Logs

Before you dive in to the log concepts outlined below, review these concepts in the official OpenTelemetry documentation, found here.

The ExportLogServiceRequest

All OpenTelemetry collectors receive OTLP logs from applications in the form of an ExportLogServiceRequest. This is a well known message, and its structure can be found in the official opentelemetry-proto repository. The diagram below provides the general structure of this message (some properties omitted for brevity).

When the OpenTelemetry Collector exports logs to an endpoint, it typically batches those logs up and sends them by resource (eg. a microservice), hence the list of resources in an ExportLogServiceRequest. Each ScopeLogs will be associated with one resource, and the same goes for the Logs that are associated with an instrumentation scope.

For each Log, then, you know what instrumentation library was used to create the Log, and you also know which Resource produced the Log.

What Are Logs?

The OpenTelemetry LogRecord is a data structure that includes details of the log message, and also correlates the log message to a TraceId and SpanId if the log was emitted within the context of a span.

The available properties of a Logthat can be queried are listed below:

message Where {
  oneof value {
    PropertyFilter property = 1;
    OrFilter or = 2;
    odddotnet.proto.common.v1.InstrumentationScopeFilter instrumentation_scope = 3;
    odddotnet.proto.resource.v1.ResourceFilter resource = 4;
    odddotnet.proto.common.v1.StringProperty instrumentation_scope_schema_url = 5;
    odddotnet.proto.common.v1.StringProperty resource_schema_url = 6;
  }
}

message PropertyFilter {
  reserved 4;
  oneof value {
    odddotnet.proto.common.v1.UInt64Property time_unix_nano = 1;
    odddotnet.proto.common.v1.UInt64Property observed_time_unix_nano = 11;
    SeverityNumberProperty severity_number = 2;
    odddotnet.proto.common.v1.StringProperty severity_text = 3;
    odddotnet.proto.common.v1.AnyValueProperty body = 5;
    odddotnet.proto.common.v1.KeyValueListProperty attributes = 6;
    odddotnet.proto.common.v1.UInt32Property dropped_attributes_count = 7;
    odddotnet.proto.common.v1.UInt32Property flags = 8;
    odddotnet.proto.common.v1.ByteStringProperty trace_id = 9;
    odddotnet.proto.common.v1.ByteStringProperty span_id = 10;
  }
}

message SeverityNumberProperty {
  odddotnet.proto.common.v1.EnumCompareAsType compare_as = 1;
  opentelemetry.proto.logs.v1.SeverityNumber compare = 2;
}

The proto files for Logs can be found here.