Slack event handler

Slack is a widely used “digital workspace” that facilitates communication among team members. Kapacitor can be configured to send alert messages to Slack.

Configuration

Configuration as well as default option values for the Slack event handler are set in your kapacitor.conf. Below is an example configuration:

[[slack]]
  enabled = true
  default = true
  workspace = "example.slack.com"
  url = "https://slack.com/api/chat.postMessage"
  token = "mY5uP3Rs3CrE7t0keN"
  channel = "#alerts"
  username = "kapacitor"
  global = false
  state-changes-only = false
  ssl-ca = "/path/to/ca.crt"
  ssl-cert = "/path/to/cert.crt"
  ssl-key = "/path/to/private-key.key"
  insecure-skip-verify = false

enabled

Set to true to enable the Slack event handler.

default

Identify one of the Slack configurations as the default if there are multiple Slack configurations.

workspace

Slack workspace ID. This can be any string that identifies this particular Slack configuration. A logical choice is the name of the Slack workspace, e.g. <workspace>.slack.com.

url

Slack webhook URL. For new Slack apps, use https://slack.com/api/chat.postMessage. For legacy Slack Incoming Webhooks, add a new webhook for Kapacitor and Slack will provide the webhook URL.

token

Slack OAuth token used with new Slack apps. For legacy Incoming Webhooks, leave token as an empty string ("").

channel

Default channel for messages.

username

Slack bot username.

global

If true all the alerts will be sent to Slack without explicitly specifying Slack in the TICKscript.

state-changes-only

Sets all alerts in state-changes-only mode, meaning alerts will only be sent if the alert state changes. Only applies if global is true.

ssl-ca

Path to certificate authority file.

ssl-cert

Path to host certificate file.

ssl-key

Path to certificate private key file.

insecure-skip-verify

Use SSL but skip chain and host verification. This is necessary if using a self-signed certificate.

Options

The following Slack event handler options can be set in a handler file or when using .slack() in a TICKscript.

Example: handler file

id: handler-id
topic: topic-name
kind: slack
options:
  workspace: 'workspace.slack.com'
  channel: '#alerts'
  username: 'kapacitor'
  icon-emoji: ':smile:'

Example: TICKscript

|alert()
  // ...
  .slack()
    .workspace('workspace.slack.com')
    .channel('#alerts')
    .username('kapacitor')
    .iconEmoji(':smile:')

Slack Setup

Legacy Slack apps

To send alerts from Kapacitor to Slack using Slack’s legacy incoming webhooks:

1. Log into to your Slack workspace
2. Create a new incoming webhook for Kapacitor.
3. Add the generated webhook URL as the url in the [[slack]] configuration section of your kapacitor.conf.

New Slack apps

To send alerts from Kapacitor to Slack using a new Slack app:

1. Visit https://api.slack.com/apps.
2. Create a new app or click on an existing app.
3. Click OAuth & Permissions to find the token.

Using the Slack event handler

With one or more Slack event handlers enabled and configured in your kapacitor.conf, use the .slack() attribute in your TICKscripts to send alerts to Slack or define a Slack handler that subscribes to a topic and sends published alerts to Slack.

The examples below use the following Slack configurations defined in the kapacitor.conf:

Slack settings in kapacitor.conf

[[slack]]
  enabled = true
  default = true
  workspace = "alerts"
  url = "https://slack.com/api/chat.postMessage"
  token = "mY5uP3Rs3CrE7t0keN1"
  channel = "#alerts"
  username = "AlertBot"
  global = false
  state-changes-only = false

[[slack]]
  enabled = true
  default = false
  workspace = "error-reports"
  url = "https://slack.com/api/chat.postMessage"
  token = "mY5uP3Rs3CrE7t0keN2"
  channel = "#error-reports"
  username = "StatsBot"
  global = false
  state-changes-only = false

Send alerts to Slack from a TICKscript

The following TICKscript uses the .slack() event handler to send the message, “Hey, check your CPU”, to the #alerts Slack channel whenever idle CPU usage drops below 20%.

slack-cpu-alert.tick

stream
  |from()
    .measurement('cpu')
  |alert()
    .warn(lambda: "usage_idle" < 20)
    .stateChangesOnly()
    .message('Hey, check your CPU')
    .slack()   
      .iconEmoji(':exclamation:')  

Send alerts to Slack from a defined handler

The following setup sends an alert to the cpu topic with the message, “Hey, check your CPU”. A Slack handler is added that subscribes to the cpu topic and publishes all alert messages to Slack.

Create a TICKscript that publishes alert messages to a topic. The TICKscript below sends an critical alert message to the cpu topic any time idle CPU usage drops below 5%.

cpu_alert.tick

stream
  |from()
    .measurement('cpu')
  |alert()
    .crit(lambda: "usage_idle" < 5)
    .stateChangesOnly()
    .message('Hey, check your CPU')
    .topic('cpu')

Add and enable the TICKscript:

kapacitor define cpu_alert -tick cpu_alert.tick
kapacitor enable cpu_alert

Create a handler file that subscribes to the cpu topic and uses the Slack event handler to send alerts to Slack. This handler using the non-default Slack handler, “critical-alerts”, which sends messages to the #critical-alerts channel in Slack.

slack_cpu_handler.yaml

id: slack-cpu-alert
topic: cpu
kind: slack
options:
  workspace: 'alerts'
  icon-emoji: ':fire:'

Add the handler:

kapacitor define-topic-handler slack_cpu_handler.yaml

Using multiple Slack configurations

Kapacitor can use multiple Slack integrations, each identified by the value of the workspace config. The TICKscript below illustrates how multiple Slack integrations can be used.

In the kapacitor.conf above, there are two Slack configurations; one for alerts and the other for daily stats. The workspace configuration for each Slack configuration act as a unique identifiers.

The following TICKscript sends alerts to the alerts Slack workspace.

slack-cpu-alert.tick

stream
  |from()
    .measurement('cpu')
  |alert()
    .crit(lambda: "usage_idle" < 5)
    .stateChangesOnly()
    .message('Hey, I think the machine is on fire.')
    .slack()
      .workspace('alerts')
      .iconEmoji(':fire:')

Error rates are also being stored in the same InfluxDB instance and we want to send daily reports of 500 errors to the error-reports Slack workspace. The following TICKscript collects 500 error occurrences and publishes them to the 500-errors topic.

500_errors.tick

stream
  |from()
    .measurement('errors')
    .groupBy('500')
  |alert()
    .info(lambda: 'count' > 0)
    .noRecoveries()
    .topic('500-errors')  

Below is an aggregate handler that subscribes to the 500-errors topic, aggregates the number of 500 errors over a 24 hour period, then publishes an aggregate message to the 500-errors-24h topic.

500_errors_24h.yaml

id: 500-errors-24h
topic: 500-errors
kind: aggregate
options:
  interval: 24h
  topic: 500-errors-24h
  message: '{{ .Count }} 500 errors last 24 hours.'

Last, but not least, a Slack handler that subscribes to the 500-errors-24h topic and publishes aggregated count messages to the error-reports Slack workspace:

slack_500_errors_daily.yaml

id: slack-500-errors-daily
topic: 500-errors-24h
kind: slack
options:
  workspace: error-reports