username => <<"tester">>}},
     Ret = emqx_hooks:run_fold('message.publish',[], Msg),
     ?assertEqual(Msg#message{payload = <<"hello broker">>}, Ret).
 
@@ -155,7 +155,7 @@ case12(_Config) ->
             "\nend",
     ok = file:write_file(ScriptName, Code), ok = emqx_lua_hook:load_scripts(),
 
-    Msg = #message{qos = 2, flags = #{retain => true}, topic = <<"a/b/c">>, payload = <<"123">>, headers = #{}},
+    Msg = #message{id = emqx_guid:gen(), qos = 2, flags = #{retain => true}, topic = <<"a/b/c">>, payload = <<"123">>, headers = #{}},
     Ret = emqx_hooks:run_fold('message.delivered', [#{clientid => <<"myclient">>, username => <<"myuser">>}], Msg),
     ?assertEqual(Msg#message{payload = <<"hello broker">>}, Ret).
 
@@ -470,8 +470,9 @@ case101(_Config) ->
             "\nend",
     ok = file:write_file(ScriptName2, Code2), ok = emqx_lua_hook:load_scripts(),
 
-    Ret = emqx_hooks:run_fold('message.publish',[], #message{qos = 2, flags = #{retain => true}, topic = <<"a/b/c">>, payload = <<"123">>, headers = #{}}),
-    ?assertEqual(#message{qos = 2, flags = #{retain => true}, topic = <<"a/b/c">>, payload = <<"hello">>, headers = #{}}, Ret),
+    ID = emqx_guid:gen(),
+    Ret = emqx_hooks:run_fold('message.publish',[], #message{id = ID, qos = 2, flags = #{retain => true}, topic = <<"a/b/c">>, payload = <<"123">>, headers = #{}}),
+    ?assertEqual(#message{id = ID, qos = 2, flags = #{retain => true}, topic = <<"a/b/c">>, payload = <<"hello">>, headers = #{}}, Ret),
 
     TopicTable = [{<<"a/b/c">>, [qos, 1]}, {<<"d/+/e">>, [{qos, 2}]}],
     Ret2 = emqx_hooks:run_fold('client.subscribe',[#{clientid => <<"myclient">>, username => <<"myuser">>}, #{}], TopicTable),
@@ -488,7 +489,7 @@ case110(_Config) ->
             "\nend",
     ok = file:write_file(ScriptName, Code), ok = emqx_lua_hook:load_scripts(),
 
-    Msg = #message{qos = 2, flags = #{retain => true}, topic = <<"a/b/c">>, payload = <<"123">>, headers = #{}},
+    Msg = #message{id = emqx_guid:gen(), qos = 2, flags = #{retain => true}, topic = <<"a/b/c">>, payload = <<"123">>, headers = #{}},
     Ret = emqx_hooks:run_fold('message.publish',[], Msg),
     ?assertEqual(Msg#message{topic = <<"changed/topic">>, payload = <<"hello">>}, Ret).
 
@@ -504,7 +505,7 @@ case111(_Config) ->
     ok = file:write_file(ScriptName, Code), ok = emqx_lua_hook:load_scripts(),
     emqx_ctl:run_command(["luahook", "unload", ScriptName]),
 
-    Msg = #message{qos = 2, flags = #{retain => true}, topic = <<"a/b/c">>, payload = <<"123">>, headers = #{}},
+    Msg = #message{id = emqx_guid:gen(), qos = 2, flags = #{retain => true}, topic = <<"a/b/c">>, payload = <<"123">>, headers = #{}},
     Ret = emqx_hooks:run_fold('message.publish',[], Msg),
     ?assertEqual(Msg, Ret).
 
@@ -523,7 +524,7 @@ case112(_Config) ->
     timer:sleep(100),
     emqx_ctl:run_command(["luahook", "load", "abc.lua"]),
 
-    Msg = #message{qos = 2, flags = #{retain => true}, topic = <<"a/b/c">>, payload = <<"123">>, headers = #{}},
+    Msg = #message{id = emqx_guid:gen(), qos = 2, flags = #{retain => true}, topic = <<"a/b/c">>, payload = <<"123">>, headers = #{}},
     Ret = emqx_hooks:run_fold('message.publish',[], Msg),
     ?assertEqual(Msg#message{topic = <<"changed/topic">>, payload = <<"hello">>}, Ret).
 
@@ -541,7 +542,7 @@ case113(_Config) ->
     file:delete(ScriptDisabled),
     emqx_ctl:run_command(["luahook", "disable", "abc.lua"]),   % this command will rename "abc.lua" to "abc.lua.x"
 
-    Msg = #message{qos = 2, flags = #{retain => true}, topic = <<"a/b/c">>, payload = <<"123">>, headers = #{}},
+    Msg = #message{id = emqx_guid:gen(), qos = 2, flags = #{retain => true}, topic = <<"a/b/c">>, payload = <<"123">>, headers = #{}},
     Ret = emqx_hooks:run_fold('message.publish',[], Msg),
     ?assertEqual(Msg, Ret),
     true = filelib:is_file(ScriptDisabled).
@@ -558,7 +559,7 @@ case114(_Config) ->
     ok = file:write_file(ScriptName, Code), ok = emqx_lua_hook:load_scripts(),
     emqx_ctl:run_command(["luahook", "enable", "abc.lua"]),
 
-    Msg = #message{qos = 2, flags = #{retain => true}, topic = <<"a/b/c">>, payload = <<"123">>, headers = #{}},
+    Msg = #message{id = emqx_guid:gen(), qos = 2, flags = #{retain => true}, topic = <<"a/b/c">>, payload = <<"123">>, headers = #{}},
     Ret = emqx_hooks:run_fold('message.publish',[], Msg),
     ?assertEqual(Msg#message{topic = <<"changed/topic">>, payload = <<"hello">>}, Ret).
 
@@ -578,7 +579,7 @@ case115(_Config) ->
     ok = file:write_file(ScriptName, Code), ok = emqx_lua_hook:load_scripts(),
     emqx_ctl:run_command(["luahook", "reload", "abc.lua"]),
 
-    Msg = #message{qos = 2, flags = #{retain => true}, topic = <<"a/b/c">>, payload = <<"123">>, headers = #{}},
+    Msg = #message{id = emqx_guid:gen(), qos = 2, flags = #{retain => true}, topic = <<"a/b/c">>, payload = <<"123">>, headers = #{}},
     Ret = emqx_hooks:run_fold('message.publish',[], Msg),
     ?assertEqual(Msg#message{topic = <<"changed/topic">>, payload = <<"hello">>}, Ret),
 
@@ -636,7 +637,7 @@ case204(_Config) ->
             "\nend",
     ok = file:write_file(ScriptName, Code), ok = emqx_lua_hook:load_scripts(),
 
-    Msg = #message{qos = 2, flags = #{retain => true}, topic = <<"a/b/c">>, payload = <<"123">>, headers = #{}},
+    Msg = #message{id = emqx_guid:gen(), qos = 2, flags = #{retain => true}, topic = <<"a/b/c">>, payload = <<"123">>, headers = #{}},
     Ret = emqx_hooks:run_fold('message.publish',[], Msg),
     ?assertEqual(Msg#message{payload = <<"123_Z">>}, Ret).
 
@@ -651,7 +652,7 @@ case205(_Config) ->
             "\nend",
     ok = file:write_file(ScriptName, Code), ok = emqx_lua_hook:load_scripts(),
 
-    Msg = #message{qos = 2, flags = #{retain => true}, topic = <<"a/b/c">>, payload = <<"123">>, headers = #{}},
+    Msg = #message{id = emqx_guid:gen(), qos = 2, flags = #{retain => true}, topic = <<"a/b/c">>, payload = <<"123">>, headers = #{}},
     Ret = emqx_hooks:run_fold('message.publish',[], Msg),
     ?assertEqual(Msg, Ret).
 
diff --git a/apps/emqx_management/src/emqx_mgmt_api_clients.erl b/apps/emqx_management/src/emqx_mgmt_api_clients.erl
index e0e5af39d..de6e96e73 100644
--- a/apps/emqx_management/src/emqx_mgmt_api_clients.erl
+++ b/apps/emqx_management/src/emqx_mgmt_api_clients.erl
@@ -406,7 +406,7 @@ run_fuzzy_match(E = {_, _, Stats}, [{Key, '=<', Int}|Fuzzy]) ->
 %%--------------------------------------------------------------------
 %% QueryString to Match Spec
 
--spec qs2ms(list()) -> ets:match_spec().
+-spec qs2ms(list()) -> {ets:match_spec(), [{_Key, _Symbol, _Val}]}.
 qs2ms(Qs) ->
     {MatchHead, Conds, FuzzyStats} = qs2ms(Qs, 2, #{}, [], []),
     {[{{'$1', MatchHead, '_'}, Conds, ['$_']}], FuzzyStats}.
diff --git a/apps/emqx_rule_engine/include/rule_engine.hrl b/apps/emqx_rule_engine/include/rule_engine.hrl
index 858d9b9b6..04cfeb06f 100644
--- a/apps/emqx_rule_engine/include/rule_engine.hrl
+++ b/apps/emqx_rule_engine/include/rule_engine.hrl
@@ -61,28 +61,49 @@
         }).
 
 -record(action_instance,
-        { id :: action_instance_id()
-        , name :: action_name()
-        , fallbacks :: list(#action_instance{})
-        , args :: #{binary() => term()} %% the args got from API for initializing action_instance
+        { id
+        , name
+        , fallbacks
+        , args %% the args got from API for initializing action_instance
         }).
+-type(action_instance()
+      :: #action_instance{ id :: action_instance_id()
+                         , name :: action_name()
+                         , fallbacks :: list(#action_instance{})
+                         , args :: #{binary() => term()} %% the args got from API for initializing action_instance
+                         }).
 
 -record(rule,
-        { id :: rule_id()
-        , for :: list(topic())
-        , rawsql :: binary()
-        , is_foreach :: boolean()
-        , fields :: list()
-        , doeach :: term()
-        , incase :: list()
-        , conditions :: tuple()
-        , on_action_failed :: continue | stop
-        , actions :: list(#action_instance{})
-        , enabled :: boolean()
-        , created_at :: integer() %% epoch in millisecond precision
-        , description :: binary()
-        , state = normal :: atom()
+        { id
+        , for
+        , rawsql
+        , is_foreach
+        , fields
+        , doeach
+        , incase
+        , conditions
+        , on_action_failed
+        , actions
+        , enabled
+        , created_at %% epoch in millisecond precision
+        , description
+        , state = normal
         }).
+-type(rule() :: #rule{ id :: rule_id()
+                     , for :: list(topic())
+                     , rawsql :: binary()
+                     , is_foreach :: boolean()
+                     , fields :: list()
+                     , doeach :: term()
+                     , incase :: list()
+                     , conditions :: tuple()
+                     , on_action_failed :: continue | stop
+                     , actions :: list(#action_instance{})
+                     , enabled :: boolean()
+                     , created_at :: integer() %% epoch in millisecond precision
+                     , description :: binary()
+                     , state :: normal | atom()
+                     }).
 
 -record(resource,
         { id :: resource_id()
diff --git a/apps/emqx_rule_engine/src/emqx_rule_engine.erl b/apps/emqx_rule_engine/src/emqx_rule_engine.erl
index 872e314cb..d5c3ba92c 100644
--- a/apps/emqx_rule_engine/src/emqx_rule_engine.erl
+++ b/apps/emqx_rule_engine/src/emqx_rule_engine.erl
@@ -64,7 +64,6 @@
 -export([alarm_name_of_resource_down/2]).
 -endif.
 
--type(rule() :: #rule{}).
 -type(action() :: #action{}).
 -type(resource() :: #resource{}).
 -type(resource_type() :: #resource_type{}).
@@ -172,7 +171,6 @@ module_attributes(Module) ->
 %% APIs for rules and resources
 %%------------------------------------------------------------------------------
 
--dialyzer([{nowarn_function, [create_rule/1, rule_id/0]}]).
 -spec create_rule(map()) -> {ok, rule()} | {error, term()}.
 create_rule(Params = #{rawsql := Sql, actions := ActArgs}) ->
     case emqx_rule_sqlparser:parse_select(Sql) of
@@ -307,7 +305,7 @@ do_check_and_update_resource(#{id := Id, type := Type, description := NewDescrip
             Config = emqx_rule_validator:validate_params(NewConfig, ParamSpec),
             case test_resource(#{type => Type, config => NewConfig}) of
                 ok ->
-                    delete_resource(Id),
+                    _ = delete_resource(Id),
                     _ = ?CLUSTER_CALL(init_resource, [Module, Create, Id, Config]),
                     emqx_rule_registry:add_resource(#resource{
                         id = Id,
diff --git a/apps/emqx_rule_engine/src/emqx_rule_runtime.erl b/apps/emqx_rule_engine/src/emqx_rule_runtime.erl
index 8b6d6f915..794c70dfd 100644
--- a/apps/emqx_rule_engine/src/emqx_rule_runtime.erl
+++ b/apps/emqx_rule_engine/src/emqx_rule_runtime.erl
@@ -52,7 +52,7 @@ apply_rules([], _Input) ->
 apply_rules([#rule{enabled = false}|More], Input) ->
     apply_rules(More, Input);
 apply_rules([Rule|More], Input) ->
-    apply_rule(Rule, Input),
+    _ = apply_rule(Rule, Input),
     apply_rules(More, Input).
 
 apply_rule(Rule = #rule{id = RuleId}, Input) ->
diff --git a/apps/emqx_rule_engine/src/emqx_rule_sqlparser.erl b/apps/emqx_rule_engine/src/emqx_rule_sqlparser.erl
index 82d3cfb64..5fbd9337c 100644
--- a/apps/emqx_rule_engine/src/emqx_rule_sqlparser.erl
+++ b/apps/emqx_rule_engine/src/emqx_rule_sqlparser.erl
@@ -48,10 +48,6 @@
 
 -export_type([select/0]).
 
-%% Dialyzer gives up on the generated code.
-%% probably due to stack depth, or inlines.
--dialyzer({nowarn_function, [parse_select/1]}).
-
 %% Parse one select statement.
 -spec(parse_select(string() | binary())
       -> {ok, select()} | {parse_error, term()} | {lex_error, term()}).
@@ -105,4 +101,3 @@ select_from(#select{from = From}) ->
 -spec(select_where(select()) -> tuple()).
 select_where(#select{where = Where}) ->
     Where.
-
diff --git a/src/emqx.erl b/src/emqx.erl
index 29c5d7020..469a4672b 100644
--- a/src/emqx.erl
+++ b/src/emqx.erl
@@ -236,7 +236,7 @@ shutdown(Reason) ->
 reboot() ->
     case is_application_running(emqx_dashboard) of
         true ->
-            application:stop(emqx_dashboard), %% dashboard must be started after mnesia
+            _ = application:stop(emqx_dashboard), %% dashboard must be started after mnesia
             lists:foreach(fun application:start/1 , default_started_applications()),
             application:start(emqx_dashboard);
 
diff --git a/src/emqx_calendar.erl b/src/emqx_calendar.erl
index 0c094df81..71fff3182 100644
--- a/src/emqx_calendar.erl
+++ b/src/emqx_calendar.erl
@@ -317,7 +317,6 @@ trans_x_second(FromUnit, ToUnit, Time) ->
         end,
     padding(XSecond, Len).
 
-do_trans_x_second(second, second, Time) -> Time div 60;
 do_trans_x_second(second, _, _Time) -> 0;
 
 do_trans_x_second(millisecond, millisecond, Time) -> Time rem 1000;
@@ -433,4 +432,3 @@ dm(9) -> 243;
 dm(10) -> 273;
 dm(11) -> 304;
 dm(12) -> 334.
-
diff --git a/src/emqx_channel.erl b/src/emqx_channel.erl
index 49f515236..f3fb6194b 100644
--- a/src/emqx_channel.erl
+++ b/src/emqx_channel.erl
@@ -1742,8 +1742,7 @@ disconnect_reason(?RC_SUCCESS) -> normal;
 disconnect_reason(ReasonCode)  -> emqx_reason_codes:name(ReasonCode).
 
 reason_code(takeovered) -> ?RC_SESSION_TAKEN_OVER;
-reason_code(discarded) -> ?RC_SESSION_TAKEN_OVER;
-reason_code(_) -> ?RC_NORMAL_DISCONNECTION.
+reason_code(discarded) -> ?RC_SESSION_TAKEN_OVER.
 
 %%--------------------------------------------------------------------
 %% Helper functions
diff --git a/src/emqx_message.erl b/src/emqx_message.erl
index 5a0ab3bbd..40779c86b 100644
--- a/src/emqx_message.erl
+++ b/src/emqx_message.erl
@@ -343,8 +343,6 @@ format(#message{id = Id,
                   [printable_msg_id(Id), QoS, Topic, From, format(flags, Flags),
                    format(headers, Headers)]).
 
-printable_msg_id(undefined) ->
-    <<>>;
 printable_msg_id(Id) ->
     emqx_guid:to_hexstr(Id).
 
@@ -352,4 +350,3 @@ format(flags, Flags) ->
     io_lib:format("~p", [[Flag || {Flag, true} <- maps:to_list(Flags)]]);
 format(headers, Headers) ->
     io_lib:format("~p", [Headers]).
-
diff --git a/src/emqx_shared_sub.erl b/src/emqx_shared_sub.erl
index 3f67c225d..337d63d15 100644
--- a/src/emqx_shared_sub.erl
+++ b/src/emqx_shared_sub.erl
@@ -251,7 +251,7 @@ maybe_nack_dropped(Msg) ->
 
         %% For retry Ref we can't reject a message if inflight is full, so we mark it as
         %% acknowledged and put it into mqueue
-        {_Sender, {retry, _Group, _Ref}} -> maybe_ack(Msg), store;
+        {_Sender, {retry, _Group, _Ref}} -> _ = maybe_ack(Msg), store;
 
         %% This clause is for backward compatibility
         Ack ->