How to get the relationship between the watcher and watcher_id for one key multi watcher.

[Zonglei Dong]

//! Watch example

use etcd_client::*;

#[tokio::main]
async fn main() -> Result<(), Error> {
    let mut client = Client::connect(["localhost:2379"], None).await?;
    let (mut watcher, mut stream) = client.watch("foo", None).await?;

    watcher.watch("foo", None).await?;
    watcher.watch("foo", None).await?;

    while let Some(resp) = stream.message().await? {
        println!("[{}] receive watch response", resp.watch_id());
        for event in resp.events() {
            println!("event type: {:?}", event.event_type());
            if let Some(kv) = event.kv() {
               println!("kv: {{{}: {}}}", kv.key_str()?, kv.value_str()?);
            }
            if EventType::Delete == event.event_type() {
                watcher.cancel_by_id(resp.watch_id()).await?;
            }
        }
        println!();
    }

    Ok(())
}

I want to register multi watcher for one key at different scenes, so I want to get the watcher_id fro every watcher registered and build the relationship between the scenes and watcher_id, because I need cancel the watcher according to the scenes.

According to the example code, I only get the watcher_id from the stream.message().

So how to get the relationship between the watcher and watcher_id for one key multi watcher?

[David Li]

You can use WatchOptions::with_watch_id to specify watch_id by yourself.

[Zonglei Dong]

You can use WatchOptions::with_watch_id to specify watch_id by yourself.

Hi @davidli2010 Thanks for your reply. I found the with_watch_id method and try to use it.

But I found if use this method, I must guarantee to be globally unique for watch_id myself. if not, maybe conflict.

If the distributed system, I should depend on third-party libraries.

Is there a better way to guarantee global uniqueness for watch_id? Thanks.

[David Li]

Perhaps a node ID plus a monotonically increasing sequence within a node would do the trick.