第 20 章： Lua 脚本

创建并修改 Lua 环境

服务器与 Lua 环境。

digraph { label = "\n图 20-1 服务器状态中的 Lua 环境"; rankdir = LR; node [shape = record]; server [label = "redisServer | ... | <lua> lua | ...", width = 2.0, height = 2.0]; lua [label = "Lua 环境", shape = circle]; server:lua -> lua; }

Lua 环境协作组件

Lua 脚本执行 Redis 命令时的通讯步骤。

digraph { label = "\n图 20-2 Lua 脚本执行 Redis 命令时的通讯步骤"; rankdir = LR; node [shape = record, height = 2.0]; splines = polyline; // lua [label = "L\nu\na\n环\n境"]; fake_client [label = "伪\n客\n户\n端"]; eval [label = "命\n令\n执\n行\n器"]; lua -> fake_client [label = "1) 传送 redis.call 函数\n想要执行的 Redis 命令"] fake_client -> eval [label = "2) 将命令传给执行器执行"]; lua -> fake_client [dir = back, label = "\n4) 将命令结果传回给 Lua 环境"]; fake_client -> eval [dir = back, label = "\n3) 返回命令的执行结果"]; }

作为例子， 图 20-3 展示了 Lua 脚本在执行以下命令时：

redis> EVAL "return redis.call('DBSIZE')" 0
(integer) 10086

Lua 环境、伪客户端、命令执行器三者之间的通讯过程。

digraph { label = "\n图 20-3 Lua 脚本执行 DBSIZE 命令时的通讯步骤"; rankdir = LR; node [shape = record, height = 2.0]; splines = polyline; // lua [label = "L\nu\na\n环\n境"]; fake_client [label = "伪\n客\n户\n端"]; eval [label = "命\n令\n执\n行\n器"]; lua -> fake_client [label = "1) 传送 DBSIZE 请求"] fake_client -> eval [label = "2) 将 DBSIZE 命令传给执行器执行"]; lua -> fake_client [dir = back, label = "\n4) 将命令结果 10086 传回给 Lua 环境"]; fake_client -> eval [dir = back, label = "\n3) 返回命令的执行结果 10086"]; }

lua_scripts 字典示例。

digraph { label = "\n 图 20-4 lua_scripts 字典示例"; rankdir = LR; node [shape = record]; // lua_scripts [label = "lua_scripts | ... | <1> \"2f31ba2bb6d6a0f42cc159d2e2dad55440778de3\" | <2> \"a27e7e8a43702b7046d4f6a7ccf5b60cef6b9bd9\" | <3> \"4475bfb5919b5ad16424cb50f74d4724ae833e72\" | ... "]; node [shape = plaintext]; one [label = "\"return 'hi'\""]; two [label = "\"return 1+1\""]; three [label = "\"return 2*2\""]; lua_scripts:1 -> one; lua_scripts:2 -> two; lua_scripts:3 -> three; }

脚本管理命令的实现

带有超时处理钩子的脚本的运行过程。

digraph { label = "\n图 20-8 带有超时处理钩子的脚本的执行过程"; node [shape = box]; start_script [label = "开始执行脚本", width = 3.5]; finish_or_not [label = "脚本执行完毕？", shape = diamond]; finish [label = "返回执行结果"]; overtime_or_not [label = "定期调用钩子\n检查脚本\n是否已超时运行？", shape = diamond]; kill_or_shutdown_arrive_or_not [label = "有 SCRIPT KILL\n或者\nSHUTDOWN NOSAVE\n到达？", shape = diamond]; stop_script [label = "执行 SCRIPT KILL \n 或者 SHUTDOWN"]; keep_running [label = "继续执行脚本"]; // start_script -> finish_or_not; finish_or_not -> finish [label = "是"]; finish_or_not -> overtime_or_not [label = "否"]; overtime_or_not -> kill_or_shutdown_arrive_or_not [label = "是"]; overtime_or_not -> keep_running [label = "否"]; kill_or_shutdown_arrive_or_not -> stop_script [label = "是"]; kill_or_shutdown_arrive_or_not -> keep_running [label = "否"]; keep_running -> finish_or_not; }

脚本复制

将脚本命令传播给从服务器。

digraph { label = "\n 图 20-9 将脚本命令传播给从服务器"; rankdir = LR; // node [shape = circle, width = 1.0]; client [label = "客户端", width = 1.3]; master [label = "主服务器", width = 1.3]; slave1 [label = "从服务器 1"]; slave2 [label = "从服务器 2"]; more [label = "...", shape = plaintext]; slaveN [label = "从服务器 N"]; // edge [label = "EVAL \n 或者 \n SCRIPT FLUSH \n 或者 \n SCRIPT LOAD"]; client -> master; master -> slave1; master -> slave2; master -> more; master -> slaveN; }

主服务器判断该传播 EVAL 命令还是 EVALSHA 命令的流程。

digraph { label = "\n 图 20-12 主服务器判断传播 EVAL 还是 EVALSHA 的过程"; node [shape = box]; command [label = " 主服务器在本机执行完命令 \n EVALSHA <sha1> <numkeys> [key ...] [arg ...] "]; sha1_exists_in_scriptcache_or_not [label = "校验和 sha1 是否存在于 \n repl_scriptcache_dict 字典？", shape = diamond]; propagate_evalsha [label = "传播 \n EVALSHA <sha1> <numkeys> [key ...] [arg ...]"]; convert_evalsha_to_eval [label = "将 EVALSHA 命令转换成等价的 EVAL 命令"]; propagate_eval [label = "传播 \n EVAL <script> <numkeys> [key ...] [arg ...]"]; add_sha1_to_scriptcache [label = "将 sha1 添加到 \n repl_scriptcache_dict 字典"]; // command -> sha1_exists_in_scriptcache_or_not; sha1_exists_in_scriptcache_or_not -> propagate_evalsha [label = "是"]; sha1_exists_in_scriptcache_or_not -> convert_evalsha_to_eval [label = "否"]; convert_evalsha_to_eval -> propagate_eval; propagate_eval -> add_sha1_to_scriptcache; }