Reloading a module

Reloading a module in Lua

Here’s an example that illustrates the most typical case – “update and reload”.

1. Update the application file.

   For example, a module in /usr/share/tarantool/app.lua:

   local function start()
     -- initial version
     box.once("myapp:v1.0", function()
       box.schema.space.create("somedata")
       box.space.somedata:create_index("primary")
       ...
     end)
   
     -- migration code from 1.0 to 1.1
     box.once("myapp:v1.1", function()
       box.space.somedata.index.primary:alter(...)
       ...
     end)
   
     -- migration code from 1.1 to 1.2
     box.once("myapp:v1.2", function()
       box.space.somedata.index.primary:alter(...)
       box.space.somedata:insert(...)
       ...
     end)
   end
   
   -- start some background fibers if you need
   
   local function stop()
     -- stop all background fibers and clean up resources
   end
   
   local function api_for_call(xxx)
     -- do some business
   end
   
   return {
     start = start,
     stop = stop,
     api_for_call = api_for_call
   }
   

2. Update the instance file.

   For example, /etc/tarantool/instances.enabled/my_app.lua:

   #!/usr/bin/env tarantool
   --
   -- hot code reload example
   --
   
   box.cfg({listen = 3302})
   
   -- ATTENTION: unload it all properly!
   local app = package.loaded['app']
   if app ~= nil then
     -- stop the old application version
     app.stop()
     -- unload the application
     package.loaded['app'] = nil
     -- unload all dependencies
     package.loaded['somedep'] = nil
   end
   
   -- load the application
   log.info('require app')
   app = require('app')
   
   -- start the application
   app.start({some app options controlled by sysadmins})
   

   The important thing here is to properly unload the application and its dependencies.

3. Manually reload the application file.

   For example, using tarantoolctl:

   $ tarantoolctl eval my_app /etc/tarantool/instances.enabled/my_app.lua
   

Reloading a module in C

After you compiled a new version of a C module (*.so shared library), call box.schema.func.reload(‘module-name’) from your Lua script to reload the module.