Travamento incomum do servidor no EC2, syslog tem linha de ^ @ ^ @ ^ @ ^ @ ^ @

Question

Tentando entender por que um servidor ficou inativo por 20 minutos, examinei o syslog daquele período e vi o seguinte:

Jan  3 07:50:01 tools CRON[17085]: (munin) CMD (if [ -x /usr/bin/munin-cron ]; then /usr/bin/munin-cron; fi)
Jan  3 07:55:01 tools CRON[17773]: (munin) CMD (if [ -x /usr/bin/munin-cron ]; then /usr/bin/munin-cron; fi)
Jan  3 07:55:01 tools CRON[17774]: (root) CMD (if [ -x /etc/munin/plugins/apt_all ]; then /etc/munin/plugins/apt_all update 7200 12 >/dev/null; elif [ -x /etc/munin/plugins/apt ]; then /etc/munin/plugins/apt update 7200 12 >/dev/null; fi)
^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@Jan  3 08:19:44 tools kernel: imklog 4.2.0, log source = /proc/kmsg started.
Jan  3 08:19:44 tools rsyslogd: [origin software="rsyslogd" swVersion="4.2.0" x-pid="470" x-info="http://www.rsyslog.com"] (re)start

O EC2 mostra essa utilização da CPU durante o tempo da falha (no meio, antes das 13:00 UTC).

Portanto, não há nada visível durante esse período de tempo. Nenhuma de nossas outras instâncias do EC2 falhou e não consigo encontrar nenhuma evidência de que foi um erro de aplicativo. De fato, isso aconteceu no nosso servidor de ferramentas (apache, mongodb e redis). O Monit também estava em execução, mas não há registros suspeitos no momento do acidente.

O que poderia ter causado essa falha e o que significam os ^@ no syslog?

    

Answer 1

A resposta veio no fórum da AWS: link

Reed,

There was a problem with the underlying hardware that caused the underlying system to crash. The artifact of the syslog lines, could be just a representation that the system was in mid write when it crashed, or the lines could have come from the the cron process that was running on the previous line.

Nathan