rds_exporter crashes when more than 100 AWS RDS instances added

PMM Server can support up to 100 AWS RDS instances. When enhanced monitoring is configured, rds_exporter will crash when attempting to add greater than 100 AWS RDS instances.

RDS exporter calls cloudwatch's method FilterLogEvents with a parameter LogStreamNames,
which cannot be longer than 100 elements:
https://docs.aws.amazon.com/AmazonCloudWatchLogs/latest/APIReference/API_FilterLogEvents.html

 

 

 

PR: https://github.com/percona/rds_exporter/pull/47

 

QA: no need to have extensive testing on 100+ RDS. Making sure we don't  have regression is good enough