Populate metrics in InfluxDB with handlers
A Sensu event handler is an action the Sensu backend executes when a specific event occurs. In this guide, you’ll use a handler to populate the time-series database InfluxDB with Sensu observability event data.
Metrics can be collected from check output (in this guide, a check that generates Prometheus metrics) or the Sensu StatsD Server.
To follow this guide, you’ll need to install the Sensu backend, have at least one Sensu agent running, and install and configure sensuctl.
Configure a Sensu entity
Every Sensu agent has a defined set of subscriptions that determine which checks the agent will execute. For an agent to execute a specific check, you must specify the same subscription in the agent configuration and the check definition.
The example in this guide uses the prometheus_metrics
check from Collect Prometheus metrics with Sensu, which includes the subscription app_tier
.
Use sensuctl to add an app_tier
subscription to one of your entities.
Before you run the following code, replace <ENTITY_NAME>
with the name of the entity on your system.
NOTE: To find your entity name, run sensuctl entity list
.
The ID
is the name of your entity.
sensuctl entity update <ENTITY_NAME>
- For
Entity Class
, press enter. - For
Subscriptions
, typeapp_tier
and press enter.
Run this command to confirm both Sensu services are running:
systemctl status sensu-backend && systemctl status sensu-agent
The response should indicate active (running)
for both the Sensu backend and agent.
Register the dynamic runtime asset
Dynamic runtime assets are shareable, reusable packages that make it easier to deploy Sensu plugins. This example uses the sensu/sensu-influxdb-handler dynamic runtime asset to power an InfluxDB handler.
Use sensuctl asset add
to register the sensu/sensu-influxdb-handler dynamic runtime asset:
sensuctl asset add sensu/sensu-influxdb-handler:3.7.0 -r sensu-influxdb-handler
The response will confirm that the asset was added:
fetching bonsai asset: sensu/sensu-influxdb-handler:3.7.0 -r sensu-influxdb-handler
added asset: sensu/sensu-influxdb-handler:3.7.0
You have successfully added the Sensu asset resource, but the asset will not get downloaded until
it's invoked by another Sensu resource (ex. check). To add this runtime asset to the appropriate
resource, populate the "runtime_assets" field with ["sensu-influxdb-handler"].
This example uses the -r
(rename) flag to specify a shorter name for the dynamic runtime asset: sensu-influxdb-handler
.
You can also download the latest dynamic runtime asset definition for your platform from Bonsai and register the asset with sensuctl create --file filename.yml
or sensuctl create --file filename.json
.
Run sensuctl asset list
to confirm that the dynamic runtime asset is ready to use.
NOTE: Sensu does not download and install dynamic runtime asset builds onto the system until they are needed for command execution. Read the asset reference for more information about dynamic runtime asset builds.
Create the handler
Now that you have registered the dynamic runtime asset, use sensuctl to create a handler called influxdb-handler
that pipes observation data (events) to InfluxDB with the sensu/sensu-influxdb-handler dynamic runtime asset.
Edit the command below to replace the placeholders for database name, address, username, and password with the information for your own InfluxDB database.
For more information about the Sensu InfluxDB handler, read the asset page in Bonsai.
sensuctl handler create influxdb-handler \
--type pipe \
--command "sensu-influxdb-handler -d sensu" \
--env-vars "INFLUXDB_ADDR=http://influxdb.default.svc.cluster.local:8086, INFLUXDB_USER=sensu, INFLUXDB_PASS=password" \
--filters not_silenced \
--runtime-assets sensu-influxdb-handler
You should receive a confirmation message:
Created
To review the complete resource definition for the handler resource you just created with sensuctl, run:
sensuctl handler info influxdb-handler --format yaml
sensuctl handler info influxdb-handler --format wrapped-json
The influxdb-handler
resource definition will be similar to this example:
---
type: Handler
api_version: core/v2
metadata:
name: influxdb-handler
spec:
command: sensu-influxdb-handler -d sensu
env_vars:
- INFLUXDB_ADDR=http://influxdb.default.svc.cluster.local:8086
- INFLUXDB_USER=sensu
- INFLUXDB_PASS=password
filters:
- not_silenced
handlers: null
runtime_assets:
- sensu-influxdb-handler
secrets: null
timeout: 0
type: pipe
{
"type": "Handler",
"api_version": "core/v2",
"metadata": {
"name": "influxdb-handler"
},
"spec": {
"command": "sensu-influxdb-handler -d sensu",
"env_vars": [
"INFLUXDB_ADDR=http://influxdb.default.svc.cluster.local:8086",
"INFLUXDB_USER=sensu",
"INFLUXDB_PASS=password"
],
"filters": [
"not_silenced"
],
"handlers": null,
"runtime_assets": [
"sensu-influxdb-handler"
],
"secrets": null,
"timeout": 0,
"type": "pipe"
}
}
You can share, reuse, and maintain this handler just like you would code: save it to a file and start building a monitoring as code repository.
Assign the InfluxDB handler to a check
With the influxdb-handler
resource created, you can assign it to a check for check output metric extraction.
For example, if you followed Collect Prometheus metrics with Sensu, you created the prometheus_metrics
check.
The prometheus_metrics
check already uses the influxdb_line
output metric format, but you will need to update the output metric handlers to extract the metrics with the influxdb-handler
.
To update the output metric handlers, run:
sensuctl check set-output-metric-handlers prometheus_metrics influxdb-handler
You should receive a confirmation message:
Updated
To review the updated check resource definition, run:
sensuctl check info prometheus_metrics --format yaml
sensuctl check info prometheus_metrics --format wrapped-json
The updated prometheus_metrics
check definition will be similar to this example:
---
type: CheckConfig
api_version: core/v2
metadata:
name: prometheus_metrics
spec:
check_hooks: null
command: sensu-prometheus-collector -prom-url http://localhost:9090 -prom-query up
env_vars: null
handlers: []
high_flap_threshold: 0
interval: 10
low_flap_threshold: 0
output_metric_format: influxdb_line
output_metric_handlers:
- influxdb-handler
proxy_entity_name: ""
publish: true
round_robin: false
runtime_assets:
- sensu-prometheus-collector
secrets: null
stdin: false
subdue: null
subscriptions:
- app_tier
timeout: 0
ttl: 0
{
"type": "CheckConfig",
"api_version": "core/v2",
"metadata": {
"name": "prometheus_metrics"
},
"spec": {
"check_hooks": null,
"command": "sensu-prometheus-collector -prom-url http://localhost:9090 -prom-query up",
"env_vars": null,
"handlers": [],
"high_flap_threshold": 0,
"interval": 10,
"low_flap_threshold": 0,
"output_metric_format": "influxdb_line",
"output_metric_handlers": [
"influxdb-handler"
],
"proxy_entity_name": "",
"publish": true,
"round_robin": false,
"runtime_assets": [
"sensu-prometheus-collector"
],
"secrets": null,
"stdin": false,
"subdue": null,
"subscriptions": [
"app_tier"
],
"timeout": 0,
"ttl": 0
}
}
Assign the InfluxDB handler to the Sensu StatsD listener
To assign your influxdb-handler
resource to the Sensu StatsD listener at agent startup and pass all StatsD metrics into InfluxDB:
sensu-agent start --statsd-event-handlers influxdb-handler
Validate the InfluxDB handler
It might take a few moments after you assign the handler to the check or StatsD server for Sensu to receive the metrics, but after an event is handled, metrics should start populating InfluxDB.
You can verify proper handler behavior with sensu-backend
logs.
Read Troubleshoot Sensu for log locations by platform.
Whenever an event is being handled, a log entry is added with the message "handler":"influxdb-handler","level":"debug","msg":"sending event to handler"
, followed by a second log entry with the message "msg":"pipelined executed event pipe handler","output":"","status":0
.
Next steps
Now that you know how to apply an InfluxDB handler to metrics, read Aggregate metrics with the Sensu StatsD listener to learn more about using Sensu to implement StatsD and take action on observability events.