Debugging discourse downtime

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3

Did the server reboot? (check uptime)

Did any messages get posted in the kernel logs? (check dmesg)

Any relevant entries in syslog? (less /var/log/syslog)

The stack traces seem to be a symptom of your downtime, I suspect you lost your networking for the duration of the outage:

/usr/local/lib/ruby/2.3.0/net/smtp.rb:542:in `initialize'
/usr/local/lib/ruby/2.3.0/net/smtp.rb:542:in `open'
/usr/local/lib/ruby/2.3.0/net/smtp.rb:542:in `tcp_socket'
...