GHOST 0.6.2 在运行过程中出现 500 连接 mysql 错误，但 mysql 无错误日志，问有人遇到过或知道是什么原因？

我昨天在digitalocean新建了个VPS来搭建我的GHOST并使用mysql来作为其数据库，到今天上午还运行正常，下午发现500错误，错误日志如下：

^[[31m
ERROR:^[[39m ^[[31mconnect ECONNREFUSED^[[39m
 ^[[37mRendering Error Page^[[39m
 ^[[32mGhost caught a processing error in the middleware layer.^[[39m
 Error: connect ECONNREFUSED
    at errnoException (net.js:905:11)
    at Object.afterConnect [as oncomplete] (net.js:896:19)
    --------------------
    at Protocol._enqueue    (/var/web/zhazham/node_modules/mysql/lib/protocol/Protocol.js:110:48)
    at Protocol.handshake (/var/web/zhazham/node_modules/mysql/lib/protocol/Protocol.js:42:41)
    at Connection.connect (/var/web/zhazham/node_modules/mysql/lib/Connection.js:98:18)
    at /var/web/zhazham/node_modules/knex/lib/dialects/mysql/index.js:105:16
    at tryCatch2 (/var/web/zhazham/node_modules/bluebird/js/main/util.js:53:21)
    at Promise._resolveFromResolver (/var/web/zhazham/node_modules/bluebird/js/main/promise.js:544:13)
    at new Promise (/var/web/zhazham/node_modules/bluebird/js/main/promise.js:84:37)
    at Client_MySQL.acquireRawConnection (/var/web/zhazham/node_modules/knex/lib/dialects/mysql/index.js:104:10)
    at Object.create (/var/web/zhazham/node_modules/knex/lib/pool.js:33:19)
    at Object.Pool.createResource (/var/web/zhazham/node_modules/knex/node_modules/generic-pool-redux/pool.js:288:12)

但检查mysql的错误日志时，没发现任何错误，现在重启mysql和GHOST后一切正常。

请问有人遇到过或知道是什么原因吗？谢谢了！

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