Merge pull request #9592 from zmstone/1221-fix-io-format-error-when-rpc-from-remsh

1221 fix io format error when rpc from remsh

scripts/start-two-nodes-in-docker.sh

@@ -26,6 +26,12 @@ NODE1="node1.$NET"
 NODE2="node2.$NET"
 COOKIE='this-is-a-secret'
 
+if [ -f EMQX_ENTERPRISE ]; then
+    REL_DIR='emqx-ee'
+else
+    REL_DIR='emqx'
+fi
+
 ## clean up
 docker rm -f "$NODE1" >/dev/null 2>&1 || true
 docker rm -f "$NODE2" >/dev/null 2>&1 || true
@@ -33,22 +39,22 @@ docker network rm "$NET" >/dev/null 2>&1 || true
 
 docker network create "$NET"
 
-docker run -d -t --restart=always --name "$NODE1" \
+docker run -d -it --restart=always --name "$NODE1" \
   --net "$NET" \
   -e EMQX_NODE_NAME="emqx@$NODE1" \
   -e EMQX_NODE_COOKIE="$COOKIE" \
   -e WAIT_FOR_ERLANG=60 \
   -p 18083:18083 \
-  -v "$PROJ_DIR"/_build/emqx/rel/emqx:/built \
+  -v "$PROJ_DIR"/_build/"${REL_DIR}"/rel/emqx:/built \
   "$IMAGE" sh -c 'cp -r /built /emqx && /emqx/bin/emqx console'
 
-docker run -d -t --restart=always --name "$NODE2" \
+docker run -d -it --restart=always --name "$NODE2" \
   --net "$NET" \
   -e EMQX_NODE_NAME="emqx@$NODE2" \
   -e EMQX_NODE_COOKIE="$COOKIE" \
   -e WAIT_FOR_ERLANG=60 \
   -p 18084:18083 \
-  -v "$PROJ_DIR"/_build/emqx/rel/emqx:/built \
+  -v "$PROJ_DIR"/_build/"${REL_DIR}"/rel/emqx:/built \
   "$IMAGE" sh -c 'cp -r /built /emqx && /emqx/bin/emqx console'
 
 wait (){

src/emqx_misc.erl

@@ -26,6 +26,7 @@
 -export([ merge_opts/2
         , maybe_apply/2
         , maybe_mute_rpc_log/0
+        , safe_io_device/0
         , compose/1
         , compose/2
         , run_fold/3
@@ -478,6 +479,34 @@ maybe_mute_rpc_log(Node) ->
             ok
     end.
 
+is_group_leader_node_connected() ->
+    GLNode = node(group_leader()),
+    case atom_to_list(GLNode) of
+        "remsh" ++ _ ->
+            {ok, Nodes} = net_kernel:nodes_info(),
+            lists:keymember(GLNode, 1, Nodes);
+        _ ->
+            %% for a non-remsh node
+            %% as long as the group leader is showing up
+            %% it should be connected
+            true
+    end.
+
+%% @doc Return 'standard_io' or 'standard_error' io device depending on the
+%% current group leader node.
+%% EMQX nodes do not use EPMD, there is no way for a EMQX node to connect to
+%% a remsh node which is not directly connected already.
+%% In this case, io:format may fail with {io,terminated} exception.
+%% For io:format calls which can be evaluated from RPC calls, call this
+%% function to get a safe io device.
+safe_io_device() ->
+    case is_group_leader_node_connected() of
+        true ->
+            standard_io;
+        false ->
+            standard_error
+    end.
+
 is_sensitive_key(token) -> true;
 is_sensitive_key("token") -> true;
 is_sensitive_key(<<"token">>) -> true;

test/emqx_misc_SUITE.erl

@@ -179,3 +179,6 @@ t_pmap_exception(_) ->
             [{2, 3}, {3, 4}, error]
         )
     ).
+
+t_safe_io_device(_) ->
+    ?assertEqual(standard_io, emqx_misc:safe_io_device()).