void evalGenericCommand(redisClient *c, int evalsha) {
lua_State *lua = server.lua;
char funcname[43];
long long numkeys;
int delhook = 0, err;
/* We want the same PRNG sequence at every call so that our PRNG is
* not affected by external state. */
redisSrand48(0);
/* We set this flag to zero to remember that so far no random command
* was called. This way we can allow the user to call commands like
* SRANDMEMBER or RANDOMKEY from Lua scripts as far as no write command
* is called (otherwise the replication and AOF would end with non
* deterministic sequences).
*
* Thanks to this flag we'll raise an error every time a write command
* is called after a random command was used. */
server.lua_random_dirty = 0;
server.lua_write_dirty = 0;
/* Get the number of arguments that are keys */
if (getLongLongFromObjectOrReply(c,c->argv[2],&numkeys,NULL) != REDIS_OK)
return;
if (numkeys > (c->argc - 3)) {
addReplyError(c,"Number of keys can't be greater than number of args");
return;
}
/* We obtain the script SHA1, then check if this function is already
* defined into the Lua state */
funcname[0] = 'f';
funcname[1] = '_';
if (!evalsha) {
/* Hash the code if this is an EVAL call */
sha1hex(funcname+2,c->argv[1]->ptr,sdslen(c->argv[1]->ptr));
} else {
/* We already have the SHA if it is a EVALSHA */
int j;
char *sha = c->argv[1]->ptr;
for (j = 0; j < 40; j++)
funcname[j+2] = tolower(sha[j]);
funcname[42] = '\0';
}
/* Push the pcall error handler function on the stack. */
lua_getglobal(lua, "__redis__err__handler");
/* Try to lookup the Lua function */
lua_getglobal(lua, funcname);
if (lua_isnil(lua,-1)) {
lua_pop(lua,1); /* remove the nil from the stack */
/* Function not defined... let's define it if we have the
* body of the function. If this is an EVALSHA call we can just
* return an error. */
if (evalsha) {
lua_pop(lua,1); /* remove the error handler from the stack. */
addReply(c, shared.noscripterr);
return;
}
if (luaCreateFunction(c,lua,funcname,c->argv[1]) == REDIS_ERR) {
lua_pop(lua,1); /* remove the error handler from the stack. */
/* The error is sent to the client by luaCreateFunction()
* itself when it returns REDIS_ERR. */
return;
}
/* Now the following is guaranteed to return non nil */
lua_getglobal(lua, funcname);
redisAssert(!lua_isnil(lua,-1));
}
/* Populate the argv and keys table accordingly to the arguments that
* EVAL received. */
luaSetGlobalArray(lua,"KEYS",c->argv+3,numkeys);
luaSetGlobalArray(lua,"ARGV",c->argv+3+numkeys,c->argc-3-numkeys);
/* Select the right DB in the context of the Lua client */
selectDb(server.lua_client,c->db->id);
/* Set a hook in order to be able to stop the script execution if it
* is running for too much time.
* We set the hook only if the time limit is enabled as the hook will
* make the Lua script execution slower. */
server.lua_caller = c;
server.lua_time_start = mstime();
server.lua_kill = 0;
if (server.lua_time_limit > 0 && server.masterhost == NULL) {
lua_sethook(lua,luaMaskCountHook,LUA_MASKCOUNT,100000);
delhook = 1;
}
/* At this point whether this script was never seen before or if it was
* already defined, we can call it. We have zero arguments and expect
* a single return value. */
err = lua_pcall(lua,0,1,-2);
/* Perform some cleanup that we need to do both on error and success. */
if (delhook) lua_sethook(lua,luaMaskCountHook,0,0); /* Disable hook */
if (server.lua_timedout) {
server.lua_timedout = 0;
/* Restore the readable handler that was unregistered when the
* script timeout was detected. */
aeCreateFileEvent(server.el,c->fd,AE_READABLE,
readQueryFromClient,c);
}
server.lua_caller = NULL;
selectDb(c,server.lua_client->db->id); /* set DB ID from Lua client */
lua_gc(lua,LUA_GCSTEP,1);
if (err) {
addReplyErrorFormat(c,"Error running script (call to %s): %s\n",
funcname, lua_tostring(lua,-1));
lua_pop(lua,2); /* Consume the Lua reply and remove error handler. */
} else {
/* On success convert the Lua return value into Redis protocol, and
* send it to * the client. */
luaReplyToRedisReply(c,lua); /* Convert and consume the reply. */
lua_pop(lua,1); /* Remove the error handler. */
}
/* EVALSHA should be propagated to Slave and AOF file as full EVAL, unless
* we are sure that the script was already in the context of all the
* attached slaves *and* the current AOF file if enabled.
*
* To do so we use a cache of SHA1s of scripts that we already propagated
* as full EVAL, that's called the Replication Script Cache.
*
* For repliation, everytime a new slave attaches to the master, we need to
* flush our cache of scripts that can be replicated as EVALSHA, while
* for AOF we need to do so every time we rewrite the AOF file. */
if (evalsha) {
if (!replicationScriptCacheExists(c->argv[1]->ptr)) {
/* This script is not in our script cache, replicate it as
* EVAL, then add it into the script cache, as from now on
* slaves and AOF know about it. */
robj *script = dictFetchValue(server.lua_scripts,c->argv[1]->ptr);
replicationScriptCacheAdd(c->argv[1]->ptr);
redisAssertWithInfo(c,NULL,script != NULL);
rewriteClientCommandArgument(c,0,
resetRefCount(createStringObject("EVAL",4)));
rewriteClientCommandArgument(c,1,script);
forceCommandPropagation(c,REDIS_PROPAGATE_REPL|REDIS_PROPAGATE_AOF);
}
}
}
void evalGenericCommand(redisClient *c, int evalsha) {
lua_State *lua = server.lua;
char funcname[43];
long long numkeys;
int delhook = 0, err;
// 随机数的种子，在产生哈希值的时候会用到
/* We want the same PRNG sequence at every call so that our PRNG is
* not affected by external state. */
redisSrand48(0);
/* We set this flag to zero to remember that so far no random command
* was called. This way we can allow the user to call commands like
* SRANDMEMBER or RANDOMKEY from Lua scripts as far as no write command
* is called (otherwise the replication and AOF would end with non
* deterministic sequences).
*
* Thanks to this flag we'll raise an error every time a write command
* is called after a random command was used. */
server.lua_random_dirty = 0;
server.lua_write_dirty = 0;
// 检查参数的有效性
/* Get the number of arguments that are keys */
if (getLongLongFromObjectOrReply(c,c->argv[2],&numkeys,NULL) != REDIS_OK)
return;
if (numkeys > (c->argc - 3)) {
addReplyError(c,"Number of keys can't be greater than number of args");
return;
}
// 函数名以 f_ 开头
/* We obtain the script SHA1, then check if this function is already
* defined into the Lua state */
funcname[0] = 'f';
funcname[1] = '_';
// 如果没有哈希值，需要计算 lua 脚本的哈希值
if (!evalsha) {
// 计算哈希值，会放入到 SHA1 -> lua_script 哈希表中
// c->argv[1]->ptr 是用户指定的 lua 脚本
// sha1hex() 产生的哈希值存在 funcname 中
/* Hash the code if this is an EVAL call */
sha1hex(funcname+2,c->argv[1]->ptr,sdslen(c->argv[1]->ptr));
} else {
// 用户自己指定了哈希值
/* We already have the SHA if it is a EVALSHA */
int j;
char *sha = c->argv[1]->ptr;
for (j = 0; j < 40; j++)
funcname[j+2] = tolower(sha[j]);
funcname[42] = '\0';
}
// 将错误处理函数入栈
// lua_getglobal() 会将读取指定的全局变量，且将其入栈
/* Push the pcall error handler function on the stack. */
lua_getglobal(lua, "__redis__err__handler");
/* Try to lookup the Lua function */
// 在 lua 中查找是否注册了此函数。这一句尝试将 funcname 入栈
lua_getglobal(lua, funcname);
if (lua_isnil(lua,-1)) { // funcname 在 lua 中不存在
// 将 nil 出栈
lua_pop(lua,1); /* remove the nil from the stack */
// 已经确定 funcname 在 lua 中没有定义，需要创建
/* Function not defined... let's define it if we have the
* body of the function. If this is an EVALSHA call we can just
* return an error. */
if (evalsha) {
lua_pop(lua,1); /* remove the error handler from the stack. */
addReply(c, shared.noscripterr);
return;
}
// 创建 lua 函数 funcname
// c->argv[1] 指向用户指定的 lua 脚本
if (luaCreateFunction(c,lua,funcname,c->argv[1]) == REDIS_ERR) {
lua_pop(lua,1); /* remove the error handler from the stack. */
/* The error is sent to the client by luaCreateFunction()
* itself when it returns REDIS_ERR. */
return;
}
// 现在 lua 中已经有 funcname 这个全局变量了，将其读取并入栈，
// 准备调用
/* Now the following is guaranteed to return non nil */
lua_getglobal(lua, funcname);
redisAssert(!lua_isnil(lua,-1));
}
// 设置参数，包括键和值
/* Populate the argv and keys table accordingly to the arguments that
* EVAL received. */
luaSetGlobalArray(lua,"KEYS",c->argv+3,numkeys);
luaSetGlobalArray(lua,"ARGV",c->argv+3+numkeys,c->argc-3-numkeys);
// 选择数据集，lua_client 有专用的数据集
/* Select the right DB in the context of the Lua client */
selectDb(server.lua_client,c->db->id);
// 设置超时回调函数，以在 lua 脚本执行过长时间的时候停止脚本的运行
/* Set a hook in order to be able to stop the script execution if it
* is running for too much time.
* We set the hook only if the time limit is enabled as the hook will
* make the Lua script execution slower. */
server.lua_caller = c;
server.lua_time_start = ustime()/1000;
server.lua_kill = 0;
if (server.lua_time_limit > 0 && server.masterhost == NULL) {
// 当 lua 解释器执行了 100000，luaMaskCountHook() 会被调用
lua_sethook(lua,luaMaskCountHook,LUA_MASKCOUNT,100000);
delhook = 1;
}
// 现在，我们确定函数已经注册成功了.可以直接调用 lua 脚本
/* At this point whether this script was never seen before or if it was
* already defined, we can call it. We have zero arguments and expect
* a single return value. */
err = lua_pcall(lua,0,1,-2);
// 删除超时回调函数
/* Perform some cleanup that we need to do both on error and success. */
if (delhook) lua_sethook(lua,luaMaskCountHook,0,0); /* Disable hook */
// 如果已经超时了，说明 lua 脚本已在超时后背 SCRPIT KILL 终结了
// 恢复监听发送 lua 脚本命令的客户端
if (server.lua_timedout) {
server.lua_timedout = 0;
/* Restore the readable handler that was unregistered when the
* script timeout was detected. */
aeCreateFileEvent(server.el,c->fd,AE_READABLE,
readQueryFromClient,c);
}
// lua_caller 置空
server.lua_caller = NULL;
// 执行 lua 脚本用的是 lua 脚本执行专用的数据集。现在恢复原有的数据集
selectDb(c,server.lua_client->db->id); /* set DB ID from Lua client */
// Garbage collection 垃圾回收
lua_gc(lua,LUA_GCSTEP,1);
// 处理执行 lua 脚本的错误
if (err) {
// 告知客户端
addReplyErrorFormat(c,"Error running script (call to %s): %s\n",
funcname, lua_tostring(lua,-1));
lua_pop(lua,2); /* Consume the Lua reply and remove error handler. */
// 成功了
} else {
/* On success convert the Lua return value into Redis protocol, and
* send it to * the client. */
luaReplyToRedisReply(c,lua); /* Convert and consume the reply. */
lua_pop(lua,1); /* Remove the error handler. */
}
// 将 lua 脚本发布到主从复制上，并写入 AOF 文件
/* EVALSHA should be propagated to Slave and AOF file as full EVAL, unless
* we are sure that the script was already in the context of all the
* attached slaves *and* the current AOF file if enabled.
*
* To do so we use a cache of SHA1s of scripts that we already propagated
* as full EVAL, that's called the Replication Script Cache.
*
* For repliation, everytime a new slave attaches to the master, we need to
* flush our cache of scripts that can be replicated as EVALSHA, while
* for AOF we need to do so every time we rewrite the AOF file. */
if (evalsha) {
if (!replicationScriptCacheExists(c->argv[1]->ptr)) {
/* This script is not in our script cache, replicate it as
* EVAL, then add it into the script cache, as from now on
* slaves and AOF know about it. */
// 从 server.lua_scripts 获取 lua 脚本
// c->argv[1]->ptr 是 SHA1
robj *script = dictFetchValue(server.lua_scripts,c->argv[1]->ptr);
// 添加到主从复制专用的脚本缓存中
replicationScriptCacheAdd(c->argv[1]->ptr);
redisAssertWithInfo(c,NULL,script != NULL);
// 重写命令
// 参数 1 为：EVAL
// 参数 2 为：lua_script
// 如此一来在执行 AOF 持久化和主从复制的时候，lua 脚本就能得到传播
rewriteClientCommandArgument(c,0,
resetRefCount(createStringObject("EVAL",4)));
rewriteClientCommandArgument(c,1,script);
}
}
}
