第 17 章： 集群 ====================== 节点 --------- 三个节点的握手过程。 .. graphviz:: digraph { label = "\n 图 17-1 三个独立的节点"; node [shape = circle]; subgraph cluster_a { label = "集群"; style = dashed; 7000; } subgraph cluster_b { label = "集群"; style = dashed; 7001; } subgraph cluster_c { label = "集群"; style = dashed; 7002; } } .. graphviz:: digraph { label = "\n 图 17-2 节点 7000 和 7001 进行握手"; rankdir = LR; node [shape = circle]; subgraph cluster_a { label = "集群"; style = dashed; 7000; } subgraph cluster_b { label = "集群"; style = dashed; 7001; } subgraph cluster_c { label = "集群"; style = dashed; 7002; } 7000 -> 7001 [label = "握手"]; 7000 -> 7001 [dir = back, label = "响应握手"]; } .. graphviz:: digraph { label = "\n 图 17-3 握手成功的 7000 与 7001 处于同一个集群"; rankdir = LR; node [shape = circle]; subgraph cluster_a { label = "集群"; style = dashed; 7000; 7001; 7000 -> 7001 [style = invis]; } subgraph cluster_c { label = "集群"; style = dashed; 7002; } } .. graphviz:: digraph { label = "\n 图 17-4 节点 7000 与节点 7002 进行握手"; rankdir = LR; node [shape = circle]; subgraph cluster_a { label = "集群"; style = dashed; 7000; 7001; 7000 -> 7001 [style = invis]; } subgraph cluster_c { label = "集群"; style = dashed; 7002; } 7000 -> 7002 [label = "握手"]; 7000 -> 7002 [dir = back, label = "响应握手"]; } .. graphviz:: digraph { label = "\n 图 17-5 握手成功的三个节点处于同一个集群"; rankdir = LR; subgraph cluster_a { label = "集群"; style = dashed; node [shape = circle]; 7000; 7002; 7001; edge [style = invis]; 7000 -> 7001; 7000 -> 7002; } } ---- ``clusterNode`` 结构的示例。 .. graphviz:: digraph { label = "\n 图 17-7 节点 7000 创建的 clusterState 结构"; rankdir = LR; // node [shape = record]; clusterState [label = " clusterState | myself | currentEpoch \n 0 | state \n REDIS_CLUSTER_FAIL | size \n 0 | nodes | ... "]; nodes [label = " nodes | <0> \"5154...2939\" | <1> \"68ee...f2ff\" | <2> \"9dfb...5c26\" "]; node7000 [label = " clusterNode | name \n \"5154...2939\" | flags \n REDIS_NODE_MASTER | configEpoch \n 0 | ip \n \"127.0.0.1\" | port \n 7000 | ... "]; node7001 [label = " clusterNode | name \n \"68ee...f2ff\"| flags \n REDIS_NODE_MASTER | configEpoch \n 0 | ip \n \"127.0.0.1\" | port \n 7001 | ... "]; node7002 [label = " clusterNode | name \n \"9dfb...5c26\"| flags \n REDIS_NODE_MASTER | configEpoch \n 0 | ip \n \"127.0.0.1\" | port \n 7002 | ... "]; //link7000 [label = " clusterLink | ctime | fd | sndbuf | rcvbuf "]; clusterState:myself -> node7000:head; clusterState:nodes -> nodes:head; nodes:0 -> node7000:head; nodes:1 -> node7001:head; nodes:2 -> node7002:head; } ---- 节点之间进行握手时的通信过程。 .. graphviz:: digraph { label = "\n 图 17-8 节点的握手过程"; rankdir = LR; splines = polyline; // node [shape = box, height = 2]; client [label = "客\n户\n端"]; A [label = "节\n点\nA"]; B [label = "节\n点\nB"]; // client -> A [label = "发送命令 \n CLUSTER MEET \n "]; A -> B [label = "发送 MEET 消息"]; A -> B [dir = back, label = "\n返回 PONG 消息"]; A -> B [label = "\n返回 PING 消息"]; } 槽指派 ----------- 图 17-9 展示了一个 ``slots`` 数组示例： 这个数组索引 ``0`` 至索引 ``7`` 上的二进制位的值都为 ``1`` ， 其余所有二进制位的值都为 ``0`` ， 这表示节点负责处理槽 ``0`` 至槽 ``7`` 。 .. graphviz:: digraph { label = "\n 图 17-9 一个 slots 数组示例"; node [shape = record]; slots [label = " { 字节 | 索引 | 值 } | { slots[0] | {{ 0 | 1} | { 1 | 1} | { 2 | 1 } | { 3 | 1} | { 4 | 1 } | { 5 | 1 } | { 6 | 1 } | { 7 | 1 } }} | { slots[1] ~ slots[2047] | {{ 8 | 0 } | { 9 | 0 } | { 10 | 0 } | { 11 | 0 } | { 12 | 0 } | { ... | ... } | { 16381 | 0 } | { 16382 | 0 } | { 16383 | 0 } }} "]; } 图 17-10 展示了另一个 ``slots`` 数组示例： 这个数组索引 ``1`` 、 ``3`` 、 ``5`` 、 ``8`` 、 ``9`` 、 ``10`` 上的二进制位的值都为 ``1`` ， 而其余所有二进制位的值都为 ``0`` ， 这表示节点负责处理槽 ``1`` 、 ``3`` 、 ``5`` 、 ``8`` 、 ``9`` 、 ``10`` 。 .. graphviz:: digraph { label = "\n 图 17-10 另一个 slots 数组示例"; node [shape = record]; slots [label = " { 字节 | 索引 | 值 } | { slots[0] | {{ 0 | 0} | { 1 | 1} | { 2 | 0 } | { 3 | 1} | { 4 | 0 } | { 5 | 1 } | { 6 | 0 } | { 7 | 0 } }} | { slots[1] | {{ 8 | 1} | { 9 | 1 } | { 10 | 1 } | { 11 | 0 } | { 12 | 0 } | { 13 | 0 } | { 14 | 0 } | { 15 | 0 }}} | { ... | ... | ... } | { slots[2047] | { { ... | ... } | { 16382 | 0 } | { 16383 | 0 }} } "]; } ---- 节点之间互相传递槽指派信息的过程。 .. graphviz:: digraph { label = "\n 图 17-11 7000 告知 7001 和 7002 自己负责处理的槽"; rankdir = LR; subgraph cluster_a { label = "集群"; style = dashed; node [shape = circle]; 7000; 7002; 7001; edge [style = dashed, label = "\n我负责处理\n槽 0 至槽 5000"]; 7000 -> 7001; 7000 -> 7002; } } .. graphviz:: digraph { label = "\n 图 17-12 7001 告知 7000 和 7002 自己负责处理的槽"; subgraph cluster_a { label = "集群"; style = dashed; node [shape = circle]; 7000; 7002; 7001; edge [style = dashed, label = "我负责处理\n槽 5001 至槽 10000"]; 7001 -> 7000; 7001 -> 7002; } } .. graphviz:: digraph { label = "\n 图 17-13 7002 告知 7000 和 7001 自己负责处理的槽"; rankdir = BT; subgraph cluster_a { label = "集群"; labelloc = "b"; style = dashed; node [shape = circle]; 7000; 7002; 7001; edge [style = dashed, label = "我负责处理\n槽 10001 至槽 16383"]; 7002 -> 7000; 7002 -> 7001; } } ---- ``clusterState`` 结构的 ``slots`` 数组示例。 .. graphviz:: digraph { label = "\n 图 17-14 clusterState 结构的 slots 数组"; rankdir = LR; node [shape = record]; clusterState [label = " clusterState | ... | slots | ... "]; slots [label = " clusterNode*[16384] | <0> 0 | <1> 1 | <2> ... | <5000> 5000 | <5001> 5001 | <5002> 5002 | <5003> ... | <10000> 10000 | <10001> 10001 | <10002> 10002 | <10003> ... | <16383> 16383 "]; node7000 [label = " clusterNode | ... | ip \n \"127.0.0.1\" | port \n 7000 | ... "]; node7001 [label = " clusterNode | ... | ip \n \"127.0.0.1\" | port \n 7001 | ... "]; node7002 [label = " clusterNode | ... | ip \n \"127.0.0.1\" | port \n 7002 | ... "]; slots:0 -> node7000:head; slots:1 -> node7000:head; slots:2 -> node7000:head; slots:5000 -> node7000:head; slots:5001 -> node7001:head; slots:5002 -> node7001:head; slots:5003 -> node7001:head; slots:10000 -> node7001:head; slots:10001 -> node7002:head; slots:10002 -> node7002:head; slots:10003 -> node7002:head; slots:16383 -> node7002:head; clusterState:slots -> slots:head; } 在集群中执行命令 ------------------------ 在集群中执行命令时的判断过程。 .. graphviz:: digraph { label = "\n 图 17-18 判断客户端是否需要转向的流程"; node [shape = box]; client_send_command [label = "客户端向节点发送数据库键命令", width = 7]; get_slot_number [label = "节点计算键属于哪个槽"]; node_handle_right_slot_or_not [label = "当前节点就是\n负责处理键所在槽的节点？", shape = diamond]; execute_command [label = "节点执行命令"]; return_moved [label = "节点向客户端返回一个\n MOVED 错误"]; client_redirect [label = "客户端根据 MOVED 错误提供的信息\n转向至正确的节点"]; // client_send_command -> get_slot_number; get_slot_number -> node_handle_right_slot_or_not; node_handle_right_slot_or_not -> execute_command [label = "是"]; node_handle_right_slot_or_not -> return_moved [label = "不是"]; return_moved -> client_redirect; client_redirect -> client_send_command [label = "重试"]; } ----- ``MOVED`` 错误引发的转向过程。 .. graphviz:: digraph { label = "\n 图 17-20 节点 7000 向客户端返回 MOVED 错误"; rankdir = LR; splines = polyline; node [shape = box]; client [label = "客户端", height = 2.5]; node7000 [label = "节点 7000", height = 2.5]; // client -> node7000 [label = "\nSET msg \"happy new year!\""]; client -> node7000 [dir = back, label = "\nMOVED 6257 127.0.0.1:7001"]; } .. graphviz:: digraph { label = "\n 图 17-21 客户端根据 MOVED 错误的指示转向至节点 7001"; rankdir = LR; splines = polyline; node [shape = box]; client [label = "客户端", height = 2.5]; node7001 [label = "节点 7001", height = 2.5]; // client -> node7001 [label = "\n转向"]; client -> node7001 [label = "\nSET msg \"happy new year!\""]; client -> node7001 [dir = back, label = "\nOK"]; } ---- 集群节点为记录键所在槽而创建的跳跃表。 .. graphviz:: digraph { rankdir = LR; node [shape = record, width = "0.5"]; // l [label = "
header | tail | level \n 5 | length \n 3 "]; subgraph cluster_nodes { style = invisible; header [label = " L32 | ... | L5 | L4 | L3 | L2 | L1 "]; bw_null [label = "NULL", shape = plaintext]; level_null [label = "NULL", shape = plaintext]; A [label = " L4 | L3 | L2 | L1 | BW | 1337.0 | StringObject \n \"book\" "]; B [label = " L2 | L1 | BW | 2022.0 | StringObject \n \"date\" "]; C [label = " L5 | L4 | L3 | L2 | L1 | BW | 3347.0 | StringObject \n \"lst\" "]; } subgraph cluster_nulls { style = invisible; n1 [label = "NULL", shape = plaintext]; n2 [label = "NULL", shape = plaintext]; n3 [label = "NULL", shape = plaintext]; n4 [label = "NULL", shape = plaintext]; n5 [label = "NULL", shape = plaintext]; } // l:header -> header; l:tail -> C; /* // 移除连接线的 span 分值 header:l32 -> level_null [label = "0"]; header:l5 -> C:l5 [label = "3"]; header:l4 -> A:l4 [label = "1"]; header:l3 -> A:l3 [label = "1"]; header:l2 -> A:l2 [label = "1"]; header:l1 -> A:l1 [label = "1"]; A:l4 -> C:l4 [label = "2"]; A:l3 -> C:l3 [label = "2"]; A:l2 -> B:l2 [label = "1"]; A:l1 -> B:l1 [label = "1"]; B:l2 -> C:l2 [label = "1"]; B:l1 -> C:l1 [label = "1"]; C:l5 -> n5 [label = "0"]; C:l4 -> n4 [label = "0"]; C:l3 -> n3 [label = "0"]; C:l2 -> n2 [label = "0"]; C:l1 -> n1 [label = "0"]; */ header:l32 -> level_null; header:l5 -> C:l5; header:l4 -> A:l4; header:l3 -> A:l3; header:l2 -> A:l2; header:l1 -> A:l1; A:l4 -> C:l4; A:l3 -> C:l3; A:l2 -> B:l2; A:l1 -> B:l1; B:l2 -> C:l2; B:l1 -> C:l1; C:l5 -> n5; C:l4 -> n4; C:l3 -> n3; C:l2 -> n2; C:l1 -> n1; bw_null -> A:backward -> B:backward -> C:backward [dir = back]; label = "\n 图 17-23 节点 7000 的 slots_to_keys 跳跃表"; } .. **/ 重新分片 ------------- 将一个键从一个节点迁移到另一个节点的过程。 .. graphviz:: digraph { label = "\n 图 17-24 迁移键的过程"; rankdir = LR; splines = polyline; // node [shape = box, height = 3]; client [label = "redis-trib"]; source [label = "源\n节\n点"]; target [label = "目\n标\n节\n点"]; // client -> source [label = "1) 发送命令 \n CLUSTER GETKEYSINSLOT "]; client -> source [dir = back, label = "\n 2) 返回最多 count 个属于槽 slot 的键"]; client -> source [label = "\n 3) 对于每个返回键\n向源节点发送一个 MIGRATE 命令"]; source -> target [label = "\n 4) 根据 MIGRATE 命令的指示 \n 将键迁移至目标节点"]; } ---- 重新分片的整个过程。 .. graphviz:: digraph { label = "\n 图 17-25 对槽 slot 进行重新分片的过程" node [shape = box] start [label = "开始对槽 slot 进行重新分片"] send_importing_to_target [label = "目标节点准备导入槽 slot 的键值对"]; send_migrating_to_source [label = "源节点准备迁移槽 slot 的键值对"]; start -> send_importing_to_target -> send_migrating_to_source; contain_slot_key_or_not [shape = diamond, label = "源节点是否保存了\n属于槽 slot 的键？"] migrate [label = "将这些键\n全部迁移至目标节点"] assign [label = "将槽 slot 指派给目标节点"] done [label = "完成对槽 slot 的重新分片"] send_migrating_to_source -> contain_slot_key_or_not contain_slot_key_or_not -> migrate [label = "是"] migrate -> assign contain_slot_key_or_not -> assign [label = "否"] assign -> done } ASK 错误 ------------- 源节点判断是否需要向客户端发送 ``ASK`` 错误的整个过程。 .. graphviz:: digraph { label = "\n 图 17-26 判断是否发送 ASK 错误的过程"; // node [shape = box]; send_command [label = "客户端向源节点发送关于键 key 的命令"]; key_in_or_not [label = "键 key 是否存在于\n源节点的数据库？", shape = diamond]; execute_command [label = "节点执行客户端发送的命令"]; reshaing_or_not [label = "节点正在迁移槽 i ？", shape = diamond]; ask_redirect [label = "向客户端返回 ASK 错误"]; // send_command -> key_in_or_not; key_in_or_not -> execute_command [label = "是"]; key_in_or_not -> reshaing_or_not [label = "否"]; reshaing_or_not -> ask_redirect [label = "是\n键 key 有可能在目标节点"]; reshaing_or_not -> execute_command [label = "否\n键 key 不存在"]; } ---- ``importing_slots_from`` 结构以及 ``migrating_slots_to`` 结构的示例。 .. graphviz:: digraph { label = "\n 图 17-27 节点 7003 的 importing_slots_from 数组"; rankdir = LR; // node [shape = record]; clusterState [label = " clusterState | ... | importing_slots_from | ... "]; slots [label = " clusterNode*[16384] | <0> 0 | <1> 1 | <2> 2 | <3> ... | <16198> 16198 | <15002> ... | <16381> 16381 | <16382> 16382 | <16383> 16383 "]; node7002 [label = " clusterNode | ... | ip \n \"127.0.0.1\" | port \n 7002 | ... "]; node [shape = plaintext, label = "NULL"]; // slots:0 -> null0; slots:1 -> null1; slots:2 -> null2; slots:16198 -> node7002:head [minlen = 2]; slots:16381 -> null16381; slots:16382 -> null16382; slots:16383 -> null16383; clusterState:slots -> slots:head; } .. graphviz:: digraph { label = "\n 图 17-28 节点 7002 的 migrating_slots_to 数组"; rankdir = LR; // node [shape = record]; clusterState [label = " clusterState | ... | migrating_slots_to | ... "]; slots [label = " clusterNode*[16384] | <0> 0 | <1> 1 | <2> 2 | <3> ... | <16198> 16198 | <15002> ... | <16381> 16381 | <16382> 16382 | <16383> 16383 "]; node7003 [label = " clusterNode | ... | ip \n \"127.0.0.1\" | port \n 7003 | ... "]; node [shape = plaintext, label = "NULL"]; // slots:0 -> null0; slots:1 -> null1; slots:2 -> null2; slots:16198 -> node7003:head [minlen = 2]; slots:16381 -> null16381; slots:16382 -> null16382; slots:16383 -> null16383; clusterState:slots -> slots:head; } ---- 客户端根据 ``ASK`` 错误进行转向的过程。 .. graphviz:: digraph { label = "\n 图 17-29 客户端接收到节点 7002 返回的 ASK 错误"; rankdir = LR; splines = polyline; // node [shape = box, height = 2]; client [label = "客户端"]; node7002 [label = "节点 7002"]; // client -> node7002 [label = "GET \"love\""]; client -> node7002 [dir = back, label = "\nASK 16198 127.0.0.1:7003"]; } .. graphviz:: digraph { label = "\n 图 17-30 客户端转向至节点 7003"; rankdir = LR; splines = polyline // node [shape = box, height = 3]; client [label = "客户端"]; node7003 [label = "节点 7003"]; // client -> node7003 [label = "转向"]; client -> node7003 [label = "ASKING"]; client -> node7003 [label = "\n GET \"love\""]; client -> node7003 [dir = back, label = "\n\"you get the key 'love'\""]; } ---- 节点判断是否执行客户端命令的过程。 .. graphviz:: digraph { label = "\n 图 17-31 节点判断是否执行客户端命令的过程"; node [shape = box]; // send_command [label = "客户端向节点发送关于槽 i 的命令"]; node_handle_slot_or_not [shape = diamond, label = "槽 i 是否指派给了节点？"]; exec_command [label = "节点执行客户端发送的命令"]; importing_slot_or_not [shape = diamond, label = "节点是否正在导入槽 i ？"]; client_get_asking_flag_or_not [shape = diamond, label = "客户端是否带有 \n ASKING 标识？"]; return_moved [label = "节点向客户端返回 MOVED 命令"]; // send_command -> node_handle_slot_or_not; node_handle_slot_or_not -> exec_command [label = "是"]; node_handle_slot_or_not -> importing_slot_or_not [label = "否"]; importing_slot_or_not -> client_get_asking_flag_or_not [label = "是"]; client_get_asking_flag_or_not -> exec_command [label = "是"]; importing_slot_or_not -> return_moved [label = "否"]; client_get_asking_flag_or_not -> return_moved [label = "否"]; } 复制与故障转移 -------------------- Redis 集群对失效节点进行故障转移的过程。 .. graphviz:: digraph { label = "\n 图 17-32 设置节点 7004 和节点 7005 成为节点 7000 的从节点"; rankdir = LR; subgraph cluster_a { label = "集群"; style = dashed; node [shape = doublecircle] 7000; 7001; 7002; 7003; node [shape = circle] 7005; 7004; edge [dir = back, label = "复制"] 7000 -> 7004 7000 -> 7005 edge [style = invis, label = ""] 7002 -> 7003 } } .. graphviz:: digraph { label = "\n 图 17-33 节点 7004 成为新的主节点"; rankdir = LR; subgraph cluster_a { label = "集群"; style = dashed; node [shape = doublecircle]; 7000 [style = dashed] 7001; 7002; 7003; 7004; node [shape = circle] 7005; edge [dir = back, label = "复制"] 7004 -> 7005 edge [style = invis, label = ""] 7000 -> 7001 7002 -> 7003 } } .. graphviz:: digraph { label = "\n 图 17-34 重新上线的节点 7000 成为节点 7004 的从节点"; rankdir = LR; subgraph cluster_a { label = "集群"; style = dashed; node [shape = doublecircle]; 7001; 7002; 7003; 7004; node [shape = circle] 7000 7005; edge [dir = back, label = "复制"] 7004 -> 7005 7004 -> 7000 edge [style = invis, label = ""] 7001 -> 7002 -> 7003 } } ---- 节点的下线报告示例。 .. graphviz:: digraph { label = "\n 图 17-38 节点 7000 的下线报告" rankdir = LR node [shape = record] node7000 [label = " clusterNode | ... | flags \n REDIS_NODE_MASTER \n & \n REDIS_NODE_PFAIL | ip \n \"127.0.0.1\" | port \n 7000 | fail_reports | ... "] node7002 [label = " clusterNode | ... | flags \n REDIS_NODE_MASTER | ip \n \"127.0.0.1\" | port \n 7002 | ... "] node7003 [label = " clusterNode | ... | flags \n REDIS_NODE_MASTER | ip \n \"127.0.0.1\" | port \n 7003 | ... "] report7002 [label = " clusterNodeFailReport | node | time \n 1390525039000"] report7003 [label = " clusterNodeFailReport | node | time \n 1390525039321"] node7000:fail_reports -> report7002:head -> report7003:head report7002:pnode -> node7002:head report7003:pnode -> node7003:head } ---- 节点向集群广播 ``FAIL`` 消息。 .. graphviz:: digraph { label = "\n 图 17-39 节点 7001 向集群广播 FAIL 消息" rankdir = LR; subgraph cluster_a { label = "集群"; style = dashed; node [shape = doublecircle] 7000 [style = dashed] 7001; 7002; 7003; node [shape = circle] 7004; 7005; edge [dir = back, label = "复制"] 7000 -> 7004 7000 -> 7005 edge [dir = forward, label = "发送 FAIL 消息"] 7001 -> 7002 7001 -> 7003 7001 -> 7004 7001 -> 7005 } } 消息 ----------- 集群中的节点通过发送消息来将一个节点标记为下线的过程。 .. graphviz:: digraph { label = "\n 图 17-42 节点 7001 将节点 7000 标记为已下线"; node [shape = circle]; subgraph cluster_cluster { label = "集群"; node7000 [label = "7000", style = dashed]; node7001 [label = "7001"]; node7002 [label = "7002"]; node7003 [label = "7003"]; node7001 -> node7000 [label = "标记为\n已下线"]; edge [style = invis]; node7001 -> node7002 [label = "发送 FAIL 消息"]; node7001 -> node7003 [label = "发送 FAIL 消息"]; style = dashed; } } .. graphviz:: digraph { label = "\n 图 17-43 节点 7001 向集群广播 FAIL 消息"; node [shape = circle]; subgraph cluster_cluster { label = "集群"; node7000 [label = "7000", style = dashed]; node7001 [label = "7001"]; node7002 [label = "7002"]; node7003 [label = "7003"]; node7001 -> node7000 [style = invis]; edge [label = "发送 \nFAIL 消息"]; node7001 -> node7002; node7001 -> node7003; style = dashed; } } .. graphviz:: digraph { label = "\n 图 17-44 节点 7002 和节点 7003 也将节点 7000 标记为已下线"; node [shape = circle]; subgraph cluster_cluster { label = "集群"; node7003 [label = "7003"]; node7002 [label = "7002"]; node7001 [label = "7001"]; node7000 [label = "7000", style = dashed]; node7001 -> node7000 [style = invis]; edge [label = "标记为\n已下线"]; node7002 -> node7000; node7003 -> node7000; style = dashed; } } ---- 接收到 ``PUBLISH`` 命令的节点向集群中的其他节点发送 ``PUBLISH`` 消息。 .. graphviz:: digraph { label = "\n 图 17-45 接收到 PUBLISH 命令的节点 7000 向集群广播 PUBLISH 消息"; node [shape = circle]; rankdir = LR; client [label = "客户端"]; subgraph cluster_cluster { label = "集群"; node7003 [label = "7003"]; node7002 [label = "7002"]; node7001 [label = "7001"]; node7000 [label = "7000"]; edge [label = "发送 \n PUBLISH \n 消息"]; node7000 -> node7001; node7000 -> node7002; node7000 -> node7003; style = dashed; } client -> node7000 [label = "发送 \n PUBLISH \n 命令"]; } ---- ``PUBLISH`` 消息中包含的 ``clusterMsgDataPublish`` 结构示例。 .. graphviz:: digraph { label = "\n 图 17-46 clusterMsgDataPublish 结构示例"; node [shape = record]; rankdir = LR; clusterMsgDataPublish [label = " clusterMsgDataPublish | channel_len \n 7 | message_len \n 5 | bulk_data "]; bulk_data [label = " { 'n' | 'e' | 'w' | 's' | '.' | 'i' | 't' | 'h' | 'e' | 'l' | 'l' | 'o' } "]; clusterMsgDataPublish:bulk_data -> bulk_data; }