From e47ef1f0d2666a0d36c8db3b56b81a082dbe6dcc Mon Sep 17 00:00:00 2001
From: JeremyHi <jiachun_feng@proton.me>
Date: Tue, 20 Jun 2023 19:03:52 +0800
Subject: [PATCH] chore: minor fix (#1801)

---
 src/meta-client/src/client.rs          |  4 +-
 src/meta-srv/src/service/store/etcd.rs | 51 +++++++++-----------------
 2 files changed, 20 insertions(+), 35 deletions(-)

diff --git a/src/meta-client/src/client.rs b/src/meta-client/src/client.rs
index 78a612f4a270..5842b431c48e 100644
--- a/src/meta-client/src/client.rs
+++ b/src/meta-client/src/client.rs
@@ -756,7 +756,7 @@ mod tests {
         let tc = new_client("test_batch_put").await;
 
         let mut req = BatchPutRequest::new();
-        for i in 0..256 {
+        for i in 0..275 {
             req = req.add_kv(
                 tc.key(&format!("key-{}", i)),
                 format!("value-{}", i).into_bytes(),
@@ -769,7 +769,7 @@ mod tests {
         let req = RangeRequest::new().with_prefix(tc.key("key-"));
         let res = tc.client.range(req).await;
         let kvs = res.unwrap().take_kvs();
-        assert_eq!(256, kvs.len());
+        assert_eq!(275, kvs.len());
     }
 
     #[tokio::test]
diff --git a/src/meta-srv/src/service/store/etcd.rs b/src/meta-srv/src/service/store/etcd.rs
index 22834b355b3b..c97543137c52 100644
--- a/src/meta-srv/src/service/store/etcd.rs
+++ b/src/meta-srv/src/service/store/etcd.rs
@@ -32,6 +32,10 @@ use crate::error::Result;
 use crate::metrics::METRIC_META_KV_REQUEST;
 use crate::service::store::kv::{KvStore, KvStoreRef};
 
+// Maximum number of operations permitted in a transaction.
+// The etcd default configuration's `--max-txn-ops` is 128.
+//
+// For more detail, see: https://etcd.io/docs/v3.5/op-guide/configuration/
 const MAX_TXN_SIZE: usize = 128;
 
 pub struct EtcdStore {
@@ -55,7 +59,7 @@ impl EtcdStore {
         Ok(Arc::new(Self { client }))
     }
 
-    async fn do_multi_txn(&self, mut txn_ops: Vec<TxnOp>) -> Result<Vec<TxnResponse>> {
+    async fn do_multi_txn(&self, txn_ops: Vec<TxnOp>) -> Result<Vec<TxnResponse>> {
         if txn_ops.len() < MAX_TXN_SIZE {
             // fast path
             let txn = Txn::new().and_then(txn_ops);
@@ -68,36 +72,17 @@ impl EtcdStore {
             return Ok(vec![txn_res]);
         }
 
-        let mut txns = vec![];
-        loop {
-            if txn_ops.is_empty() {
-                break;
-            }
-
-            if txn_ops.len() < MAX_TXN_SIZE {
-                let txn = Txn::new().and_then(txn_ops);
-                txns.push(txn);
-                break;
-            }
-
-            let part = txn_ops.drain(..MAX_TXN_SIZE).collect::<Vec<_>>();
-            let txn = Txn::new().and_then(part);
-            txns.push(txn);
-        }
+        let txns = txn_ops
+            .chunks(MAX_TXN_SIZE)
+            .map(|part| async move {
+                let txn = Txn::new().and_then(part);
+                self.client.kv_client().txn(txn).await
+            })
+            .collect::<Vec<_>>();
 
-        let mut txn_responses = Vec::with_capacity(txns.len());
-        // Considering the pressure on etcd, it would be more appropriate to execute txn in
-        // a serial manner.
-        for txn in txns {
-            let txn_res = self
-                .client
-                .kv_client()
-                .txn(txn)
-                .await
-                .context(error::EtcdFailedSnafu)?;
-            txn_responses.push(txn_res);
-        }
-        Ok(txn_responses)
+        futures::future::try_join_all(txns)
+            .await
+            .context(error::EtcdFailedSnafu)
     }
 }
 
@@ -241,7 +226,7 @@ impl KvStore for EtcdStore {
                             prev_kvs.push(KvPair::from_etcd_kv(prev_kv));
                         }
                     }
-                    _ => unreachable!(), // never get here
+                    _ => unreachable!(),
                 }
             }
         }
@@ -283,7 +268,7 @@ impl KvStore for EtcdStore {
                             prev_kvs.push(KvPair::from_etcd_kv(kv));
                         });
                     }
-                    _ => unreachable!(), // never get here
+                    _ => unreachable!(),
                 }
             }
         }
@@ -343,7 +328,7 @@ impl KvStore for EtcdStore {
         let prev_kv = match op_res {
             TxnOpResponse::Put(res) => res.prev_key().map(KvPair::from_etcd_kv),
             TxnOpResponse::Get(res) => res.kvs().first().map(KvPair::from_etcd_kv),
-            _ => unreachable!(), // never get here
+            _ => unreachable!(),
         };
 
         let header = Some(ResponseHeader::success(cluster_id));