Builder Specs v0.2.0 (#3134)

## Issue Addressed

https://github.com/sigp/lighthouse/issues/3091

Extends https://github.com/sigp/lighthouse/pull/3062, adding pre-bellatrix block support on blinded endpoints and allowing the normal proposal flow (local payload construction) on blinded endpoints. This resulted in better fallback logic because the VC will not have to switch endpoints on failure in the BN <> Builder API, the BN can just fallback immediately and without repeating block processing that it shouldn't need to. We can also keep VC fallback from the VC<>BN API's blinded endpoint to full endpoint.

## Proposed Changes

- Pre-bellatrix blocks on blinded endpoints
- Add a new `PayloadCache` to the execution layer
- Better fallback-from-builder logic

## Todos

- [x] Remove VC transition logic
- [x] Add logic to only enable builder flow after Merge transition finalization
- [x] Tests
- [x] Fix metrics
- [x] Rustdocs


Co-authored-by: Mac L <mjladson@pm.me>
Co-authored-by: realbigsean <sean@sigmaprime.io>

beacon_node/builder_client/src/lib.rs

@@ -1,4 +1,3 @@
-use eth2::ok_or_error;
 use eth2::types::builder_bid::SignedBuilderBid;
 use eth2::types::{
     BlindedPayload, EthSpec, ExecPayload, ExecutionBlockHash, ExecutionPayload,
@@ -6,23 +5,33 @@ use eth2::types::{
     Slot,
 };
 pub use eth2::Error;
+use eth2::{ok_or_error, StatusCode};
 use reqwest::{IntoUrl, Response};
 use sensitive_url::SensitiveUrl;
 use serde::de::DeserializeOwned;
 use serde::Serialize;
 use std::time::Duration;
 
-pub const DEFAULT_GET_HEADER_TIMEOUT_MILLIS: u64 = 500;
+pub const DEFAULT_TIMEOUT_MILLIS: u64 = 15000;
+
+/// This timeout is in accordance with v0.2.0 of the [builder specs](https://github.com/flashbots/mev-boost/pull/20).
+pub const DEFAULT_GET_HEADER_TIMEOUT_MILLIS: u64 = 1000;
 
 #[derive(Clone)]
 pub struct Timeouts {
     get_header: Duration,
+    post_validators: Duration,
+    post_blinded_blocks: Duration,
+    get_builder_status: Duration,
 }
 
 impl Default for Timeouts {
     fn default() -> Self {
         Self {
             get_header: Duration::from_millis(DEFAULT_GET_HEADER_TIMEOUT_MILLIS),
+            post_validators: Duration::from_millis(DEFAULT_TIMEOUT_MILLIS),
+            post_blinded_blocks: Duration::from_millis(DEFAULT_TIMEOUT_MILLIS),
+            get_builder_status: Duration::from_millis(DEFAULT_TIMEOUT_MILLIS),
         }
     }
 }
@@ -51,14 +60,6 @@ impl BuilderHttpClient {
         })
     }
 
-    async fn get<T: DeserializeOwned, U: IntoUrl>(&self, url: U) -> Result<T, Error> {
-        self.get_response_with_timeout(url, None)
-            .await?
-            .json()
-            .await
-            .map_err(Error::Reqwest)
-    }
-
     async fn get_with_timeout<T: DeserializeOwned, U: IntoUrl>(
         &self,
         url: U,
@@ -104,14 +105,13 @@ impl BuilderHttpClient {
         &self,
         url: U,
         body: &T,
+        timeout: Option<Duration>,
     ) -> Result<Response, Error> {
-        let response = self
-            .client
-            .post(url)
-            .json(body)
-            .send()
-            .await
-            .map_err(Error::Reqwest)?;
+        let mut builder = self.client.post(url);
+        if let Some(timeout) = timeout {
+            builder = builder.timeout(timeout);
+        }
+        let response = builder.json(body).send().await.map_err(Error::Reqwest)?;
         ok_or_error(response).await
     }
 
@@ -129,7 +129,8 @@ impl BuilderHttpClient {
             .push("builder")
             .push("validators");
 
-        self.post_generic(path, &validator, None).await?;
+        self.post_generic(path, &validator, Some(self.timeouts.post_validators))
+            .await?;
         Ok(())
     }
 
@@ -148,7 +149,11 @@ impl BuilderHttpClient {
             .push("blinded_blocks");
 
         Ok(self
-            .post_with_raw_response(path, &blinded_block)
+            .post_with_raw_response(
+                path,
+                &blinded_block,
+                Some(self.timeouts.post_blinded_blocks),
+            )
             .await?
             .json()
             .await?)
@@ -160,7 +165,7 @@ impl BuilderHttpClient {
         slot: Slot,
         parent_hash: ExecutionBlockHash,
         pubkey: &PublicKeyBytes,
-    ) -> Result<ForkVersionedResponse<SignedBuilderBid<E, Payload>>, Error> {
+    ) -> Result<Option<ForkVersionedResponse<SignedBuilderBid<E, Payload>>>, Error> {
         let mut path = self.server.full.clone();
 
         path.path_segments_mut()
@@ -173,7 +178,13 @@ impl BuilderHttpClient {
             .push(format!("{parent_hash:?}").as_str())
             .push(pubkey.as_hex_string().as_str());
 
-        self.get_with_timeout(path, self.timeouts.get_header).await
+        let resp = self.get_with_timeout(path, self.timeouts.get_header).await;
+
+        if matches!(resp, Err(Error::StatusCode(StatusCode::NO_CONTENT))) {
+            Ok(None)
+        } else {
+            resp.map(Some)
+        }
     }
 
     /// `GET /eth/v1/builder/status`
@@ -187,6 +198,7 @@ impl BuilderHttpClient {
             .push("builder")
             .push("status");
 
-        self.get(path).await
+        self.get_with_timeout(path, self.timeouts.get_builder_status)
+            .await
     }
 }