110 lines
2.7 KiB
Markdown
110 lines
2.7 KiB
Markdown
---
|
|
title: Log event handler
|
|
list_title: Log
|
|
description: >
|
|
The "log" event handler allows you to send Kapacitor alert messages to a log file. This page includes options and usage examples.
|
|
menu:
|
|
kapacitor_1_6_ref:
|
|
name: Log
|
|
weight: 700
|
|
parent: Event handlers
|
|
---
|
|
|
|
The log event handler writes to a specified log file with one alert event per line.
|
|
If the specified log file does not exist, it will be created.
|
|
|
|
## Options
|
|
The following log event handler options can be set in a
|
|
[handler file](/kapacitor/v1.6/event_handlers/#create-a-topic-handler-with-a-handler-file) or when using
|
|
`.log()` in a TICKscript.
|
|
|
|
| Name | Type | Description |
|
|
| ---- | ---- | ----------- |
|
|
| path | string | Absolute path to the log file. |
|
|
| mode | int | File mode and permissions to use when creating the file. Default is `0600`. _**The leading 0 is required to interpret the value as an octal integer.**_ |
|
|
|
|
### Example: handler file
|
|
```yaml
|
|
id: handler-id
|
|
topic: topic-name
|
|
kind: log
|
|
options:
|
|
path: '/tmp/alerts.log'
|
|
mode: 0644
|
|
```
|
|
|
|
### Example: TICKscript
|
|
```js
|
|
|alert()
|
|
// ...
|
|
.log('/tmp/alerts.log')
|
|
.mode(0644)
|
|
```
|
|
|
|
## Using the log event handler
|
|
The log event handler can be used in both TICKscripts and handler files to log
|
|
messages to a log file.
|
|
|
|
### Log messages from a TICKscript
|
|
|
|
The following TICKscript uses the `.log()` event handler to log a message to the
|
|
`/tmp/alerts.log` log file whenever idle CPU usage drops below 10%.
|
|
|
|
_**log-cpu-alert.tick**_
|
|
```js
|
|
stream
|
|
|from()
|
|
.measurement('cpu')
|
|
|alert()
|
|
.crit(lambda: "usage_idle" < 10)
|
|
.message('{{ .Time }}: CPU usage over 90%')
|
|
.log('/tmp/alerts.log')
|
|
```
|
|
|
|
### Log messages from a defined handler
|
|
|
|
The following setup sends an alert to the `cpu` topic with the message,
|
|
"'{{ .Time }}: CPU usage over 90%'".
|
|
A log handler is added that subscribes to the `cpu` topic and logs messages to
|
|
`/tmp/alerts.log` whenever a new message is published.
|
|
|
|
Create a TICKscript that publishes alert messages to a topic.
|
|
The TICKscript below sends an alert message to the `cpu` topic any time idle CPU
|
|
usage drops below 10%.
|
|
|
|
_**cpu\_alert.tick**_
|
|
```js
|
|
stream
|
|
|from()
|
|
.measurement('cpu')
|
|
|alert()
|
|
.crit(lambda: "usage_idle" < 10)
|
|
.message('{{ .Time }}: CPU usage over 90%')
|
|
.topic('cpu')
|
|
```
|
|
|
|
Add and enable the TICKscript:
|
|
|
|
```bash
|
|
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 log event
|
|
handler to log messages to the `/tmp/alerts.log` log file.
|
|
|
|
_**log\_cpu\_handler.yaml**_
|
|
```yaml
|
|
id: log-cpu-alert
|
|
topic: cpu
|
|
kind: log
|
|
options:
|
|
path: '/tmp/alerts.log'
|
|
```
|
|
|
|
Add the handler:
|
|
|
|
```bash
|
|
kapacitor define-topic-handler log_cpu_handler.yaml
|
|
```
|