Query/Response Events

Metrics or "Stats"

Participating nodes in a Query/Response topology will broadcast events of structured statistics for the UI and monitoring applications to consume. The common data-shape encapsulates a way to communicate measurements, events, and node-identifying and describing meta-data.

The entry structure and format is encoded as a JSON UTF-8 encoded string.

{
  "elements": [
    {
      "key": "<string>",
      "value": "<string|number|boolean>",
      "timestamp": "<OPTIONAL:number>",
      "uuid": "<OPTIONAL:string>"
    }
    // ...
  ]
}

The key and value property pairs are used to encode any measurement. The timestamp is an optional property, that can be used to associate a measurement with a point in time since the EPOCH, in milliseconds.

The uuid property is used to identify the publishing node during its lifetime—effectively creating an aggregate for statistics to present. This means that in practice there are operational metrics which may come and go as well as logical statistics which may pertain to the topology or cluster of nodes.

Table of published statistics

Key	Value	Timestamp	UUID	Description
name	string	-	✓	Name or identity of the node, or application
pid	string	-	✓	Node process id, or -
host	string	-	✓	Node hostname, or unknown
uptime	string	-	✓	Node uptime, or -
only_responses	boolean	-	✓	Whether node has only responded true, or published queries false
count_queries	number	-	✓	Number of published queries
count_consumed_responses	number	-	✓	Number of consumed responses
count_published_responses	number	-	✓	Number of published responses
count_fallbacks	number	-	✓	Number of fallbacks (no responses)
max_latency	number	-	✓	Largest recorded time between query and response, in milliseconds
min_latency	number	-	✓	Smallest recorded time between query and response, in milliseconds
avg_latency	number	-	✓	Average time between query and response, in milliseconds
throughput_queries	number	✓	✓	Number of queries published, since last notification
throughput_responses	number	✓	✓	Number of responses consumed, since last notification