第 16 章： Sentinel¶
Sentinel 状态以及已连接的两个 Sentinel 实例结构。
![digraph {
label = "\n 图 16-5 master1 的实例结构";
rankdir = LR;
node [shape = record];
//
master1 [label = " <head> sentinelRedisInstance | flags \n SRI_MASTER | name \n \"master1\" | runid \n \"ee07959afc9d061233191c0f5bfe29580dfad0f4\" | config_epoch \n 0 | <addr> addr | down_after_period \n 30000 | quorum \n 2 | parallel_syncs \n 1 | failover_timeout \n 900000 | ... "];
addr [label = " <head> sentinelAddr | ip \n \"127.0.0.1\" | port \n 6379 "];
//
master1:addr -> addr:head;
}](_images/graphviz-bd4b7182673260277e8a82b509192fe2e4e2f662.png)
![digraph {
label = "\n 图 16-6 master2 的实例结构";
rankdir = LR;
node [shape = record];
//
master2 [label = " <head> sentinelRedisInstance | flags \n SRI_MASTER | name \n \"master2\" | runid \n \"a68408b775438a5dee54a638b3a6f3461920158a\" | config_epoch \n 0 | <addr> addr | down_after_period \n 50000 | quorum \n 5 | parallel_syncs \n 5 | failover_timeout \n 450000 | ... "];
addr [label = " <head> sentinelAddr | ip \n \"127.0.0.1\" | port \n 12345 "];
//
master2:addr -> addr:head;
}](_images/graphviz-3bfd988c3abd31392b4c1ff362740ac5b5e087b3.png)
![digraph {
label = "\n 图 16-7 Sentinel 状态以及 masters 字典";
rankdir = LR;
node [shape = record];
//
sentinelState [label = " sentinelState | <masters> masters | ... "];
masters [label = " <head> dict | <master1> \"master1\" | <master2> \"master2\" "];
master1 [label = " <head> sentinelRedisInstance | ... | name \n \"master1\" | ... "];
master2 [label = " <head> sentinelRedisInstance | ... | name \n \"master2\" | ... "];
//
sentinelState:masters -> masters:head;
masters:master1 -> master1:head;
masters:master2 -> master2:head;
}](_images/graphviz-b5c3067016489ac273ea53daa4d5fd47a5a27546.png)
Sentinel 通过向主服务器发送 INFO 命令来获得从服务器的信息。
![digraph {
label = "\n 图 16-9 Sentinel 向带有三个从服务器的主服务器发送 INFO 命令";
sentinel [label = "Sentinel", shape = box, width = 4.5, height = 1.0];
master [shape = doublecircle];
node [shape = circle];
edge [dir = none];
master -> slave0;
master -> slave1;
master -> slave2;
edge [dir = forward];
sentinel -> master [label = "INFO"];
}](_images/graphviz-e4867873c20993b8f7ec58b4534f23f9ca480fd2.png)
以及 Sentinel 为这个主服务器以及三个从服务器创建的信息结构。
![digraph {
label = "\n 图 16-10 主服务器和它的三个从服务器";
rankdir = LR;
node [shape = record];
master [label = " sentinelRedisInstance | flags \n SRI_MASTER | run_id \n \"7611c59dc3a29aa6fa0609f841bb6a1019008a9c\" | name \n \"master\" | ... | <slaves> slaves | ... "];
slaves [label = " <head> dict | <slave0> \"127.0.0.1:11111\" | <slave1> \"127.0.0.1:22222\" | <slave2> \"127.0.0.1:33333\" "];
slave0 [label = " <head> sentinelRedisInstance | flags \n SRI_SLAVE | name \n \"127.0.0.1:11111\" | ... "];
slave1 [label = " <head> sentinelRedisInstance | flags \n SRI_SLAVE | name \n \"127.0.0.1:22222\" | ... "];
slave2 [label = " <head> sentinelRedisInstance | flags \n SRI_SLAVE | name \n \"127.0.0.1:33333\" | ... "];
master:slaves -> slaves:head;
slaves:slave0 -> slave0:head;
slaves:slave1 -> slave1:head;
slaves:slave2 -> slave2:head;
}](_images/graphviz-0aaa934bbba0242636272cfe7b7e4840dee7c2f7.png)
Sentinel 通过命令连接向频道发送信息， 并通过订阅连接从频道中获取信息。
![digraph {
label = "\n 图 16-13 Sentinel 同时向服务器发送和接收信息";
rankdir = LR;
sentinel [label = "Sentinel", shape = box, height = 1.8];
master [label = "服务器", shape = circle];
sentinel -> master [label = "通过命令连接\n发送信息到频道"];
sentinel -> master [dir = back, label = "通过订阅连接\n从频道中接收信息"];
}](_images/graphviz-05e950c33ef0b91d3d0160f944d7460a16b86354.png)
示例：一个 Sentinel 向包括它自己在内的三个 Sentinel 发送信息。
![digraph {
label = "\n 图 16-14 向服务器发送信息";
node [shape = box];
sentinel1 [label = "sentinel1", width = 2.0];
sentinel2 [label = "sentinel2", width = 2.0];
sentinel3 [label = "sentinel3", width = 2.0];
server [label = "服务器", shape = circle];
edge [label = "发送信息\n（命令连接）"];
sentinel1 -> server;
edge [style = dashed];
edge [dir = back, label = "接收信息\n（订阅连接）"];
sentinel1 -> server;
sentinel2 -> server;
sentinel3 -> server;
}](_images/graphviz-e6387dd1193deb5d0efcdce04c3e250b8cfd914a.png)
Redis Sentinel 执行故障转移的整个过程。
![digraph {
label = "\n 图 16-22 将 server2 升级为主服务器";
subgraph cluster_servers {
style = invis;
node [shape = circle, width = 1.2];
edge [dir = none, style = dashed];
server1 [label = "server1", shape = doublecircle, style = dashed];
server2 [label = "server2"];
server3 [label = "server3"];
server4 [label = "server4"];
server1 -> server2;
server1 -> server3;
server1 -> server4;
}
sentinel_system [label = "领头 Sentinel", shape = box, width = 5.0, height = 1.0];
edge [label = "监视"];
sentinel_system -> server1 [style = dashed, label = "已下线", dir = none];
sentinel_system -> server2 [label = "发送命令\nSLAVEOF no one"];
sentinel_system -> server3 [dir = none];
sentinel_system -> server4 [dir = none];
}](_images/graphviz-2013e850c53fcfcda176421f6e1ac85052eb92d7.png)
![digraph {
label = "\n 图 16-23 server2 成功升级为主服务器";
subgraph cluster_servers {
style = invis;
node [shape = circle, width = 1.2];
edge [dir = none, style = dashed];
server1 [label = "server1", shape = doublecircle, style = dashed];
server2 [label = "server2", shape = doublecircle];
server3 [label = "server3"];
server4 [label = "server4"];
server1 -> server3;
server1 -> server4;
}
sentinel_system [label = "领头 Sentinel", shape = box, width = 5.0, height = 1.0];
edge [label = "监视", dir = none];
sentinel_system -> server1 [style = dashed, label = "已下线"];
sentinel_system -> server2;
sentinel_system -> server3;
sentinel_system -> server4;
}](_images/graphviz-fd12fbc76da1db8568db9dbca567335432be9857.png)
![digraph {
label = "\n 图 16-24 让从服务器复制新的主服务器";
subgraph cluster_servers {
style = invis;
node [shape = circle, width = 1.2];
edge [dir = none, style = dashed];
server1 [label = "server1", shape = doublecircle, style = dashed];
server2 [label = "server2", shape = doublecircle];
server3 [label = "server3"];
server4 [label = "server4"];
server1 -> server3;
server1 -> server4;
}
sentinel_system [label = "领头 Sentinel", shape = box, width = 5.0, height = 1.0];
sentinel_system -> server1 [style = dashed, label = "已下线", dir = none];
sentinel_system -> server2 [label = "监视", dir = none];
edge [label = "发送命令\nSLAVEOF\n<server2_ip>\n<server2_port>"];
sentinel_system -> server3;
sentinel_system -> server4;
}](_images/graphviz-9a97ef81f9a7fc395f3dd3a51f5ff129143eae48.png)
![digraph {
label = "\n 图 16-25 server3 和 server4 成为 server2 的从服务器";
subgraph cluster_servers {
style = invis;
node [shape = circle, width = 1.2];
edge [dir = none];
server1 [label = "server1", shape = doublecircle, style = dashed];
server2 [label = "server2", shape = doublecircle];
server3 [label = "server3"];
server4 [label = "server4"];
server2 -> server3;
server2 -> server4;
}
sentinel_system [label = "领头 Sentinel", shape = box, width = 5.0, height = 1.0];
sentinel_system -> server1 [style = dashed, label = "已下线", dir = none];
edge [label = "监视", dir = none];
sentinel_system -> server2;
sentinel_system -> server3;
sentinel_system -> server4;
}](_images/graphviz-5aa0e25464655bd036662f49dc4fc00644e4b801.png)
![digraph {
label = "\n 图 16-26 server1 被设置为新主服务器的从服务器";
subgraph cluster_servers {
style = invis;
node [shape = circle, width = 1.2];
edge [dir = none];
server1 [label = "server1", shape = circle, style = dashed];
server2 [label = "server2", shape = doublecircle];
server3 [label = "server3"];
server4 [label = "server4"];
server2 -> server1 [style = dashed];
server2 -> server3;
server2 -> server4;
}
sentinel_system [label = "Sentinel 系统", shape = box, width = 5.0, height = 1.0];
edge [dir = none];
sentinel_system -> server1 [style = dashed, label = "已下线"];
edge [label = "监视"];
sentinel_system -> server2;
sentinel_system -> server3;
sentinel_system -> server4;
}](_images/graphviz-077c570250a5be513411c91f510912fb67044a85.png)
![digraph {
label = "\n 图 16-27 server1 重新上线并成为 server2 的从服务器";
subgraph cluster_servers {
style = invis;
node [shape = circle, width = 1.2];
edge [dir = none];
server1 [label = "server1"];
server2 [label = "server2", shape = doublecircle];
server3 [label = "server3"];
server4 [label = "server4"];
server2 -> server1;
server2 -> server3;
server2 -> server4;
}
sentinel_system [label = "Sentinel 系统", shape = box, width = 5.0, height = 1.0];
edge [label = "监视", dir = none];
sentinel_system -> server1;
sentinel_system -> server2;
sentinel_system -> server3;
sentinel_system -> server4;
}](_images/graphviz-5f855165d6b42d40d2dcf9c9ab3c8ddcea5a5d5a.png)