Template

Templates concept in Siren is used for abstraction. The usage is versatile enough to be used to abstract out rules and notification format. It utilises go-templates to provide data-driven templates for generating textual output. The template delimiter used is [[ and ]].

One can create templates using either HTTP APIs or CLI.

API interface

Template creation/update

Templates can be created using Siren APIs. The below snippet describes an example.

CLI

$ siren template upsert --file template.yaml

HTTP

$ curl --request PUT
  --url http://localhost:8080/v1beta1/templates
  --header 'content-type: application/json'
  --data-raw '{
    "name": "CPU",
    "body": "- alert: CPUHighWarning
  expr: avg by (host) (cpu_usage_user{cpu="cpu-total"}) > [[.warning]]
  for: '[[.for]]'
  labels:
    severity: WARNING
    team: '[[ .team ]]'
  annotations:
    dashboard: https://example.com
    description: CPU has been above [[.warning]] for last [[.for]] {{ $labels.host }}
- alert: CPUHighCritical
  expr: avg by (host) (cpu_usage_user{cpu="cpu-total"}) > [[.critical]]
  for: '[[.for]]'
  labels:
    severity: CRITICAL
    team: '[[ .team ]]'
  annotations:
    dashboard: example.com
    description: CPU has been above [[.critical]] for last [[.for]] {{ $labels.host }}
",
    "tags": [
        "firehose",
        "dagger"
    ],
    "variables": [
        {
            "name": "team",
            "type": "string",
            "default": "gotocompany",
            "description": "Name of the team that owns the deployment"
        },
        {
            "name": "for",
            "type": "string",
            "default": "10m",
            "description": "For eg 5m, 2h; Golang duration format"
        },
        {
            "name": "warning",
            "type": "int",
            "default": "85",
            "description": ""
        },
        {
            "name": "critical",
            "type": "int",
            "default": "95",
            "description": ""
        }
    ]
}'

Terminology of the request body

Term	Description	Example/Default
Name	Name of the template	CPUHigh
Body	Array of rule body. The body can be templatized in go template format.	See example above
Variables	Array of variables that were templatized in the body with their data type, default value and description.	See example above
Tags	Array of resources/applications that can utilize this template	VM

The response body will look like this:

{
  "id": 38,
  "CreatedAt": "2021-04-29T16:20:48.061862+05:30",
  "UpdatedAt": "2021-04-29T16:22:19.978837+05:30",
  "name": "CPU",
  "body": "- alert: CPUHighWarning\n  expr: avg by (host) (cpu_usage_user{cpu=\"cpu-total\"}) > [[.warning]]\n  for: '[[.for]]'\n  labels:\n    severity: WARNING\n    team: '[[ .team ]]'\n  annotations:\n    dashboard: https://example.com\n    description: CPU has been above [[.warning]] for last [[.for]] {{ $labels.host }}\n- alert: CPUHighCritical\n  expr: avg by (host) (cpu_usage_user{cpu=\"cpu-total\"}) > [[.critical]]\n  for: '[[.for]]'\n  labels:\n    severity: CRITICAL\n    team: '[[ .team ]]'\n  annotations:\n    dashboard: example.com\n    description: CPU has been above [[.critical]] for last [[.for]] {{ $labels.host }}\n",
  "tags": ["firehose", "dagger"],
  "variables": [
    {
      "name": "team",
      "type": "string",
      "default": "gotocompany",
      "description": "Name of the team that owns the deployment"
    },
    {
      "name": "for",
      "type": "string",
      "default": "10m",
      "description": "For eg 5m, 2h; Golang duration format"
    },
    {
      "name": "warning",
      "type": "int",
      "default": "85",
      "description": ""
    },
    {
      "name": "critical",
      "type": "int",
      "default": "95",
      "description": ""
    }
  ]
}

Fetching a template

Fetching by Name

Here is an example to fetch a template using name.

CLI

$ siren template view cpu

HTTP

$ curl --request GET
  --url http://localhost:8080/v1beta1/templates/cpu

Fetching by Tags

Here is an example to fetch a templates matching the tag.

CLI

$ siren template list --tag firehose

HTTP

$ curl --request GET
  --url http://localhost:8080/v1beta1/templates?tag=firehose

Deleting a template

DELETE /v1beta1/templates/cpu HTTP/1.1
Host: localhost:3000

CLI

$ siren template delete cpu

HTTP

$ curl --request DELETE
  --url http://localhost:8080/v1beta1/templates/cpu

Note:

1. Updating a template via API will not upload the associated rules.

CLI interface

With CLI, you will need a YAML file in the below specified format to create/update templates. The CLI calls Siren service templates APIs in turn.

Example template file

apiVersion: v2
type: template
name: CPU
body:
  - alert: CPUWarning
    expr: avg by (host) (cpu_usage_user{cpu="cpu-total"}) > [[.warning]]
    for: "[[.for]]"
    labels:
      severity: WARNING
    annotations:
      description: CPU has been above [[.warning]] for last [[.for]] {{ $labels.host }}
  - alert: CPUCritical
    expr: avg by (host) (cpu_usage_user{cpu="cpu-total"}) > [[.critical]]
    for: "[[.for]]"
    labels:
      severity: CRITICAL
    annotations:
      description: CPU has been above [[.critical]] for last [[.for]] {{ $labels.host }}
variables:
  - name: for
    type: string
    default: 10m
    description: For eg 5m, 2h; Golang duration format
  - name: warning
    type: int
    default: 80
  - name: critical
    type: int
    default: 90
tags:
  - systems

In the above example, we are using one template to define rules of two severity labels viz WARNING and CRITICAL. Here we have made 3 templates variables for, warning and critical which denote the appropriate alerting thresholds. They will be given a value while actual rule(alert) creating.

siren template upload cpu_template.yaml

Terminology

Term	Description	Example/Default
API Version	Which API to use to parse the YAML file	v2
Type	Describes the type of object represented by YAML file	template
Name	Name of the template	CPUHigh
Body	Array of rule body. The body can be templatized in go template format.	See example file
Variables	Array of variables that were templatized in the body with their data type, default value and description.	See example file
Tags	Array of resources/applications that can utilize this template	VM

Note:

1. It's suggested to always provide default value for the templated variables.
2. Updating a template used by rules via CLI will update all associated rules.