refactor(state): improve error propagation for ReconsiderError (#9919)

Author: syszery

zebra-state/src/error.rs

@@ -59,6 +59,15 @@ pub enum ReconsiderError {
     #[error("Invalidated blocks list is empty when it should contain at least one block")]
     InvalidatedBlocksEmpty,
 
+    #[error("cannot reconsider blocks while still committing checkpointed blocks")]
+    CheckpointCommitInProgress,
+
+    #[error("failed to send reconsider block request to block write task")]
+    ReconsiderSendFailed,
+
+    #[error("reconsider block request was unexpectedly dropped")]
+    ReconsiderResponseDropped,
+
     #[error("{0}")]
     ValidationError(#[from] Box<ValidateContextError>),
 }

zebra-state/src/service.rs

@@ -45,6 +45,7 @@ use crate::{
     constants::{
         MAX_FIND_BLOCK_HASHES_RESULTS, MAX_FIND_BLOCK_HEADERS_RESULTS, MAX_LEGACY_CHAIN_BLOCKS,
     },
+    error::ReconsiderError,
     response::NonFinalizedBlocksListener,
     service::{
         block_iter::any_ancestor_blocks,
@@ -842,13 +843,11 @@ impl StateService {
     fn send_reconsider_block(
         &self,
         hash: block::Hash,
-    ) -> oneshot::Receiver<Result<Vec<block::Hash>, BoxError>> {
+    ) -> oneshot::Receiver<Result<Vec<block::Hash>, ReconsiderError>> {
         let (rsp_tx, rsp_rx) = oneshot::channel();
 
         let Some(sender) = &self.block_write_sender.non_finalized else {
-            let _ = rsp_tx.send(Err(
-                "cannot reconsider blocks while still committing checkpointed blocks".into(),
-            ));
+            let _ = rsp_tx.send(Err(ReconsiderError::CheckpointCommitInProgress));
             return rsp_rx;
         };
 
@@ -859,9 +858,7 @@ impl StateService {
                 unreachable!("should return the same Reconsider message could not be sent");
             };
 
-            let _ = rsp_tx.send(Err(
-                "failed to send reconsider block request to block write task".into(),
-            ));
+            let _ = rsp_tx.send(Err(ReconsiderError::ReconsiderSendFailed));
         }
 
         rsp_rx
@@ -1204,11 +1201,11 @@ impl Service<Request> for StateService {
                     rsp_rx
                         .await
                         .map_err(|_recv_error| {
-                            BoxError::from("reconsider block request was unexpectedly dropped")
+                            BoxError::from(ReconsiderError::ReconsiderResponseDropped)
                         })
                         // TODO: replace with Result::flatten once it stabilises
                         // https://github.com/rust-lang/rust/issues/70142
-                        .and_then(convert::identity)
+                        .and_then(|res| res.map_err(BoxError::from))
                         .map(Response::Reconsidered)
                 }
                 .instrument(span)

zebra-state/src/service/write.rs

@@ -21,7 +21,7 @@ use crate::{
         finalized_state::{FinalizedState, ZebraDb},
         non_finalized_state::NonFinalizedState,
         queued_blocks::{QueuedCheckpointVerified, QueuedSemanticallyVerified},
-        BoxError, ChainTipBlock, ChainTipSender,
+        BoxError, ChainTipBlock, ChainTipSender, ReconsiderError,
     },
     CommitSemanticallyVerifiedError, SemanticallyVerifiedBlock,
 };
@@ -145,7 +145,7 @@ pub enum NonFinalizedWriteMessage {
     /// reconsidered and reinserted into the non-finalized state.
     Reconsider {
         hash: block::Hash,
-        rsp_tx: oneshot::Sender<Result<Vec<block::Hash>, BoxError>>,
+        rsp_tx: oneshot::Sender<Result<Vec<block::Hash>, ReconsiderError>>,
     },
 }
 
@@ -349,11 +349,8 @@ impl WriteBlockWorkerTask {
                 }
                 NonFinalizedWriteMessage::Reconsider { hash, rsp_tx } => {
                     tracing::info!(?hash, "reconsidering a block in the non-finalized state");
-                    let _ = rsp_tx.send(
-                        non_finalized_state
-                            .reconsider_block(hash, &finalized_state.db)
-                            .map_err(BoxError::from),
-                    );
+                    let _ = rsp_tx
+                        .send(non_finalized_state.reconsider_block(hash, &finalized_state.db));
                     None
                 }
             };