Add distro README

README.md

@@ -33,7 +33,7 @@ Table of Contents:
 
 This Splunk distribution comes with the following defaults:
 
-- [B3 context propagation](https://github.com/openzipkin/b3-propagation).
+- [W3C tracecontext propagation](https://www.w3.org/TR/trace-context/).
 - [Jaeger Thrift over HTTP
   exporter](https://pkg.go.dev/go.opentelemetry.io/otel/exporters/jaeger)
   configured to send spans to a locally running [Splunk OpenTelemetry Connector](https://github.com/signalfx/splunk-otel-collector)
@@ -93,6 +93,8 @@ As well as in Go code before executing `distro.Run()`:
 os.Setenv("OTEL_RESOURCE_ATTRIBUTES", "service.name=my-app,service.version=1.2.3,deployment.environment=development")
 ```
 
+For advanced configuration options, refer to the [`distro` package documentation](./distro/README.md#Configuration).
+
 ## Library Instrumentation
 
 Supported libraries are listed

distro/README.md

@@ -0,0 +1,73 @@
+# Package `github.com/signalfx/splunk-otel-go/distro`
+
+This package provides a Splunk distributed of the OpenTelemetry Go SDK. It is
+designed to provide an SDK properly configured to be used with the Splunk
+platform out-of-the-box.
+
+## Getting Started
+
+The main entry point for the package is the [`Run`][] function. Use this
+function to create an SDK that is ready to be used with OpenTelemetry and
+forward all telemetry to Splunk. See [`example_test.go`](./example_test.go) for
+a complete example.
+
+## Configuration
+
+The [`SDK`][] is configured with the following options.
+
+| Option Name | Default Value | Environment Variable |
+| ---| --- | --- |
+| `WithAccessToken` | `""` | `SPLUNK_ACCESS_TOKEN` |
+| `WithEndpoint` | `"localhost:4317"` or `"http://127.0.0.1:9080/v1/trace"`(1) | none |
+| `WithPropagator` | `tracecontext,baggage` | `OTEL_PROPAGATORS` |
+
+(1): The default value depends on the exporter used. See the
+[`WithEndpoint`](#withendpoint) section for more details.
+
+Environment variable can be used to set related option values, but the value
+set in code will take precedence. This is the same behavior the default
+OpenTelemetry SDK has.
+
+The following sections contain specific information for each option.
+
+### `WithAccessToken`
+
+`WithAccessToken` configures the authentication token used to authenticate
+telemetry delivery requests to a Splunk back-end.
+
+- Default value: empty (i.e. `""`)
+- Environment variable: `SPLUNK_ACCESS_TOKEN`
+
+### `WithEndpoint`
+
+`WithEndpoint` configures the Splunk endpoint that telemetry is sent to.
+
+- Default value: depends on the exporter used.
+  - For the `otlp` over gRPC exporter: `"localhost:4317"`
+  - For the `jaeger-thrift-splunk` exporter: `"http://127.0.0.1:9080/v1/trace"`
+
+### `WithPropagator`
+
+`WithPropagator` configures the OpenTelemetry `TextMapPropagator` set as the
+global `TextMapPropagator`. Setting to `nil` will prevent any global
+`TextMapPropagator` from being set.
+
+- Default value: A W3C tracecontext and baggage `TextMapPropagator`
+- Environment variable: `OTEL_PROPAGATORS`
+
+  The environment variable values are restricted to the following.
+
+  - `"tracecontext"`: W3C tracecontext
+  - `"baggage"`: W3C baggage
+  - `"b3"`: B3 single-header format
+  - `"b3multi"`: B3 multi-header format
+  - `"jaeger"`: Jaeger
+  - `"xray"`: AWS X-Ray
+  - `"ottrace"`: OpenTracing
+  - `"none"`: None, explicitly do not set a global propagator
+
+  Values can be joined with a comma (`","`) to produce a composite
+  `TextMapPropagator`.
+
+[`Run`]: https://pkg.go.dev/github.com/signalfx/splunk-otel-go/distro#Run
+[`SDK`]: https://pkg.go.dev/github.com/signalfx/splunk-otel-go/distro#SDK

distro/config.go

@@ -94,7 +94,7 @@ var propagators = map[string]func() propagation.TextMapPropagator{
 	"b3": func() propagation.TextMapPropagator {
 		return b3.New(b3.WithInjectEncoding(b3.B3SingleHeader))
 	},
-	//  B3 Multi
+	// B3 Multi
 	"b3multi": func() propagation.TextMapPropagator {
 		return b3.New(b3.WithInjectEncoding(b3.B3MultipleHeader))
 	},
@@ -106,7 +106,7 @@ var propagators = map[string]func() propagation.TextMapPropagator{
 	"xray": func() propagation.TextMapPropagator {
 		return xray.Propagator{}
 	},
-	//  OpenTracing Trace
+	// OpenTracing Trace
 	"ottrace": func() propagation.TextMapPropagator {
 		return ot.OT{}
 	},