Display Formatting

Canary checker can format the results of checks using the display field. All expressions must return a string (or a Go struct with a .String() method)

Go Text Templates

In this example we get the current exchange rate:

display-with-gotemplate.yaml

apiVersion: canaries.flanksource.com/v1
kind: Canary
metadata:
  name: http-check
spec:
  http:
    - name: USD
      url: https://api.frankfurter.app/latest?from=USD&to=GBP,EUR,ILS,ZAR
      display:
        template: "$1 = €{{.json.rates.EUR}}, £{{.json.rates.GBP}}, ₪{{.json.rates.ILS}}"

Which would display:

$1 = €0.94913, £0.82394, ₪3.8455

See Go Template

CEL Expressions

The equivalent using CEL expressions would be:

display-with-cel.yaml

apiVersion: canaries.flanksource.com/v1
kind: Canary
metadata:
  name: http-check
spec:
  http:
    - name: USD
      url: https://api.frankfurter.app/latest?from=USD&to=GBP,EUR,ILS,ZAR
      display:
         expr: "'$1 = €' + string(json.rates.EUR) + ', £' + string(json.rates.GBP) + ', ₪' + string(json.rates.ILS)"

See CEL for a function reference

Javascript

display-with-javascript.yaml

apiVersion: canaries.flanksource.com/v1
kind: Canary
metadata:
  name: http-check
spec:
  http:
    - name: USD
      url: https://api.frankfurter.app/latest?from=USD&to=GBP,EUR,ILS
      display:
        javascript: |
          currencyCodes = { "EUR": "€", "GBP": "£", "ILS": "₪"}

          display = ""
          for (var currency in json.rates) {
            if (display != "") {
              display += ", "
            }
            display += currency + " = " + currencyCodes[currency] + json.rates[currency] + ", "
          }
          "$1 = " + display

info

Do not return anything from the function, e.g. instead of return "hello" + "world" use just "hello" + "world"

See Javascript for more details and a function reference.

Variables

Each check exposes different variables to use in the display expression, See the Result Variables section for each check.