lua randomseed per worker

rootfs/etc/nginx/lua/lua_ingress.lua

@@ -0,0 +1,26 @@
+local _M = {}
+
+local seeds = {}
+local original_randomseed = math.randomseed
+math.randomseed = function(seed)
+  local pid = ngx.worker.pid()
+
+  if seeds[pid] then
+    ngx.log(ngx.WARN,
+      string.format("ignoring math.randomseed(%d) since PRNG is already seeded for worker %d", seed, pid))
+    return
+  end
+
+  original_randomseed(seed)
+  seeds[pid] = seed
+end
+
+local function randomseed()
+  math.randomseed(ngx.time() + ngx.worker.pid())
+end
+
+function _M.init_worker()
+  randomseed()
+end
+
+return _M

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

@@ -0,0 +1,9 @@
+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(100)
+    assert.spy(s).was_called_with(ngx.WARN,
+      string.format("ignoring math.randomseed(%d) since PRNG is already seeded for worker %d", 100, ngx.worker.pid()))
+  end)
+end)

rootfs/etc/nginx/lua/test/run.lua

@@ -1,4 +1,5 @@
 local ffi = require("ffi")
+local lua_ingress = require("lua_ingress")
 
 -- without this we get errors such as "attempt to redefine XXX"
 local old_cdef = ffi.cdef
@@ -32,7 +33,6 @@ end
 ngx.log = function(...) end
 ngx.print = function(...) end
 
--- TODO(elvinefendi) once this is implemented for production (should be!), share the same code
-math.randomseed(ngx.time() + ngx.worker.pid())
+lua_ingress.init_worker()
 
 require "busted.runner"({ standalone = false })