Can I use Tarantool instead of Redis?

Question

I'd like to use Tarantool to store data. How can I store data with TTL and simple logic (without the spaces)?

Like this:

box:setx(key, value, ttl);
box:get(key)

Answer 1

Yes, you can expire data in Tarantool and in a much more flexible way than in Redis. Though you can't do this without spaces, because space is a container for data in Tarantool (like database or table in other database systems).

In order to expire data, you have to install expirationd tarantool rock using tarantoolctl rocks install expirationd command. Full documentation on expirationd daemon can be found here.

Feel free to use a sample code below:

#!/usr/bin/env tarantool

package.path = './.rocks/share/tarantool/?.lua;' .. package.path

local fiber = require('fiber')
local expirationd = require('expirationd')


-- setup the database

box.cfg{}
box.once('init', function()
    box.schema.create_space('test')
    box.space.test:create_index('primary', {parts = {1, 'unsigned'}})
end)

-- print all fields of all tuples in a given space
local print_all = function(space_id)
    for _, v in ipairs(box.space[space_id]:select()) do
        local s = ''
        for i = 1, #v do s = s .. tostring(v[i]) .. '\t' end
        print(s)
    end
end

-- return true if tuple is more than 10 seconds old
local is_expired = function(args, tuple)
    return (fiber.time() - tuple[3]) > 10
end

-- simply delete a tuple from a space
local delete_tuple = function(space_id, args, tuple)
    box.space[space_id]:delete{tuple[1]}
end

local space = box.space.test

print('Inserting tuples...')

space:upsert({1, '0 seconds', fiber.time()}, {})
fiber.sleep(5)
space:upsert({2, '5 seconds', fiber.time()}, {})
fiber.sleep(5)
space:upsert({3, '10 seconds', fiber.time()}, {})

print('Tuples are ready:\n')

print_all('test')

print('\nStarting expiration daemon...\n')

-- start expiration daemon
-- in a production full_scan_time should be bigger than 1 sec
expirationd.start('expire_old_tuples', space.id, is_expired, {
    process_expired_tuple = delete_tuple, args = nil,
    tuples_per_iteration = 50, full_scan_time = 1
})

fiber.sleep(5)
print('\n\n5 seconds passed...')
print_all('test')

fiber.sleep(5)
print('\n\n10 seconds passed...')
print_all('test')

fiber.sleep(5)
print('\n\n15 seconds passed...')
print_all('test')

os.exit()