Managing modules

This section covers the installation and reloading of Tarantool modules. To learn about writing your own module and contributing it, check the Contributing a module section.

Modules in Lua and C that come from Tarantool developers and community contributors are available in the following locations:

• Tarantool modules repository (see below)
• Tarantool deb/rpm repositories (see below)

See README in tarantool/rocks repository for detailed instructions.

Follow these steps:

1. Install Tarantool as recommended on the download page.

2. Install the module you need. Look up the module's name on Tarantool rocks page and put the prefix "tarantool-" before the module name to avoid ambiguity:

    
   $ # for Ubuntu/Debian:$ sudo apt-get install tarantool-<module-name>$ # for RHEL/CentOS/Amazon:$ sudo yum install tarantool-<module-name>

   For example, to install the module vshard on Ubuntu, say:

    
   $ sudo apt-get install tarantool-vshard

Once these steps are complete, you can:

• load any module with

   
  tarantool> name = require('module-name')

  for example:

   
  tarantool> vshard = require('vshard')

• search locally for installed modules using package.path (Lua) or package.cpath (C):

   
  tarantool> package.path---- ./?.lua;./?/init.lua; /usr/local/share/tarantool/?.lua;/usr/local/share/tarantool/?/init.lua;/usr/share/tarantool/?.lua;/usr/share/tarantool/?/init.lua;/usr/local/share/lua/5.1/?.lua;/usr/local/share/lua/5.1/?/init.lua;/usr/share/lua/5.1/?.lua;/usr/share/lua/5.1/?/init.lua;...tarantool> package.cpath---- ./?.so;/usr/local/lib/x86_64-linux-gnu/tarantool/?.so;/usr/lib/x86_64-linux-gnu/tarantool/?.so;/usr/local/lib/tarantool/?.so;/usr/local/lib/x86_64-linux-gnu/lua/5.1/?.so;/usr/lib/x86_64-linux-gnu/lua/5.1/?.so;/usr/local/lib/lua/5.1/?.so;...

You can reload any Tarantool application or module with zero downtime.

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 needlocal function stop()  -- stop all background fibers and clean up resourcesendlocal function api_for_call(xxx)  -- do some businessendreturn {  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'] = nilend-- load the applicationlog.info('require app')app = require('app')-- start the applicationapp.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 tt:

    
   $ tt connect my_app -f /etc/tarantool/instances.enabled/my_app.lua

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.