Exemple #1
0
void scriptCommand(rliteClient *c) {
	if (c->argc == 2 && !strcasecmp(c->argv[1],"flush")) {
		scriptingReset();
		c->reply = createStatusObject(RLITE_STR_OK);
	} else if (c->argc >= 2 && !strcasecmp(c->argv[1],"exists")) {
		int j;

		c->reply = createArrayObject(c->argc - 2);
		for (j = 2; j < c->argc; j++) {
			c->reply->element[j - 2] = createLongLongObject(getScript(c, c->argv[j], NULL, NULL) == RL_OK ? 1 : 0);
		}
	} else if (c->argc == 3 && !strcasecmp(c->argv[1],"load")) {
		char sha[41];

		sha1hex(sha,c->argv[2],c->argvlen[2]);
		setScript(c, c->argv[2], c->argvlen[2]);
		c->reply = createStringObject(sha,40);
	} else if (c->argc == 2 && !strcasecmp(c->argv[1],"kill")) {
		if (lua_caller == NULL) {
			c->reply = createCStringObject("NOTBUSY No scripts in execution right now.\r\n");
		} else if (lua_write_dirty) {
			c->reply = createCStringObject("UNKILLABLE Sorry the script already executed write commands against the dataset. You can either wait the script termination or kill the server in a hard way using the SHUTDOWN NOSAVE command.\r\n");
		} else {
			lua_kill = 1;
			c->reply = createStatusObject(RLITE_STR_OK);
		}
	} else {
		c->reply = createErrorObject("ERR Unknown SCRIPT subcommand or wrong # of args.");
	}
}
Exemple #2
0
static int setScript(rliteClient *c, char *script, long scriptlen) {
	int retval;
	char hash[40];
	sha1hex(hash, script, scriptlen);
	RL_CALL(rl_select_internal, RL_OK, c->context->db, RLITE_INTERNAL_DB_LUA);

	RL_CALL(rl_set, RL_OK, c->context->db, (unsigned char *)hash, 40, (unsigned char *)script, scriptlen, 0, 0);

cleanup:
	rl_select_internal(c->context->db, RLITE_INTERNAL_DB_NO);
	return retval;
}
Exemple #3
0
/* This adds redis.sha1hex(string) to Lua scripts using the same hashing
 * function used for sha1ing lua scripts. */
int luaRedisSha1hexCommand(lua_State *lua) {
    int argc = lua_gettop(lua);
    char digest[41];
    size_t len;
    char *s;

    if (argc != 1) {
        luaPushError(lua, "wrong number of arguments");
        return 1;
    }

    s = (char*)lua_tolstring(lua,1,&len);
    sha1hex(digest,s,len);
    lua_pushstring(lua,digest);
    return 1;
}
Exemple #4
0
void scriptCommand(redisClient *c) {
    if (c->argc == 2 && !strcasecmp(c->argv[1]->ptr,"flush")) {
        scriptingReset();
        addReply(c,shared.ok);
        replicationScriptCacheFlush();
        server.dirty++; /* Propagating this command is a good idea. */
    } else if (c->argc >= 2 && !strcasecmp(c->argv[1]->ptr,"exists")) {
        int j;

        addReplyMultiBulkLen(c, c->argc-2);
        for (j = 2; j < c->argc; j++) {
            if (dictFind(server.lua_scripts,c->argv[j]->ptr))
                addReply(c,shared.cone);
            else
                addReply(c,shared.czero);
        }
    } else if (c->argc == 3 && !strcasecmp(c->argv[1]->ptr,"load")) {
        char funcname[43];
        sds sha;

        funcname[0] = 'f';
        funcname[1] = '_';
        sha1hex(funcname+2,c->argv[2]->ptr,sdslen(c->argv[2]->ptr));
        sha = sdsnewlen(funcname+2,40);
        if (dictFind(server.lua_scripts,sha) == NULL) {
            if (luaCreateFunction(c,server.lua,funcname,c->argv[2])
                    == REDIS_ERR) {
                sdsfree(sha);
                return;
            }
        }
        addReplyBulkCBuffer(c,funcname+2,40);
        sdsfree(sha);
        forceCommandPropagation(c,REDIS_PROPAGATE_REPL|REDIS_PROPAGATE_AOF);
    } else if (c->argc == 2 && !strcasecmp(c->argv[1]->ptr,"kill")) {
        if (server.lua_caller == NULL) {
            addReplySds(c,sdsnew("-NOTBUSY No scripts in execution right now.\r\n"));
        } else if (server.lua_write_dirty) {
            addReplySds(c,sdsnew("-UNKILLABLE Sorry the script already executed write commands against the dataset. You can either wait the script termination or kill the server in a hard way using the SHUTDOWN NOSAVE command.\r\n"));
        } else {
            server.lua_kill = 1;
            addReply(c,shared.ok);
        }
    } else {
        addReplyError(c, "Unknown SCRIPT subcommand or wrong # of args.");
    }
}
Exemple #5
0
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);
        }
    }
}
Exemple #6
0
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);
        }
    }
}
Exemple #7
0
void evalGenericCommand(rliteClient *c, int evalsha) {
	scriptingInit();
	lua_client->context = c->context;
	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. */
	rliteSrand48(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. */
	lua_random_dirty = 0;
	lua_write_dirty = 0;

	/* Get the number of arguments that are keys */
	if (getLongLongFromObjectOrReply(c,c->argv[2],c->argvlen[2],&numkeys,NULL) != RLITE_OK)
		return;
	if (numkeys > (c->argc - 3)) {
		c->reply = createErrorObject("Number of keys can't be greater than number of args");
		return;
	} else if (numkeys < 0) {
		c->reply = createErrorObject("Number of keys can't be negative");
		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],c->argvlen[1]);
	} else {
		/* We already have the SHA if it is a EVALSHA */
		int j;
		char *sha = c->argv[1];

		/* Convert to lowercase. We don't use tolower since the function
		 * managed to always show up in the profiler output consuming
		 * a non trivial amount of time. */
		for (j = 0; j < 40; j++)
			funcname[j+2] = (sha[j] >= 'A' && sha[j] <= 'Z') ?
				sha[j]+('a'-'A') : sha[j];
		funcname[42] = '\0';

		char *body;
		long bodylen;
		int retval = getScript(c, funcname + 2, &body, &bodylen);
		if (retval != RL_OK) {
			c->reply = createErrorObject(RLITE_NOSCRIPTERR);
			return;
		}
		luaCreateFunction(c, lua, funcname, body, bodylen);
		rl_free(body);
	}

	/* Push the pcall error handler function on the stack. */
	lua_getglobal(lua, "__rlite__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. */
			c->reply = createErrorObject(RLITE_NOSCRIPTERR);
			return;
		}
		if (luaCreateFunction(c,lua,funcname,c->argv[1], c->argvlen[1]) == RLITE_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 RLITE_ERR. */
			return;
		}
		/* Now the following is guaranteed to return non nil */
		lua_getglobal(lua, funcname);
		if (lua_isnil(lua,-1)) {
			// TODO: panic
			return;
		}
	}

	/* Populate the argv and keys table accordingly to the arguments that
	 * EVAL received. */
	luaSetGlobalArray(lua,"KEYS",c->argv+3,c->argvlen+3,numkeys);
	luaSetGlobalArray(lua,"ARGV",c->argv+3+numkeys,c->argvlen+3+numkeys,c->argc-3-numkeys);

	/* 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. */
	lua_caller = c;
	lua_time_start = rl_mstime();
	lua_kill = 0;
	if (lua_time_limit > 0) {
		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 (lua_timedout) {
		lua_timedout = 0;
		/* Restore the readable handler that was unregistered when the
		 * script timeout was detected. */
	}
	lua_caller = NULL;

	/* Call the Lua garbage collector from time to time to avoid a
	 * full cycle performed by Lua, which adds too latency.
	 *
	 * The call is performed every LUA_GC_CYCLE_PERIOD executed commands
	 * (and for LUA_GC_CYCLE_PERIOD collection steps) because calling it
	 * for every command uses too much CPU. */
	#define LUA_GC_CYCLE_PERIOD 50
	{
		static long gc_count = 0;

		gc_count++;
		if (gc_count == LUA_GC_CYCLE_PERIOD) {
			lua_gc(lua,LUA_GCSTEP,LUA_GC_CYCLE_PERIOD);
			gc_count = 0;
		}
	}

	if (err) {
		char err[1024];
		snprintf(err, 1024, "Error running script (call to %s): %s\n",
			funcname, lua_tostring(lua,-1));
		c->reply = createErrorObject(err);
		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. */
	}
}
Exemple #8
0
void evalGenericCommand(redisClient *c, int evalsha)
{
    lua_State *lua = server.lua;
    char funcname[43];
    long long numkeys;
    int delhook = 0;

    /* We want the same PRNG sequence at every call so that our PRNG is
     * not affected by external state.
     *
     * 在每次执行 EVAL 时重置随机 seed ,从而保证可以生成相同的随机序列。
     */
    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.
     *
     * 用两个变量,对命令进行检查
     * 确保在调用随机命令之后,再调用写命令将出现错误
     */
    server.lua_random_dirty = 0;
    server.lua_write_dirty = 0;

    /* Get the number of arguments that are keys */
    // 获取输入键的数量
    if (getLongLongFromObjectOrReply(c,c->argv[2],&numkeys,NULL) != REDIS_OK)
        return;
    // 对键的正确性做一个快速检查
    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 */
    // 组合出函数的名字,例如 f_282297a0228f48cd3fc6a55de6316f31422f5d17
    funcname[0] = 'f';
    funcname[1] = '_';
    if (!evalsha)
    {
        /* Hash the code if this is an EVAL call */
        // 如果执行的是 EVAL 命令,那么计算脚本的 SHA1 校验和
        sha1hex(funcname+2,c->argv[1]->ptr,sdslen(c->argv[1]->ptr));
    }
    else
    {
        // 如果执行的是 EVALSHA 命令,直接使用传入的 SHA1 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';
    }

    /* Try to lookup the Lua function */
    // 按名查找函数
    lua_getglobal(lua, funcname);
    if (lua_isnil(lua,1))
    {

        // 没找到脚本相应的脚本

        lua_pop(lua,1); /* remove the nil from the stack */
        /* Function not defined... let's define it if we have the
         * body of the funciton. If this is an EVALSHA call we can just
         * return an error. */
        if (evalsha)
        {
            // 如果执行的是 EVALSHA ,返回脚本未找到错误
            addReply(c, shared.noscripterr);
            return;
        }
        // 如果执行的是 EVAL ,那么创建并执行新函数,然后将代码添加到脚本字典中
        if (luaCreateFunction(c,lua,funcname,c->argv[1]) == 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. */
    // 设置 KEYS 和 ARGV 全局变量到 Lua 环境
    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 */
    // 为 Lua 所属的(伪)客户端设置数据库
    selectDb(server.lua_client,c->db->id);

    /* Set an hook in order to be able to stop the script execution if it
     * is running for too much time.
     *
     * 设置一个钩子,用于在运行时间过长时停止脚本的运作。
     *
     * We set the hook only if the time limit is enabled as the hook will
     * make the Lua script execution slower.
     *
     * 只在开启了时间限制选项时使用钩子,因为它会拖慢脚本的运行速度。
     */
    // 调用客户端
    server.lua_caller = c;
    // 脚本开始时间
    server.lua_time_start = ustime()/1000;
    // 是否杀死脚本
    server.lua_kill = 0;
    // 只在开启时间限制时使用钩子
    if (server.lua_time_limit > 0 && server.masterhost == NULL)
    {
        lua_sethook(lua,luaMaskCountHook,LUA_MASKCOUNT,100000);
        delhook = 1;
    }

    /* At this point whatever 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. */
    // 执行脚本(所属的函数)
    if (lua_pcall(lua,0,1,0))
    {

        // 以下是脚本执行出错的代码。。。

        // 删除钩子
        if (delhook) lua_sethook(lua,luaMaskCountHook,0,0); /* Disable hook */

        // 脚本执行已超时
        if (server.lua_timedout)
        {
            // 清除超时 FLAG
            server.lua_timedout = 0;
            /* Restore the readable handler that was unregistered when the
             * script timeout was detected. */
            // 将超时钩子里删除的读事件重新加上
            aeCreateFileEvent(server.el,c->fd,AE_READABLE,
                              readQueryFromClient,c);
        }

        // 清空调用者
        server.lua_caller = NULL;
        // 更新目标数据库
        selectDb(c,server.lua_client->db->id); /* set DB ID from Lua client */
        addReplyErrorFormat(c,"Error running script (call to %s): %s\n",
                            funcname, lua_tostring(lua,-1));
        // 弹出函数
        lua_pop(lua,1);
        // 执行完整的废料回首循环(full garbage-collection cycle)
        lua_gc(lua,LUA_GCCOLLECT,0);
        // 返回
        return;
    }

    // 以下是脚本执行成功时执行的代码。。。

    // 删除钩子
    if (delhook) lua_sethook(lua,luaMaskCountHook,0,0); /* Disable hook */

    // 清空超时 FLAG
    server.lua_timedout = 0;

    // 清空调用者
    server.lua_caller = NULL;

    // 更新 DB
    selectDb(c,server.lua_client->db->id); /* set DB ID from Lua client */

    // 将 Lua 回复转换成 Redis 回复
    luaReplyToRedisReply(c,lua);

    // 执行 1 步渐进式 GC
    lua_gc(lua,LUA_GCSTEP,1);

    /* If we have slaves attached we want to replicate this command as
     * EVAL instead of EVALSHA. We do this also in the AOF as currently there
     * is no easy way to propagate a command in a different way in the AOF
     * and in the replication link.
     *
     * 如果有附属节点,那么使用 EVAL 而不是 EVALSHA 来传播脚本
     * 因为目前还没有代码可以检测脚本是否已经传送到附属节点中
     *
     * IMPROVEMENT POSSIBLE:
     * 1) Replicate this command as EVALSHA in the AOF.
     * 2) Remember what slave already received a given script, and replicate
     *    the EVALSHA against this slaves when possible.
     */
    // 如果执行的是 EVALSHA 命令
    if (evalsha)
    {
        // 取出脚本代码体(body)
        robj *script = dictFetchValue(server.lua_scripts,c->argv[1]->ptr);

        redisAssertWithInfo(c,NULL,script != NULL);
        // 重写客户端命令为 EVAL
        rewriteClientCommandArgument(c,0,
                                     resetRefCount(createStringObject("EVAL",4)));
        rewriteClientCommandArgument(c,1,script);
    }
}
void evalGenericCommand(redisClient *c, int evalsha) {
    lua_State *lua = server.lua;
    char funcname[43];
    long long numkeys;
    int delhook = 0;

    /* 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';
    }

    /* 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 funciton. If this is an EVALSHA call we can just
         * return an error. */
        if (evalsha) {
            addReply(c, shared.noscripterr);
            return;
        }
        if (luaCreateFunction(c,lua,funcname,c->argv[1]) == 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 an 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) {
        lua_sethook(lua,luaMaskCountHook,LUA_MASKCOUNT,100000);
        delhook = 1;
    }

    /* At this point whatever 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. */
    if (lua_pcall(lua,0,1,0)) {
        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 */
        addReplyErrorFormat(c,"Error running script (call to %s): %s\n",
            funcname, lua_tostring(lua,-1));
        lua_pop(lua,1);
        lua_gc(lua,LUA_GCCOLLECT,0);
        return;
    }
    if (delhook) lua_sethook(lua,luaMaskCountHook,0,0); /* Disable hook */
    server.lua_timedout = 0;
    server.lua_caller = NULL;
    selectDb(c,server.lua_client->db->id); /* set DB ID from Lua client */
    luaReplyToRedisReply(c,lua);
    lua_gc(lua,LUA_GCSTEP,1);

    /* If we have slaves attached we want to replicate this command as
     * EVAL instead of EVALSHA. We do this also in the AOF as currently there
     * is no easy way to propagate a command in a different way in the AOF
     * and in the replication link.
     *
     * IMPROVEMENT POSSIBLE:
     * 1) Replicate this command as EVALSHA in the AOF.
     * 2) Remember what slave already received a given script, and replicate
     *    the EVALSHA against this slaves when possible.
     */
    if (evalsha) {
        robj *script = dictFetchValue(server.lua_scripts,c->argv[1]->ptr);

        redisAssertWithInfo(c,NULL,script != NULL);
        rewriteClientCommandArgument(c,0,
            resetRefCount(createStringObject("EVAL",4)));
        rewriteClientCommandArgument(c,1,script);
    }
}