auto peer discovery: gossip known peers during sync, discover from_hash automatically

tests/test_sync.py

@@ -334,6 +334,50 @@ def test_sync_updated_content():
         shutil.rmtree(dir_b)
 
 
+def test_sync_peer_discovery():
+    """Peers should discover each other through sync gossip."""
+    dir_a = tempfile.mkdtemp()
+    dir_b = tempfile.mkdtemp()
+    dir_c = tempfile.mkdtemp()
+    try:
+        db_a, ha = make_handler(dir_a)
+        db_b, hb = make_handler(dir_b)
+        db_c, hc = make_handler(dir_c)
+
+        now = "2026-06-05T12:00:00"
+        db_a.create_thread("t1", "From A", "", "", "", "aaa", "", now)
+        db_b.create_thread("t2", "From B", "", "", "", "bbb", "", now)
+        db_c.create_thread("t3", "From C", "", "", "", "ccc", "", now)
+
+        # Seed: A knows B, B knows C
+        db_a.add_known_peer("bbb")
+        db_b.add_known_peer("ccc")
+        # C doesn't know anyone yet
+
+        # B syncs with C — B sends its known peers (ccc's hash not in B's known peers since B is talking to C)
+        # Actually, B knows C (bbb -> ccc), so when B sends sync request to C,
+        # B includes known_peers. C learns about B.
+        hc.handle_sync_request({
+            "query": {},
+            "threads": [dict(db_b.get_thread("t2"))],
+            "posts": [], "upvotes": [],
+            "from_hash": "bbb",
+            "blocks": {"mine": [], "peers": []},
+            "retractions": [],
+            "known_peers": ["aaa"],  # B tells C about A
+        })
+
+        # C should now know about B (from auto-discovery of from_hash) and A (from known_peers)
+        known = [r["instance_hash"] for r in db_c.get_synced_instances()]
+        assert "bbb" in known, "C should auto-discover B from from_hash"
+        assert "aaa" in known, "C should discover A from known_peers gossip"
+    finally:
+        import shutil
+        shutil.rmtree(dir_a)
+        shutil.rmtree(dir_b)
+        shutil.rmtree(dir_c)
+
+
 if __name__ == "__main__":
     test_sync_thread()
     test_sync_reply()
@@ -343,4 +387,5 @@ if __name__ == "__main__":
     test_sync_bidirectional()
     test_sync_block_gossip()
     test_sync_updated_content()
+    test_sync_peer_discovery()
     print("all sync tests passed")

tinyweb_forum/db.py

@@ -246,6 +246,28 @@ class ForumDB:
         finally:
             self.return_db(db)
 
+    def add_known_peer(self, instance_hash):
+        """Add a discovered peer to the sync list (auto-discovery)."""
+        db = self.get_db()
+        try:
+            db.execute(
+                "INSERT OR IGNORE INTO synced_instances (instance_hash) VALUES (?)",
+                (instance_hash,),
+            )
+            db.commit()
+        finally:
+            self.return_db(db)
+
+    def get_all_known_hashes(self):
+        """Get all known instance hashes for peer discovery gossip."""
+        db = self.get_db()
+        try:
+            return [r["instance_hash"] for r in db.execute(
+                "SELECT instance_hash FROM synced_instances"
+            ).fetchall()]
+        finally:
+            self.return_db(db)
+
     def upsert_synced_instance(self, instance_hash, name=""):
         db = self.get_db()
         try:

tinyweb_forum/handlers.py

@@ -604,6 +604,14 @@ class ForumHandlers:
             if r.get("id") and r.get("type") and r.get("author") and r.get("at"):
                 self.fdb.merge_retraction(r["id"], r["type"], r["author"], r["at"])
 
+        # Auto-discover the peer that synced with us and their known peers
+        from_hash = data.get("from_hash", "")
+        if from_hash and from_hash not in blocked:
+            self.fdb.add_known_peer(from_hash)
+        for peer_hash in data.get("known_peers", []):
+            if peer_hash and peer_hash != from_hash and peer_hash not in blocked:
+                self.fdb.add_known_peer(peer_hash)
+
         my_blocks = list(blocked)
         my_peer_blocks = self.fdb.get_peer_block_list()
         threads, posts, upvote_threads = [], [], []
@@ -616,6 +624,8 @@ class ForumHandlers:
         retracted = [{"id": cid, "type": ct, "author": ai, "at": ra}
                      for cid, ct, ai, ra in self.fdb.get_raw_retractions()]
 
+        known_peers = [h for h in self.fdb.get_all_known_hashes() if h != from_hash]
+
         return {
             "status": 200,
             "content_type": "application/json",
@@ -625,6 +635,7 @@ class ForumHandlers:
                 "upvote_threads": upvote_threads,
                 "blocks": {"mine": my_blocks, "peers": my_peer_blocks},
                 "retractions": retracted,
+                "known_peers": known_peers,
             }),
             "headers": {},
         }

tinyweb_forum/sync.py

@@ -116,14 +116,18 @@ class ForumSync:
             retracted = [{"id": cid, "type": ct, "author": ai, "at": ra}
                          for cid, ct, ai, ra in self.fdb.get_raw_retractions()]
 
+            my_hash = self.identity.hash.hex() if self.identity else "local"
+            known_peers = [h for h in self.fdb.get_all_known_hashes() if h != instance_hash and h != my_hash]
+
             request_data = {
                 "query": {"since": [since]} if since else {},
                 "threads": threads,
                 "posts": posts,
                 "upvotes": upvotes,
-                "from_hash": self.identity.hash.hex() if self.identity else "local",
+                "from_hash": my_hash,
                 "blocks": {"mine": my_blocks, "peers": my_peer_blocks},
                 "retractions": retracted,
+                "known_peers": known_peers,
             }
 
             receipt = link.request("/forum", data=request_data, timeout=REQUEST_TIMEOUT)
@@ -162,6 +166,10 @@ class ForumSync:
                     for r in data.get("retractions", []):
                         if r.get("id") and r.get("type") and r.get("author") and r.get("at"):
                             self.fdb.merge_retraction(r["id"], r["type"], r["author"], r["at"])
+                    # Discover new peers from gossip
+                    for peer_hash in data.get("known_peers", []):
+                        if peer_hash and peer_hash != my_hash and peer_hash != instance_hash:
+                            self.fdb.add_known_peer(peer_hash)
                 now = time.strftime("%Y-%m-%dT%H:%M:%S")
                 self.fdb.set_last_sync(instance_hash, now)
             else: