add state file

This allows storing the swarm ID and additionally discovered seeds,
which prevents a formerly genesis node to start a new document.

1 files changed, 18 insertions, 2 deletions

diff --git a/src/swarm/bootstrap.rs b/src/swarm/bootstrap.rs
index 1ae5173..84ff156 100644
--- a/src/swarm/bootstrap.rs
+++ b/src/swarm/bootstrap.rs
@@ -31,8 +31,22 @@ const RESOLVE_RETRY_MAX: Duration = Duration::from_secs(300);
 
 pub(crate) async fn bootstrap(state: &AppState, seeds: &[String], genesis: bool) -> Result<()> {
     if genesis {
-        let swarm_id = Uuid::new_v4().to_string();
-        info!(swarm_id = %swarm_id, "Starting a new swarm as its genesis node (--genesis)");
+        // A remembered swarm starts again under its ID: nodes of it still running then
+        // merge with this one instead of ending up in another swarm.
+        let swarm_id = match state.swarm_id().await {
+            Some(remembered) => {
+                warn!(
+                    swarm_id = %remembered,
+                    "--genesis with a remembered swarm: starting it again, empty; nodes of it still running merge with this one"
+                );
+                remembered
+            }
+            None => {
+                let swarm_id = Uuid::new_v4().to_string();
+                info!(swarm_id = %swarm_id, "Starting a new swarm as its genesis node (--genesis)");
+                swarm_id
+            }
+        };
         let recorded = JsonValue::String(swarm_id.clone());
         state
             .mutate_doc(move |doc| store::write_path(doc, &swarm_id_path(), &recorded))
@@ -40,6 +54,8 @@ pub(crate) async fn bootstrap(state: &AppState, seeds: &[String], genesis: bool)
             .context("Recording the swarm ID")?;
         state.initial_sync_done.store(true, Ordering::Release);
         state.mark_ready(swarm_id).await?;
+        // Remembered members, if any, to find those still running.
+        resolve_seeds(state, &mut seeds.to_vec()).await;
         return Ok(());
     }