[hibernate-dev] Redis and TTL

[Mark Paluch]

Hi Sanne, 

not sure I follow.

The use case is: Two applications (clients) share one Redis instance. The first (non-OGM) client writes some data and sets an expiry (TTL). The second (OGM) client updates the data stored inside of Redis and preserves the remaining TTL. Note that the first (non-OGM) client wrote an expiry and expects the key to disappear sooner or later.

The TTL is not configured in OGM for this use-case because the TTL might be determined somehow dynamic by the first client.

Greetings, Mark

> Am 27.06.2016 um 15:52 schrieb Sanne Grinovero <sanne at hibernate.org>:
> 
> Hi Mark,
> 
> you wouldn't expect the timeout to be "reset" to some default value
> when your code writes to an entity?
> 
> If you could explain the use case, that might help us to understand this.
> 
> Thanks,
> Sanne
> 
> On 27 June 2016 at 14:47, Mark Paluch <mpaluch at paluch.biz> wrote:
>> 
>> Hi Guillaume,
>> 
>> TTL preservation behavior originates from Redis’ behavior and is to preserve interoperability:
>> 
>>> http://redis.io/commands/set <http://redis.io/commands/set>
>>> Set key to hold the string value. [...] Any previous time to live associated with the key is discarded on successful SET operation.
>> 
>> 
>> Keys written with SET loose their TTL value and the entry is persisted without any further TTL. Reading and re-applying TTL is to preserve the expiry.
>> The general idea behind is to either apply the remaining TTL from the key, because TTL is not configured in the entity model or to set the configured TTL from the entity model.
>> I see it from an integration-perspective in which Hibernate OGM and other tools share Redis data and so you’re opting-in for features but things are not broken.
>> 
>> Best regards, Mark
>> 
>> 
>>> Am 27.06.2016 um 14:43 schrieb Guillaume Smet <guillaume.smet at gmail.com>:
>>> 
>>> Hi,
>>> 
>>> So, I'm currently working on reducing the number of calls issued to Redis
>>> in OGM as part of OGM-1064.
>>> 
>>> At the moment, we execute a call to Redis to get the TTL already configured
>>> on an object before saving it. If the TTL is not explicitly configured with
>>> @TTL, we set this TTL again after having stored this entity (see
>>> RedisJsonDialect#storeEntity). Same for associations stored in a different
>>> document.
>>> 
>>> In fact, this call returns the time remaining before expiration, not the
>>> TTL previously configured,  so I find this behavior quite weird. Basically,
>>> we store information which will expire sooner than expected. I can't really
>>> get a use case for this and I don't think we should have an additional call
>>> every time we store an object for a so obscure thing. Do we really expect
>>> people to mess with TTLs of objects stored by OGM without relying on OGM
>>> @TTL management?
>>> 
>>> IMHO, we should get rid of this call and only deal with TTL when it's
>>> configured via the @TTL annotation.
>>> 
>>> Thoughts?
>>> 
>>> --
>>> Guillaume
>>> _______________________________________________
>>> hibernate-dev mailing list
>>> hibernate-dev at lists.jboss.org
>>> https://lists.jboss.org/mailman/listinfo/hibernate-dev
>> 
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