redis限频

做法

使用redis的lua脚本功能来限频
在redis中定时刷新系统时间来作为一个全局的时钟

限频脚本：

/**
* 获取令牌的lua脚本
*/
public final static String SCRIPT = "local epoch = redis.call("hget",KEYS[1],'Epoch');\n" +
"local currentEpoch = tonumber(ARGV[1]);\n" +
"if(epoch == false and currentEpoch ~= epoch) then\n" +
" redis.call('hset', KEYS[1], 'Epoch',currentEpoch);\n" +
" redis.call("hset", KEYS[1], 'Count', tonumber(ARGV[2]));\n" +
" redis.call('pexpire', KEYS[1], 2000);\n" +
" return 1;\n" +
"end; \n" +
"local currentCount = redis.call("HINCRBY", KEYS[1],'Count', tonumber(ARGV[3]));\n" +
"if(currentCount > 0) then \n" +
" return 1;\n" +
"else \n" +
" return 2;\n" +
"end;";

/**
* 同步系统时间到redis 中的lua脚本
*/
public final static String SET_SYSTEM_TIME_SCRIPT = "local clientId = redis.call("hget",KEYS[1],'Client'); \n" +
"if (clientId == false or clientId == ARGV[1]) then \n" +
" redis.call('hset', KEYS[1], 'Client', ARGV[1]);\n" +
" redis.call('hset', KEYS[1], 'Time' ,ARGV[2]);\n" +
" redis.call('pexpire', KEYS[1], tonumber(ARGV[3]));\n" +
" return 1;\n" +
"end;\n" +
"return 2;";

java调用代码：

List keys = new ArrayList();
keys.add("JRateLimit-Key-" + source);

List args = new ArrayList();
args.add(currentEpoch + ""); //currentEpoch是通过获取全局时钟来做的
args.add(permitsPerEpoch + "");
args.add((0 - permits) + "");

Object result = client.evalsha(LIMIT_LUA_SCRIPT_SHA, keys, args, false); //result的类型即为lua脚本中的返回值类型，Long

策略

通过redis实现全局时钟
通过一次多取几个令牌放到内存中来解决超大调用频率导致的redis请求单机ops极限问题