Alertmanager: Slack Notification - x509: certificate signed by unknown authority

Question

I am trying to configure the Prometheus alert-manager with slack for the notification. But it fails with below error.

alertmanager    | level=warn ts=2021-01-11T05:53:56.925Z caller=notify.go:674 component=dispatcher receiver=slack integration=slack[0] msg="Notify attempt failed, will retry later" attempts=1 err="Post \"<redacted>\": x509: certificate signed by unknown authority"
alertmanager    | level=error ts=2021-01-11T05:54:06.019Z caller=dispatch.go:309 component=dispatcher msg="Notify for alerts failed" num_alerts=1 err="slack/slack[0]: notify retry canceled after 7 attempts: Post \"<redacted>\": x509: certificate signed by unknown authority"

my alertmanager.yml config file as follows.

global:
  resolve_timeout: 5m

route:
  group_by: ['alertname']
  group_wait: 10s
  group_interval: 10s
  repeat_interval: 1h
  receiver: 'slack'
receivers:
- name: 'slack'
  slack_configs:
  - api_url: "Slack webhook api"
    channel: '#slack channel'
    send_resolved: true

What is the way to resolve this in alertmanager?

Answer 1

The below additional entries to skip the certificate helped to get the notification in slack.

  http_config:
    tls_config:
      insecure_skip_verify: true