add node aliases

1 files changed, 78 insertions, 11 deletions

diff --git a/src/swarm/members.rs b/src/swarm/members.rs
index e64dd20..e02dba4 100644
--- a/src/swarm/members.rs
+++ b/src/swarm/members.rs
@@ -7,6 +7,12 @@
 //! while it is alive. An operator's forget (`DELETE /peers/{pk}`) removes the entry
 //! together with writing the forget record; a forgotten node that turns out to be alive
 //! cancels the record and registers again.
+//!
+//! Besides its tier, an entry holds the alias a node gives itself (`--alias`), a name
+//! for people reading /peers, metrics and logs. Not unique and never an identity: the
+//! public key stays that.
+
+use std::collections::HashMap;
 
 use automerge::AutoCommit;
 use serde_json::{Value as JsonValue, json};
@@ -69,27 +75,88 @@ pub(crate) fn set_tier(doc: &mut AutoCommit, pk: &str, tier: Tier) -> Result<(),
     store::write_path(doc, &tier_path(pk), &json!(tier.as_str()))
 }
 
-/// Registers this node if it is ready and its entry is missing.
+fn alias_path(pk: &str) -> Vec<String> {
+    let mut path = member_path(pk);
+    path.push("alias".to_owned());
+    path
+}
+
+/// `pk`'s alias, if it gave itself one.
+pub(crate) fn alias(doc: &AutoCommit, pk: &str) -> Option<String> {
+    match store::read_path(doc, &alias_path(pk)) {
+        Ok(Some(JsonValue::String(alias))) => Some(alias),
+        _ => None,
+    }
+}
+
+/// The aliases of all members that have one.
+pub(crate) fn aliases(doc: &AutoCommit) -> HashMap<String, String> {
+    members(doc)
+        .into_iter()
+        .filter_map(|pk| alias(doc, &pk).map(|alias| (pk, alias)))
+        .collect()
+}
+
+fn set_alias(doc: &mut AutoCommit, pk: &str, alias: Option<&str>) -> Result<(), StoreError> {
+    match alias {
+        Some(alias) => store::write_path(doc, &alias_path(pk), &json!(alias)),
+        None => match store::delete_path(doc, &alias_path(pk), false) {
+            Err(StoreError::NotFound) => Ok(()),
+            result => result,
+        },
+    }
+}
+
+/// Registers this node if it is ready and its entry is missing, and keeps its alias
+/// as configured (set, changed or removed after a restart with another `--alias`).
 pub(crate) async fn ensure_registered(state: &AppState) {
     if !state.is_ready().await {
         return;
     }
-    let own = member_path(state.local_id());
-    let registered = store::read_path(&state.doc.read().await.doc, &own)
-        .ok()
-        .flatten()
-        .is_some();
-    if registered {
+    let local = state.local_id().to_owned();
+    let own = member_path(&local);
+    let (registered, recorded_alias) = {
+        let replica = state.doc.read().await;
+        let registered = store::read_path(&replica.doc, &own)
+            .ok()
+            .flatten()
+            .is_some();
+        (registered, alias(&replica.doc, &local))
+    };
+    let wanted = state.alias.clone();
+
+    if !registered {
+        let mut entry = json!({ "since": unix_millis() });
+        if let Some(alias) = &wanted {
+            entry["alias"] = json!(alias);
+        }
+        match state
+            .mutate_doc(move |doc| store::write_path(doc, &own, &entry))
+            .await
+        {
+            Ok(()) => info!(
+                alias = wanted.as_deref(),
+                "Registered in the swarm's member list"
+            ),
+            Err(error) => warn!(error = %error, "Failed to register in the member list"),
+        }
         return;
     }
 
-    let entry = json!({ "since": unix_millis() });
+    if recorded_alias == wanted {
+        return;
+    }
+    let alias = wanted.clone();
     match state
-        .mutate_doc(move |doc| store::write_path(doc, &own, &entry))
+        .mutate_doc(move |doc| set_alias(doc, &local, alias.as_deref()))
         .await
     {
-        Ok(()) => info!("Registered in the swarm's member list"),
-        Err(error) => warn!(error = %error, "Failed to register in the member list"),
+        Ok(()) => info!(
+            alias = wanted.as_deref(),
+            previous = recorded_alias.as_deref(),
+            "Alias updated in the member list"
+        ),
+        Err(error) => warn!(error = %error, "Failed to record our alias"),
     }
 }