From 52949f825a98277db96ad850df0116740a6e29f2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?J=C4=99drzej=20Stuczy=C5=84ski?=
 <jedrzej.stuczynski@gmail.com>
Date: Wed, 10 Jun 2026 09:54:36 +0100
Subject: [PATCH] chore: add retries for retrieving chain data (#6847)

* chore: add retries for retrieving chain data

* added retry backoff
---
 common/nyxd-scraper-shared/src/rpc_client.rs | 76 ++++++++++++++++++--
 1 file changed, 70 insertions(+), 6 deletions(-)

diff --git a/common/nyxd-scraper-shared/src/rpc_client.rs b/common/nyxd-scraper-shared/src/rpc_client.rs
index 0d41e907e0..d57e090ee3 100644
--- a/common/nyxd-scraper-shared/src/rpc_client.rs
+++ b/common/nyxd-scraper-shared/src/rpc_client.rs
@@ -10,6 +10,7 @@ use crate::{Any, MessageRegistry, ParsedTransactionDetails, default_message_regi
 use futures::StreamExt;
 use futures::future::join3;
 use std::collections::BTreeMap;
+use std::future::Future;
 use std::sync::Arc;
 use tendermint::{Block, Hash};
 use tendermint_rpc::endpoint::{block, block_results, tx, validators};
@@ -18,6 +19,38 @@ use tokio::sync::Mutex;
 use tracing::{debug, instrument, warn};
 use url::Url;
 
+const MAX_QUERY_ATTEMPTS: usize = 3;
+
+/// Runs `op` up to `max_attempts` times (at least once), returning the first success or, on full
+/// exhaustion, the last error encountered.
+async fn query_with_retries<F, Fut, T>(mut max_attempts: usize, op: F) -> Result<T, ScraperError>
+where
+    F: Fn() -> Fut,
+    Fut: Future<Output = Result<T, ScraperError>>,
+{
+    if max_attempts == 0 {
+        max_attempts = 1;
+    }
+
+    let mut last_err = None;
+
+    for i in 0..max_attempts {
+        match op().await {
+            Ok(result) => return Ok(result),
+            Err(err) => {
+                debug!("query failed, retrying {}/{max_attempts} - {err}", i + 1);
+                last_err = Some(err);
+            }
+        }
+
+        tokio::time::sleep(std::time::Duration::from_millis(300 * (i as u64 + 1))).await;
+    }
+
+    // SAFETY: max_attempts >= 1, so we only reach here after at least one recorded failure
+    #[allow(clippy::unwrap_used)]
+    Err(last_err.unwrap())
+}
+
 #[derive(Debug, Clone, Copy)]
 pub struct RetrievalConfig {
     pub get_validators: bool,
@@ -173,13 +206,24 @@ impl RpcClient {
         })
     }
 
+    #[instrument(skip(self), err(Display))]
+    async fn get_block_results_with_retries(
+        &self,
+        height: u32,
+        max_attempts: usize,
+    ) -> Result<block_results::Response, ScraperError> {
+        query_with_retries(max_attempts, || self.get_block_results(height)).await
+    }
+
     async fn maybe_get_block_results(
         &self,
         height: u32,
         retrieve: bool,
     ) -> Result<Option<block_results::Response>, ScraperError> {
         if retrieve {
-            self.get_block_results(height).await.map(Some)
+            self.get_block_results_with_retries(height, MAX_QUERY_ATTEMPTS)
+                .await
+                .map(Some)
         } else {
             Ok(None)
         }
@@ -219,8 +263,6 @@ impl RpcClient {
 
         // "Data is just a wrapper for a list of transactions, where transactions are arbitrary byte arrays"
         // source: https://github.com/tendermint/spec/blob/d46cd7f573a2c6a2399fcab2cde981330aa63f37/spec/core/data_structures.md#data
-        //
-        // I hate that zip as much as you, dear reader, but for some reason the compiler didn't let me remove the `move`
         futures::stream::iter(
             raw.iter()
                 .map(tx_hash)
@@ -228,12 +270,14 @@ impl RpcClient {
                 .zip(std::iter::repeat(ordered_results.clone())),
         )
         .for_each_concurrent(4, |((id, tx_hash), ordered_results)| async move {
-            let res = self.get_transaction_result(tx_hash).await;
+            let res = self
+                .get_transaction_result_with_retries(tx_hash, MAX_QUERY_ATTEMPTS)
+                .await;
             ordered_results.lock().await.insert(id, res);
         })
         .await;
 
-        // safety the futures have completed so we MUST have the only arc reference
+        // safety: the futures have completed so we MUST have the only arc reference
         #[allow(clippy::unwrap_used)]
         let inner = Arc::into_inner(ordered_results).unwrap().into_inner();
 
@@ -266,6 +310,15 @@ impl RpcClient {
             })
     }
 
+    #[instrument(skip(self, tx_hash), fields(tx_hash = %tx_hash), err(Display))]
+    async fn get_transaction_result_with_retries(
+        &self,
+        tx_hash: Hash,
+        max_attempts: usize,
+    ) -> Result<tx::Response, ScraperError> {
+        query_with_retries(max_attempts, || self.get_transaction_result(tx_hash)).await
+    }
+
     #[instrument(skip(self))]
     pub async fn get_validators_details(
         &self,
@@ -282,13 +335,24 @@ impl RpcClient {
             })
     }
 
+    #[instrument(skip(self), err(Display))]
+    async fn get_validators_details_with_retries(
+        &self,
+        height: u32,
+        max_attempts: usize,
+    ) -> Result<validators::Response, ScraperError> {
+        query_with_retries(max_attempts, || self.get_validators_details(height)).await
+    }
+
     async fn maybe_get_validators_details(
         &self,
         height: u32,
         retrieve: bool,
     ) -> Result<Option<validators::Response>, ScraperError> {
         if retrieve {
-            self.get_validators_details(height).await.map(Some)
+            self.get_validators_details_with_retries(height, MAX_QUERY_ATTEMPTS)
+                .await
+                .map(Some)
         } else {
             Ok(None)
         }