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Implement cascade deregistering #27

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Nov 7, 2024
Merged

Implement cascade deregistering #27

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52 changes: 50 additions & 2 deletions src/admin/registry.rs
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Original file line number Diff line number Diff line change
@@ -1,12 +1,12 @@
use std::collections::hash_map::HashMap;
use std::sync::{Arc, Mutex};

use super::entry::RegistryEntry;
use super::entry::{Placement, RegistryEntry};
use crate::types::*;
use anyhow::{anyhow, bail};
use givc_common::query::{Event, QueryResult};
use tokio::sync::broadcast;
use tracing::{debug, info};
use tracing::{debug, error, info};

#[derive(Clone, Debug)]
pub struct Registry {
Expand Down Expand Up @@ -48,6 +48,22 @@ impl Registry {
let mut state = self.map.lock().unwrap();
match state.remove(name) {
Some(entry) => {
let cascade: Vec<String> = state
.values()
.filter_map(|re| match &re.placement {
Placement::Managed(within) if within == name => Some(re.name.clone()),
_ => None,
})
.collect();
for each in cascade {
match state.remove(&each) {
Some(entry1) => {
info!("Cascade deregistering {:#?}", entry1);
self.send_event(Event::UnitShutdown(entry1.into()))
}
None => error!("Problems due cascade deregistering {each} (via {name})"),
}
}
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Annoyingly there's a nightly feature providing .extract_if() that would provide exactly what we'd need here; I guess the closest would be to rebuild the hashmap:

                *state = state
                    .drain()
                    .filter_map(|(k, v)| {
                        if matches!(v.placement, Placement::Managed(ref within) if within == name) {
                            info!("Cascade deregistering {:#?}", v);
                            self.send_event(Event::UnitShutdown(v.into()));
                            None
                        } else {
                            Some((k, v))
                        }
                    })
                    .collect();

But I'm guessing the number of cascaded services should normally be rather small, so probably the current way is better. As a chaining over-user, I would write this as:

                for entry in state
                    .values()
                    .filter_map(|re| {
                        matches!(&re.placement, Placement::Managed(within) if within == name)
                            .then(|| re.name.clone())
                    })
                    .collect::<Vec<_>>()
                    .into_iter()
                    .filter_map(|re| state.remove(&re))
                {
                    info!("Cascade deregistering {entry:#?}");
                    self.send_event(Event::UnitShutdown(entry.into()))
                }

Third option; shortest, but involves cloning the whole entry:

                state.retain(|_, val| if matches!(&val.placement, Placement::Managed(within) if within == name) {
                    info!("Cascade deregistering {entry:#?}");
                    self.send_event(Event::UnitShutdown(val.clone().into()));
                    false
                } else {
                    true
                });

info!("Deregistering {:#?}", entry);
self.send_event(Event::UnitShutdown(entry.into()));
Ok(())
Expand Down Expand Up @@ -183,6 +199,38 @@ mod tests {
Ok(())
}

#[test]
fn test_cascade_deregister() -> anyhow::Result<()> {
let r = Registry::new();
let foo = RegistryEntry::dummy("foo".to_string());
let bar = RegistryEntry {
placement: Placement::Managed("foo".into()),
..RegistryEntry::dummy("bar".to_string())
};
let baz = RegistryEntry {
placement: Placement::Managed("foo".into()),
..RegistryEntry::dummy("baz".to_string())
};

r.register(foo);
r.register(bar);
r.register(baz);
assert!(r.contains("foo"));
assert!(r.contains("bar"));
assert!(r.contains("baz"));

r.deregister("baz");
assert!(r.contains("foo"));
assert!(r.contains("bar"));
assert!(!r.contains("baz"));

r.deregister("foo");
assert!(!r.contains("foo"));
assert!(!r.contains("bar"));

Ok(())
}

#[test]
fn test_unique_name() -> anyhow::Result<()> {
let r = Registry::new();
Expand Down