Bug: .expect() in request handlers can crash entire service

[drmingdrmer]

Summary

Request handling code uses .expect() which will panic and crash the service on unexpected responses.

Locations

crates/service/src/meta_node/meta_handle.rs:266-268

let applied_state: AppliedState = forward_resp.try_into().expect("expect AppliedState");
let txn_reply: TxnReply = applied_state.try_into().expect("expect TxnReply");

crates/service/src/meta_node/meta_node.rs:1440

let res: AppliedState = res.try_into().expect("expect AppliedState");

Problem

These .expect() calls are in the request processing path. If the conversion fails due to:

• Protocol version mismatch
• Corrupted response from leader
• Serialization bugs

The entire meta service will crash, causing complete cluster unavailability.

Impact

• Single malformed response crashes the service
• No graceful error handling for clients
• Cascading failures if leader sends bad responses

Suggested Fix

let applied_state: AppliedState = forward_resp
    .try_into()
    .map_err(|e| MetaAPIError::Internal(format!("Invalid AppliedState: {:?}", e)))?;

let txn_reply: TxnReply = applied_state
    .try_into()
    .map_err(|e| MetaAPIError::Internal(format!("Invalid TxnReply: {:?}", e)))?;

Priority

P1 - Service stability