Uninstall canisters of empty users (#6018)

backend/canisters/user_index/CHANGELOG.md

@@ -6,6 +6,10 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 ## [unreleased]
 
+### Added
+
+- Uninstall canisters of empty users ([#6018](https://github.com/open-chat-labs/open-chat/pull/6018))
+
 ## [[2.0.1231](https://github.com/open-chat-labs/open-chat/releases/tag/v2.0.1231-user_index)] - 2024-07-08
 
 ### Fixed

backend/canisters/user_index/impl/src/lib.rs

@@ -231,6 +231,8 @@ impl RuntimeState {
             oc_public_key: self.data.oc_key_pair.public_key_pem().to_string(),
             empty_users: self.data.empty_users.iter().take(100).copied().collect(),
             empty_users_length: self.data.empty_users.len(),
+            deleted_users: self.data.deleted_users.iter().take(100).map(|u| u.user_id).collect(),
+            deleted_users_length: self.data.deleted_users.len(),
         }
     }
 }
@@ -490,6 +492,8 @@ pub struct Metrics {
     pub oc_public_key: String,
     pub empty_users: Vec<UserId>,
     pub empty_users_length: usize,
+    pub deleted_users: Vec<UserId>,
+    pub deleted_users_length: usize,
 }
 
 #[derive(Serialize, Debug)]

backend/canisters/user_index/impl/src/lifecycle/post_upgrade.rs

@@ -1,9 +1,10 @@
 use crate::lifecycle::{init_env, init_state};
 use crate::memory::get_upgrades_memory;
-use crate::Data;
+use crate::{mutate_state, Data};
 use canister_logger::LogEntry;
 use canister_tracing_macros::trace;
 use ic_cdk::post_upgrade;
+use local_user_index_canister::{DeleteUser, Event};
 use stable_memory::get_reader;
 use tracing::info;
 use user_index_canister::post_upgrade::Args;
@@ -25,16 +26,18 @@ fn post_upgrade(args: Args) {
 
     info!(version = %args.wasm_version, "Post-upgrade complete");
 
-    // Enable this code block once Users and LocalUserIndexes have been upgraded
-    // mutate_state(|state| {
-    //     for user_id in state.data.empty_users.iter().copied() {
-    //         state.push_event_to_local_user_index(
-    //             user_id,
-    //             Event::DeleteUser(DeleteUser {
-    //                 user_id,
-    //                 triggered_by_user: false,
-    //             }),
-    //         );
-    //     }
-    // })
+    mutate_state(|state| {
+        for user_id in std::mem::take(&mut state.data.empty_users) {
+            if let Some(canister_id) = state.data.local_index_map.get_index_canister(&user_id) {
+                state.data.user_index_event_sync_queue.push(
+                    canister_id,
+                    Event::DeleteUser(DeleteUser {
+                        user_id,
+                        triggered_by_user: false,
+                    }),
+                );
+            }
+        }
+        crate::jobs::sync_events_to_local_user_index_canisters::start_job_if_required(state);
+    })
 }

backend/canisters/user_index/impl/src/model/local_user_index_map.rs

@@ -44,6 +44,18 @@ impl LocalUserIndexMap {
         false
     }
 
+    pub fn remove_user(&mut self, user_id: &UserId) -> bool {
+        if let Some(index) = self.user_to_index.remove(user_id) {
+            self.index_map
+                .entry(index)
+                .and_modify(|i| i.user_count = i.user_count.saturating_sub(1));
+
+            true
+        } else {
+            false
+        }
+    }
+
     pub fn index_for_new_user(&self) -> Option<CanisterId> {
         self.index_map
             .iter()

backend/canisters/user_index/impl/src/updates/c2c_notify_events.rs

@@ -90,6 +90,8 @@ fn handle_event(event: Event, state: &mut RuntimeState) {
         Event::UserDeleted(ev) => {
             let now = state.env.now();
             state.data.users.delete_user(ev.user_id, now);
+            state.data.local_index_map.remove_user(&ev.user_id);
+            state.data.empty_users.remove(&ev.user_id);
             state.data.deleted_users.push(DeletedUser {
                 user_id: ev.user_id,
                 triggered_by_user: false,