Move PageserverFeedback to utils.

It allows to replace u64 with proper Lsn and pretty print PageserverFeedback
with serde(_json). Now walsenders on safekeepers queried with debug_dump look
like

"walsenders": [
  {
    "ttid": "fafe0cf39a99c608c872706149de9d2a/b4fb3be6f576935e7f0fcb84bdb909a1",
    "addr": "127.0.0.1:48774",
    "conn_id": 3,
    "appname": "pageserver",
    "feedback": {
      "Pageserver": {
	"current_timeline_size": 32096256,
	"last_received_lsn": "0/2415298",
	"disk_consistent_lsn": "0/1696628",
	"remote_consistent_lsn": "0/0",
	"replytime": "2023-04-12T13:54:53.958856+00:00"
      }
    }
  }
],

safekeeper/src/json_ctrl.rs

@@ -50,7 +50,7 @@ pub struct AppendLogicalMessage {
     pub pg_version: u32,
 }
 
-#[derive(Debug, Serialize, Deserialize)]
+#[derive(Debug, Serialize)]
 struct AppendResult {
     // safekeeper state after append
     state: SafeKeeperState,
@@ -133,7 +133,7 @@ fn send_proposer_elected(tli: &Arc<Timeline>, term: Term, lsn: Lsn) -> anyhow::R
     Ok(())
 }
 
-#[derive(Debug, Serialize, Deserialize)]
+#[derive(Debug, Serialize)]
 pub struct InsertedWAL {
     begin_lsn: Lsn,
     pub end_lsn: Lsn,

safekeeper/src/metrics.rs

@@ -15,7 +15,7 @@ use metrics::{
 use once_cell::sync::Lazy;
 
 use postgres_ffi::XLogSegNo;
-use pq_proto::PageserverFeedback;
+use utils::pageserver_feedback::PageserverFeedback;
 use utils::{id::TenantTimelineId, lsn::Lsn};
 
 use crate::{
@@ -557,7 +557,7 @@ impl Collector for TimelineCollector {
 
             self.ps_last_received_lsn
                 .with_label_values(labels)
-                .set(tli.ps_feedback.last_received_lsn);
+                .set(tli.ps_feedback.last_received_lsn.0);
             if let Ok(unix_time) = tli
                 .ps_feedback
                 .replytime

safekeeper/src/safekeeper.rs

@@ -18,7 +18,8 @@ use crate::control_file;
 use crate::send_wal::HotStandbyFeedback;
 
 use crate::wal_storage;
-use pq_proto::{PageserverFeedback, SystemId};
+use pq_proto::SystemId;
+use utils::pageserver_feedback::PageserverFeedback;
 use utils::{
     bin_ser::LeSer,
     id::{NodeId, TenantId, TenantTimelineId, TimelineId},
@@ -346,7 +347,7 @@ pub struct AppendRequestHeader {
 }
 
 /// Report safekeeper state to proposer
-#[derive(Debug, Serialize, Deserialize)]
+#[derive(Debug, Serialize)]
 pub struct AppendResponse {
     // Current term of the safekeeper; if it is higher than proposer's, the
     // compute is out of date.

safekeeper/src/send_wal.rs

@@ -13,12 +13,13 @@ use postgres_backend::PostgresBackend;
 use postgres_backend::{CopyStreamHandlerEnd, PostgresBackendReader, QueryError};
 use postgres_ffi::get_current_timestamp;
 use postgres_ffi::{TimestampTz, MAX_SEND_SIZE};
-use pq_proto::{BeMessage, PageserverFeedback, WalSndKeepAlive, XLogDataBody};
+use pq_proto::{BeMessage, WalSndKeepAlive, XLogDataBody};
 use serde::{Deserialize, Serialize};
 use tokio::io::{AsyncRead, AsyncWrite};
 use utils::http::json::display_serialize;
 use utils::id::TenantTimelineId;
 use utils::lsn::AtomicLsn;
+use utils::pageserver_feedback::PageserverFeedback;
 
 use std::cmp::{max, min};
 use std::net::SocketAddr;
@@ -155,7 +156,7 @@ impl WalSenders {
         let mut shared = self.mutex.lock();
         shared.get_slot_mut(id).feedback = ReplicationFeedback::Pageserver(*feedback);
         shared.update_ps_feedback();
-        self.update_remote_consistent_lsn(Lsn(shared.agg_ps_feedback.remote_consistent_lsn));
+        self.update_remote_consistent_lsn(shared.agg_ps_feedback.remote_consistent_lsn);
     }
 
     /// Record standby reply.
@@ -195,7 +196,7 @@ impl WalSenders {
         let shared = self.mutex.lock();
         let slot = shared.get_slot(id);
         match slot.feedback {
-            ReplicationFeedback::Pageserver(feedback) => Some(Lsn(feedback.remote_consistent_lsn)),
+            ReplicationFeedback::Pageserver(feedback) => Some(feedback.remote_consistent_lsn),
             _ => None,
         }
     }