Test: add test to reproduce issue #584

Error After change_membership: `assertion failed: value > prev`,
when changing membership by converting a learner to a voter.

Because the replication streams are re-spawned, thus progress reverts to
zero. Then a reverted progress causes the panic.

Author: drmingdrmer

openraft/tests/membership/main.rs

@@ -21,4 +21,5 @@ mod t30_step_down;
 mod t40_removed_follower;
 mod t45_remove_unreachable_follower;
 mod t99_issue_471_adding_learner_uses_uninit_leader_id;
+mod t99_issue_584_replication_state_reverted;
 mod t99_new_leader_auto_commit_uniform_config;

openraft/tests/membership/t10_add_learner.rs

@@ -1,4 +1,3 @@
-use std::option::Option::None;
 use std::sync::Arc;
 use std::time::Duration;
 

openraft/tests/membership/t99_issue_584_replication_state_reverted.rs

@@ -0,0 +1,53 @@
+use std::sync::Arc;
+use std::time::Duration;
+
+use anyhow::Result;
+use maplit::btreeset;
+use openraft::Config;
+
+use crate::fixtures::init_default_ut_tracing;
+use crate::fixtures::RaftRouter;
+
+#[async_entry::test(worker_threads = 8, init = "init_default_ut_tracing()", tracing_span = "debug")]
+async fn t99_issue_584_replication_state_reverted() -> Result<()> {
+    // - Add a learner and replicate all logs to it.
+    // - Add the learner as a voter. When membership changes, openraft internally restarts all replication.
+    //
+    // This case asserts it does not break the internal monotonic-replication-progress guarantee.
+
+    let config = Arc::new(
+        Config {
+            max_in_snapshot_log_to_keep: 2000, // prevent snapshot
+            enable_tick: false,
+            ..Default::default()
+        }
+        .validate()?,
+    );
+    let mut router = RaftRouter::new(config.clone());
+
+    let mut log_index = router.new_nodes_from_single(btreeset! {0}, btreeset! {1}).await?;
+
+    let n = 500u64;
+    tracing::info!("--- write up to {} logs", n);
+    {
+        router.client_request_many(0, "foo", (n - log_index) as usize).await?;
+        log_index = n;
+
+        router.wait(&1, timeout()).log(Some(log_index), "replicate all logs to learner").await?;
+    }
+
+    tracing::info!("--- change-membership: make learner node-1 a voter. This should not panic");
+    {
+        let leader = router.get_raft_handle(&0)?;
+        leader.change_membership(btreeset![0, 1], true, false).await?;
+        log_index += 2; // 2 change_membership log
+
+        let _ = log_index;
+    }
+
+    Ok(())
+}
+
+fn timeout() -> Option<Duration> {
+    Some(Duration::from_millis(1_000))
+}