✓ H Heartbeat 8 Reading DataConn enum class message_type { unknown, request, cancel, acknowledge_request, reject_request, intermediate_chunk, final_chunk, error, acknowledge_cancel, heartbeat }; templateheartbeat_reason { wait, write }; struct async_heartbeat_statistics { std::size_t bytes_transferred; std::size_t messages; std::size_t waits; async_heartbeat_reason reason; }; void(std::error_code, async_heartbeat_statistics); template decltype(auto) async_heartbeat(AsyncWriteStream& stream

。MDS包含以下几个部分： • Topology: 管理集群的 topo 元数据信息。 • Nameserver: 管理文件的元数据信息。 • Copyset: 副本放置策略。 • Heartbeat: 心跳模块。跟chunkserver进行交互，收集chunkserver上的负载信息、 copyset信息等。 • Scheduler: 调度模块。用于自动容错和负载均衡。TOPOLOGY CopysetId, chunkId, offset in chunk, length in chunk), Chunkserver 完成后通知； 5. Client通知用户请求完成。HEARTBEAT 心跳用于中心节点和数据节点的数据交互，详细功能如下： • 通过chunkserver的定期心跳，检测chunkserver的在线状态（online, unstable, offline） 检测chunkserver的copyset与mds差异，同 步两者的copyset信息 • 支持配置变更功能，在心跳回复报文中下发mds发起的配置变更命令，并在后续心跳中获取配置 变更进度。HEARTBEAT MDS端：mds 端的心跳主要由三个部分组成： • TopoUpdater: 根据 chunkserver 上报的 copyset 信息更新拓扑 中的信息。 • ConfGenerator:

traffic for selected devices . . . . . . . . . . . . . . . . . . . . . . 234 9.30 Configuring the heartbeat service . . . . . . . . . . . . . . . . . . . . . . . . . . 234 9.31 Encryption of disk images the heartbeat service VirtualBox ships a simple heartbeat service. Once the Guest Additions are active, the guest sends frequent heartbeat pings to the host. If the guest stops sending the heartbeat pings configure. The heartbeat interval defines the time between two heartbeat pings. The default value is 2 seconds, that is, the heartbeat service of the VirtualBox Guest Additions will send a heartbeat ping every

traffic for selected devices . . . . . . . . . . . . . . . . . . . . . . 233 9.30 Configuring the heartbeat service . . . . . . . . . . . . . . . . . . . . . . . . . . 233 9.31 Encryption of disk images the heartbeat service VirtualBox ships a simple heartbeat service. Once the Guest Additions are active, the guest sends frequent heartbeat pings to the host. If the guest stops sending the heartbeat pings configure. The heartbeat interval defines the time between two heartbeat pings. The default value is 2 seconds, that is, the heartbeat service of the VirtualBox Guest Additions will send a heartbeat ping every

metadata metadata Data and metadata store in different devices File data/metadata Heartbeat Heartbeat metabata Heartbeat metabata data 存储 openebs localPV Why: 1. 获得裸机磁盘性能 2. 多租户之间可以通过块进行隔离 3. 简单，非常轻量

number of snapshots being applied #17078 @hbisheng • PD • Improve the performance of Region heartbeat processing #7897 @nolouch @rleungx @JmPotato • pd-ctl supports querying hot Regions by the byte �→ pd �→ - �→ heartbeat �→ - �→ tick �→ - �→ interval �→ The time inter- val at which a Re- gion’s heart- beat to PD is trig- gered raftstore �→ . �→ pd �→ - �→ store �→ - �→ heartbeat �→ - �→ tick �→ retried multiple times. Usually, the estimated duration is 3 to 10 periods of store heartbeat (one period of store heartbeat is 10 seconds by default). After the recovery is completed, the last stage in the

�→ pd �→ - �→ heartbeat �→ - �→ tick �→ - �→ interval �→ The time inter- val at which a Re- gion’s heart- beat to PD is trig- gered raftstore �→ . �→ pd �→ - �→ store �→ - �→ heartbeat �→ - �→ tick �→ retried multiple times. Usually, the estimated duration is 3 to 10 periods of store heartbeat (one period of store heartbeat is 10 seconds by default). After the recovery is completed, the last stage in the "2019-03-21T14:09:32+08:00", # The starting timestamp. "last_heartbeat_ts": "2019-03-21T14:14:22.961171958+08:00", # The �→ timestamp of the last heartbeat. "uptime": "4m50.961171958s" } } ] 9.2.2 Use the

�→ pd �→ - �→ heartbeat �→ - �→ tick �→ - �→ interval �→ The time inter- val at which a Re- gion’s heart- beat to PD is trig- gered raftstore �→ . �→ pd �→ - �→ store �→ - �→ heartbeat �→ - �→ tick �→ retried multiple times. Usually, the estimated duration is 3 to 10 periods of store heartbeat (one period of store heartbeat is 10 seconds by default). After the recovery is completed, the last stage in the "2019-03-21T14:09:32+08:00", # The starting timestamp. "last_heartbeat_ts": "2019-03-21T14:14:22.961171958+08:00", # The �→ timestamp of the last heartbeat. "uptime": "4m50.961171958s" } } ] 9.2.2 Use the

�→ pd �→ - �→ heartbeat �→ - �→ tick �→ - �→ interval �→ The time inter- val at which a Re- gion’s heart- beat to PD is trig- gered raftstore �→ . �→ pd �→ - �→ store �→ - �→ heartbeat �→ - �→ tick �→ retried multiple times. Usually, the estimated duration is 3 to 10 periods of store heartbeat (one period of store heartbeat is 10 seconds by default). After the recovery is completed, the last stage in the "2019-03-21T14:09:32+08:00", # The starting timestamp. "last_heartbeat_ts": "2019-03-21T14:14:22.961171958+08:00", # The �→ timestamp of the last heartbeat. "uptime": "4m50.961171958s" } } ] 9.2.2 Use the

�→ pd �→ - �→ heartbeat �→ - �→ tick �→ - �→ interval �→ The time inter- val at which a Re- gion’s heart- beat to PD is trig- gered raftstore �→ . �→ pd �→ - �→ store �→ - �→ heartbeat �→ - �→ tick �→ retried multiple times. Usually, the estimated duration is 3 to 10 periods of store heartbeat (one period of store heartbeat is 10 seconds by default). After the recovery is completed, the last stage in the "2019-03-21T14:09:32+08:00", # The starting timestamp. "last_heartbeat_ts": "2019-03-21T14:14:22.961171958+08:00", # The �→ timestamp of the last heartbeat. "uptime": "4m50.961171958s" } } ] 9.2.2 Use the