fix: when called checker:get_target_status got err, we should log it~ (…

…apache#3424)

Co-authored-by: nieyong <[email protected]>

apisix/balancer.lua

@@ -55,10 +55,13 @@ local function fetch_health_nodes(upstream, checker)
     local port = upstream.checks and upstream.checks.active and upstream.checks.active.port
     local up_nodes = core.table.new(0, #nodes)
     for _, node in ipairs(nodes) do
-        local ok = checker:get_target_status(node.host, port or node.port, host)
+        local ok, err = checker:get_target_status(node.host, port or node.port, host)
         if ok then
             -- TODO filter with metadata
             up_nodes[node.host .. ":" .. node.port] = node.weight
+        elseif err then
+            core.log.error("failed to get health check target status, addr: ",
+                node.host, ":", port or node.port, ", host: ", host, ", err: ", err)
         end
     end