Why lua script block redis-server?

Question

I have a simple Lua script:

while ( i < 500000 ) do
    redis.call("zadd", 'test1', i, i)
    redis.call( "expire", 'test1', 600 )
    i = i + 1
end

local res = redis.call("zrange", "test1", 0, 500000 )

for k,a in pairs(res) do
    redis.call("zadd", 'test2',k,a)
end

Why this script blocking the Redis server? If I run in another console command, for example: set test 1, result:

 BUSY Redis is busy running a script. You can only call SCRIPT KILL or SHUTDOWN NOSAVE.

Sergio Tulentsev · Accepted Answer · 2012-06-29 12:19:18Z

7

Redis is single-threaded. Every command blocks it. EVAL is also a command, therefore it blocks redis.

answered Jun 29, 2012 at 12:19

Sergio Tulentsev

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Dennis Anikin · Accepted Answer · 2015-07-11 07:04:46Z

3

That is why we at Mail.Ru and at myMail use Tarantool NoSQL database instead of Redis that we also were trying to use. In Tarantool every command is being executed in a separate fiber and doesn't block another one. The same thing to Lua scripts - they don't block each other.

answered Jul 11, 2015 at 7:04

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