Are there any good posts on transactions? I've found articles around but nothing very concise that explains the exact behavior of MULTI/EXEC when things go bad.
I had read that MULTI/EXEC would not "rollback" incase a command fails (e.g. you do first SET, second SET, third SET fails, then the two initial SETs would still be applied). I guess this doesn't so much have to do specifically with persistance problems (system crash, process crash, etc..) but more with just how transactions work in general.
redis> multi
OK
redis> set hi 'hello'
QUEUED
redis> rpop hi
QUEUED
redis> set okay 'done'
QUEUED
redis> exec
1. OK
2. (error) ERR Operation against a key holding the wrong kind of value
3. OK
redis> get okay
"'done'"
redis> get hi
"'hello'"
redis>
Note that it keeps on processing, even though the second command fails. This also has nothing to do with persistence, as the exhibited behavior will be the same in a fully-alive system and from disk and anything else, because redis maintains a perfect total ordering of operations in its log format and sync behavior.
Maybe SET wasnt a good example .. but lets say you are writing to the wrong type or something like that. I know that its unlikely something will fail in production like that since you should catch it during dev but bugs can happen.
