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Alertmanager Module

This is a terraform module used to install the alertmanager application into Cloud Foundry, and setting some of the configuration.

It is deployed using the official docker image.

Inputs

  monitoring_space_id         MANDATORY
  monitoring_instance_name    MANDATORY
  config                      OPTIONAL
  slack_url                   OPTIONAL
  slack_receivers             OPTIONAL
  • monitoring_instance_name: A unique name given to the application
  • monitoring_space_id: The Cloud Foundry space you wish to deploy the application to
  • config: The contents of an alertmanager.yml file, as specified in the documentation. If not specified, a dummy configuration is deployed.
  • slack_url An incoming webhook created at https://api.slack.com/apps/appid/incoming-webhooks? (replace appid with AppId value). Incoming webhooks are assigned to a single channel so the channel does not need to be specified. The default destination for all alerts that do not satisfy the matches defined in other routes.
  • slack_receivers A map of route\receiver names and webhook URLs. These can be used to route alerts to different channels based on alert labels. Alerts should include a label called receiver whose value is the same as the name of the receiver defined in this config property.

Example

module alertmanager {
  source                   = "git::https://github.com/DFE-Digital/bat-platform-building-blocks.git//terraform/modules/alertmanager"
  monitoring_space_id      = data.cloudfoundry_space.space.id
  monitoring_instance_name = "test-alertmanager"
  config                   = file("${path.module}/files/alertmanager.yml")
  slack_url                = https://hooks.slack.com/services/XXXXXXXXX/YYYYYYYYYYY/xxxxxxxxxxxxxxxxxxxxxxxx
  slack_receivers          = {
    "service_one_tech": "https://hooks.slack.com/services/XXXXXXXXX/YYYYYYYYYYY/xxxxxxxxxxxxxxxxxxxxxxxx",
    "service_two_tech": "https://hooks.slack.com/services/XXXXXXXXX/YYYYYYYYYYY/xxxxxxxxxxxxxxxxxxxxxxxx"
  }
}

Prometheus alerts

- alert: TooManyRequests
  expr: 'sum(increase(tta_requests_total{path!~"csp_reports",status=~"429"}[1m])) > 0'
  labels:
    severity: high
  annotations:
    summary: Alert when any user hits a rate limit (excluding the /csp_reports endpoint).
    runbook: https://dfedigital.atlassian.net/wiki/spaces/GGIT/pages/2152497153/Rate+Limit

Alert Routes

A route has been added which will ensure alerts are only sent to slack once every 24 hours. To implement this route you need to add the label period: daily

- alert: TooManyRequests
  expr: 'sum(increase(tta_requests_total{path!~"csp_reports",status=~"429"}[1m])) > 0'
  labels:
    severity: high
    period: daily
  annotations:
    summary: Alert when any user hits a rate limit (excluding the /csp_reports endpoint).
    runbook: https://dfedigital.atlassian.net/wiki/spaces/GGIT/pages/2152497153/Rate+Limit

Testing Alertmanager

Install amtool with go get github.com/prometheus/alertmanager/cmd/amtool if testing locally. amtool is already installed in alertmanager paas instance.

  1. Check if alertmanager is accessible

amtool --alertmanager.url=https://alertmanager-tra-monitoring-dev.london.cloudapps.digital config show Above command displays alertmanager.yaml config.

  1. Checking where alerts go

amtool --alertmanager.url=https://alertmanager-tra-monitoring-dev.london.cloudapps.digital config routes show

Routing tree:
└──	default-route  receiver: slack-notifications
		├── {period="daily"}  receiver: slack-notifications
		└── {period="'out-of-hours'"}  receiver: slack-notifications
  1. amtool --alertmanager.url=https://alertmanager-tra-monitoring-dev.london.cloudapps.digital config routes test period=daily prints slack-notifications

Simulating an alert

Either ssh into alertmanager instance or run below command locally.

amtool --alertmanager.url=https://alertmanager-tra-monitoring-dev.london.cloudapps.digital alert add this-is-a-test-alert period=hourly

Above command will send a test alert to the SLACK_WEBHOOK.

Templates

A default set of slack templates have been provided

Acknowledgements to

https://gist.github.com/milesbxf/e2744fc90e9c41b47aa47925f8ff6512