save (update) operation on repository deletes the key and inserts it back [DATAREDIS-560]

sumanth yamala opened DATAREDIS-560 and commented

When using the KeyValueRepository interface and enableRedisRepositories:

After the initial creation - repository.save() - everything is fine here.
When doing an update operation: calling repository.save() - correctly detects that this is an update and calls
SimpleKeyValueRepository().save() --> KeyValueTemplate.update(....) --> which calls the callback method:
doInRedis(RedisConnection connection ).. In this method I see an issue:

Issue: A call is being made to delete the key
boolean isNew = connection.del(objectKey) == 0;
and it is promptly added back in the same callback method.

During this period if another thread is looking up the key - it indicates the key is not there and shortly afterwards it reappears.

Two issues here:

1. Integrity of redis is not maintained - a key is being deleted in the process of an update.
2. In the event of a crash around this critical section I believe the integrity of the data is getting compromised.

How to reproduce this:
Do an update operation on the repository in a debugger and suspend the thread after the delete operation. Use another client to look up the key.

Should the connection.del(objectKey) be changed to connection.exisits(objectKey) to fix this.

Affects: 1.7.4 (Hopper SR4)

Issue Links:

• DATAREDIS-741 Improve repository operation documentation