Fix documentation format issues

libs/pageserver_api/src/models.rs

@@ -841,21 +841,21 @@ impl TryFrom<u8> for PagestreamBeMessageTag {
 
 #[derive(Debug, PartialEq, Eq)]
 pub struct PagestreamExistsRequest {
-    pub latest: bool,
+    pub horizon: Lsn,
     pub lsn: Lsn,
     pub rel: RelTag,
 }
 
 #[derive(Debug, PartialEq, Eq)]
 pub struct PagestreamNblocksRequest {
-    pub latest: bool,
+    pub horizon: Lsn,
     pub lsn: Lsn,
     pub rel: RelTag,
 }
 
 #[derive(Debug, PartialEq, Eq)]
 pub struct PagestreamGetPageRequest {
-    pub latest: bool,
+    pub horizon: Lsn,
     pub lsn: Lsn,
     pub rel: RelTag,
     pub blkno: u32,
@@ -863,14 +863,14 @@ pub struct PagestreamGetPageRequest {
 
 #[derive(Debug, PartialEq, Eq)]
 pub struct PagestreamDbSizeRequest {
-    pub latest: bool,
+    pub horizon: Lsn,
     pub lsn: Lsn,
     pub dbnode: u32,
 }
 
 #[derive(Debug, PartialEq, Eq)]
 pub struct PagestreamGetSlruSegmentRequest {
-    pub latest: bool,
+    pub horizon: Lsn,
     pub lsn: Lsn,
     pub kind: u8,
     pub segno: u32,
@@ -923,8 +923,8 @@ impl PagestreamFeMessage {
 
         match self {
             Self::Exists(req) => {
-                bytes.put_u8(0);
-                bytes.put_u8(u8::from(req.latest));
+                bytes.put_u8(10);
+                bytes.put_u64(req.horizon.0);
                 bytes.put_u64(req.lsn.0);
                 bytes.put_u32(req.rel.spcnode);
                 bytes.put_u32(req.rel.dbnode);
@@ -933,8 +933,8 @@ impl PagestreamFeMessage {
             }
 
             Self::Nblocks(req) => {
-                bytes.put_u8(1);
-                bytes.put_u8(u8::from(req.latest));
+                bytes.put_u8(11);
+                bytes.put_u64(req.horizon.0);
                 bytes.put_u64(req.lsn.0);
                 bytes.put_u32(req.rel.spcnode);
                 bytes.put_u32(req.rel.dbnode);
@@ -943,8 +943,8 @@ impl PagestreamFeMessage {
             }
 
             Self::GetPage(req) => {
-                bytes.put_u8(2);
-                bytes.put_u8(u8::from(req.latest));
+                bytes.put_u8(12);
+                bytes.put_u64(req.horizon.0);
                 bytes.put_u64(req.lsn.0);
                 bytes.put_u32(req.rel.spcnode);
                 bytes.put_u32(req.rel.dbnode);
@@ -954,15 +954,15 @@ impl PagestreamFeMessage {
             }
 
             Self::DbSize(req) => {
-                bytes.put_u8(3);
-                bytes.put_u8(u8::from(req.latest));
+                bytes.put_u8(13);
+                bytes.put_u64(req.horizon.0);
                 bytes.put_u64(req.lsn.0);
                 bytes.put_u32(req.dbnode);
             }
 
             Self::GetSlruSegment(req) => {
-                bytes.put_u8(4);
-                bytes.put_u8(u8::from(req.latest));
+                bytes.put_u8(14);
+                bytes.put_u64(req.horizon.0);
                 bytes.put_u64(req.lsn.0);
                 bytes.put_u8(req.kind);
                 bytes.put_u32(req.segno);
@@ -979,11 +979,32 @@ impl PagestreamFeMessage {
         //
         // TODO: consider using protobuf or serde bincode for less error prone
         // serialization.
-        let msg_tag = body.read_u8()?;
+        let mut msg_tag = body.read_u8()?;
+        //
+        // Old version of protocol use commands with tags started with 0 and containing `latest` flag.
+        // New version of protocol shift command tags by 10 and pass LSN range instead of `latest` flag.
+        // Server should be able to handle both protocol version. As far as we are not passing no=w,
+        // protocol version from client to server, we make a decision based on tag range.
+        // So this code actually provides backward compatibility.
+        //
+        let horizon = if msg_tag >= 10 {
+            // new protocol
+            msg_tag -= 10; // commands tags in new protocol starts with 10
+            Lsn::from(body.read_u64::<BigEndian>()?)
+        } else {
+            // old_protocol
+            let latest = body.read_u8()? != 0;
+            if latest {
+                Lsn::MAX // get latest version
+            } else {
+                Lsn::INVALID // get version on specified LSN
+            }
+        };
+        let lsn = Lsn::from(body.read_u64::<BigEndian>()?);
         match msg_tag {
             0 => Ok(PagestreamFeMessage::Exists(PagestreamExistsRequest {
-                latest: body.read_u8()? != 0,
-                lsn: Lsn::from(body.read_u64::<BigEndian>()?),
+                horizon,
+                lsn,
                 rel: RelTag {
                     spcnode: body.read_u32::<BigEndian>()?,
                     dbnode: body.read_u32::<BigEndian>()?,
@@ -992,8 +1013,8 @@ impl PagestreamFeMessage {
                 },
             })),
             1 => Ok(PagestreamFeMessage::Nblocks(PagestreamNblocksRequest {
-                latest: body.read_u8()? != 0,
-                lsn: Lsn::from(body.read_u64::<BigEndian>()?),
+                horizon,
+                lsn,
                 rel: RelTag {
                     spcnode: body.read_u32::<BigEndian>()?,
                     dbnode: body.read_u32::<BigEndian>()?,
@@ -1002,8 +1023,8 @@ impl PagestreamFeMessage {
                 },
             })),
             2 => Ok(PagestreamFeMessage::GetPage(PagestreamGetPageRequest {
-                latest: body.read_u8()? != 0,
-                lsn: Lsn::from(body.read_u64::<BigEndian>()?),
+                horizon,
+                lsn,
                 rel: RelTag {
                     spcnode: body.read_u32::<BigEndian>()?,
                     dbnode: body.read_u32::<BigEndian>()?,
@@ -1013,14 +1034,14 @@ impl PagestreamFeMessage {
                 blkno: body.read_u32::<BigEndian>()?,
             })),
             3 => Ok(PagestreamFeMessage::DbSize(PagestreamDbSizeRequest {
-                latest: body.read_u8()? != 0,
-                lsn: Lsn::from(body.read_u64::<BigEndian>()?),
+                horizon,
+                lsn,
                 dbnode: body.read_u32::<BigEndian>()?,
             })),
             4 => Ok(PagestreamFeMessage::GetSlruSegment(
                 PagestreamGetSlruSegmentRequest {
-                    latest: body.read_u8()? != 0,
-                    lsn: Lsn::from(body.read_u64::<BigEndian>()?),
+                    horizon,
+                    lsn,
                     kind: body.read_u8()?,
                     segno: body.read_u32::<BigEndian>()?,
                 },
@@ -1148,7 +1169,7 @@ mod tests {
         // Test serialization/deserialization of PagestreamFeMessage
         let messages = vec![
             PagestreamFeMessage::Exists(PagestreamExistsRequest {
-                latest: true,
+                horizon: Lsn::MAX,
                 lsn: Lsn(4),
                 rel: RelTag {
                     forknum: 1,
@@ -1158,7 +1179,7 @@ mod tests {
                 },
             }),
             PagestreamFeMessage::Nblocks(PagestreamNblocksRequest {
-                latest: false,
+                horizon: Lsn::INVALID,
                 lsn: Lsn(4),
                 rel: RelTag {
                     forknum: 1,
@@ -1168,8 +1189,8 @@ mod tests {
                 },
             }),
             PagestreamFeMessage::GetPage(PagestreamGetPageRequest {
-                latest: true,
-                lsn: Lsn(4),
+                horizon: Lsn::MAX,
+                lsn: Lsn::INVALID,
                 rel: RelTag {
                     forknum: 1,
                     spcnode: 2,
@@ -1179,7 +1200,7 @@ mod tests {
                 blkno: 7,
             }),
             PagestreamFeMessage::DbSize(PagestreamDbSizeRequest {
-                latest: true,
+                horizon: Lsn::MAX,
                 lsn: Lsn(4),
                 dbnode: 7,
             }),

pageserver/pagebench/src/cmd/getpage_latest_lsn.rs

@@ -312,7 +312,11 @@ async fn main_impl(
                     let (rel_tag, block_no) =
                         key_to_rel_block(key).expect("we filter non-rel-block keys out above");
                     PagestreamGetPageRequest {
-                        latest: rng.gen_bool(args.req_latest_probability),
+                        horizon: if rng.gen_bool(args.req_latest_probability) {
+                            Lsn::MAX
+                        } else {
+                            r.timeline_lsn
+                        },
                         lsn: r.timeline_lsn,
                         rel: rel_tag,
                         blkno: block_no,

pageserver/src/basebackup.rs

@@ -361,9 +361,10 @@ where
 
     /// Add contents of relfilenode `src`, naming it as `dst`.
     async fn add_rel(&mut self, src: RelTag, dst: RelTag) -> anyhow::Result<()> {
+        let horizon = self.lsn; // we do not need latest version
         let nblocks = self
             .timeline
-            .get_rel_size(src, Version::Lsn(self.lsn), false, self.ctx)
+            .get_rel_size(src, Version::Lsn(self.lsn), horizon, self.ctx)
             .await?;
 
         // If the relation is empty, create an empty file
@@ -384,7 +385,7 @@ where
             for blknum in startblk..endblk {
                 let img = self
                     .timeline
-                    .get_rel_page_at_lsn(src, blknum, Version::Lsn(self.lsn), false, self.ctx)
+                    .get_rel_page_at_lsn(src, blknum, Version::Lsn(self.lsn), horizon, self.ctx)
                     .await?;
                 segment_data.extend_from_slice(&img[..]);
             }

pageserver/src/page_service.rs

@@ -847,69 +847,66 @@ impl PageServerHandler {
     /// In either case, if the page server hasn't received the WAL up to the
     /// requested LSN yet, we will wait for it to arrive. The return value is
     /// the LSN that should be used to look up the page versions.
+    ///
+    /// Compute needs to specify:
+    /// 1. "desired" LSN - which LSN compute expects to be acceptable
+    /// 2. Upper boundary LSN - PS should not send page with greater LSN to preserver consistency
+    ///
+    /// In case of primary node then upper boundary is always +inf: nobody except this node can produce more recent version of the page.
+    /// In case of replica it is not true: replica can lag from primary node and PS and should not receive pages newer than its last_replay_lsn.
+    /// But it is not good always to request pages at `last_replay_lsn` because replica can be ahead PS and so it has to wait
+    /// until PS caught up (while for this particular page it is not needed).
+    ///
+    /// We actually need to handle just three cases:
+    /// \[page_last_written_lsn, +inf\] - primary node
+    /// \[page_last_written_lsn, last_replay_lsn\] - hot-standby replica (receiving WAL from primary)
+    /// \[snapshot_lsn, snapshot_lsn\] - static RO replica (not receiving WAL fro primary)
+    ///
+    /// Case \[0, lsn\] is not actually needed and added mostly for convenience as alias for \[lsn,lsn\]
+
     async fn wait_or_get_last_lsn(
         timeline: &Timeline,
-        mut lsn: Lsn,
-        latest: bool,
+        lsn: Lsn,
+        horizon: Lsn,
         latest_gc_cutoff_lsn: &RcuReadGuard<Lsn>,
         ctx: &RequestContext,
     ) -> Result<Lsn, PageStreamError> {
-        if latest {
-            // Latest page version was requested. If LSN is given, it is a hint
-            // to the page server that there have been no modifications to the
-            // page after that LSN. If we haven't received WAL up to that point,
-            // wait until it arrives.
-            let last_record_lsn = timeline.get_last_record_lsn();
-
-            // Note: this covers the special case that lsn == Lsn(0). That
-            // special case means "return the latest version whatever it is",
-            // and it's used for bootstrapping purposes, when the page server is
-            // connected directly to the compute node. That is needed because
-            // when you connect to the compute node, to receive the WAL, the
-            // walsender process will do a look up in the pg_authid catalog
-            // table for authentication. That poses a deadlock problem: the
-            // catalog table lookup will send a GetPage request, but the GetPage
-            // request will block in the page server because the recent WAL
-            // hasn't been received yet, and it cannot be received until the
-            // walsender completes the authentication and starts streaming the
-            // WAL.
-            if lsn <= last_record_lsn {
-                lsn = last_record_lsn;
-            } else {
-                timeline
-                    .wait_lsn(
-                        lsn,
-                        crate::tenant::timeline::WaitLsnWaiter::PageService,
-                        ctx,
-                    )
-                    .await?;
-                // Since we waited for 'lsn' to arrive, that is now the last
-                // record LSN. (Or close enough for our purposes; the
-                // last-record LSN can advance immediately after we return
-                // anyway)
-            }
+        let last_record_lsn = timeline.get_last_record_lsn();
+        // Horizon = 0 (INVALID) is treated as LSN interval degenerated to point [lsn,lsn].
+        // It as done mostly for convenience (because such get_page commands are widely used in tests) and
+        // also seems to be logical: Lsn::MAX moves upper boundary of LSN interval till last_record_lsn and
+        // Lsn(0) moves upper boundary to lower boundary.
+        let request_horizon = if horizon == Lsn::INVALID {
+            lsn
         } else {
-            if lsn == Lsn(0) {
-                return Err(PageStreamError::BadRequest(
-                    "invalid LSN(0) in request".into(),
-                ));
-            }
+            horizon
+        };
+        let effective_lsn = Lsn::max(lsn, Lsn::min(request_horizon, last_record_lsn));
+        if effective_lsn > last_record_lsn {
             timeline
                 .wait_lsn(
-                    lsn,
+                    effective_lsn,
                     crate::tenant::timeline::WaitLsnWaiter::PageService,
                     ctx,
                 )
                 .await?;
+            // Since we waited for 'lsn' to arrive, that is now the last
+            // record LSN. (Or close enough for our purposes; the
+            // last-record LSN can advance immediately after we return
+            // anyway)
+        } else if effective_lsn == Lsn(0) {
+            return Err(PageStreamError::BadRequest(
+                "invalid LSN(0) in request".into(),
+            ));
         }
 
-        if lsn < **latest_gc_cutoff_lsn {
+        if effective_lsn < **latest_gc_cutoff_lsn {
             return Err(PageStreamError::BadRequest(format!(
                 "tried to request a page version that was garbage collected. requested at {} gc cutoff {}",
-                lsn, **latest_gc_cutoff_lsn
+                effective_lsn, **latest_gc_cutoff_lsn
             ).into()));
         }
-        Ok(lsn)
+        Ok(effective_lsn)
     }
 
     #[instrument(skip_all, fields(shard_id))]
@@ -927,11 +924,11 @@ impl PageServerHandler {
 
         let latest_gc_cutoff_lsn = timeline.get_latest_gc_cutoff_lsn();
         let lsn =
-            Self::wait_or_get_last_lsn(timeline, req.lsn, req.latest, &latest_gc_cutoff_lsn, ctx)
+            Self::wait_or_get_last_lsn(timeline, req.lsn, req.horizon, &latest_gc_cutoff_lsn, ctx)
                 .await?;
 
         let exists = timeline
-            .get_rel_exists(req.rel, Version::Lsn(lsn), req.latest, ctx)
+            .get_rel_exists(req.rel, Version::Lsn(lsn), req.horizon, ctx)
             .await?;
 
         Ok(PagestreamBeMessage::Exists(PagestreamExistsResponse {
@@ -955,11 +952,11 @@ impl PageServerHandler {
 
         let latest_gc_cutoff_lsn = timeline.get_latest_gc_cutoff_lsn();
         let lsn =
-            Self::wait_or_get_last_lsn(timeline, req.lsn, req.latest, &latest_gc_cutoff_lsn, ctx)
+            Self::wait_or_get_last_lsn(timeline, req.lsn, req.horizon, &latest_gc_cutoff_lsn, ctx)
                 .await?;
 
         let n_blocks = timeline
-            .get_rel_size(req.rel, Version::Lsn(lsn), req.latest, ctx)
+            .get_rel_size(req.rel, Version::Lsn(lsn), req.horizon, ctx)
             .await?;
 
         Ok(PagestreamBeMessage::Nblocks(PagestreamNblocksResponse {
@@ -983,7 +980,7 @@ impl PageServerHandler {
 
         let latest_gc_cutoff_lsn = timeline.get_latest_gc_cutoff_lsn();
         let lsn =
-            Self::wait_or_get_last_lsn(timeline, req.lsn, req.latest, &latest_gc_cutoff_lsn, ctx)
+            Self::wait_or_get_last_lsn(timeline, req.lsn, req.horizon, &latest_gc_cutoff_lsn, ctx)
                 .await?;
 
         let total_blocks = timeline
@@ -991,7 +988,7 @@ impl PageServerHandler {
                 DEFAULTTABLESPACE_OID,
                 req.dbnode,
                 Version::Lsn(lsn),
-                req.latest,
+                req.horizon,
                 ctx,
             )
             .await?;
@@ -1161,11 +1158,11 @@ impl PageServerHandler {
 
         let latest_gc_cutoff_lsn = timeline.get_latest_gc_cutoff_lsn();
         let lsn =
-            Self::wait_or_get_last_lsn(timeline, req.lsn, req.latest, &latest_gc_cutoff_lsn, ctx)
+            Self::wait_or_get_last_lsn(timeline, req.lsn, req.horizon, &latest_gc_cutoff_lsn, ctx)
                 .await?;
 
         let page = timeline
-            .get_rel_page_at_lsn(req.rel, req.blkno, Version::Lsn(lsn), req.latest, ctx)
+            .get_rel_page_at_lsn(req.rel, req.blkno, Version::Lsn(lsn), req.horizon, ctx)
             .await?;
 
         Ok(PagestreamBeMessage::GetPage(PagestreamGetPageResponse {
@@ -1189,7 +1186,7 @@ impl PageServerHandler {
 
         let latest_gc_cutoff_lsn = timeline.get_latest_gc_cutoff_lsn();
         let lsn =
-            Self::wait_or_get_last_lsn(timeline, req.lsn, req.latest, &latest_gc_cutoff_lsn, ctx)
+            Self::wait_or_get_last_lsn(timeline, req.lsn, req.horizon, &latest_gc_cutoff_lsn, ctx)
                 .await?;
 
         let kind = SlruKind::from_repr(req.kind)

pageserver/src/pgdatadir_mapping.rs

@@ -175,7 +175,7 @@ impl Timeline {
         tag: RelTag,
         blknum: BlockNumber,
         version: Version<'_>,
-        latest: bool,
+        horizon: Lsn,
         ctx: &RequestContext,
     ) -> Result<Bytes, PageReconstructError> {
         if tag.relnode == 0 {
@@ -184,7 +184,7 @@ impl Timeline {
             ));
         }
 
-        let nblocks = self.get_rel_size(tag, version, latest, ctx).await?;
+        let nblocks = self.get_rel_size(tag, version, horizon, ctx).await?;
         if blknum >= nblocks {
             debug!(
                 "read beyond EOF at {} blk {} at {}, size is {}: returning all-zeros page",
@@ -206,7 +206,7 @@ impl Timeline {
         spcnode: Oid,
         dbnode: Oid,
         version: Version<'_>,
-        latest: bool,
+        horizon: Lsn,
         ctx: &RequestContext,
     ) -> Result<usize, PageReconstructError> {
         let mut total_blocks = 0;
@@ -214,7 +214,7 @@ impl Timeline {
         let rels = self.list_rels(spcnode, dbnode, version, ctx).await?;
 
         for rel in rels {
-            let n_blocks = self.get_rel_size(rel, version, latest, ctx).await?;
+            let n_blocks = self.get_rel_size(rel, version, horizon, ctx).await?;
             total_blocks += n_blocks as usize;
         }
         Ok(total_blocks)
@@ -225,7 +225,7 @@ impl Timeline {
         &self,
         tag: RelTag,
         version: Version<'_>,
-        latest: bool,
+        horizon: Lsn,
         ctx: &RequestContext,
     ) -> Result<BlockNumber, PageReconstructError> {
         if tag.relnode == 0 {
@@ -239,7 +239,7 @@ impl Timeline {
         }
 
         if (tag.forknum == FSM_FORKNUM || tag.forknum == VISIBILITYMAP_FORKNUM)
-            && !self.get_rel_exists(tag, version, latest, ctx).await?
+            && !self.get_rel_exists(tag, version, horizon, ctx).await?
         {
             // FIXME: Postgres sometimes calls smgrcreate() to create
             // FSM, and smgrnblocks() on it immediately afterwards,
@@ -252,14 +252,8 @@ impl Timeline {
         let mut buf = version.get(self, key, ctx).await?;
         let nblocks = buf.get_u32_le();
 
-        if latest {
-            // Update relation size cache only if "latest" flag is set.
-            // This flag is set by compute when it is working with most recent version of relation.
-            // Typically master compute node always set latest=true.
-            // Please notice, that even if compute node "by mistake" specifies old LSN but set
-            // latest=true, then it can not cause cache corruption, because with latest=true
-            // pageserver choose max(request_lsn, last_written_lsn) and so cached value will be
-            // associated with most recent value of LSN.
+        if horizon == Lsn::MAX {
+            // Update relation size cache only if latest version is requested.
             self.update_cached_rel_size(tag, version.get_lsn(), nblocks);
         }
         Ok(nblocks)
@@ -270,7 +264,7 @@ impl Timeline {
         &self,
         tag: RelTag,
         version: Version<'_>,
-        _latest: bool,
+        _horizon: Lsn,
         ctx: &RequestContext,
     ) -> Result<bool, PageReconstructError> {
         if tag.relnode == 0 {
@@ -1088,7 +1082,7 @@ impl<'a> DatadirModification<'a> {
     ) -> anyhow::Result<()> {
         let total_blocks = self
             .tline
-            .get_db_size(spcnode, dbnode, Version::Modified(self), true, ctx)
+            .get_db_size(spcnode, dbnode, Version::Modified(self), Lsn::MAX, ctx)
             .await?;
 
         // Remove entry from dbdir
@@ -1187,7 +1181,7 @@ impl<'a> DatadirModification<'a> {
         anyhow::ensure!(rel.relnode != 0, RelationError::InvalidRelnode);
         if self
             .tline
-            .get_rel_exists(rel, Version::Modified(self), true, ctx)
+            .get_rel_exists(rel, Version::Modified(self), Lsn::MAX, ctx)
             .await?
         {
             let size_key = rel_size_to_key(rel);

pageserver/src/walingest.rs

@@ -1034,7 +1034,7 @@ impl WalIngest {
 
             let nblocks = modification
                 .tline
-                .get_rel_size(src_rel, Version::Modified(modification), true, ctx)
+                .get_rel_size(src_rel, Version::Modified(modification), Lsn::MAX, ctx)
                 .await?;
             let dst_rel = RelTag {
                 spcnode: tablespace_id,
@@ -1072,7 +1072,7 @@ impl WalIngest {
                         src_rel,
                         blknum,
                         Version::Modified(modification),
-                        true,
+                        Lsn::MAX,
                         ctx,
                     )
                     .await?;
@@ -1242,7 +1242,7 @@ impl WalIngest {
                 };
                 if modification
                     .tline
-                    .get_rel_exists(rel, Version::Modified(modification), true, ctx)
+                    .get_rel_exists(rel, Version::Modified(modification), Lsn::MAX, ctx)
                     .await?
                 {
                     self.put_rel_drop(modification, rel, ctx).await?;
@@ -1541,7 +1541,7 @@ impl WalIngest {
             nblocks
         } else if !modification
             .tline
-            .get_rel_exists(rel, Version::Modified(modification), true, ctx)
+            .get_rel_exists(rel, Version::Modified(modification), Lsn::MAX, ctx)
             .await?
         {
             // create it with 0 size initially, the logic below will extend it
@@ -1553,7 +1553,7 @@ impl WalIngest {
         } else {
             modification
                 .tline
-                .get_rel_size(rel, Version::Modified(modification), true, ctx)
+                .get_rel_size(rel, Version::Modified(modification), Lsn::MAX, ctx)
                 .await?
         };
 
@@ -1650,14 +1650,14 @@ async fn get_relsize(
 ) -> anyhow::Result<BlockNumber> {
     let nblocks = if !modification
         .tline
-        .get_rel_exists(rel, Version::Modified(modification), true, ctx)
+        .get_rel_exists(rel, Version::Modified(modification), Lsn::MAX, ctx)
         .await?
     {
         0
     } else {
         modification
             .tline
-            .get_rel_size(rel, Version::Modified(modification), true, ctx)
+            .get_rel_size(rel, Version::Modified(modification), Lsn::MAX, ctx)
             .await?
     };
     Ok(nblocks)
@@ -1732,29 +1732,29 @@ mod tests {
         // The relation was created at LSN 2, not visible at LSN 1 yet.
         assert_eq!(
             tline
-                .get_rel_exists(TESTREL_A, Version::Lsn(Lsn(0x10)), false, &ctx)
+                .get_rel_exists(TESTREL_A, Version::Lsn(Lsn(0x10)), Lsn::INVALID, &ctx)
                 .await?,
             false
         );
         assert!(tline
-            .get_rel_size(TESTREL_A, Version::Lsn(Lsn(0x10)), false, &ctx)
+            .get_rel_size(TESTREL_A, Version::Lsn(Lsn(0x10)), Lsn::INVALID, &ctx)
             .await
             .is_err());
         assert_eq!(
             tline
-                .get_rel_exists(TESTREL_A, Version::Lsn(Lsn(0x20)), false, &ctx)
+                .get_rel_exists(TESTREL_A, Version::Lsn(Lsn(0x20)), Lsn::INVALID, &ctx)
                 .await?,
             true
         );
         assert_eq!(
             tline
-                .get_rel_size(TESTREL_A, Version::Lsn(Lsn(0x20)), false, &ctx)
+                .get_rel_size(TESTREL_A, Version::Lsn(Lsn(0x20)), Lsn::INVALID, &ctx)
                 .await?,
             1
         );
         assert_eq!(
             tline
-                .get_rel_size(TESTREL_A, Version::Lsn(Lsn(0x50)), false, &ctx)
+                .get_rel_size(TESTREL_A, Version::Lsn(Lsn(0x50)), Lsn::INVALID, &ctx)
                 .await?,
             3
         );
@@ -1762,46 +1762,46 @@ mod tests {
         // Check page contents at each LSN
         assert_eq!(
             tline
-                .get_rel_page_at_lsn(TESTREL_A, 0, Version::Lsn(Lsn(0x20)), false, &ctx)
+                .get_rel_page_at_lsn(TESTREL_A, 0, Version::Lsn(Lsn(0x20)), Lsn::INVALID, &ctx)
                 .await?,
             test_img("foo blk 0 at 2")
         );
 
         assert_eq!(
             tline
-                .get_rel_page_at_lsn(TESTREL_A, 0, Version::Lsn(Lsn(0x30)), false, &ctx)
+                .get_rel_page_at_lsn(TESTREL_A, 0, Version::Lsn(Lsn(0x30)), Lsn::INVALID, &ctx)
                 .await?,
             test_img("foo blk 0 at 3")
         );
 
         assert_eq!(
             tline
-                .get_rel_page_at_lsn(TESTREL_A, 0, Version::Lsn(Lsn(0x40)), false, &ctx)
+                .get_rel_page_at_lsn(TESTREL_A, 0, Version::Lsn(Lsn(0x40)), Lsn::INVALID, &ctx)
                 .await?,
             test_img("foo blk 0 at 3")
         );
         assert_eq!(
             tline
-                .get_rel_page_at_lsn(TESTREL_A, 1, Version::Lsn(Lsn(0x40)), false, &ctx)
+                .get_rel_page_at_lsn(TESTREL_A, 1, Version::Lsn(Lsn(0x40)), Lsn::INVALID, &ctx)
                 .await?,
             test_img("foo blk 1 at 4")
         );
 
         assert_eq!(
             tline
-                .get_rel_page_at_lsn(TESTREL_A, 0, Version::Lsn(Lsn(0x50)), false, &ctx)
+                .get_rel_page_at_lsn(TESTREL_A, 0, Version::Lsn(Lsn(0x50)), Lsn::INVALID, &ctx)
                 .await?,
             test_img("foo blk 0 at 3")
         );
         assert_eq!(
             tline
-                .get_rel_page_at_lsn(TESTREL_A, 1, Version::Lsn(Lsn(0x50)), false, &ctx)
+                .get_rel_page_at_lsn(TESTREL_A, 1, Version::Lsn(Lsn(0x50)), Lsn::INVALID, &ctx)
                 .await?,
             test_img("foo blk 1 at 4")
         );
         assert_eq!(
             tline
-                .get_rel_page_at_lsn(TESTREL_A, 2, Version::Lsn(Lsn(0x50)), false, &ctx)
+                .get_rel_page_at_lsn(TESTREL_A, 2, Version::Lsn(Lsn(0x50)), Lsn::INVALID, &ctx)
                 .await?,
             test_img("foo blk 2 at 5")
         );
@@ -1817,19 +1817,19 @@ mod tests {
         // Check reported size and contents after truncation
         assert_eq!(
             tline
-                .get_rel_size(TESTREL_A, Version::Lsn(Lsn(0x60)), false, &ctx)
+                .get_rel_size(TESTREL_A, Version::Lsn(Lsn(0x60)), Lsn::INVALID, &ctx)
                 .await?,
             2
         );
         assert_eq!(
             tline
-                .get_rel_page_at_lsn(TESTREL_A, 0, Version::Lsn(Lsn(0x60)), false, &ctx)
+                .get_rel_page_at_lsn(TESTREL_A, 0, Version::Lsn(Lsn(0x60)), Lsn::INVALID, &ctx)
                 .await?,
             test_img("foo blk 0 at 3")
         );
         assert_eq!(
             tline
-                .get_rel_page_at_lsn(TESTREL_A, 1, Version::Lsn(Lsn(0x60)), false, &ctx)
+                .get_rel_page_at_lsn(TESTREL_A, 1, Version::Lsn(Lsn(0x60)), Lsn::INVALID, &ctx)
                 .await?,
             test_img("foo blk 1 at 4")
         );
@@ -1837,13 +1837,13 @@ mod tests {
         // should still see the truncated block with older LSN
         assert_eq!(
             tline
-                .get_rel_size(TESTREL_A, Version::Lsn(Lsn(0x50)), false, &ctx)
+                .get_rel_size(TESTREL_A, Version::Lsn(Lsn(0x50)), Lsn::INVALID, &ctx)
                 .await?,
             3
         );
         assert_eq!(
             tline
-                .get_rel_page_at_lsn(TESTREL_A, 2, Version::Lsn(Lsn(0x50)), false, &ctx)
+                .get_rel_page_at_lsn(TESTREL_A, 2, Version::Lsn(Lsn(0x50)), Lsn::INVALID, &ctx)
                 .await?,
             test_img("foo blk 2 at 5")
         );
@@ -1856,7 +1856,7 @@ mod tests {
         m.commit(&ctx).await?;
         assert_eq!(
             tline
-                .get_rel_size(TESTREL_A, Version::Lsn(Lsn(0x68)), false, &ctx)
+                .get_rel_size(TESTREL_A, Version::Lsn(Lsn(0x68)), Lsn::INVALID, &ctx)
                 .await?,
             0
         );
@@ -1869,19 +1869,19 @@ mod tests {
         m.commit(&ctx).await?;
         assert_eq!(
             tline
-                .get_rel_size(TESTREL_A, Version::Lsn(Lsn(0x70)), false, &ctx)
+                .get_rel_size(TESTREL_A, Version::Lsn(Lsn(0x70)), Lsn::INVALID, &ctx)
                 .await?,
             2
         );
         assert_eq!(
             tline
-                .get_rel_page_at_lsn(TESTREL_A, 0, Version::Lsn(Lsn(0x70)), false, &ctx)
+                .get_rel_page_at_lsn(TESTREL_A, 0, Version::Lsn(Lsn(0x70)), Lsn::INVALID, &ctx)
                 .await?,
             ZERO_PAGE
         );
         assert_eq!(
             tline
-                .get_rel_page_at_lsn(TESTREL_A, 1, Version::Lsn(Lsn(0x70)), false, &ctx)
+                .get_rel_page_at_lsn(TESTREL_A, 1, Version::Lsn(Lsn(0x70)), Lsn::INVALID, &ctx)
                 .await?,
             test_img("foo blk 1")
         );
@@ -1894,21 +1894,27 @@ mod tests {
         m.commit(&ctx).await?;
         assert_eq!(
             tline
-                .get_rel_size(TESTREL_A, Version::Lsn(Lsn(0x80)), false, &ctx)
+                .get_rel_size(TESTREL_A, Version::Lsn(Lsn(0x80)), Lsn::INVALID, &ctx)
                 .await?,
             1501
         );
         for blk in 2..1500 {
             assert_eq!(
                 tline
-                    .get_rel_page_at_lsn(TESTREL_A, blk, Version::Lsn(Lsn(0x80)), false, &ctx)
+                    .get_rel_page_at_lsn(
+                        TESTREL_A,
+                        blk,
+                        Version::Lsn(Lsn(0x80)),
+                        Lsn::INVALID,
+                        &ctx
+                    )
                     .await?,
                 ZERO_PAGE
             );
         }
         assert_eq!(
             tline
-                .get_rel_page_at_lsn(TESTREL_A, 1500, Version::Lsn(Lsn(0x80)), false, &ctx)
+                .get_rel_page_at_lsn(TESTREL_A, 1500, Version::Lsn(Lsn(0x80)), Lsn::INVALID, &ctx)
                 .await?,
             test_img("foo blk 1500")
         );
@@ -1935,13 +1941,13 @@ mod tests {
         // Check that rel exists and size is correct
         assert_eq!(
             tline
-                .get_rel_exists(TESTREL_A, Version::Lsn(Lsn(0x20)), false, &ctx)
+                .get_rel_exists(TESTREL_A, Version::Lsn(Lsn(0x20)), Lsn::INVALID, &ctx)
                 .await?,
             true
         );
         assert_eq!(
             tline
-                .get_rel_size(TESTREL_A, Version::Lsn(Lsn(0x20)), false, &ctx)
+                .get_rel_size(TESTREL_A, Version::Lsn(Lsn(0x20)), Lsn::INVALID, &ctx)
                 .await?,
             1
         );
@@ -1954,7 +1960,7 @@ mod tests {
         // Check that rel is not visible anymore
         assert_eq!(
             tline
-                .get_rel_exists(TESTREL_A, Version::Lsn(Lsn(0x30)), false, &ctx)
+                .get_rel_exists(TESTREL_A, Version::Lsn(Lsn(0x30)), Lsn::INVALID, &ctx)
                 .await?,
             false
         );
@@ -1972,13 +1978,13 @@ mod tests {
         // Check that rel exists and size is correct
         assert_eq!(
             tline
-                .get_rel_exists(TESTREL_A, Version::Lsn(Lsn(0x40)), false, &ctx)
+                .get_rel_exists(TESTREL_A, Version::Lsn(Lsn(0x40)), Lsn::INVALID, &ctx)
                 .await?,
             true
         );
         assert_eq!(
             tline
-                .get_rel_size(TESTREL_A, Version::Lsn(Lsn(0x40)), false, &ctx)
+                .get_rel_size(TESTREL_A, Version::Lsn(Lsn(0x40)), Lsn::INVALID, &ctx)
                 .await?,
             1
         );
@@ -2011,24 +2017,24 @@ mod tests {
         // The relation was created at LSN 20, not visible at LSN 1 yet.
         assert_eq!(
             tline
-                .get_rel_exists(TESTREL_A, Version::Lsn(Lsn(0x10)), false, &ctx)
+                .get_rel_exists(TESTREL_A, Version::Lsn(Lsn(0x10)), Lsn::INVALID, &ctx)
                 .await?,
             false
         );
         assert!(tline
-            .get_rel_size(TESTREL_A, Version::Lsn(Lsn(0x10)), false, &ctx)
+            .get_rel_size(TESTREL_A, Version::Lsn(Lsn(0x10)), Lsn::INVALID, &ctx)
             .await
             .is_err());
 
         assert_eq!(
             tline
-                .get_rel_exists(TESTREL_A, Version::Lsn(Lsn(0x20)), false, &ctx)
+                .get_rel_exists(TESTREL_A, Version::Lsn(Lsn(0x20)), Lsn::INVALID, &ctx)
                 .await?,
             true
         );
         assert_eq!(
             tline
-                .get_rel_size(TESTREL_A, Version::Lsn(Lsn(0x20)), false, &ctx)
+                .get_rel_size(TESTREL_A, Version::Lsn(Lsn(0x20)), Lsn::INVALID, &ctx)
                 .await?,
             relsize
         );
@@ -2039,7 +2045,7 @@ mod tests {
             let data = format!("foo blk {} at {}", blkno, lsn);
             assert_eq!(
                 tline
-                    .get_rel_page_at_lsn(TESTREL_A, blkno, Version::Lsn(lsn), false, &ctx)
+                    .get_rel_page_at_lsn(TESTREL_A, blkno, Version::Lsn(lsn), Lsn::INVALID, &ctx)
                     .await?,
                 test_img(&data)
             );
@@ -2056,7 +2062,7 @@ mod tests {
         // Check reported size and contents after truncation
         assert_eq!(
             tline
-                .get_rel_size(TESTREL_A, Version::Lsn(Lsn(0x60)), false, &ctx)
+                .get_rel_size(TESTREL_A, Version::Lsn(Lsn(0x60)), Lsn::INVALID, &ctx)
                 .await?,
             1
         );
@@ -2066,7 +2072,13 @@ mod tests {
             let data = format!("foo blk {} at {}", blkno, lsn);
             assert_eq!(
                 tline
-                    .get_rel_page_at_lsn(TESTREL_A, blkno, Version::Lsn(Lsn(0x60)), false, &ctx)
+                    .get_rel_page_at_lsn(
+                        TESTREL_A,
+                        blkno,
+                        Version::Lsn(Lsn(0x60)),
+                        Lsn::INVALID,
+                        &ctx
+                    )
                     .await?,
                 test_img(&data)
             );
@@ -2075,7 +2087,7 @@ mod tests {
         // should still see all blocks with older LSN
         assert_eq!(
             tline
-                .get_rel_size(TESTREL_A, Version::Lsn(Lsn(0x50)), false, &ctx)
+                .get_rel_size(TESTREL_A, Version::Lsn(Lsn(0x50)), Lsn::INVALID, &ctx)
                 .await?,
             relsize
         );
@@ -2084,7 +2096,13 @@ mod tests {
             let data = format!("foo blk {} at {}", blkno, lsn);
             assert_eq!(
                 tline
-                    .get_rel_page_at_lsn(TESTREL_A, blkno, Version::Lsn(Lsn(0x50)), false, &ctx)
+                    .get_rel_page_at_lsn(
+                        TESTREL_A,
+                        blkno,
+                        Version::Lsn(Lsn(0x50)),
+                        Lsn::INVALID,
+                        &ctx
+                    )
                     .await?,
                 test_img(&data)
             );
@@ -2104,13 +2122,13 @@ mod tests {
 
         assert_eq!(
             tline
-                .get_rel_exists(TESTREL_A, Version::Lsn(Lsn(0x80)), false, &ctx)
+                .get_rel_exists(TESTREL_A, Version::Lsn(Lsn(0x80)), Lsn::INVALID, &ctx)
                 .await?,
             true
         );
         assert_eq!(
             tline
-                .get_rel_size(TESTREL_A, Version::Lsn(Lsn(0x80)), false, &ctx)
+                .get_rel_size(TESTREL_A, Version::Lsn(Lsn(0x80)), Lsn::INVALID, &ctx)
                 .await?,
             relsize
         );
@@ -2120,7 +2138,13 @@ mod tests {
             let data = format!("foo blk {} at {}", blkno, lsn);
             assert_eq!(
                 tline
-                    .get_rel_page_at_lsn(TESTREL_A, blkno, Version::Lsn(Lsn(0x80)), false, &ctx)
+                    .get_rel_page_at_lsn(
+                        TESTREL_A,
+                        blkno,
+                        Version::Lsn(Lsn(0x80)),
+                        Lsn::INVALID,
+                        &ctx
+                    )
                     .await?,
                 test_img(&data)
             );
@@ -2154,7 +2178,7 @@ mod tests {
 
         assert_eq!(
             tline
-                .get_rel_size(TESTREL_A, Version::Lsn(Lsn(lsn)), false, &ctx)
+                .get_rel_size(TESTREL_A, Version::Lsn(Lsn(lsn)), Lsn::INVALID, &ctx)
                 .await?,
             RELSEG_SIZE + 1
         );
@@ -2168,7 +2192,7 @@ mod tests {
         m.commit(&ctx).await?;
         assert_eq!(
             tline
-                .get_rel_size(TESTREL_A, Version::Lsn(Lsn(lsn)), false, &ctx)
+                .get_rel_size(TESTREL_A, Version::Lsn(Lsn(lsn)), Lsn::INVALID, &ctx)
                 .await?,
             RELSEG_SIZE
         );
@@ -2183,7 +2207,7 @@ mod tests {
         m.commit(&ctx).await?;
         assert_eq!(
             tline
-                .get_rel_size(TESTREL_A, Version::Lsn(Lsn(lsn)), false, &ctx)
+                .get_rel_size(TESTREL_A, Version::Lsn(Lsn(lsn)), Lsn::INVALID, &ctx)
                 .await?,
             RELSEG_SIZE - 1
         );
@@ -2201,7 +2225,7 @@ mod tests {
             m.commit(&ctx).await?;
             assert_eq!(
                 tline
-                    .get_rel_size(TESTREL_A, Version::Lsn(Lsn(lsn)), false, &ctx)
+                    .get_rel_size(TESTREL_A, Version::Lsn(Lsn(lsn)), Lsn::INVALID, &ctx)
                     .await?,
                 size as BlockNumber
             );

pgxn/neon/libpagestore.c

@@ -49,6 +49,8 @@ char	   *neon_auth_token;
 int			readahead_buffer_size = 128;
 int			flush_every_n_requests = 8;
 
+int         neon_protocol_version;
+
 static int	n_reconnect_attempts = 0;
 static int	max_reconnect_attempts = 60;
 static int	stripe_size;
@@ -844,6 +846,14 @@ pg_init_libpagestore(void)
 							PGC_USERSET,
 							0,	/* no flags required */
 							NULL, (GucIntAssignHook) &readahead_buffer_resize, NULL);
+	DefineCustomIntVariable("neon.protocol_version",
+							"Version of compute<->page server protocol",
+							NULL,
+							&neon_protocol_version,
+							NEON_PROTOCOL_VERSION, 1, INT_MAX,
+							PGC_USERSET,
+							0,	/* no flags required */
+							NULL, NULL, NULL);
 
 	relsize_hash_init();
 

pgxn/neon/pagestore_client.h

@@ -28,10 +28,17 @@
 #define MAX_SHARDS 128
 #define MAX_PAGESERVER_CONNSTRING_SIZE 256
 
+/*
+ * Right now protocal version is not set to the server.
+ * So it is ciritical that format of existed commands is not changed.
+ * New protocl versions can just add new commands.
+ */
+#define NEON_PROTOCOL_VERSION  2
+
 typedef enum
 {
 	/* pagestore_client -> pagestore */
-	T_NeonExistsRequest = 0,
+	T_NeonExistsRequest = 10, /* new protocol message tags start from 10 */
 	T_NeonNblocksRequest,
 	T_NeonGetPageRequest,
 	T_NeonDbSizeRequest,
@@ -72,14 +79,20 @@ typedef enum {
 /*
  * supertype of all the Neon*Request structs below
  *
- * If 'latest' is true, we are requesting the latest page version, and 'lsn'
+ * In old version of Neon we have 'latest' flag indicating that we are requesting the latest page version, and 'lsn'
  * is just a hint to the server that we know there are no versions of the page
  * (or relation size, for exists/nblocks requests) later than the 'lsn'.
+ * 
+ * But it doesn't work for hot-standby replica because it may be not at the latest LSN position.
+ * So we need to be able to specify upper boundary for LSN which page server can send to us.
+ * This is why 'latest' flag is replaced with 'horizon'. MAX_LSN=~0 value of 'horizon' means that we are requesting latest version.
+ * If we need version on exact LSN (for static RO replicas), 'horizon' should be set to 0: in this case range [lsn,lsn] is used by page server.
+ * Otherwise for hot-standby replica we specify in 'horizon' current replay position.
  */
 typedef struct
 {
 	NeonMessageTag tag;
-	bool		latest;			/* if true, request latest page version */
+	XLogRecPtr	horizon;		/* upper boundary for page LSN */
 	XLogRecPtr	lsn;			/* request page version @ this LSN */
 } NeonRequest;
 
@@ -193,6 +206,7 @@ extern int	readahead_buffer_size;
 extern char *neon_timeline;
 extern char *neon_tenant;
 extern int32 max_cluster_size;
+extern int  neon_protocol_version;
 
 extern shardno_t get_shard_number(BufferTag* tag);
 

pgxn/neon/pagestore_smgr.c

@@ -110,6 +110,20 @@ static UnloggedBuildPhase unlogged_build_phase = UNLOGGED_BUILD_NOT_IN_PROGRESS;
 static bool neon_redo_read_buffer_filter(XLogReaderState *record, uint8 block_id);
 static bool (*old_redo_read_buffer_filter) (XLogReaderState *record, uint8 block_id) = NULL;
 
+#define MAX_LSN ((XLogRecPtr)~0)
+
+/*
+ * There are three kinds of get_page :
+ * 1. Master compute: get the latest page not older than specified LSN (horizon=Lsn::MAX)
+ * 2. RO replica: get the latest page not newer than current WAL position replica already applied (horizon=GetXLogReplayRecPtr(NULL))
+ * 3. Snapshot: get latest page not new than specified LSN (horizon=request_lsn)
+ */
+static XLogRecPtr
+neon_get_horizon(bool latest)
+{
+	return latest ? MAX_LSN : RecoveryInProgress() ? GetXLogReplayRecPtr(NULL) : InvalidXLogRecPtr; /* horizon=InvalidXlogRecPtr is replaced with request_lsn at PS */
+}
+
 /*
  * Prefetch implementation:
  *
@@ -687,9 +701,10 @@ static void
 prefetch_do_request(PrefetchRequest *slot, bool *force_latest, XLogRecPtr *force_lsn)
 {
 	bool		found;
+	bool        latest;
 	NeonGetPageRequest request = {
 		.req.tag = T_NeonGetPageRequest,
-		.req.latest = false,
+		.req.horizon = 0,
 		.req.lsn = 0,
 		.rinfo = BufTagGetNRelFileInfo(slot->buftag),
 		.forknum = slot->buftag.forkNum,
@@ -699,13 +714,13 @@ prefetch_do_request(PrefetchRequest *slot, bool *force_latest, XLogRecPtr *force
 	if (force_lsn && force_latest)
 	{
 		request.req.lsn = *force_lsn;
-		request.req.latest = *force_latest;
+		latest = *force_latest;
 		slot->actual_request_lsn = slot->effective_request_lsn = *force_lsn;
 	}
 	else
 	{
 		XLogRecPtr	lsn = neon_get_request_lsn(
-											   &request.req.latest,
+											   &latest,
 											   BufTagGetNRelFileInfo(slot->buftag),
 											   slot->buftag.forkNum,
 											   slot->buftag.blockNum
@@ -733,6 +748,7 @@ prefetch_do_request(PrefetchRequest *slot, bool *force_latest, XLogRecPtr *force
 		prefetch_lsn = Max(prefetch_lsn, lsn);
 		slot->effective_request_lsn = prefetch_lsn;
 	}
+	request.req.horizon = neon_get_horizon(latest);
 
 	Assert(slot->response == NULL);
 	Assert(slot->my_ring_index == MyPState->ring_unused);
@@ -997,7 +1013,19 @@ nm_pack_request(NeonRequest *msg)
 	StringInfoData s;
 
 	initStringInfo(&s);
-	pq_sendbyte(&s, msg->tag);
+
+	if (neon_protocol_version >= 2)
+	{
+		pq_sendbyte(&s, msg->tag);
+		pq_sendint64(&s, msg->horizon);
+	}
+	else
+	{
+		/* Old protocol with latest flag */
+		pq_sendbyte(&s, msg->tag - T_NeonExistsRequest); /* old protocol command tags start from zero */
+		pq_sendbyte(&s, msg->horizon == MAX_LSN);
+	}
+	pq_sendint64(&s, msg->lsn);
 
 	switch (messageTag(msg))
 	{
@@ -1006,8 +1034,6 @@ nm_pack_request(NeonRequest *msg)
 			{
 				NeonExistsRequest *msg_req = (NeonExistsRequest *) msg;
 
-				pq_sendbyte(&s, msg_req->req.latest);
-				pq_sendint64(&s, msg_req->req.lsn);
 				pq_sendint32(&s, NInfoGetSpcOid(msg_req->rinfo));
 				pq_sendint32(&s, NInfoGetDbOid(msg_req->rinfo));
 				pq_sendint32(&s, NInfoGetRelNumber(msg_req->rinfo));
@@ -1019,8 +1045,6 @@ nm_pack_request(NeonRequest *msg)
 			{
 				NeonNblocksRequest *msg_req = (NeonNblocksRequest *) msg;
 
-				pq_sendbyte(&s, msg_req->req.latest);
-				pq_sendint64(&s, msg_req->req.lsn);
 				pq_sendint32(&s, NInfoGetSpcOid(msg_req->rinfo));
 				pq_sendint32(&s, NInfoGetDbOid(msg_req->rinfo));
 				pq_sendint32(&s, NInfoGetRelNumber(msg_req->rinfo));
@@ -1032,8 +1056,6 @@ nm_pack_request(NeonRequest *msg)
 			{
 				NeonDbSizeRequest *msg_req = (NeonDbSizeRequest *) msg;
 
-				pq_sendbyte(&s, msg_req->req.latest);
-				pq_sendint64(&s, msg_req->req.lsn);
 				pq_sendint32(&s, msg_req->dbNode);
 
 				break;
@@ -1042,8 +1064,6 @@ nm_pack_request(NeonRequest *msg)
 			{
 				NeonGetPageRequest *msg_req = (NeonGetPageRequest *) msg;
 
-				pq_sendbyte(&s, msg_req->req.latest);
-				pq_sendint64(&s, msg_req->req.lsn);
 				pq_sendint32(&s, NInfoGetSpcOid(msg_req->rinfo));
 				pq_sendint32(&s, NInfoGetDbOid(msg_req->rinfo));
 				pq_sendint32(&s, NInfoGetRelNumber(msg_req->rinfo));
@@ -1057,8 +1077,6 @@ nm_pack_request(NeonRequest *msg)
 			{
 				NeonGetSlruSegmentRequest *msg_req = (NeonGetSlruSegmentRequest *) msg;
 
-				pq_sendbyte(&s, msg_req->req.latest);
-				pq_sendint64(&s, msg_req->req.lsn);
 				pq_sendbyte(&s, msg_req->kind);
 				pq_sendint32(&s, msg_req->segno);
 
@@ -1209,7 +1227,7 @@ nm_to_string(NeonMessage *msg)
 				appendStringInfo(&s, ", \"rinfo\": \"%u/%u/%u\"", RelFileInfoFmt(msg_req->rinfo));
 				appendStringInfo(&s, ", \"forknum\": %d", msg_req->forknum);
 				appendStringInfo(&s, ", \"lsn\": \"%X/%X\"", LSN_FORMAT_ARGS(msg_req->req.lsn));
-				appendStringInfo(&s, ", \"latest\": %d", msg_req->req.latest);
+				appendStringInfo(&s, ", \"horizon\": \"%X/%X\"", LSN_FORMAT_ARGS(msg_req->req.horizon));
 				appendStringInfoChar(&s, '}');
 				break;
 			}
@@ -1222,7 +1240,7 @@ nm_to_string(NeonMessage *msg)
 				appendStringInfo(&s, ", \"rinfo\": \"%u/%u/%u\"", RelFileInfoFmt(msg_req->rinfo));
 				appendStringInfo(&s, ", \"forknum\": %d", msg_req->forknum);
 				appendStringInfo(&s, ", \"lsn\": \"%X/%X\"", LSN_FORMAT_ARGS(msg_req->req.lsn));
-				appendStringInfo(&s, ", \"latest\": %d", msg_req->req.latest);
+				appendStringInfo(&s, ", \"horizon\": \"%X/%X\"", LSN_FORMAT_ARGS(msg_req->req.horizon));
 				appendStringInfoChar(&s, '}');
 				break;
 			}
@@ -1236,7 +1254,7 @@ nm_to_string(NeonMessage *msg)
 				appendStringInfo(&s, ", \"forknum\": %d", msg_req->forknum);
 				appendStringInfo(&s, ", \"blkno\": %u", msg_req->blkno);
 				appendStringInfo(&s, ", \"lsn\": \"%X/%X\"", LSN_FORMAT_ARGS(msg_req->req.lsn));
-				appendStringInfo(&s, ", \"latest\": %d", msg_req->req.latest);
+				appendStringInfo(&s, ", \"horizon\": \"%X/%X\"", LSN_FORMAT_ARGS(msg_req->req.horizon));
 				appendStringInfoChar(&s, '}');
 				break;
 			}
@@ -1247,7 +1265,7 @@ nm_to_string(NeonMessage *msg)
 				appendStringInfoString(&s, "{\"type\": \"NeonDbSizeRequest\"");
 				appendStringInfo(&s, ", \"dbnode\": \"%u\"", msg_req->dbNode);
 				appendStringInfo(&s, ", \"lsn\": \"%X/%X\"", LSN_FORMAT_ARGS(msg_req->req.lsn));
-				appendStringInfo(&s, ", \"latest\": %d", msg_req->req.latest);
+				appendStringInfo(&s, ", \"horizon\": \"%X/%X\"", LSN_FORMAT_ARGS(msg_req->req.horizon));
 				appendStringInfoChar(&s, '}');
 				break;
 			}
@@ -1259,7 +1277,7 @@ nm_to_string(NeonMessage *msg)
 				appendStringInfo(&s, ", \"kind\": %u", msg_req->kind);
 				appendStringInfo(&s, ", \"segno\": %u", msg_req->segno);
 				appendStringInfo(&s, ", \"lsn\": \"%X/%X\"", LSN_FORMAT_ARGS(msg_req->req.lsn));
-				appendStringInfo(&s, ", \"latest\": %d", msg_req->req.latest);
+				appendStringInfo(&s, ", \"horizon\": \"%X/%X\"", LSN_FORMAT_ARGS(msg_req->req.horizon));
 				appendStringInfoChar(&s, '}');
 				break;
 			}
@@ -1664,7 +1682,7 @@ neon_exists(SMgrRelation reln, ForkNumber forkNum)
 	{
 		NeonExistsRequest request = {
 			.req.tag = T_NeonExistsRequest,
-			.req.latest = latest,
+			.req.horizon = neon_get_horizon(latest),
 			.req.lsn = request_lsn,
 			.rinfo = InfoFromSMgrRel(reln),
 		.forknum = forkNum};
@@ -2474,7 +2492,7 @@ neon_nblocks(SMgrRelation reln, ForkNumber forknum)
 	{
 		NeonNblocksRequest request = {
 			.req.tag = T_NeonNblocksRequest,
-			.req.latest = latest,
+			.req.horizon = neon_get_horizon(latest),
 			.req.lsn = request_lsn,
 			.rinfo = InfoFromSMgrRel(reln),
 			.forknum = forknum,
@@ -2531,7 +2549,7 @@ neon_dbsize(Oid dbNode)
 	{
 		NeonDbSizeRequest request = {
 			.req.tag = T_NeonDbSizeRequest,
-			.req.latest = latest,
+			.req.horizon = neon_get_horizon(latest),
 			.req.lsn = request_lsn,
 			.dbNode = dbNode,
 		};
@@ -2827,7 +2845,7 @@ neon_read_slru_segment(SMgrRelation reln, const char* path, int segno, void* buf
 	NeonResponse *resp;
 	NeonGetSlruSegmentRequest request = {
 		.req.tag = T_NeonGetSlruSegmentRequest,
-		.req.latest = false,
+		.req.horizon =  InvalidXLogRecPtr,
 		.req.lsn = request_lsn,
 
 		.kind = kind,
@@ -2980,7 +2998,7 @@ neon_extend_rel_size(NRelFileInfo rinfo, ForkNumber forknum, BlockNumber blkno,
 		NeonNblocksRequest request = {
 			.req = (NeonRequest) {
 				.lsn = end_recptr,
-				.latest = false,
+				.horizon = neon_get_horizon(false),
 				.tag = T_NeonNblocksRequest,
 			},
 			.rinfo = rinfo,

test_runner/regress/test_protocol_version.py

@@ -0,0 +1,9 @@
+from fixtures.neon_fixtures import NeonEnv
+
+
+def test_protocol_version(neon_simple_env: NeonEnv):
+    env = neon_simple_env
+    endpoint = env.endpoints.create_start("main", config_lines=["neon.protocol_version=1"])
+    cur = endpoint.connect().cursor()
+    cur.execute("show neon.protocol_version")
+    assert cur.fetchone() == ("1",)