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#pragma once
#include <Core/Types.h>
#include <map>
#include <unordered_set>
namespace DB
{
enum class AccessEntityType;
/// This class is used by hosts to coordinate the access entities of ReplicatedAccessStorage they're writing to a backup.
/// It's designed to make all hosts save the same access entities to the backup even in case the ReplicatedAccessStorage changes
/// while the backup is being produced. This is important to make RESTORE more predicitible.
///
/// For example, let's consider three replicas having a ReplicatedAccessStorage on them.
/// This class ensures that the following files in the backup are the same:
/// /shards/1/replicas/1/data/system/users/access01.txt
/// /shards/1/replicas/2/data/system/users/access01.txt
/// /shards/1/replicas/3/data/system/users/access01.txt
///
/// To implement that this class chooses one host to write access entities for all the hosts so in fact all those files
/// in the example above are written by the same host.
class BackupCoordinationReplicatedAccess
{
public:
BackupCoordinationReplicatedAccess();
~BackupCoordinationReplicatedAccess();
struct FilePathForAccessEntitry
{
String access_zk_path;
AccessEntityType access_entity_type;
String host_id;
String file_path;
};
/// Adds a path to access*.txt file keeping access entities of a ReplicatedAccessStorage.
void addFilePath(FilePathForAccessEntitry && file_path_for_access_entity);
/// Returns all paths added by addFilePath() if `host_id` is a host chosen to store access.
Strings getFilePaths(const String & access_zk_path, AccessEntityType access_entity_type, const String & host_id) const;
private:
using ZkPathAndEntityType = std::pair<String, AccessEntityType>;
struct FilePathsAndHost
{
std::unordered_set<String> file_paths;
String host_to_store_access;
};
std::map<ZkPathAndEntityType, FilePathsAndHost> file_paths_by_zk_path;
};
}
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