resty.lock for synchronizing mysql call

rohit.c.joshi · 2015-11-16T23:14:36+00:00

Hello! On Wed, Nov 18, 2015 at 9:58 AM, Bino Oetomo wrote: > > Just courious .. about ngx_stream_lua_module > > Will it 'play' with the stream{}...

resty.lock for synchronizing mysql call

rohit.c.joshi

Hello,

In my application, I am using ngx.shared.DICT cache and user data are retrieved from MySQL.

Can I use resty.lock to lock the function which is retrieving data from MySQL?

e.g

local lock = require "resty.lock"
function _M.init_users()
  local lock = lock:new("my_locks")
  local elapsed, err = lock:lock("init_users")
  local users  = cache.get("users_cache")
  if users then
   local ok, err = lock:unlock()
   return users
  end
  
  local users = dao.get_users()
  -- set to lurcache and shared dict cache
  cache.set("users_cache", users)
  local ok, err = lock:unlock()
  return users
end

local users  = cache.get("users_cache")
if not users then
  users =  _M.init_users()
end

agentzh

Hello!

On Mon, Nov 16, 2015 at 11:14 PM, RJoshi wrote:
>   In my application,  I am using ngx.shared.DICT cache and user data are
> retrieved from MySQL.
>   Can I use resty.lock to lock the function which is retrieving data from
> MySQL?
>

I don't understand why you need this. Are you trying to ensure that
only one MySQL connection is used for all the nginx worker processes
in a single server instance? This can enforce all your client requests
queueing serially, which can be a really bad thing for performance.

Be very careful about Lua exceptions aborting your "critical sections"
and the timeout threshold of the lock itself.

Regards,
-agentzh

rohit.c.joshi

Thanks. I was trying to prevent multiple queries and update to lru/shared cache when cache expires. may be not worth it.

On Monday, 16 November 2015 21:21:52 UTC-5, agentzh wrote:

Hello!

On Mon, Nov 16, 2015 at 11:14 PM, RJoshi wrote:
> In my application, I am using ngx.shared.DICT cache and user data are
> retrieved from MySQL.
> Can I use resty.lock to lock the function which is retrieving data from
> MySQL?
>

I don't understand why you need this. Are you trying to ensure that
only one MySQL connection is used for all the nginx worker processes
in a single server instance? This can enforce all your client requests
queueing serially, which can be a really bad thing for performance.

Be very careful about Lua exceptions aborting your "critical sections"
and the timeout threshold of the lock itself.

Regards,
-agentzh