Is attaching to S3 container mandatory for Slack notification?

I setup Slack notification channel and unchecked ‘Include image’ option, but when sending alert I got below error, and Slack received nothing:

INFO[10-18|13:14:01] New state change logger=alerting.resultHandler alertId=1 newState=no_data prev state=alerting
INFO[10-18|13:14:01] Sending notifications for logger=alerting.notifier ruleId=1 sent count=2
INFO[10-18|13:14:01] Rendering logger=png-renderer path="dashboard-solo/db/druid1?&panelId=1"
Loading a web page: http://localhost:3000/dashboard-solo/db/druid1?&panelId=1 status: success 30000
EROR[10-18|13:14:31] Failed to upload alert panel image. logger=alerting.notifier error=“Timeout error. You can set timeout in seconds with &timeout url parameter”

This behavior apparently changed since 4.6.0-pre1, before that, even when I selected ‘upload image’ option, the message just took time to be sent(usually ~30 seconds), if the option was de-selected, messages were sent immediately.

My question:

  • Is S3 container mandatory now for Slack? if it’s not attached, notification to Slack would fail?
  • Slack test messages can be sent just fine, so it may not be a network issue

No that should not be mandatory.

Looking at your logs it seems like you have 2 notifiers configured for this alert. Is the second one using images? Then we would upload first and then send notifications to external services.

Created an github issue for this. Please move the conversation there. https://github.com/grafana/grafana/issues/9592