CODEWITHSUNDEEP
redis
Henley Wing Chiu
Henley Wing Chiu

Reputation: 22535

Redis ltrim - possible race condition?

Is there a possible race condition with Redis' ltrim and rpush?

For instance, suppose my redis list has these items: [1, 2, 3, 4, 5]

And I call ltrim list 4 -1 This basically should slice the list to just [5]

BUT let's say: a millisecond after ltrim has started and before ltrim is finished, another thread is pushing items to the list:

rpush list 6
rpush list 7

When both the 2 rpushes, and ltrims are finished, will the resulting list consist of [5, 6, 7]?

could it possibly be just [5]? In other words, is there a possibility of a race condition where ltrim does something like creating a temporary list with [5], and overwrites [5,6,7] with [5] after the 2 rpushes are done?

Upvotes: 0

Views: 327

Answers (1)

Supr
Supr

Reputation: 19042

Short answer: No, because commands are atomic.

Honest answer: I don't think so because I think operations are atomic; however, the website doesn't explicitly state that they are atomic so I'm only 99.99999999% sure that they are.

Logical answer: Redis is single-threaded, so there are no other threads that could preempt the ltrim command. For a race condition to occur in a single threaded application it would have to explicitly jump out of the ltrim operation before it's done and start doing something else, which doesn't make much sense.

Upvotes: 4

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