chore(forrestrie/examples): add example of matching eth block to beac…

…on slot

Cargo.toml

@@ -14,7 +14,7 @@ clap = { version = "4.4.10", features = ["derive"] }
 criterion = { version = "0.5.1", features = ["html_reports"] }
 dotenv = "0.15.0"
 dotenvy = "0.15.7"
-env_logger = "0.11.2"
+env_logger = "0.11.5"
 ethereum-types = "=0.14.1"
 ethportal-api = { git = "https://github.com/ethereum/trin.git", version = "0.2.2", tag = "v0.1.0-alpha.35" }
 futures = "0.3.31"
@@ -53,6 +53,7 @@ tokio-test = "0.4.3"
 tonic = "0.12.0"
 tonic-build = "0.12.0"
 tracing = "0.1.40"
+tracing-subscriber = "0.3"
 tree_hash = "0.6.0"
 trin-validation = { git = "https://github.com/ethereum/trin.git", version = "0.1.0", tag = "v0.1.0-alpha.35" }
 types = { git = "https://github.com/semiotic-ai/lighthouse.git", branch = "stable" }

crates/forrestrie/Cargo.toml

@@ -20,6 +20,7 @@ merkle_proof.workspace = true
 primitive-types.workspace = true
 serde = { workspace = true, features = ["derive"] }
 sf-protos = { path = "../sf-protos" }
+tracing.workspace = true
 tree_hash.workspace = true
 types.workspace = true
 
@@ -29,3 +30,4 @@ insta.workspace = true
 reqwest.workspace = true
 serde_json.workspace = true
 tokio = { workspace = true, features = ["macros", "rt-multi-thread"] }
+tracing-subscriber = "0.3"

crates/forrestrie/examples/match_ethereum_to_beacon.rs

@@ -0,0 +1,119 @@
+//! # Ethereum Block to Beacon Slot Lookup Example
+//!
+//! This example performs a binary search to find the corresponding Beacon chain
+//! slot for a given Ethereum execution block number. The problem being addressed
+//! is that, due to missed slots in the Beacon chain, Ethereum execution blocks
+//! and Beacon chain slots are not always aligned. Therefore, finding the correct
+//! Beacon slot that contains the execution block requires searching through
+//! Beacon blocks until the execution block is located.
+//!
+//! ## Key Concepts
+//!
+//! - **Execution Block Number**: This refers to the Ethereum block number that
+//!   we're trying to locate within the Beacon chain.
+//! - **Beacon Slot Number**: The slot number in the Beacon chain that contains
+//!   the corresponding Ethereum execution block.
+//! - **Deneb Fork**: This is the Ethereum fork that the blocks in the example
+//!   are from. We can imagine using `const` values to represent the start slot
+//!   of the Deneb fork and other upgrades, as well as the offsets between Ethereum
+//!   and Beacon block numbers at different known points along the chain.
+//!
+//! ## Approach
+//!
+//! The example uses a binary search algorithm to locate the Beacon slot that
+//! contains the execution block. It starts with a search range defined by
+//! `DENEB_START_SLOT` and an upper bound based on an estimated offset.
+//! During each iteration of the search, the Beacon block is fetched, and its
+//! execution payload is examined to check if it contains the target Ethereum
+//! block number. The search range is adjusted based on the result of this
+//! comparison until the correct Beacon slot is found.
+//!
+
+use firehose_client::client::{Chain, FirehoseClient};
+use forrestrie::beacon_state::{DENEB_START_SLOT, ETHEREUM_BEACON_DENEB_OFFSET};
+use sf_protos::beacon::r#type::v1::{block, Block as FirehoseBeaconBlock};
+use std::cmp::Ordering::*;
+use tracing::info;
+use tracing_subscriber::FmtSubscriber;
+
+/// This block relates to the slot represented by [`BEACON_SLOT_NUMBER`].
+/// The execution block is in the execution payload of the Beacon block in slot [`BEACON_SLOT_NUMBER`].
+const EXECUTION_BLOCK_NUMBER: u64 = 20759937;
+/// This slot is the slot of the Beacon block that contains the execution block with [`EXECUTION_BLOCK_NUMBER`].
+#[allow(unused)]
+const BEACON_SLOT_NUMBER: u64 = 9968872; // Beacon slot 9968872 pairs with Ethereum block 20759937.
+
+#[tokio::main]
+async fn main() {
+    let subscriber = FmtSubscriber::builder()
+        .with_max_level(tracing::Level::INFO)
+        .finish();
+    tracing::subscriber::set_global_default(subscriber).expect("setting default subscriber failed");
+
+    let mut beacon_client = FirehoseClient::new(Chain::Beacon);
+
+    let mut low = DENEB_START_SLOT as u64;
+    let mut high = EXECUTION_BLOCK_NUMBER - ETHEREUM_BEACON_DENEB_OFFSET as u64 + 2_000_000;
+
+    let mut guesses = 0;
+
+    while low <= high {
+        guesses += 1;
+
+        let mid = low + (high - low) / 2;
+
+        info!(guess = mid, "Current guess for Beacon slot");
+
+        let response = beacon_client.fetch_block(mid).await.unwrap().unwrap();
+        let block = FirehoseBeaconBlock::try_from(response.into_inner()).unwrap();
+
+        let Some(block::Body::Deneb(body)) = &block.body else {
+            panic!("Unsupported block version!");
+        };
+
+        let execution_payload = body.execution_payload.as_ref().unwrap();
+        let block_number = execution_payload.block_number;
+
+        if block_number == EXECUTION_BLOCK_NUMBER {
+            info!(beacon_slot = block.slot, "Found matching Beacon block!");
+            break;
+        }
+
+        match block_number.cmp(&EXECUTION_BLOCK_NUMBER) {
+            Less => low = mid + 1,
+            Greater => high = mid - 1,
+            _ => unreachable!(),
+        }
+
+        if high == low || high == low + 1 {
+            if let Some(final_result) = try_final_fetches(low, high, &mut beacon_client).await {
+                println!(
+                    "Found final result: matching execution block at Beacon slot: {}",
+                    final_result
+                );
+                break;
+            }
+        }
+    }
+    info!(guesses, "Guesses");
+}
+
+/// Helper function to fetch both `low` and `high` Beacon slots when binary search is down to two options
+async fn try_final_fetches(low: u64, high: u64, client: &mut FirehoseClient) -> Option<u64> {
+    for slot in &[low, high] {
+        let response = client.fetch_block(*slot).await.unwrap().unwrap();
+
+        let block = FirehoseBeaconBlock::try_from(response.into_inner()).unwrap();
+
+        let Some(block::Body::Deneb(body)) = &block.body else {
+            return None;
+        };
+
+        let execution_payload = body.execution_payload.as_ref().unwrap();
+
+        if execution_payload.block_number == EXECUTION_BLOCK_NUMBER {
+            return Some(block.slot);
+        }
+    }
+    None
+}