add file exists checking in my_uuid

scripts/lib/commons.lua

@@ -0,0 +1,13 @@
+local _M = {}
+
+function _M.file_exists(name)
+    local f = io.open(name, "r")
+    if f ~= nil then
+        io.close(f)
+        return true
+    else
+        return false
+    end
+end
+
+return _M

scripts/lib/my_uuid.lua

@@ -1,14 +1,23 @@
+local commons = require("lib.commons")
+
 local _M = {}
 
 function _M.uuid()
     local uuid_cmd = "/usr/bin/uuid"
 
-    local handle = io.popen(uuid_cmd)
-    local result = handle:read("*a")
-    local r2 = string.gsub(result, "%s+", "")
-    local r3 = string.gsub(r2,"\n","")
-    ngx.log(ngx.INFO, "uuid -> ", r3)
-    return r3
+    if commons.file_exists(uuid_cmd) then
+        local handle = io.popen(uuid_cmd)
+        local result = handle:read("*a")
+        local r2 = string.gsub(result, "%s+", "")
+        local r3 = string.gsub(r2,"\n","")
+        ngx.log(ngx.INFO, "uuid -> ", r3)
+        return r3
+    else
+        ngx.status = 500
+        ngx.log(ngx.ERR, "my_uuid *FAILED* `/usr/bin/uuid` not exists!")
+        ngx.say("my_uuid *FAILED* `/usr/bin/uuid` not exists!")
+        ngx.exit()
+    end
 end
 
 return _M