Retry block_pointer_from_number on deploy

Add retry to avoid a single failure while making the call prevent the subsgraph from being deployed
Add warning for failed attempts

core/src/subgraph/registrar.rs

@@ -13,6 +13,9 @@ use graph::prelude::{
     CreateSubgraphResult, SubgraphAssignmentProvider as SubgraphAssignmentProviderTrait,
     SubgraphRegistrar as SubgraphRegistrarTrait, *,
 };
+use graph::tokio_retry::strategy::jitter;
+use graph::tokio_retry::strategy::ExponentialBackoff;
+use graph::tokio_retry::Retry;
 
 pub struct SubgraphRegistrar<P, S, SM> {
     logger: Logger,
@@ -518,18 +521,41 @@ async fn resolve_start_block(
         .expect("cannot identify minimum start block because there are no data sources")
     {
         0 => Ok(None),
-        min_start_block => chain
-            .block_pointer_from_number(logger, min_start_block - 1)
+        min_start_block => {
+            let chain = chain.clone();
+            Retry::spawn(retry_strategy(Some(2)), move || {
+                chain
+                    .block_pointer_from_number(&logger, min_start_block - 1)
+                    .inspect_err(move |e| warn!(&logger, "Failed to get block number: {}", e))
+            })
             .await
             .map(Some)
             .map_err(move |_| {
                 SubgraphRegistrarError::ManifestValidationError(vec![
                     SubgraphManifestValidationError::BlockNotFound(min_start_block.to_string()),
                 ])
-            }),
+            })
+        }
     }
 }
 
+fn retry_strategy(limit_opt: Option<usize>) -> Box<dyn Iterator<Item = Duration> + Send> {
+    // Exponential backoff, but with a maximum
+    let max_delay_ms = 30_000;
+    let backoff = ExponentialBackoff::from_millis(2)
+        .max_delay(Duration::from_millis(max_delay_ms))
+        .map(jitter);
+
+    // Apply limit (maximum retry count)
+    match limit_opt {
+        Some(limit) => {
+            // Items are delays *between* attempts,
+            // so subtract 1 from limit.
+            Box::new(backoff.take(limit - 1))
+        }
+        None => Box::new(backoff),
+    }
+}
 /// Resolves the manifest's graft base block
 async fn resolve_graft_block(
     base: &Graft,

graph/src/lib.rs

@@ -53,6 +53,7 @@ pub use semver;
 pub use slog;
 pub use stable_hash_legacy;
 pub use tokio;
+pub use tokio_retry;
 pub use tokio_stream;
 pub use url;