allow setting attrs at the end of a backgrounded trace (#255)

otelcli/span_background_server.go

@@ -36,8 +36,9 @@ type BgSpanEvent struct {
 
 // BgEnd is an empty struct that can be sent to call End().
 type BgEnd struct {
-	StatusCode string `json:"status_code"`
-	StatusDesc string `json:"status_description"`
+	Attributes map[string]string `json:"span_attributes" env:"OTEL_CLI_ATTRIBUTES"`
+	StatusCode string            `json:"status_code"`
+	StatusDesc string            `json:"status_description"`
 }
 
 // AddEvent takes a BgSpanEvent from the client and attaches an event to the span.
@@ -70,9 +71,18 @@ func (bs BgSpan) Wait(in, reply *struct{}) error {
 // End takes a BgEnd (empty) struct, replies with the usual trace info, then
 // ends the span end exits the background process.
 func (bs BgSpan) End(in *BgEnd, reply *BgSpan) error {
+	// handle --attrs arg to span end by retrieving and merging with/overwriting existing attribtues
+	attrs := make(map[string]string)
+	for k, v := range otlpclient.SpanAttributesToStringMap(bs.span) {
+		attrs[k] = v
+	}
+	for key, value := range in.Attributes {
+		attrs[key] = value
+	}
 	// handle --status-code and --status-description args to span end
-	c := bs.config.WithStatusCode(in.StatusCode).WithStatusDescription(in.StatusDesc)
+	c := bs.config.WithStatusCode(in.StatusCode).WithStatusDescription(in.StatusDesc).WithAttributes(attrs)
 	otlpclient.SetSpanStatus(bs.span, c.StatusCode, c.StatusDescription)
+	bs.span.Attributes = otlpclient.StringMapAttrsToProtobuf(c.Attributes)
 
 	// running the shutdown as a goroutine prevents the client from getting an
 	// error here when the server gets closed. defer didn't do the trick.

otelcli/span_end.go

@@ -16,7 +16,8 @@ func spanEndCmd(config *Config) *cobra.Command {
 
 See: otel-cli span background
 
-	otel-cli span end --sockdir $sockdir
+	otel-cli span end --sockdir $sockdir \
+		--attrs "output.length=$(wc -l < output.txt | sed -e 's/^[[:space:]]*//')
 `,
 		Run: doSpanEnd,
 	}
@@ -32,6 +33,7 @@ See: otel-cli span background
 	cmd.Flags().StringVar(&config.SpanEndTime, "end", defaults.SpanEndTime, "an Unix epoch or RFC3339 timestamp for the end of the span")
 
 	addSpanStatusParams(&cmd, config)
+	addAttrParams(&cmd, config)
 
 	return &cmd
 }
@@ -41,6 +43,7 @@ func doSpanEnd(cmd *cobra.Command, args []string) {
 	client, shutdown := createBgClient(config)
 
 	rpcArgs := BgEnd{
+		Attributes: config.Attributes,
 		StatusCode: config.StatusCode,
 		StatusDesc: config.StatusDescription,
 	}

otlpclient/protobuf_span.go

@@ -186,7 +186,6 @@ func StringMapAttrsToProtobuf(attributes map[string]string) []*commonpb.KeyValue
 }
 
 // SpanAttributesToStringMap converts the span's attributes to a string map.
-// Only used by tests for now.
 func SpanAttributesToStringMap(span *tracepb.Span) map[string]string {
 	out := make(map[string]string)
 	for _, attr := range span.Attributes {