[AWS] Check error log when RDS was crashed

Problem

I found a event “DB instance shutdown” in RDS Management Console and why happened?

Solution

I check a log error/mysql-error-running.log, this is seen in below(you should change id as your cluster name of rds): https://ap-northeast-1.console.aws.amazon.com/rds/home?region=ap-northeast-1#database:id=staging-hoge-db-02-01;is-cluster=false;tab=logs-and-events

In my case RDS’s log said as below:

Available memory is low. Trying to avoid OOM crash: system KB: 2014212 available KB: 0 low-threshold KB: 100710 print victim: yes decline query: no tune caches: yes kill query: no kill connection: no
OOM crash avoidance: kill option to avoid low memory: MySQL thread id 416, OS thread handle 47468632368896, query id 1820326 255.255.255.255 hoge_database FULLTEXT initialization
SELECT ...
OOM crash avoidance: kill option to avoid low memory: MySQL thread id 417, OS thread handle 47468645209856, query id 1820492 255.255.255.255 hoge_database Sending data

I suppose what some query caused OOM is the reason.