We are running Zimbra 8.8.5_GA_1894.RHEL7_64_20171026035615 RHEL7_64 for some weeks and have using about 100-120 users Zimbra Webapp. once/twice a week, the server is getting very slow and finally shows Error 502 Bad Gateway.
The log /opt/zimbra/log/nginx.log shows the following:
[warn] 7378#0: *423124 zmauth: an error occurs during zm lookup: timeout occurs when reading lookup response from handler, fall back to IPHASH to get the upstream route while SSL handshaking to lookup handler, client: xxx.xxx.xxx.xxx, server: XXXXXXXXX.com, request: "POST /service/soap/NoOpRequest HTTP/1.1", host: "XXXXXXXXX.com", referrer: "https://XXXXXXXXX.com/"
After I restart Zimbra, all is back to normal for the next 2-3 days.