Module net.box
Module net.box

Module net.box

Module net.box

The net.box module contains connectors to remote database systems. One variant, to be discussed later, is for connecting to MySQL or MariaDB or PostgreSQL — that variant is the subject of the SQL DBMS modules reference. In this section the subject is the built-in variant, net.box. This is for connecting to tarantool servers via a network.

Call require('net.box') to get a net.box object, which will be called net_box for examples in this section. Call net_box.new() to connect and get a connection object, which will be called conn for examples in this section. Call the other net.box() routines, passing conn:, to execute requests on the remote box. Call conn:close to disconnect.

All net.box methods are fiber-safe, that is, it is safe to share and use the same connection object across multiple concurrent fibers. In fact, it’s perhaps the best programming practice with Tarantool. When multiple fibers use the same connection, all requests are pipelined through the same network socket, but each fiber gets back a correct response. Reducing the number of active sockets lowers the overhead of system calls and increases the overall server performance. There are, however, cases when a single connection is not enough — for example when it’s necessary to prioritize requests or to use different authentication ids.

net_box.new(URI[, {option[s]}])

Create a new connection. The connection is established on demand, at the time of the first request. It is re-established automatically after a disconnect. The returned conn object supports methods for making remote requests, such as select, update or delete.

For the local tarantool server there is a pre-created always-established connection object named net_box.self. Its purpose is to make polymorphic use of the net_box API easier. Therefore conn = net_box.new('localhost:3301') can be replaced by conn = net_box.self. However, there is an important difference between the embedded connection and a remote one. With the embedded connection, requests which do not modify data do not yield. When using a remote connection, due to the implicit rules any request can yield, and database state may have changed by the time it regains control.

Parameters:
  • URI (string) – the URI of the target for the connection
  • options – a possible option is wait_connect
Return:

conn object

Rtype:

userdata

Example:

conn = net_box.new('localhost:3301')
conn = net_box.new('127.0.0.1:3306', {wait_connect = false})
object conn
conn:ping()

Execute a PING command.

Return:true on success, false on error
Rtype:boolean

Example:

net_box.self:ping()
conn:wait_connected([timeout])

Wait for connection to be active or closed.

Parameters:
  • timeout (number) –
Return:

true when connected, false on failure.

Rtype:

boolean

Example:

net_box.self:wait_connected()
conn:is_connected()

Show whether connection is active or closed.

Return:true if connected, false on failure.
Rtype:boolean

Example:

net_box.self:is_connected()
conn:close()

Close a connection.

Connection objects are garbage collected just like any other objects in Lua, so an explicit destruction is not mandatory. However, since close() is a system call, it is good programming practice to close a connection explicitly when it is no longer needed, to avoid lengthy stalls of the garbage collector.

Example:

conn:close()
conn.space.<space-name>:select{field-value, ...}

conn.space.space-name:select{...} is the remote-call equivalent of the local call box.space.space-name:select{...}.

Note

due to the implicit yield rules a local box.space.space-name:select{...} does not yield, but a remote conn.space.space-name:select{...} call does yield, so global variables or database tuples data may change when a remote conn.space.space-name:select{...} occurs.

conn.space.<space-name>:get{field-value, ...}

conn.space.space-name:get(...) is the remote-call equivalent of the local call box.space.space-name:get(...).

conn.space.<space-name>:insert{field-value, ...}

conn.space.space-name:insert(...) is the remote-call equivalent of the local call box.space.space-name:insert(...).

conn.space.<space-name>:replace{field-value, ...}

conn.space.space-name:replace(...) is the remote-call equivalent of the local call box.space.space-name:replace(...).

conn.space.<space-name>:update{field-value, ...}

conn.space.space-name:update(...) is the remote-call equivalent of the local call box.space.space-name:update(...).

conn.space.<space-name>:upsert{field-value, ...}

conn.space.space-name:upsert(...) is the remote-call equivalent of the local call box.space.space-name:upsert(...).

conn.space.<space-name>:delete{field-value, ...}

conn.space.space-name:delete(...) is the remote-call equivalent of the local call box.space.space-name:delete(...).

conn:call(function-name[, arguments])

conn:call('func', '1', '2', '3') is the remote-call equivalent of func('1', '2', '3'). That is, conn:call is a remote stored-procedure call.

Example:

conn:call('function5')
conn:eval(Lua-string)

conn:eval(Lua-string) evaluates and executes the expression in Lua-string, which may be any statement or series of statements. An execute privilege is required; if the user does not have it, an administrator may grant it with box.schema.user.grant(username, 'execute', 'universe').

Example:

conn:eval('return 5+5')
conn:timeout(timeout)

timeout(...) is a wrapper which sets a timeout for the request that follows it.

Example:

conn:timeout(0.5).space.tester:update({1}, {{'=', 2, 15}})

All remote calls support execution timeouts. Using a wrapper object makes the remote connection API compatible with the local one, removing the need for a separate timeout argument, which the local version would ignore. Once a request is sent, it cannot be revoked from the remote server even if a timeout expires: the timeout expiration only aborts the wait for the remote server response, not the request itself.

Example showing use of most of the net.box methods

This example will work with the sandbox configuration described in the preface. That is, there is a space named tester with a numeric primary key. Assume that the database is nearly empty. Assume that the tarantool server is running on localhost 127.0.0.1:3301.

tarantool> net_box = require('net.box')
---
...
tarantool> function example()
         >   local conn, wtuple
         >   if net_box.self:ping() then
         >     table.insert(ta, 'self:ping() succeeded')
         >     table.insert(ta, '  (no surprise -- self connection is pre-established)')
         >   end
         >   if box.cfg.listen == '3301' then
         >     table.insert(ta,'The local server listen address = 3301')
         >   else
         >     table.insert(ta, 'The local server listen address is not 3301')
         >     table.insert(ta, '(  (maybe box.cfg{...listen="3301"...} was not stated)')
         >     table.insert(ta, '(  (so connect will fail)')
         >   end
         >   conn = net_box.new('127.0.0.1:3301')
         >   conn.space.tester:delete{800}
         >   table.insert(ta, 'conn delete done on tester.')
         >   conn.space.tester:insert{800, 'data'}
         >   table.insert(ta, 'conn insert done on tester, index 0')
         >   table.insert(ta, '  primary key value = 800.')
         >   wtuple = conn.space.tester:select{800}
         >   table.insert(ta, 'conn select done on tester, index 0')
         >   table.insert(ta, '  number of fields = ' .. #wtuple)
         >   conn.space.tester:delete{800}
         >   table.insert(ta, 'conn delete done on tester')
         >   conn.space.tester:replace{800, 'New data', 'Extra data'}
         >   table.insert(ta, 'conn:replace done on tester')
         >   conn:timeout(0.5).space.tester:update({800}, {{'=', 2, 'Fld#1'}})
         >   table.insert(ta, 'conn update done on tester')
         >   conn:close()
         >   table.insert(ta, 'conn close done')
         > end
---
...
tarantool> ta = {}
---
...
tarantool> example()
---
...
tarantool> ta
---
- - self:ping() succeeded
  - '  (no surprise -- self connection is pre-established)'
  - The local server listen address = 3301
  - conn delete done on tester.
  - conn insert done on tester, index 0
  - '  primary key value = 800.'
  - conn select done on tester, index 0
  - '  number of fields = 1'
  - conn delete done on tester
  - conn:replace done on tester
  - conn update done on tester
  - conn close done
...