luci-app-nlbw: fix sporadic premature EOF when rendering JSON data

Specific timing patterns sometimes caused the LuCI controller to prematurely
stop reading data, resulting in truncated JSON output.

Turn the nonblocking waitpid() call into a blocking call after the IO read
loop to avoid this issue.

Signed-off-by: Jo-Philipp Wich <jo@mein.io>

diff --git a/applications/luci-app-nlbwmon/luasrc/controller/nlbw.lua b/applications/luci-app-nlbwmon/luasrc/controller/nlbw.lua
index bb56bc6..a8c5779 100644 (file)
--- a/applications/luci-app-nlbwmon/luasrc/controller/nlbw.lua
+++ b/applications/luci-app-nlbwmon/luasrc/controller/nlbw.lua
@@ -28,16 +28,17 @@ local function exec(cmd, args, writer)
 
                while true do
                        local buffer = fdi:read(2048)
-                       local wpid, stat, code = nixio.waitpid(pid, "nohang")
 
-                       if writer and buffer and #buffer > 0 then
-                               writer(buffer)
+                       if not buffer or #buffer == 0 then
+                               break
                        end
 
-                       if wpid and stat == "exited" then
-                               break
+                       if writer then
+                               writer(buffer)
                        end
                end
+
+               nixio.waitpid(pid)
        elseif pid == 0 then
                nixio.dup(fdo, nixio.stdout)
                fdi:close()