上传超时，出现的非常频繁

版本：7.2.1

2019-06-21 11:31:49,098 ERROR 14137 nodejs.ResponseTimeoutError: Response timeout for 120000ms, POST http://upload-z2.qiniup.com/mkblk/3647951 -1 (connected: true, keepalive socket: false)
headers: {} (uncaughtException throw 1 times on pid:14137)
headers: {} (uncaughtException throw 1 times on pid:14137)
    at Timeout._onTimeout (/home/webroot/repos/www-rd/node_modules/qiniu/node_modules/urllib/lib/urllib.js:734:15)
    at ontimeout (timers.js:498:11)
    at tryOnTimeout (timers.js:323:5)
    at Timer.listOnTimeout (timers.js:290:5)
name: "ResponseTimeoutError"
requestId: 11
data: undefined
path: "/mkblk/3647951"
status: -1
headers: {}
res: {"status":-1,"statusCode":-1,"headers":{},"size":0,"aborted":false,"rt":120075,"keepAliveSocket":false,"requestUrls":["http://upload-z2.qiniup.com/mkblk/3647951"],"timing":null,"remoteAddress":"113.105.138.13","remotePort":80}
pid: 14137
hostname: al-bj-jrd-prod01

2019-06-21 11:31:49,235 ERROR 14131 nodejs.ResponseTimeoutError: Response timeout for 120000ms, POST http://upload-z2.qiniup.com/mkblk/3642044 -1 (connected: true, keepalive socket: false)
headers: {} (uncaughtException throw 2 times on pid:14131)
headers: {} (uncaughtException throw 2 times on pid:14131)
    at Timeout._onTimeout (/home/webroot/repos/www-rd/node_modules/qiniu/node_modules/urllib/lib/urllib.js:734:15)
    at ontimeout (timers.js:498:11)
    at tryOnTimeout (timers.js:323:5)
    at Timer.listOnTimeout (timers.js:290:5)
name: "ResponseTimeoutError"
requestId: 12
data: undefined
path: "/mkblk/3642044"
status: -1
headers: {}
res: {"status":-1,"statusCode":-1,"headers":{},"size":0,"aborted":false,"rt":120041,"keepAliveSocket":false,"requestUrls":["http://upload-z2.qiniup.com/mkblk/3642044"],"timing":null,"remoteAddress":"14.152.37.25","remotePort":80}
pid: 14131
hostname: al-bj-jrd-prod01

Start by reviewing the 7.2.1 upload path and the reported stack location in node_modules/qiniu/node_modules/urllib/lib/urllib.js, then try to reproduce the 120000ms timeout against the /mkblk endpoint. Compare both logged failures and determine the affected request or retry behavior. Done means the timeout cause and an appropriate, verified resolution are documented in a regression test or reproducible check.