use peer center instance to gatter peers info (#21)

* use peer center instance to gatter peers info

easytier-cli/src/main.rs

@@ -5,7 +5,8 @@ use easytier_core::{
     common::stun::{StunInfoCollector, UdpNatTypeDetector},
     rpc::{
         connector_manage_rpc_client::ConnectorManageRpcClient,
-        peer_manage_rpc_client::PeerManageRpcClient, *,
+        peer_center_rpc_client::PeerCenterRpcClient, peer_manage_rpc_client::PeerManageRpcClient,
+        *,
     },
 };
 use humansize::format_size;
@@ -30,6 +31,7 @@ enum SubCommand {
     Connector(ConnectorArgs),
     Stun,
     Route,
+    PeerCenter,
 }
 
 #[derive(Args, Debug)]
@@ -202,6 +204,12 @@ impl CommandHandler {
         Ok(ConnectorManageRpcClient::connect(self.addr.clone()).await?)
     }
 
+    async fn get_peer_center_client(
+        &self,
+    ) -> Result<PeerCenterRpcClient<tonic::transport::Channel>, Error> {
+        Ok(PeerCenterRpcClient::connect(self.addr.clone()).await?)
+    }
+
     async fn list_peers(&self) -> Result<ListPeerResponse, Error> {
         let mut client = self.get_peer_manager_client().await?;
         let request = tonic::Request::new(ListPeerRequest::default());
@@ -424,6 +432,46 @@ async fn main() -> Result<(), Error> {
             let stun = UdpNatTypeDetector::new(StunInfoCollector::get_default_servers());
             println!("udp type: {:?}", stun.get_udp_nat_type(0).await);
         }
+        SubCommand::PeerCenter => {
+            let mut peer_center_client = handler.get_peer_center_client().await?;
+            let resp = peer_center_client
+                .get_global_peer_map(GetGlobalPeerMapRequest::default())
+                .await?
+                .into_inner();
+
+            #[derive(tabled::Tabled)]
+            struct PeerCenterTableItem {
+                node_id: String,
+                direct_peers: String,
+            }
+
+            let mut table_rows = vec![];
+            for (k, v) in resp.global_peer_map.iter() {
+                let node_id = k;
+                let direct_peers = v
+                    .direct_peers
+                    .iter()
+                    .map(|(k, v)| {
+                        format!(
+                            "{}:{:?}",
+                            k,
+                            LatencyLevel::try_from(v.latency_level).unwrap()
+                        )
+                    })
+                    .collect::<Vec<_>>();
+                table_rows.push(PeerCenterTableItem {
+                    node_id: node_id.clone(),
+                    direct_peers: direct_peers.join("\n"),
+                });
+            }
+
+            println!(
+                "{}",
+                tabled::Table::new(table_rows)
+                    .with(Style::modern())
+                    .to_string()
+            );
+        }
     }
 
     Ok(())

easytier-core/build.rs

@@ -92,6 +92,9 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
 
     tonic_build::configure()
         .type_attribute(".", "#[derive(serde::Serialize, serde::Deserialize)]")
+        .type_attribute("cli.DirectConnectedPeerInfo", "#[derive(Hash)]")
+        .type_attribute("cli.PeerInfoForGlobalMap", "#[derive(Hash)]")
+        .btree_map(&["."])
         .compile(&["proto/cli.proto"], &["proto/"])
         .unwrap();
     // tonic_build::compile_protos("proto/cli.proto")?;

easytier-core/proto/cli.proto

@@ -115,3 +115,29 @@ service ConnectorManageRpc {
     rpc ListConnector (ListConnectorRequest) returns (ListConnectorResponse);
     rpc ManageConnector (ManageConnectorRequest) returns (ManageConnectorResponse);
 }
+
+enum LatencyLevel {
+    VeryLow = 0;
+    Low = 1;
+    Normal = 2;
+    High = 3;
+    VeryHigh = 4;
+}
+
+message DirectConnectedPeerInfo {
+    LatencyLevel latency_level = 2;
+}
+
+message PeerInfoForGlobalMap {
+    map<string, DirectConnectedPeerInfo> direct_peers = 1;
+}
+
+message GetGlobalPeerMapRequest {}
+
+message GetGlobalPeerMapResponse {
+    map<string, PeerInfoForGlobalMap> global_peer_map = 1;
+}
+
+service PeerCenterRpc {
+    rpc GetGlobalPeerMap (GetGlobalPeerMapRequest) returns (GetGlobalPeerMapResponse);
+}

easytier-core/src/instance/instance.rs

@@ -20,6 +20,7 @@ use crate::connector::manual::{ConnectorManagerRpcService, ManualConnectorManage
 use crate::connector::udp_hole_punch::UdpHolePunchConnector;
 use crate::gateway::icmp_proxy::IcmpProxy;
 use crate::gateway::tcp_proxy::TcpProxy;
+use crate::peer_center::instance::PeerCenterInstance;
 use crate::peers::peer_manager::PeerManager;
 use crate::peers::rpc_service::PeerManagerRpcService;
 use crate::tunnels::SinkItem;
@@ -85,6 +86,8 @@ pub struct Instance {
     tcp_proxy: Arc<TcpProxy>,
     icmp_proxy: Arc<IcmpProxy>,
 
+    peer_center: Arc<PeerCenterInstance>,
+
     global_ctx: ArcGlobalCtx,
 }
 
@@ -141,6 +144,8 @@ impl Instance {
         let arc_tcp_proxy = TcpProxy::new(global_ctx.clone(), peer_manager.clone());
         let arc_icmp_proxy = IcmpProxy::new(global_ctx.clone(), peer_manager.clone()).unwrap();
 
+        let peer_center = Arc::new(PeerCenterInstance::new(peer_manager.clone()));
+
         Instance {
             inst_name: inst_name.to_string(),
             id,
@@ -158,6 +163,8 @@ impl Instance {
             tcp_proxy: arc_tcp_proxy,
             icmp_proxy: arc_icmp_proxy,
 
+            peer_center,
+
             global_ctx,
         }
     }
@@ -281,6 +288,8 @@ impl Instance {
 
         self.udp_hole_puncher.lock().await.run().await?;
 
+        self.peer_center.init().await;
+
         Ok(())
     }
 
@@ -312,6 +321,7 @@ impl Instance {
         let peer_mgr = self.peer_manager.clone();
         let conn_manager = self.conn_manager.clone();
         let net_ns = self.global_ctx.net_ns.clone();
+        let peer_center = self.peer_center.clone();
 
         self.tasks.spawn(async move {
             let _g = net_ns.guard();
@@ -327,6 +337,11 @@ impl Instance {
                         ConnectorManagerRpcService(conn_manager.clone()),
                     ),
                 )
+                .add_service(
+                    crate::rpc::peer_center_rpc_server::PeerCenterRpcServer::new(
+                        peer_center.get_rpc_service(),
+                    ),
+                )
                 .serve(addr)
                 .await
                 .unwrap();

easytier-core/src/peer_center/instance.rs

@@ -9,20 +9,27 @@ use std::{
 };
 
 use futures::Future;
-use tokio::{sync::Mutex, task::JoinSet};
+use tokio::{
+    sync::{Mutex, RwLock},
+    task::JoinSet,
+};
 use tracing::Instrument;
 
-use crate::peers::{peer_manager::PeerManager, rpc_service::PeerManagerRpcService, PeerId};
+use crate::{
+    peers::{peer_manager::PeerManager, rpc_service::PeerManagerRpcService, PeerId},
+    rpc::{GetGlobalPeerMapRequest, GetGlobalPeerMapResponse},
+};
 
 use super::{
     server::PeerCenterServer,
-    service::{PeerCenterService, PeerCenterServiceClient, PeerInfoForGlobalMap},
+    service::{GlobalPeerMap, PeerCenterService, PeerCenterServiceClient, PeerInfoForGlobalMap},
     Digest, Error,
 };
 
-pub struct PeerCenterClient {
+struct PeerCenterBase {
     peer_mgr: Arc<PeerManager>,
     tasks: Arc<Mutex<JoinSet<()>>>,
+    lock: Arc<Mutex<()>>,
 }
 
 static SERVICE_ID: u32 = 5;
@@ -32,7 +39,7 @@ struct PeridicJobCtx<T> {
     job_ctx: T,
 }
 
-impl PeerCenterClient {
+impl PeerCenterBase {
     pub async fn init(&self) -> Result<(), Error> {
         self.peer_mgr.get_peer_rpc_mgr().run_service(
             SERVICE_ID,
@@ -67,21 +74,22 @@ impl PeerCenterClient {
     ) -> () {
         let my_node_id = self.peer_mgr.my_node_id();
         let peer_mgr = self.peer_mgr.clone();
+        let lock = self.lock.clone();
         self.tasks.lock().await.spawn(
             async move {
                 let ctx = Arc::new(PeridicJobCtx {
                     peer_mgr: peer_mgr.clone(),
                     job_ctx,
                 });
-                tracing::warn!(?my_node_id, "before periodic job loop");
                 loop {
                     let Some(center_peer) = Self::select_center_peer(&peer_mgr).await else {
                         tracing::warn!("no center peer found, sleep 1 second");
                         tokio::time::sleep(Duration::from_secs(1)).await;
                         continue;
                     };
-                    tracing::warn!(?center_peer, "run periodic job");
+                    tracing::info!(?center_peer, "run periodic job");
                     let rpc_mgr = peer_mgr.get_peer_rpc_mgr();
+                    let _g = lock.lock().await;
                     let ret = rpc_mgr
                         .do_client_rpc_scoped(SERVICE_ID, center_peer, |c| async {
                             let client =
@@ -90,6 +98,7 @@ impl PeerCenterClient {
                             job_fn(client, ctx.clone()).await
                         })
                         .await;
+                    drop(_g);
 
                     let Ok(sleep_time_ms) = ret else {
                         tracing::error!("periodic job to center server rpc failed: {:?}", ret);
@@ -106,35 +115,85 @@ impl PeerCenterClient {
         );
     }
 
-    pub async fn new(peer_mgr: Arc<PeerManager>) -> Self {
+    pub fn new(peer_mgr: Arc<PeerManager>) -> Self {
-        PeerCenterClient {
+        PeerCenterBase {
             peer_mgr,
             tasks: Arc::new(Mutex::new(JoinSet::new())),
+            lock: Arc::new(Mutex::new(())),
         }
     }
 }
 
-struct PeerCenterInstance {
+pub struct PeerCenterInstanceService {
+    global_peer_map: Arc<RwLock<GlobalPeerMap>>,
+    global_peer_map_digest: Arc<RwLock<Digest>>,
+}
+
+#[tonic::async_trait]
+impl crate::rpc::cli::peer_center_rpc_server::PeerCenterRpc for PeerCenterInstanceService {
+    async fn get_global_peer_map(
+        &self,
+        _request: tonic::Request<GetGlobalPeerMapRequest>,
+    ) -> Result<tonic::Response<GetGlobalPeerMapResponse>, tonic::Status> {
+        let global_peer_map = self.global_peer_map.read().await.clone();
+        Ok(tonic::Response::new(GetGlobalPeerMapResponse {
+            global_peer_map: global_peer_map
+                .map
+                .into_iter()
+                .map(|(k, v)| (k.to_string(), v))
+                .collect(),
+        }))
+    }
+}
+
+pub struct PeerCenterInstance {
     peer_mgr: Arc<PeerManager>,
-    client: Arc<PeerCenterClient>,
+
+    client: Arc<PeerCenterBase>,
+    global_peer_map: Arc<RwLock<GlobalPeerMap>>,
+    global_peer_map_digest: Arc<RwLock<Digest>>,
 }
 
 impl PeerCenterInstance {
-    pub async fn new(peer_mgr: Arc<PeerManager>) -> Self {
+    pub fn new(peer_mgr: Arc<PeerManager>) -> Self {
-        let client = Arc::new(PeerCenterClient::new(peer_mgr.clone()).await);
+        PeerCenterInstance {
-        client.init().await.unwrap();
+            peer_mgr: peer_mgr.clone(),
+            client: Arc::new(PeerCenterBase::new(peer_mgr.clone())),
+            global_peer_map: Arc::new(RwLock::new(GlobalPeerMap::new())),
+            global_peer_map_digest: Arc::new(RwLock::new(Digest::default())),
+        }
+    }
 
-        PeerCenterInstance { peer_mgr, client }
+    pub async fn init(&self) {
+        self.client.init().await.unwrap();
+        self.init_get_global_info_job().await;
+        self.init_report_peers_job().await;
     }
 
     async fn init_get_global_info_job(&self) {
+        struct Ctx {
+            global_peer_map: Arc<RwLock<GlobalPeerMap>>,
+            global_peer_map_digest: Arc<RwLock<Digest>>,
+        }
+
+        let ctx = Arc::new(Ctx {
+            global_peer_map: self.global_peer_map.clone(),
+            global_peer_map_digest: self.global_peer_map_digest.clone(),
+        });
+
         self.client
-            .init_periodic_job({}, |client, _ctx| async move {
+            .init_periodic_job(ctx, |client, ctx| async move {
+                let mut rpc_ctx = tarpc::context::current();
+                rpc_ctx.deadline = SystemTime::now() + Duration::from_secs(3);
+
                 let ret = client
-                    .get_global_peer_map(tarpc::context::current(), 0)
+                    .get_global_peer_map(
+                        rpc_ctx,
+                        ctx.job_ctx.global_peer_map_digest.read().await.clone(),
+                    )
                     .await?;
 
-                let Ok(global_peer_map) = ret else {
+                let Ok(resp) = ret else {
                     tracing::error!(
                         "get global info from center server got error result: {:?}",
                         ret
@@ -142,7 +201,18 @@ impl PeerCenterInstance {
                     return Ok(1000);
                 };
 
-                tracing::warn!("get global info from center server: {:?}", global_peer_map);
+                let Some(resp) = resp else {
+                    return Ok(1000);
+                };
+
+                tracing::info!(
+                    "get global info from center server: {:?}, digest: {:?}",
+                    resp.global_peer_map,
+                    resp.digest
+                );
+
+                *ctx.job_ctx.global_peer_map.write().await = resp.global_peer_map;
+                *ctx.job_ctx.global_peer_map_digest.write().await = resp.digest;
 
                 Ok(5000)
             })
@@ -196,10 +266,19 @@ impl PeerCenterInstance {
             })
             .await;
     }
+
+    pub fn get_rpc_service(&self) -> PeerCenterInstanceService {
+        PeerCenterInstanceService {
+            global_peer_map: self.global_peer_map.clone(),
+            global_peer_map_digest: self.global_peer_map_digest.clone(),
+        }
+    }
 }
 
 #[cfg(test)]
 mod tests {
+    use std::ops::Deref;
+
     use crate::{
         peer_center::server::get_global_data,
         peers::tests::{connect_peer_manager, create_mock_peer_manager, wait_route_appear},
@@ -213,13 +292,14 @@ mod tests {
         let peer_mgr_b = create_mock_peer_manager().await;
         let peer_mgr_c = create_mock_peer_manager().await;
 
-        let peer_center_a = PeerCenterInstance::new(peer_mgr_a.clone()).await;
+        let peer_center_a = PeerCenterInstance::new(peer_mgr_a.clone());
-        let peer_center_b = PeerCenterInstance::new(peer_mgr_b.clone()).await;
+        let peer_center_b = PeerCenterInstance::new(peer_mgr_b.clone());
-        let peer_center_c = PeerCenterInstance::new(peer_mgr_c.clone()).await;
+        let peer_center_c = PeerCenterInstance::new(peer_mgr_c.clone());
 
-        peer_center_a.init_report_peers_job().await;
+        let peer_centers = vec![&peer_center_a, &peer_center_b, &peer_center_c];
-        peer_center_b.init_report_peers_job().await;
+        for pc in peer_centers.iter() {
-        peer_center_c.init_report_peers_job().await;
+            pc.init().await;
+        }
 
         connect_peer_manager(peer_mgr_a.clone(), peer_mgr_b.clone()).await;
         connect_peer_manager(peer_mgr_b.clone(), peer_mgr_c.clone()).await;
@@ -228,7 +308,7 @@ mod tests {
             .await
             .unwrap();
 
-        let center_peer = PeerCenterClient::select_center_peer(&peer_mgr_a)
+        let center_peer = PeerCenterBase::select_center_peer(&peer_mgr_a)
             .await
             .unwrap();
         let center_data = get_global_data(center_peer);
@@ -248,5 +328,29 @@ mod tests {
             }
             tokio::time::sleep(Duration::from_millis(100)).await;
         }
+
+        let mut digest = None;
+        for pc in peer_centers.iter() {
+            let rpc_service = pc.get_rpc_service();
+            let now = std::time::Instant::now();
+            while now.elapsed().as_secs() < 10 {
+                if rpc_service.global_peer_map.read().await.map.len() == 3 {
+                    break;
+                }
+                tokio::time::sleep(Duration::from_millis(100)).await;
+            }
+            assert_eq!(rpc_service.global_peer_map.read().await.map.len(), 3);
+            println!("rpc service ready, {:#?}", rpc_service.global_peer_map);
+
+            if digest.is_none() {
+                digest = Some(rpc_service.global_peer_map_digest.read().await.clone());
+            } else {
+                let v = rpc_service.global_peer_map_digest.read().await;
+                assert_eq!(digest.as_ref().unwrap(), v.deref());
+            }
+        }
+
+        let global_digest = get_global_data(center_peer).read().await.digest.clone();
+        assert_eq!(digest.as_ref().unwrap(), &global_digest);
     }
 }

easytier-core/src/peer_center/mod.rs

@@ -5,7 +5,7 @@
 // peer center is not guaranteed to be stable and can be changed when peer enter or leave.
 // it's used to reduce the cost to exchange infos between peers.
 
-mod instance;
+pub mod instance;
 mod server;
 mod service;
 

easytier-core/src/peer_center/server.rs

@@ -5,12 +5,12 @@ use std::{
 
 use dashmap::DashMap;
 use once_cell::sync::Lazy;
-use tokio::sync::RwLock;
+use tokio::{sync::RwLock, task::JoinSet};
 
 use crate::peers::PeerId;
 
 use super::{
-    service::{GlobalPeerMap, PeerCenterService, PeerInfoForGlobalMap},
+    service::{GetGlobalPeerMapResponse, GlobalPeerMap, PeerCenterService, PeerInfoForGlobalMap},
     Digest, Error,
 };
 
@@ -18,6 +18,7 @@ pub(crate) struct PeerCenterServerGlobalData {
     pub global_peer_map: GlobalPeerMap,
     pub digest: Digest,
     pub update_time: std::time::Instant,
+    pub peer_update_time: DashMap<PeerId, std::time::Instant>,
 }
 
 impl PeerCenterServerGlobalData {
@@ -26,6 +27,7 @@ impl PeerCenterServerGlobalData {
             global_peer_map: GlobalPeerMap::new(),
             digest: Digest::default(),
             update_time: std::time::Instant::now(),
+            peer_update_time: DashMap::new(),
         }
     }
 }
@@ -47,13 +49,41 @@ pub struct PeerCenterServer {
     // every peer has its own server, so use per-struct dash map is ok.
     my_node_id: PeerId,
     digest_map: DashMap<PeerId, Digest>,
+
+    tasks: Arc<JoinSet<()>>,
 }
 
 impl PeerCenterServer {
     pub fn new(my_node_id: PeerId) -> Self {
+        let mut tasks = JoinSet::new();
+        tasks.spawn(async move {
+            loop {
+                tokio::time::sleep(std::time::Duration::from_secs(10)).await;
+                PeerCenterServer::clean_outdated_peer(my_node_id).await;
+            }
+        });
+
         PeerCenterServer {
             my_node_id,
             digest_map: DashMap::new(),
+
+            tasks: Arc::new(tasks),
+        }
+    }
+
+    async fn clean_outdated_peer(my_node_id: PeerId) {
+        let data = get_global_data(my_node_id);
+        let mut locked_data = data.write().await;
+        let now = std::time::Instant::now();
+        let mut to_remove = Vec::new();
+        for kv in locked_data.peer_update_time.iter() {
+            if now.duration_since(*kv.value()).as_secs() > 10 {
+                to_remove.push(*kv.key());
+            }
+        }
+        for peer_id in to_remove {
+            locked_data.global_peer_map.map.remove(&peer_id);
+            locked_data.peer_update_time.remove(&peer_id);
         }
     }
 }
@@ -70,6 +100,12 @@ impl PeerCenterService for PeerCenterServer {
     ) -> Result<(), Error> {
         tracing::warn!("receive report_peers");
 
+        let data = get_global_data(self.my_node_id);
+        let mut locked_data = data.write().await;
+        locked_data
+            .peer_update_time
+            .insert(my_peer_id, std::time::Instant::now());
+
         let old_digest = self.digest_map.get(&my_peer_id);
         // if digest match, no need to update
         if let Some(old_digest) = old_digest {
@@ -83,8 +119,6 @@ impl PeerCenterService for PeerCenterServer {
         }
 
         self.digest_map.insert(my_peer_id, digest);
-        let data = get_global_data(self.my_node_id);
-        let mut locked_data = data.write().await;
         locked_data
             .global_peer_map
             .map
@@ -93,6 +127,7 @@ impl PeerCenterService for PeerCenterServer {
         let mut hasher = std::collections::hash_map::DefaultHasher::new();
         locked_data.global_peer_map.map.hash(&mut hasher);
         locked_data.digest = hasher.finish() as Digest;
+        locked_data.update_time = std::time::Instant::now();
 
         Ok(())
     }
@@ -101,7 +136,7 @@ impl PeerCenterService for PeerCenterServer {
         self,
         _: tarpc::context::Context,
         digest: Digest,
-    ) -> Result<Option<GlobalPeerMap>, Error> {
+    ) -> Result<Option<GetGlobalPeerMapResponse>, Error> {
         let data = get_global_data(self.my_node_id);
         if digest == data.read().await.digest {
             return Ok(None);
@@ -109,6 +144,9 @@ impl PeerCenterService for PeerCenterServer {
 
         let data = get_global_data(self.my_node_id);
         let locked_data = data.read().await;
-        Ok(Some(locked_data.global_peer_map.clone()))
+        Ok(Some(GetGlobalPeerMapResponse {
+            global_peer_map: locked_data.global_peer_map.clone(),
+            digest: locked_data.digest,
+        }))
     }
 }

easytier-core/src/peer_center/service.rs

@@ -1,18 +1,11 @@
 use std::collections::BTreeMap;
 
-use crate::peers::PeerId;
+use crate::{peers::PeerId, rpc::DirectConnectedPeerInfo};
 
 use super::{Digest, Error};
 use crate::rpc::PeerInfo;
 
-#[derive(Debug, Clone, Hash, serde::Deserialize, serde::Serialize)]
+pub type LatencyLevel = crate::rpc::cli::LatencyLevel;
-pub enum LatencyLevel {
-    VeryLow,
-    Low,
-    Normal,
-    High,
-    VeryHigh,
-}
 
 impl LatencyLevel {
     pub const fn from_latency_ms(lat_ms: u32) -> Self {
@@ -30,33 +23,25 @@ impl LatencyLevel {
     }
 }
 
-#[derive(Debug, Clone, Hash, serde::Deserialize, serde::Serialize)]
+pub type PeerInfoForGlobalMap = crate::rpc::cli::PeerInfoForGlobalMap;
-pub struct PeerConnInfoForGlobalMap {
-    to_peer_id: PeerId,
-    latency_level: LatencyLevel,
-}
-
-#[derive(Debug, Clone, Hash, serde::Deserialize, serde::Serialize)]
-pub struct PeerInfoForGlobalMap {
-    pub direct_peers: BTreeMap<PeerId, Vec<PeerConnInfoForGlobalMap>>,
-}
 
 impl From<Vec<PeerInfo>> for PeerInfoForGlobalMap {
     fn from(peers: Vec<PeerInfo>) -> Self {
         let mut peer_map = BTreeMap::new();
         for peer in peers {
-            let mut conn_info = Vec::new();
+            let min_lat = peer
-            for conn in peer.conns {
+                .conns
-                conn_info.push(PeerConnInfoForGlobalMap {
+                .iter()
-                    to_peer_id: conn.peer_id.parse().unwrap(),
+                .map(|conn| conn.stats.as_ref().unwrap().latency_us)
-                    latency_level: LatencyLevel::from_latency_ms(
+                .min()
-                        conn.stats.unwrap().latency_us as u32 / 1000,
+                .unwrap_or(0);
-                    ),
+
-                });
+            let dp_info = DirectConnectedPeerInfo {
-            }
+                latency_level: LatencyLevel::from_latency_ms(min_lat as u32 / 1000) as i32,
+            };
+
             // sort conn info so hash result is stable
-            conn_info.sort_by(|a, b| a.to_peer_id.cmp(&b.to_peer_id));
+            peer_map.insert(peer.peer_id, dp_info);
-            peer_map.insert(peer.peer_id.parse().unwrap(), conn_info);
         }
         PeerInfoForGlobalMap {
             direct_peers: peer_map,
@@ -78,6 +63,12 @@ impl GlobalPeerMap {
     }
 }
 
+#[derive(Debug, Clone, serde::Deserialize, serde::Serialize)]
+pub struct GetGlobalPeerMapResponse {
+    pub global_peer_map: GlobalPeerMap,
+    pub digest: Digest,
+}
+
 #[tarpc::service]
 pub trait PeerCenterService {
     // report center server which peer is directly connected to me
@@ -88,5 +79,6 @@ pub trait PeerCenterService {
         digest: Digest,
     ) -> Result<(), Error>;
 
-    async fn get_global_peer_map(digest: Digest) -> Result<Option<GlobalPeerMap>, Error>;
+    async fn get_global_peer_map(digest: Digest)
+        -> Result<Option<GetGlobalPeerMapResponse>, Error>;
 }