Stateful Metrics

Metrics can be generated from time based data, e.g. logs per minute, logins per second by using the output of one check execution as the input to the next.

apiVersion: canaries.flanksource.com/v1
kind: Canary
metadata:
  name: 'container-log-counts'
  namespace: observability
  # The schedule can be as short or as long as you want, the query will always search for log
  # since the last query
  schedule: '@every 5m'
  http:
    - name: container_log_volume
      url: 'https://elasticsearch/logstash-*/_search'
      headers:
        - name: Content-Type
          value: application/json
      templateBody: true
      test:
        # if no logs are found, fail the health check
        expr: json.?aggregations.logs.doc_count.orValue(0) > 0
      # query for log counts by namespace, container and pod that have been created since the last check
      body: >-
        {
          "size": 0,
          "aggs": {
            "logs": {
              "filter": {
                "range": {
                  "@timestamp" : {
                    {{-  if last_result.results.max }}
                    "gte": "{{ last_result.results.max }}"
                    {{- else }}
                    "gte": "now-5m"
                    {{- end }}
                  }
                }
              },
              "aggs": {
                "age": {
                  "max": {
                    "field": "@timestamp"
                  }
                },
                "labels": {
                  "multi_terms": {
                    "terms": [
                      { "field": "kubernetes_namespace_name.keyword"},
                      { "field": "kubernetes_container_name.keyword"},
                      { "field": "kubernetes_pod_name.keyword"}
                    ],
                    "size": 1000
                  }
                }
              }
            }
          }
        }
      transform:
        # Save the maximum age for usage in subsequent queries and create a metric for each pair
        expr: |
          json.orValue(null) != null ?
          [{
            'detail': { 'max': string(json.?aggregations.logs.age.value_as_string.orValue(last_result().?results.max.orValue(time.Now()))) },
            'metrics': json.?aggregations.logs.labels.buckets.orValue([]).map(k,  {
              'name': "namespace_log_count",
              'type': "counter",
              'value': double(k.doc_count),
              'labels': {
                "namespace": k.key[0],
                "container": k.key[1],
                "pod": k.key[2]
              }
            })
          }].toJSON()
          : '{}'

This snippet retrieves the last_result.results.max value from the last execution ensuring data is not duplicated or missed

"@timestamp" : {
  {{-  if last_result.results.max }}
  "gte": "{{ last_result.results.max }}"
  {{- else }}
  "gte": "now-5m"
  {{- end }}
}

The max value is saved in the transform section using:

#...
'detail': { 'max': string(json.?aggregations.logs.age.value_as_string.orValue(last_result().?results.max.orValue(time.Now()))) },
#...