pageserver: support full gRPC basebackups (#12269)

## Problem

Full basebackups are used in tests, and may be useful for debugging as
well, so we should support them in the gRPC API.

Touches #11728.

## Summary of changes

Add `GetBaseBackupRequest::full` to generate full base backups.

The libpq implementation also allows specifying `prev_lsn` for full
backups, i.e. the end LSN of the previous WAL record. This is omitted in
the gRPC API, since it's not used by any tests, and presumably of
limited value since it's autodetected. We can add it later if we find
that we need it.

pageserver/page_api/proto/page_service.proto

@@ -108,6 +108,8 @@ message GetBaseBackupRequest {
   uint64 lsn = 1;
   // If true, logical replication slots will not be created.
   bool replica = 2;
+  // If true, include relation files in the base backup. Mainly for debugging and tests.
+  bool full = 3;
 }
 
 // Base backup response chunk, returned as an ordered stream.

pageserver/page_api/src/model.rs

@@ -189,6 +189,8 @@ pub struct GetBaseBackupRequest {
     pub lsn: Option<Lsn>,
     /// If true, logical replication slots will not be created.
     pub replica: bool,
+    /// If true, include relation files in the base backup. Mainly for debugging and tests.
+    pub full: bool,
 }
 
 impl From<proto::GetBaseBackupRequest> for GetBaseBackupRequest {
@@ -196,6 +198,7 @@ impl From<proto::GetBaseBackupRequest> for GetBaseBackupRequest {
         Self {
             lsn: (pb.lsn != 0).then_some(Lsn(pb.lsn)),
             replica: pb.replica,
+            full: pb.full,
         }
     }
 }
@@ -205,6 +208,7 @@ impl From<GetBaseBackupRequest> for proto::GetBaseBackupRequest {
         Self {
             lsn: request.lsn.unwrap_or_default().0,
             replica: request.replica,
+            full: request.full,
         }
     }
 }

pageserver/src/page_service.rs

@@ -3572,9 +3572,6 @@ impl proto::PageService for GrpcPageServiceHandler {
         }
 
         // Spawn a task to run the basebackup.
-        //
-        // TODO: do we need to support full base backups, for debugging? This also requires passing
-        // the prev_lsn parameter.
         let span = Span::current();
         let (mut simplex_read, mut simplex_write) = tokio::io::simplex(CHUNK_SIZE);
         let jh = tokio::spawn(async move {
@@ -3583,7 +3580,7 @@ impl proto::PageService for GrpcPageServiceHandler {
                 &timeline,
                 req.lsn,
                 None,
-                false,
+                req.full,
                 req.replica,
                 &ctx,
             )