mysql nodejs 并发

并发

在一条sql执行的时间内，如果来了1000条访问请求，那么一次查询结果将返回给1000条请求，

var EventProxy = require('eventproxy');
var proxy = new EventProxy();
var status = "ready";
var select = function(callback){proxy.once("selected",callback);if(status == "ready"){status = "pending";db.select("SQL", function(results){proxy.emit("selected",results);status = "ready";});}
}

function query(sql, sqlParams, callback) {pool.getConnection(function (err, conn) {if (err) {callback(err, null, null);} else {conn.query(sql, sqlParams, function (qerr, vals, fields) {callback(qerr, vals, fields);});}// conn.release(); // not work!!!pool.releaseConnection(conn);});
};exports.init = function (config) {pool = mysql.createPool({host: config.HOST,user: config.USER,password: config.PSWD,database: config.DB,port: config.PORT,});
};

并发访问时，通过conn.release()释放连接不成功，导致一定访问达到连接数上限后，pool.getConnection直接卡死没有任何的回调！
需要改成pool.releaseConnection(conn)

//上面其实是错误的，应该是这样，放到query以后

let pool  = mysql.createPool(mysql_config);module.exports={select : function(sql,params,callback){if(sql.toLowerCase().indexOf('select') == -1){console.log('非查询语句不可使用！');return false;}pool.getConnection(function(err,connection){if(err){callback(err,null,null);return false;}connection.query(sql,params,function(err,results,fields){//释放连接connection.release();//事件驱动回调callback(err,results,fields);});});}
};

mysql连接查看

1:查看当前连接

Threads_connected 跟show processlist结果相同，表示当前连接数。准确的来说，Threads_running是代表当前并发数

2：这是是查询数据库当前设置的最大连接数

mysql> show variables like ‘%max_connections%’;
±----------------±------+
| Variable_name | Value |
±----------------±------+
| max_connections | 1000 |
±----------------±------+

3：显示连接列表

mysql> show processlist;

4：显示连接状态

mysql> SHOW STATUS LIKE ‘%connect%’;

linux 配置

net.core.rmem_max = 33554432
net.core.wmem_max = 33554432
net.ipv4.tcp_rmem = 4096 16384 33554432
net.ipv4.tcp_wmem = 4096 16384 33554432
net.ipv4.tcp_mem = 786432 1048576 26777216
net.ipv4.tcp_max_tw_buckets = 360000
net.core.netdev_max_backlog = 2500
vm.min_free_kbytes = 65536
vm.swappiness = 0
net.ipv4.ip_local_port_range = 1024 65535

sysctl -w net.ipv4.tcp_tw_recycle=1
sysctl -w net.ipv4.tcp_tw_reuse=1
sysctl -w net.ipv4.ip_local_port_range=“2000 65535”
如果可以，增加远端服务的 IP 数量也是一个有效且非常推荐的方法。