Kapacitor alerts overview

Kapacitor makes it possible to handle alert messages in two different ways.

  • The messages can be pushed directly to an event handler exposed through the Alert node.
  • The messages can be published to a topic namespace to which one or more alert handlers can subscribe.

No matter which approach is used, the handlers need to be enabled and configured in the configuration file. If the handler requires sensitive information such as tokens and passwords, it can also be configured using the Kapacitor HTTP API.

Push to handler

Pushing messages to a handler is the basic approach presented in the Getting started with Kapacitor guide. This involves simply calling the relevant chaining method made available through the alert node. Messages can be pushed to log() files, the email() service, the httpOut() cache and many third party services.

Publish and subscribe

An alert topic is simply a namespace where alerts are grouped. When an alert event fires it can be published to a topic. Multiple handlers can subscribe (can be bound) to that topic and all handlers process each alert event for the topic. Handlers get bound to topics through the kapacitor command line client and handler binding files. Handler binding files can be written in yaml or json. They contain four key fields and one optional one.

  • topic: declares the topic to which the handler will subscribe.
  • id: declares the identity of the binding.
  • kind: declares the type of event handler to be used. Note that this needs to be enabled in the kapacitord configuration.
  • match: (optional) declares a match expression used to filter which alert events will be processed. See the Match Expressions section below.
  • options: options specific to the handler in question. These are listed below in the section List of handlers

Example 1: A handler binding file for the slack handler and cpu topic

topic: cpu
id: slack
kind: slack
  channel: '#kapacitor'

Example 1 could be saved into a file named slack_cpu_handler.yaml.

This can then be generated into a Kapacitor topic handler through the command line client.

$ kapacitor define-topic-handler slack_cpu_handler.yaml

Handler bindings can also be created over the HTTP API. See the Create a Handler section of the HTTP API document.

For a walk through on defining and using alert topics see the Using Alert Topics walk-through.


A handler takes action on incoming alert events for a specific topic. Each handler operates on exactly one topic.

List of handlers

The following is a list of available alert event handlers:

aggregateAggregate alert messages over a specified interval.
AlertaPost alert messages to Alerta.
BigPandaSend alert messages to BigPanda.
DiscordSend alert messages to Discord.
emailSend and email with alert data.
execExecute a command passing alert data over STDIN.
HipChatPost alert messages to HipChat room.
KafkaSend alerts to a Apache Kafka cluster.
logLog alert data to file.
Microsoft TeamsSend alert messages to a Microsoft Teams channel.
MQTTPost alert messages to MQTT.
OpsGenie v1Send alerts to OpsGenie using their v1 API. (Deprecated)
OpsGenie v2Send alerts to OpsGenie using their v2 API.
PagerDuty v1Send alerts to PagerDuty using their v1 API. (Deprecated)
PagerDuty v2Send alerts to PagerDuty using their v2 API.
postHTTP POST data to a specified URL.
publishPublish alerts to multiple Kapacitor topics.
PushoverSend alerts to Pushover.
SensuPost alert messages to Sensu client.
ServiceNowSend alerts to ServiceNow.
SlackPost alert messages to Slack channel.
SNMPTrapTrigger SNMP traps.
tcpSend data to a specified address via raw TCP.
TelegramPost alert messages to Telegram client.
VictorOpsSend alerts to VictorOps.
ZenossSend alerts to Zenoss.

Match expressions

Alert handlers support match expressions that filter which alert events the handler processes.

A match expression is a TICKscript lambda expression. The data that triggered the alert is available to the match expression, including all fields and tags.

In addition to the data that triggered the alert metadata about the alert is available. This alert metadata is available via various functions.

levelintThe alert level of the event, one of ‘0’, ‘1’, ‘2’, or ‘3’ corresponding to ‘OK’, ‘INFO’, ‘WARNING’, and ‘CRITICAL’.
changedboolIndicates whether the alert level changed with this event.
namestringReturns the measurement name of the triggering data.
taskNamestringReturns the task name that generated the alert event.
durationdurationReturns the duration of the event in a non OK state.

Additionally the vars OK, INFO, WARNING, and CRITICAL have been defined to correspond with the return value of the level function.

For example to send only critical alerts to a handler, use this match expression:

match: level() == CRITICAL


Send only changed events to the handler:

match: changed() == TRUE

Send only WARNING and CRITICAL events to the handler:

match: level() >= WARNING

Send events with the tag “host” equal to to the handler:

match: "\"host\" == ''"

Alert event data

Each alert event that gets sent to a handler contains the following alert data:

IDThe ID of the alert, user defined.
MessageThe alert message, user defined.
DetailsThe alert details, user defined HTML content.
TimeThe time the alert occurred.
DurationThe duration of the alert in nanoseconds.
Datainfluxql.Result containing the data that triggered the alert.
RecoverableIndicates whether the alert is auto-recoverable. Determined by the .noRecoveries() property.

This data is used by event handlers in their handling of alert events.

Alert messages use Golang Template and have access to the alert data.

  // ...
  .message('{{ .ID }} is {{ .Level }} value:{{ index .Fields "value" }}, {{ if not .Recoverable }}non-recoverable{{ end }}')

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