Force backup_threads and restore_threads to be non zero

Author: Algunenano

src/Core/ServerSettings.cpp

@@ -139,9 +139,9 @@ namespace DB
     A value of `0` (default) means unlimited.
     :::
     )", 0) \
-    DECLARE(UInt64, backup_threads, 16, R"(The maximum number of threads to execute `BACKUP` requests.)", 0) \
+    DECLARE(NonZeroUInt64, backup_threads, 16, R"(The maximum number of threads to execute `BACKUP` requests.)", 0) \
     DECLARE(UInt64, max_backup_bandwidth_for_server, 0, R"(The maximum read speed in bytes per second for all backups on server. Zero means unlimited.)", 0) \
-    DECLARE(UInt64, restore_threads, 16, R"(The maximum number of threads to execute RESTORE requests.)", 0) \
+    DECLARE(NonZeroUInt64, restore_threads, 16, R"(The maximum number of threads to execute RESTORE requests.)", 0) \
     DECLARE(Bool, shutdown_wait_backups_and_restores, true, R"(If set to true ClickHouse will wait for running backups and restores to finish before shutdown.)", 0) \
     DECLARE(Double, cannot_allocate_thread_fault_injection_probability, 0, R"(For testing purposes.)", 0) \
     DECLARE(Int32, max_connections, 4096, R"(Max server connections.)", 0) \

src/Core/ServerSettings.h

@@ -21,6 +21,7 @@ struct ServerSettingsImpl;
     M(CLASS_NAME, Double) \
     M(CLASS_NAME, GroupArrayActionWhenLimitReached) \
     M(CLASS_NAME, Float) \
+    M(CLASS_NAME, NonZeroUInt64) \
     M(CLASS_NAME, Int32) \
     M(CLASS_NAME, Seconds) \
     M(CLASS_NAME, String) \

src/Interpreters/Context.cpp

@@ -196,7 +196,6 @@ namespace Setting
     extern const SettingsUInt64 allow_experimental_parallel_reading_from_replicas;
     extern const SettingsMilliseconds async_insert_poll_timeout_ms;
     extern const SettingsBool azure_allow_parallel_part_upload;
-    extern const SettingsUInt64 backup_threads;
     extern const SettingsString cluster_for_parallel_replicas;
     extern const SettingsBool enable_filesystem_cache;
     extern const SettingsBool enable_filesystem_cache_log;
@@ -244,7 +243,6 @@ namespace Setting
     extern const SettingsUInt64 page_cache_block_size;
     extern const SettingsUInt64 page_cache_lookahead_blocks;
     extern const SettingsInt64 read_priority;
-    extern const SettingsUInt64 restore_threads;
     extern const SettingsString remote_filesystem_read_method;
     extern const SettingsBool remote_filesystem_read_prefetch;
     extern const SettingsUInt64 remote_fs_read_max_backoff_ms;
@@ -3249,9 +3247,8 @@ BackupsWorker & Context::getBackupsWorker() const
 {
     callOnce(shared->backups_worker_initialized, [&] {
         const auto & config = getConfigRef();
-        const auto & settings_ref = getSettingsRef();
-        UInt64 backup_threads = config.getUInt64("backup_threads", settings_ref[Setting::backup_threads]);
-        UInt64 restore_threads = config.getUInt64("restore_threads", settings_ref[Setting::restore_threads]);
+        UInt64 backup_threads = std::max(UInt64{1}, config.getUInt64("backup_threads", 16));
+        UInt64 restore_threads = std::max(UInt64{1}, config.getUInt64("restore_threads", 16));
 
         shared->backups_worker.emplace(getGlobalContext(), backup_threads, restore_threads);
     });