Redo #655 with fix: Allow LeSer/BeSer impls missing either Serialize or Deserialize

Commit message copied below:

* Allow LeSer/BeSer impls missing Serialize/Deserialize

Currently, using `LeSer` or `BeSer` requires that the type implements
both `Serialize` and `DeserializeOwned`, even if we're only using the
trait for one of those functionalities.

Moving the bounds to the methods gives the convenience of the traits
without requiring unnecessary derives.

* Remove unused #[derive(Serialize/Deserialize)]

This should hopefully reduce compile times - if only by a little bit.

Some of these were already unused (we weren't using LeSer/BeSer for the
types), but most are have *become* unused with the change to
LeSer/BeSer.

pageserver/src/walredo.rs

@@ -22,7 +22,7 @@ use byteorder::{ByteOrder, LittleEndian};
 use bytes::{Buf, BufMut, Bytes, BytesMut};
 use lazy_static::lazy_static;
 use log::*;
-use serde::{Deserialize, Serialize};
+use serde::Serialize;
 use std::fs;
 use std::fs::OpenOptions;
 use std::io::prelude::*;
@@ -59,7 +59,7 @@ use postgres_ffi::XLogRecord;
 /// In Postgres `BufferTag` structure is used for exactly the same purpose.
 /// [See more related comments here](https://github.com/postgres/postgres/blob/99c5852e20a0987eca1c38ba0c09329d4076b6a0/src/include/storage/buf_internals.h#L91).
 ///
-#[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Clone, Copy, Serialize, Deserialize)]
+#[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Clone, Copy, Serialize)]
 pub struct BufferTag {
     pub rel: RelTag,
     pub blknum: u32,

proxy/src/mgmt.rs

@@ -5,7 +5,7 @@ use std::{
 
 use anyhow::bail;
 use bytes::Bytes;
-use serde::{Deserialize, Serialize};
+use serde::Deserialize;
 use zenith_utils::{
     postgres_backend::{self, query_from_cstring, AuthType, PostgresBackend},
     pq_proto::{BeMessage, SINGLE_COL_ROWDESC},
@@ -60,13 +60,13 @@ struct MgmtHandler {
 //         "Failure": "oops"
 //     }
 // }
-#[derive(Serialize, Deserialize)]
+#[derive(Deserialize)]
 pub struct PsqlSessionResponse {
     session_id: String,
     result: PsqlSessionResult,
 }
 
-#[derive(Serialize, Deserialize)]
+#[derive(Deserialize)]
 pub enum PsqlSessionResult {
     Success(DatabaseInfo),
     Failure(String),

walkeeper/src/safekeeper.rs

@@ -111,7 +111,7 @@ impl Default for SafeKeeperState {
 // protocol messages
 
 /// Initial Proposer -> Acceptor message
-#[derive(Debug, Serialize, Deserialize)]
+#[derive(Debug, Deserialize)]
 pub struct ProposerGreeting {
     /// proposer-acceptor protocol version
     pub protocol_version: u32,
@@ -128,19 +128,19 @@ pub struct ProposerGreeting {
 
 /// Acceptor -> Proposer initial response: the highest term known to me
 /// (acceptor voted for).
-#[derive(Debug, Serialize, Deserialize)]
+#[derive(Debug, Serialize)]
 pub struct AcceptorGreeting {
     term: u64,
 }
 
 /// Vote request sent from proposer to safekeepers
-#[derive(Debug, Serialize, Deserialize)]
+#[derive(Debug, Deserialize)]
 pub struct VoteRequest {
     term: Term,
 }
 
 /// Vote itself, sent from safekeeper to proposer
-#[derive(Debug, Serialize, Deserialize)]
+#[derive(Debug, Serialize)]
 pub struct VoteResponse {
     term: Term,      // not really needed, just a sanity check
     vote_given: u64, // fixme u64 due to padding
@@ -152,12 +152,12 @@ pub struct VoteResponse {
 
 /// Request with WAL message sent from proposer to safekeeper. Along the way it
 /// announces 1) successful election (with epoch_start_lsn); 2) commit_lsn.
-#[derive(Debug, Serialize, Deserialize)]
+#[derive(Debug)]
 pub struct AppendRequest {
     pub h: AppendRequestHeader,
     pub wal_data: Bytes,
 }
-#[derive(Debug, Clone, Serialize, Deserialize)]
+#[derive(Debug, Clone, Deserialize)]
 pub struct AppendRequestHeader {
     pub term: Term,
     // LSN since the proposer appends WAL; determines epoch switch point.

zenith_utils/src/bin_ser.rs

@@ -94,9 +94,12 @@ pub fn le_coder() -> impl Options {
 
 /// Binary serialize/deserialize helper functions (Big Endian)
 ///
-pub trait BeSer: Serialize + DeserializeOwned {
+pub trait BeSer {
     /// Serialize into a byte slice
-    fn ser_into_slice(&self, mut b: &mut [u8]) -> Result<(), SerializeError> {
+    fn ser_into_slice(&self, mut b: &mut [u8]) -> Result<(), SerializeError>
+    where
+        Self: Serialize,
+    {
         // &mut [u8] implements Write, but `ser_into` needs a mutable
         // reference to that. So we need the slightly awkward "mutable
         // reference to a mutable reference.
@@ -107,19 +110,28 @@ pub trait BeSer: Serialize + DeserializeOwned {
     ///
     /// This is useful for most `Write` types except `&mut [u8]`, which
     /// can more easily use [`ser_into_slice`](Self::ser_into_slice).
-    fn ser_into<W: Write>(&self, w: &mut W) -> Result<(), SerializeError> {
+    fn ser_into<W: Write>(&self, w: &mut W) -> Result<(), SerializeError>
+    where
+        Self: Serialize,
+    {
         be_coder().serialize_into(w, &self).map_err(|e| e.into())
     }
 
     /// Serialize into a new heap-allocated buffer
-    fn ser(&self) -> Result<Vec<u8>, SerializeError> {
+    fn ser(&self) -> Result<Vec<u8>, SerializeError>
+    where
+        Self: Serialize,
+    {
         be_coder().serialize(&self).map_err(|e| e.into())
     }
 
     /// Deserialize from the full contents of a byte slice
     ///
     /// See also: [`BeSer::des_prefix`]
-    fn des(buf: &[u8]) -> Result<Self, DeserializeError> {
+    fn des(buf: &[u8]) -> Result<Self, DeserializeError>
+    where
+        Self: DeserializeOwned,
+    {
         be_coder()
             .deserialize(buf)
             .or(Err(DeserializeError::BadInput))
@@ -131,7 +143,10 @@ pub trait BeSer: Serialize + DeserializeOwned {
     /// type, but does not guarantee that the entire slice is used.
     ///
     /// See also: [`BeSer::des`]
-    fn des_prefix(buf: &[u8]) -> Result<Self, DeserializeError> {
+    fn des_prefix(buf: &[u8]) -> Result<Self, DeserializeError>
+    where
+        Self: DeserializeOwned,
+    {
         be_coder()
             .allow_trailing_bytes()
             .deserialize(buf)
@@ -139,7 +154,10 @@ pub trait BeSer: Serialize + DeserializeOwned {
     }
 
     /// Deserialize from a reader
-    fn des_from<R: Read>(r: &mut R) -> Result<Self, DeserializeError> {
+    fn des_from<R: Read>(r: &mut R) -> Result<Self, DeserializeError>
+    where
+        Self: DeserializeOwned,
+    {
         be_coder().deserialize_from(r).map_err(|e| e.into())
     }
 
@@ -147,16 +165,22 @@ pub trait BeSer: Serialize + DeserializeOwned {
     ///
     /// Note: it may be faster to serialize to a buffer and then measure the
     /// buffer length, than to call `serialized_size` and then `ser_into`.
-    fn serialized_size(&self) -> Result<u64, SerializeError> {
+    fn serialized_size(&self) -> Result<u64, SerializeError>
+    where
+        Self: Serialize,
+    {
         be_coder().serialized_size(self).map_err(|e| e.into())
     }
 }
 
 /// Binary serialize/deserialize helper functions (Little Endian)
 ///
-pub trait LeSer: Serialize + DeserializeOwned {
+pub trait LeSer {
     /// Serialize into a byte slice
-    fn ser_into_slice(&self, mut b: &mut [u8]) -> Result<(), SerializeError> {
+    fn ser_into_slice(&self, mut b: &mut [u8]) -> Result<(), SerializeError>
+    where
+        Self: Serialize,
+    {
         // &mut [u8] implements Write, but `ser_into` needs a mutable
         // reference to that. So we need the slightly awkward "mutable
         // reference to a mutable reference.
@@ -167,19 +191,28 @@ pub trait LeSer: Serialize + DeserializeOwned {
     ///
     /// This is useful for most `Write` types except `&mut [u8]`, which
     /// can more easily use [`ser_into_slice`](Self::ser_into_slice).
-    fn ser_into<W: Write>(&self, w: &mut W) -> Result<(), SerializeError> {
+    fn ser_into<W: Write>(&self, w: &mut W) -> Result<(), SerializeError>
+    where
+        Self: Serialize,
+    {
         le_coder().serialize_into(w, &self).map_err(|e| e.into())
     }
 
     /// Serialize into a new heap-allocated buffer
-    fn ser(&self) -> Result<Vec<u8>, SerializeError> {
+    fn ser(&self) -> Result<Vec<u8>, SerializeError>
+    where
+        Self: Serialize,
+    {
         le_coder().serialize(&self).map_err(|e| e.into())
     }
 
     /// Deserialize from the full contents of a byte slice
     ///
     /// See also: [`LeSer::des_prefix`]
-    fn des(buf: &[u8]) -> Result<Self, DeserializeError> {
+    fn des(buf: &[u8]) -> Result<Self, DeserializeError>
+    where
+        Self: DeserializeOwned,
+    {
         le_coder()
             .deserialize(buf)
             .or(Err(DeserializeError::BadInput))
@@ -191,7 +224,10 @@ pub trait LeSer: Serialize + DeserializeOwned {
     /// type, but does not guarantee that the entire slice is used.
     ///
     /// See also: [`LeSer::des`]
-    fn des_prefix(buf: &[u8]) -> Result<Self, DeserializeError> {
+    fn des_prefix(buf: &[u8]) -> Result<Self, DeserializeError>
+    where
+        Self: DeserializeOwned,
+    {
         le_coder()
             .allow_trailing_bytes()
             .deserialize(buf)
@@ -199,7 +235,10 @@ pub trait LeSer: Serialize + DeserializeOwned {
     }
 
     /// Deserialize from a reader
-    fn des_from<R: Read>(r: &mut R) -> Result<Self, DeserializeError> {
+    fn des_from<R: Read>(r: &mut R) -> Result<Self, DeserializeError>
+    where
+        Self: DeserializeOwned,
+    {
         le_coder().deserialize_from(r).map_err(|e| e.into())
     }
 
@@ -207,14 +246,18 @@ pub trait LeSer: Serialize + DeserializeOwned {
     ///
     /// Note: it may be faster to serialize to a buffer and then measure the
     /// buffer length, than to call `serialized_size` and then `ser_into`.
-    fn serialized_size(&self) -> Result<u64, SerializeError> {
+    fn serialized_size(&self) -> Result<u64, SerializeError>
+    where
+        Self: Serialize,
+    {
         le_coder().serialized_size(self).map_err(|e| e.into())
     }
 }
 
-impl<T> BeSer for T where T: Serialize + DeserializeOwned {}
-
-impl<T> LeSer for T where T: Serialize + DeserializeOwned {}
+// Because usage of `BeSer` or `LeSer` can be done with *either* a Serialize or
+// DeserializeOwned implementation, the blanket implementation has to be for every type.
+impl<T> BeSer for T {}
+impl<T> LeSer for T {}
 
 #[cfg(test)]
 mod tests {

zenith_utils/tests/bin_ser_test.rs

@@ -1,10 +1,10 @@
 use bytes::{Buf, BytesMut};
 use hex_literal::hex;
-use serde::{Deserialize, Serialize};
+use serde::Deserialize;
 use std::io::Read;
 use zenith_utils::bin_ser::LeSer;
 
-#[derive(Debug, PartialEq, Serialize, Deserialize)]
+#[derive(Debug, PartialEq, Deserialize)]
 pub struct HeaderData {
     magic: u16,
     info: u16,