fix(Bulkload): Avoid use reference of _metadata.files in

download_sst_file (#2006)

    replica_bulk_loader::clear_bulk_load_states function cannot cancel already
downloading sst task, which access `_metadata.files` references.
But clear_bulk_load_states function will clear `_metadata.files`. It's
cause core dump. I use a copy of `_metadata.files` to solve this
problem.

src/replica/bulk_load/replica_bulk_loader.cpp

@@ -519,41 +519,39 @@ void replica_bulk_loader::download_files(const std::string &provider_name,
     }
 
     // download sst files asynchronously
-    if (!_metadata.files.empty()) {
-        const file_meta &f_meta = _metadata.files[0];
-        _download_files_task[f_meta.name] = tasking::enqueue(
-            LPC_BACKGROUND_BULK_LOAD,
-            tracker(),
-            std::bind(&replica_bulk_loader::download_sst_file, this, remote_dir, local_dir, 0, fs));
+    std::vector<::dsn::replication::file_meta> download_file_metas;
+    {
+        zauto_read_lock l(_lock);
+        std::copy(_metadata.files.begin(),
+                  _metadata.files.end(),
+                  std::back_inserter(download_file_metas));
+    }
+    if (!download_file_metas.empty()) {
+        _download_files_task[download_file_metas.back().name] =
+            tasking::enqueue(LPC_BACKGROUND_BULK_LOAD,
+                             tracker(),
+                             std::bind(&replica_bulk_loader::download_sst_file,
+                                       this,
+                                       remote_dir,
+                                       local_dir,
+                                       download_file_metas,
+                                       fs));
     }
 }
 
 // ThreadPool: THREAD_POOL_DEFAULT
-void replica_bulk_loader::download_sst_file(const std::string &remote_dir,
-                                            const std::string &local_dir,
-                                            int32_t file_index,
-                                            dist::block_service::block_filesystem *fs)
+void replica_bulk_loader::download_sst_file(
+    const std::string &remote_dir,
+    const std::string &local_dir,
+    std::vector<::dsn::replication::file_meta> &download_file_metas,
+    dist::block_service::block_filesystem *fs)
 {
     if (_status != bulk_load_status::BLS_DOWNLOADING) {
-        LOG_WARNING_PREFIX("Cancel download_sst_file task, because bulk_load local_status is {}. "
-                           "local_dir: {} , file_index is {}.",
-                           enum_to_string(_status),
-                           local_dir,
-                           file_index);
-        return;
-    }
-    file_meta f_meta;
-    {
-        zauto_read_lock l(_lock);
-        if (file_index < _metadata.files.size()) {
-            f_meta = _metadata.files[file_index];
-        }
-    }
-    if (f_meta.name.empty()) {
-        LOG_WARNING_PREFIX("Cannot get file_meta of {}, cancel download_sst_file task.",
-                           file_index);
+        LOG_WARNING_PREFIX("Cancel download_sst_file task, because bulk_load local_status is {}.",
+                           enum_to_string(_status));
         return;
     }
+    const file_meta &f_meta = download_file_metas.back();
     uint64_t f_size = 0;
     std::string f_md5;
     error_code ec = _stub->_block_service_manager.download_file(
@@ -604,26 +602,21 @@ void replica_bulk_loader::download_sst_file(const std::string &remote_dir,
         return;
     }
     // download file succeed, update progress
+    download_file_metas.pop_back();
     update_bulk_load_download_progress(f_size, f_meta.name);
     METRIC_VAR_INCREMENT(bulk_load_download_file_successful_count);
     METRIC_VAR_INCREMENT_BY(bulk_load_download_file_bytes, f_size);
 
     // download next file
-    {
-        zauto_read_lock l(_lock);
-        if (file_index + 1 < _metadata.files.size()) {
-            f_meta = _metadata.files[file_index + 1];
-        }
-    }
-    if (!f_meta.name.empty()) {
-        _download_files_task[f_meta.name] =
+    if (!download_file_metas.empty()) {
+        _download_files_task[download_file_metas.back().name] =
             tasking::enqueue(LPC_BACKGROUND_BULK_LOAD,
                              tracker(),
                              std::bind(&replica_bulk_loader::download_sst_file,
                                        this,
                                        remote_dir,
                                        local_dir,
-                                       file_index + 1,
+                                       download_file_metas,
                                        fs));
     }
 }

src/replica/bulk_load/replica_bulk_loader.h

@@ -89,7 +89,7 @@ class replica_bulk_loader : replica_base
     // download sst files from remote provider
     void download_sst_file(const std::string &remote_dir,
                            const std::string &local_dir,
-                           int32_t file_index,
+                           std::vector<::dsn::replication::file_meta> &download_file_metas,
                            dist::block_service::block_filesystem *fs);
 
     // \return ERR_PATH_NOT_FOUND: file not exist