Event structure.

Honeycomb events bind a timestamp to data as described in t/0 below. The data corresponds to Opencensus span attributes, with limitations dictated by the intersection of OpenCensus' and Honeycomb's data models.

Supported Value Types

Honeycomb

Honeycomb supports events (spans, when strung together in a trace) with dozens or hundreds of attributes. Keys MUST be strings, like in OpenCensus. Values MUST be JSON encodable, but MAY include objects (Elixir maps) and arrays -- neither of which are supported by OpenCensus.

Honeycomb makes no distinction between measurements and metadata, unlike :telemetry.

Honeycomb's keys for trace handling can be configured on a per-dataset basis, but default to:

• duration_ms
• name
• service_name
• trace.parent_id
• trace.span_id
• trace.trace_id

OpenCensus

To be compatible with the OpenCensus protobuf protocol, attribute values MUST be one of:

• TruncatableString
• int64
• bool_value
• double_value

Opencensus.Honeycomb

The data models being quite similar, the Jason.Encoder implementation for Opencensus.Honeycomb.Event.t/0:

• Flattens map values as described below
• Converts atom keys and values to strings
• Drops any other values not compatible with the OpenCensus protobuf definition
• Over-writes any keys that clash with the default trace handling keys

Flattening

Map flattening uses periods (.) to delimit keys from nested maps, much like can be configured on a dataset basis at the Honeycomb end. These span attributes before flattening:

%{
  http: %{
    host:  "localhost",
    method: "POST",
    path: "/api"
  }
}

... becomes this event after flattening:

%{
  "http.host" => "localhost",
  "http.method" => "POST",
  "http.path" => "/api",
}