From 60556abc4f9d6818cfda809c97102f9cc3a8e53c Mon Sep 17 00:00:00 2001
From: Ilya Averyanov <av@rubybox.dev>
Date: Wed, 29 May 2024 16:45:23 +0300
Subject: [PATCH] fix(dashboard_monitor): correctly merge old and new sample
 data

---
 .../src/emqx_dashboard_monitor.erl            |  4 +--
 .../test/emqx_dashboard_monitor_SUITE.erl     | 36 +++++++++++++++++++
 changes/ce/fix-13156.en.md                    |  1 +
 3 files changed, 39 insertions(+), 2 deletions(-)
 create mode 100644 changes/ce/fix-13156.en.md

diff --git a/apps/emqx_dashboard/src/emqx_dashboard_monitor.erl b/apps/emqx_dashboard/src/emqx_dashboard_monitor.erl
index a82be6a11..c4195e449 100644
--- a/apps/emqx_dashboard/src/emqx_dashboard_monitor.erl
+++ b/apps/emqx_dashboard/src/emqx_dashboard_monitor.erl
@@ -209,7 +209,7 @@ do_call(Request) ->
     gen_server:call(?MODULE, Request, 5000).
 
 do_sample(all, Time) ->
-    do_sample(mria:cluster_nodes(running), Time, #{});
+    do_sample(emqx:running_nodes(), Time, #{});
 do_sample(Node, Time) when Node == node() ->
     MS = match_spec(Time),
     internal_format(ets:select(?TAB, MS));
@@ -259,7 +259,7 @@ merge_cluster_sampler_map(M1, M2) ->
                 Key =:= subscriptions_durable;
                 Key =:= disconnected_durable_sessions
             ->
-                Map#{Key => maps:get(Key, M1)};
+                Map#{Key => maps:get(Key, M1, maps:get(Key, M2, 0))};
             (Key, Map) ->
                 Map#{Key => maps:get(Key, M1, 0) + maps:get(Key, M2, 0)}
         end,
diff --git a/apps/emqx_dashboard/test/emqx_dashboard_monitor_SUITE.erl b/apps/emqx_dashboard/test/emqx_dashboard_monitor_SUITE.erl
index 8f561deca..c82367faf 100644
--- a/apps/emqx_dashboard/test/emqx_dashboard_monitor_SUITE.erl
+++ b/apps/emqx_dashboard/test/emqx_dashboard_monitor_SUITE.erl
@@ -27,6 +27,7 @@
 -include_lib("common_test/include/ct.hrl").
 -include_lib("snabbkaffe/include/snabbkaffe.hrl").
 -include_lib("emqx/include/emqx_mqtt.hrl").
+-include_lib("emqx/include/asserts.hrl").
 
 -define(SERVER, "http://127.0.0.1:18083").
 -define(BASE_PATH, "/api/v5").
@@ -191,6 +192,41 @@ t_monitor_sampler_format(_Config) ->
     [?assert(lists:member(SamplerName, SamplerKeys)) || SamplerName <- ?SAMPLER_LIST],
     ok.
 
+t_handle_old_monitor_data(_Config) ->
+    Now = erlang:system_time(second),
+    FakeOldData = maps:from_list(
+        lists:map(
+            fun(N) ->
+                Time = (Now - N) * 1000,
+                {Time, #{foo => 123}}
+            end,
+            lists:seq(0, 9)
+        )
+    ),
+
+    Self = self(),
+
+    ok = meck:new(emqx, [passthrough, no_history]),
+    ok = meck:expect(emqx, running_nodes, fun() -> [node(), 'other@node'] end),
+    ok = meck:new(emqx_dashboard_proto_v1, [passthrough, no_history]),
+    ok = meck:expect(emqx_dashboard_proto_v1, do_sample, fun('other@node', _Time) ->
+        Self ! sample_called,
+        FakeOldData
+    end),
+
+    {ok, _} =
+        snabbkaffe:block_until(
+            ?match_event(#{?snk_kind := dashboard_monitor_flushed}),
+            infinity
+        ),
+    ?assertMatch(
+        #{},
+        hd(emqx_dashboard_monitor:samplers())
+    ),
+    ?assertReceive(sample_called, 1_000),
+    ok = meck:unload([emqx, emqx_dashboard_proto_v1]),
+    ok.
+
 t_monitor_api(_) ->
     {ok, _} =
         snabbkaffe:block_until(
diff --git a/changes/ce/fix-13156.en.md b/changes/ce/fix-13156.en.md
new file mode 100644
index 000000000..6f4dffd07
--- /dev/null
+++ b/changes/ce/fix-13156.en.md
@@ -0,0 +1 @@
+Fix crashes on monitor dashboard page happening after update to v5.7.0.