Revert "adding retryable to scan" (#1)

This reverts commit dddf519.

Author: limbooverlambda

src/raw/client.rs

@@ -1,35 +1,30 @@
 // Copyright 2019 TiKV Project Authors. Licensed under Apache-2.0.
 
-use async_recursion::async_recursion;
 use core::ops::Range;
 use std::str::FromStr;
 use std::sync::Arc;
 use std::u32;
 
+use futures::StreamExt;
 use log::debug;
-use tokio::sync::Semaphore;
-use tokio::time::sleep;
 
-use crate::backoff::{DEFAULT_REGION_BACKOFF, DEFAULT_STORE_BACKOFF};
+use crate::backoff::DEFAULT_REGION_BACKOFF;
 use crate::common::Error;
 use crate::config::Config;
 use crate::pd::PdClient;
 use crate::pd::PdRpcClient;
-use crate::proto::kvrpcpb::{RawScanRequest, RawScanResponse};
 use crate::proto::metapb;
 use crate::raw::lowering::*;
+use crate::request::Collect;
 use crate::request::CollectSingle;
 use crate::request::EncodeKeyspace;
 use crate::request::KeyMode;
 use crate::request::Keyspace;
 use crate::request::Plan;
 use crate::request::TruncateKeyspace;
-use crate::request::{plan, Collect};
-use crate::store::{HasRegionError, RegionStore};
 use crate::Backoff;
 use crate::BoundRange;
 use crate::ColumnFamily;
-use crate::Error::RegionError;
 use crate::Key;
 use crate::KvPair;
 use crate::Result;
@@ -761,42 +756,57 @@ impl<PdC: PdClient> Client<PdC> {
                 max_limit: MAX_RAW_KV_SCAN_LIMIT,
             });
         }
-        let backoff = DEFAULT_STORE_BACKOFF;
-        let permits = Arc::new(Semaphore::new(16));
-        let range = range.into().encode_keyspace(self.keyspace, KeyMode::Raw);
+
+        let mut cur_range = range.into().encode_keyspace(self.keyspace, KeyMode::Raw);
         let mut result = Vec::new();
-        let mut current_limit = limit;
-        let (start_key, end_key) = range.clone().into_keys();
-        let mut current_key: Option<Key> = Some(start_key);
-        while current_limit > 0 {
-            let scan_args = ScanInnerArgs {
-                start_key: current_key.clone(),
-                range: range.clone(),
-                limit,
+        let mut scan_regions = self.rpc.clone().stores_for_range(cur_range.clone()).boxed();
+        let mut region_store =
+            scan_regions
+                .next()
+                .await
+                .ok_or(Error::RegionForRangeNotFound {
+                    range: (cur_range.clone()),
+                })??;
+        let mut cur_limit = limit;
+
+        while cur_limit > 0 {
+            let request = new_raw_scan_request(
+                cur_range.clone(),
+                cur_limit,
                 key_only,
                 reverse,
-                permits: permits.clone(),
-                backoff: backoff.clone(),
-            };
-            let (res, next_key) = self.retryable_scan(scan_args).await?;
-
-            let mut kvs = res
-                .map(|r| r.kvs.into_iter().map(Into::into).collect::<Vec<KvPair>>())
-                .unwrap_or(Vec::new());
-
-            if !kvs.is_empty() {
-                current_limit -= kvs.len() as u32;
-                result.append(&mut kvs);
-            }
-            if end_key
-                .as_ref()
-                .map(|ek| ek <= next_key.as_ref() && !ek.is_empty())
-                .unwrap_or(false)
-                || next_key.is_empty()
-            {
-                break;
+                self.cf.clone(),
+            );
+            let resp = crate::request::PlanBuilder::new(self.rpc.clone(), self.keyspace, request)
+                .single_region_with_store(region_store.clone())
+                .await?
+                .plan()
+                .execute()
+                .await?;
+            let mut region_scan_res = resp
+                .kvs
+                .into_iter()
+                .map(Into::into)
+                .collect::<Vec<KvPair>>();
+            let res_len = region_scan_res.len();
+            result.append(&mut region_scan_res);
+
+            // if the number of results is less than cur_limit, it means this scan range contains more than one region, so we need to scan next region
+            if res_len < cur_limit as usize {
+                region_store = match scan_regions.next().await {
+                    Some(Ok(rs)) => {
+                        cur_range = BoundRange::new(
+                            std::ops::Bound::Included(region_store.region_with_leader.range().1),
+                            cur_range.to,
+                        );
+                        rs
+                    }
+                    Some(Err(e)) => return Err(e),
+                    None => break,
+                };
+                cur_limit -= res_len as u32;
             } else {
-                current_key = Some(next_key);
+                break;
             }
         }
 
@@ -809,61 +819,6 @@ impl<PdC: PdClient> Client<PdC> {
         Ok(result)
     }
 
-    #[async_recursion]
-    async fn retryable_scan(
-        &self,
-        mut scan_args: ScanInnerArgs,
-    ) -> Result<(Option<RawScanResponse>, Key)> {
-        let start_key = match scan_args.start_key {
-            None => return Ok((None, Key::EMPTY)),
-            Some(ref sk) => sk,
-        };
-        let permit = scan_args.permits.acquire().await.unwrap();
-        let region = self.rpc.clone().region_for_key(start_key).await?;
-        let store = self.rpc.clone().store_for_id(region.id()).await?;
-        let request = new_raw_scan_request(
-            scan_args.range.clone(),
-            scan_args.limit,
-            scan_args.key_only,
-            scan_args.reverse,
-            self.cf.clone(),
-        );
-        let resp = self.do_store_scan(store.clone(), request).await;
-        drop(permit);
-        match resp {
-            Ok(mut r) => {
-                if let Some(err) = r.region_error() {
-                    let status =
-                        plan::handle_region_error(self.rpc.clone(), err.clone(), store.clone())
-                            .await?;
-                    return if status {
-                        self.retryable_scan(scan_args.clone()).await
-                    } else if let Some(duration) = scan_args.backoff.next_delay_duration() {
-                        sleep(duration).await;
-                        self.retryable_scan(scan_args.clone()).await
-                    } else {
-                        Err(RegionError(Box::new(err)))
-                    };
-                }
-                Ok((Some(r), region.end_key()))
-            }
-            Err(err) => Err(err),
-        }
-    }
-
-    async fn do_store_scan(
-        &self,
-        store: RegionStore,
-        scan_request: RawScanRequest,
-    ) -> Result<RawScanResponse> {
-        crate::request::PlanBuilder::new(self.rpc.clone(), self.keyspace, scan_request)
-            .single_region_with_store(store.clone())
-            .await?
-            .plan()
-            .execute()
-            .await
-    }
-
     async fn batch_scan_inner(
         &self,
         ranges: impl IntoIterator<Item = impl Into<BoundRange>>,
@@ -910,17 +865,6 @@ impl<PdC: PdClient> Client<PdC> {
     }
 }
 
-#[derive(Clone)]
-struct ScanInnerArgs {
-    start_key: Option<Key>,
-    range: BoundRange,
-    limit: u32,
-    key_only: bool,
-    reverse: bool,
-    permits: Arc<Semaphore>,
-    backoff: Backoff,
-}
-
 #[cfg(test)]
 mod tests {
     use std::any::Any;