added more error info and keep test cases.

rootfs/etc/nginx/lua/lua_ingress.lua

@@ -5,37 +5,50 @@ local original_randomseed = math.randomseed
 
 local function get_seed_from_urandom()
   local seed
-  local frandom = io.open("/dev/urandom", "rb")
+  local frandom, err = io.open("/dev/urandom", "rb")
-  if frandom then
+  if not frandom then
-    local str = frandom:read(4)
+    ngx.log(ngx.WARN, 'failed to open /dev/urandom: ', err)
-    frandom:close()
+    return nil
-    seed = 0
-    for i = 1, 4 do
-        seed = 256 * seed + str:byte(i)
-    end
   end
+
+  local str = frandom:read(4)
+  frandom:close()
+  if not str then
+    ngx.log(ngx.WARN, 'failed to read data from /dev/urandom')
+    return nil
+  end
+
+  seed = 0
+  for i = 1, 4 do
+      seed = 256 * seed + str:byte(i)
+  end
+
   return seed
 end
 
-math.randomseed = function()
+math.randomseed = function(seed)
   local pid = ngx.worker.pid()
-  local seed = seeds[pid]
+  if seeds[pid] then
-  if seed then
     ngx.log(ngx.WARN,
-      string.format("ignoring math.randomseed() since PRNG is already seeded for worker %d", pid))
+      string.format("ignoring math.randomseed(%d) since PRNG is already seeded for worker %d", seed, pid))
     return
   end
 
-  seed = get_seed_from_urandom()
-  if not seed then
-    seed = ngx.now() * 1000 + pid
-  end
   original_randomseed(seed)
   seeds[pid] = seed
 end
 
+local function randomseed()
+  local seed = get_seed_from_urandom()
+  if not seed then
+    ngx.log(ngx.WARN, 'failed to get seed from urandom')
+    seed = ngx.now() * 1000 + ngx.worker.pid()
+  end
+  math.randomseed(seed)
+end
+
 function _M.init_worker()
-  math.randomseed()
+  randomseed()
 end
 
 return _M

rootfs/etc/nginx/lua/test/lua_ingress_test.lua

@@ -2,8 +2,8 @@ describe("lua_ingress", function()
   it("patches math.randomseed to not be called more than once per worker", function()
     local s = spy.on(ngx, "log")
 
-    math.randomseed()
+    math.randomseed(100)
     assert.spy(s).was_called_with(ngx.WARN,
-      string.format("ignoring math.randomseed() since PRNG is already seeded for worker %d", ngx.worker.pid()))
+      string.format("ignoring math.randomseed(%d) since PRNG is already seeded for worker %d", 100, ngx.worker.pid()))
   end)
 end)