FATAL log is marked as INFO on Google Cloud Kubernetes - kubernetes

Question

I have an app using Rails 2.5.1 which is deployed on Google Cloud Kubernetes but the logs are not working good.The FATAL errors are displayed as INFO logs instead of ERROR or CRITICAL.
Extra context:
Rails 5.2.1
This view is from Logs Viewer
I'm using RAILS_LOG_TO_STDOUT=true. If I remove this, logs are not displayed at all
Thanks.
[UPDATE]
I updated my cluster to use the newest Stackdriver API but it stills not working and Rails.logger.error is displayed as INFO.

Answer 1

I got this working changing the log format to use JSON.
config.log_formatter = proc do |severity, datetime, progname, msg|
message = msg
message << " from #{progname}" if progname.present?
content = JSON.dump(timestamp: datetime.to_s, severity: severity, message: message)
content << "\n"
content
end

Answer 2

Have a look at the documentation Cloud Logging for Legacy Logging and Monitoring section Best practices:
Severities: By default, logs written to the standard output are on the
INFO level and logs written to the standard error are on the ERROR
level. Structured logs can include a severity field, which defines the
log's severity.
and because you're using RAILS_LOG_TO_STDOUT=true log events generated by Ruby you can see with severity INFO.
Keep in mind that you should migrate to Kubernetes Engine Monitoring:
Warning: Legacy Logging and Monitoring support for Google Kubernetes
Engine is deprecated. If you are using Legacy Logging and Monitoring,
then you must migrate to Kubernetes Engine Monitoring before support
for Legacy Logging and Monitoring is removed.
it's better to return to this "issue" after migration.
EDIT Have a look at the documentation Writing Logs section Writing log entries where you can find an example for Ruby:
Here is some sample code to write a single log entry to mylog. The
service, region, labels, and other content will change depending on
the entry and the application doing the writing.
require "google/cloud/logging"
logging = Google::Cloud::Logging.new project: "my-gcp-project-id"
entry = logging.entry entry.log_name = "my_application_log"
entry.payload = "Log message"
entry.severity = :NOTICE
entry.resource.type = "gae_app"
entry.resource.labels[:module_id] = "default"
entry.resource.labels[:version_id] = "20160101t163030"
logging.write_entries entry