Tikv: Is it feasible to enable watch mechanism on top of Tikv

[CindyXing]

Is it feasible to enable watch (pub/sub) mechanism on top of tiKV? Rather than pulling a key value for changes, I'd the client be notified in case of the change and know the change version.

Thanks

[siddontang]

Hi @CindyXing

It is a cool idea, but now we haven't supported it yet. We can have a deep discussion if you have some ideas on how to implement it :-)

[CindyXing]

@siddontang, sounds good. Sent email to your gmail account. We can start from there.

[Hoverbear]

Hi @CindyXing, @siddontang maybe this could be an RFC?

[only-cliches]

Perhaps an http client can be setup for this. You set an http endpoint in the TiKV config and each time a key is updated the http client sends a request to the configured endpoint.

Need this functionality for a project, wouldn’t mind putting a PR together if this sounds good...

[socketpair]

Please implement the watch functionality exactly as in etcd. First of all -- ability to watch since the specified revision. This thing guarantees we don't lose events on watcher reconnects. Also do not forget about compactions of db (i.e. removing of old/obsolete revisions).

[socketpair]

Having this in tidb (not only in tikv) would make it killer-feature. Now I know only the two DBs with the feature: etcd and Apple Foundation DB.

[jmjoy]

After added Watch and TTL feature, tikv can repace etcd. :sweat_smile:

[marcosflobo]

Has been this implemented already? Does TiKV support watch mechanism as etcd does? Thanks!