Version using events for call joins / leaves and matrix events

This is probably conceptually nicer although isn't quite as nice in
the jaeger / stalk UI.

Also this may no loger work with the posthog exporter (unsure what it
will do with events on spans).

src/otel/OTelGroupCallMembership.ts

@@ -14,7 +14,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import opentelemetry, { Context, Span } from "@opentelemetry/api";
+import opentelemetry, { Span, Attributes } from "@opentelemetry/api";
 import {
   GroupCall,
   MatrixClient,
@@ -26,20 +26,25 @@ import { VoipEvent } from "matrix-js-sdk/src/webrtc/call";
 import { tracer } from "./otel";
 
 /**
- * Recursively sets the contents of a todevice event object as attributes on a span
+ * Flattens out an object into a single layer with components
+ * of the key separated by dots
  */
-function setNestedAttributesFromEvent(span: Span, event: VoipEvent) {
-  setSpanEventAttributesRecursive(
-    span,
+function flattenVoipEvent(event: VoipEvent): Attributes {
+  const flatObject = {};
+
+  flattenVoipEventRecursive(
     event as unknown as Record<string, unknown>, // XXX Types
+    flatObject,
     "matrix.event.",
     0
   );
+
+  return flatObject;
 }
 
-function setSpanEventAttributesRecursive(
-  span: Span,
+function flattenVoipEventRecursive(
   obj: Record<string, unknown>,
+  flatObject: Record<string, unknown>,
   prefix: string,
   depth: number
 ) {
@@ -50,11 +55,11 @@ function setSpanEventAttributesRecursive(
 
   for (const [k, v] of Object.entries(obj)) {
     if (["string", "number"].includes(typeof v)) {
-      span.setAttribute(prefix + k, v as string | number);
+      flatObject[prefix + k] = v;
     } else if (typeof v === "object") {
-      setSpanEventAttributesRecursive(
-        span,
+      flattenVoipEventRecursive(
         v as Record<string, unknown>,
+        flatObject,
         prefix + k + ".",
         depth + 1
       );
@@ -66,7 +71,6 @@ function setSpanEventAttributesRecursive(
  * Represent the span of time which we intend to be joined to a group call
  */
 export class OTelGroupCallMembership {
-  private context: Context;
   private callMembershipSpan: Span;
   private myUserId: string;
   private myMember: RoomMember;
@@ -83,7 +87,6 @@ export class OTelGroupCallMembership {
 
     // Create the main span that tracks the time we intend to be in the call
     this.callMembershipSpan = tracer.startSpan("otel_groupCallMembershipSpan");
-
     this.callMembershipSpan.setAttribute(
       "matrix.confId",
       this.groupCall.groupCallId
@@ -94,30 +97,16 @@ export class OTelGroupCallMembership {
       this.myMember.name
     );
 
-    this.context = opentelemetry.trace.setSpan(
+    opentelemetry.trace.setSpan(
       opentelemetry.context.active(),
       this.callMembershipSpan
     );
 
-    // Here we start a very short span. This is a hack to trigger the posthog exporter.
-    // Only ended spans are processed by the exporter.
-    // We want the exporter to know that a call has started
-    const joinCallSpan = tracer.startSpan(
-      "otel_joinCallSpan",
-      undefined,
-      this.context
-    );
-    joinCallSpan.end();
+    this.callMembershipSpan.addEvent("matrix.joinCall");
   }
 
   public onLeaveCall() {
-    // A very short span to represent us leaving the call
-    const startCallSpan = tracer.startSpan(
-      "otel_leaveCallSpan",
-      undefined,
-      this.context
-    );
-    startCallSpan.end();
+    this.callMembershipSpan.addEvent("matrix.leaveCall");
 
     // and end the main span to indicate we've left
     if (this.callMembershipSpan) this.callMembershipSpan.end();
@@ -128,17 +117,14 @@ export class OTelGroupCallMembership {
       !event ||
       (!event.getType().startsWith("m.call") &&
         !event.getType().startsWith("org.matrix.msc3401.call"))
-    )
+    ) {
       return;
+    }
 
-    const span = tracer.startSpan(
+    this.callMembershipSpan.addEvent(
       `otel_onRoomStateEvent_${event.getType()}`,
-      undefined,
-      this.context
+      flattenVoipEvent(event.getContent())
     );
-
-    setNestedAttributesFromEvent(span, event.getContent());
-    span.end();
   }
 
   public onSendEvent(event: VoipEvent) {
@@ -146,23 +132,15 @@ export class OTelGroupCallMembership {
     if (!eventType.startsWith("m.call")) return;
 
     if (event.type === "toDevice") {
-      const span = tracer.startSpan(
-        `otel_sendToDeviceEvent_${event.eventType}`,
-        undefined,
-        this.context
+      this.callMembershipSpan.addEvent(
+        `matrix.sendToDeviceEvent_${event.eventType}`,
+        flattenVoipEvent(event)
       );
-
-      setNestedAttributesFromEvent(span, event);
-      span.end();
     } else if (event.type === "sendEvent") {
-      const span = tracer.startSpan(
-        `otel_sendToRoomEvent_${event.eventType}`,
-        undefined,
-        this.context
+      this.callMembershipSpan.addEvent(
+        `matrix.sendToRoomEvent_${event.eventType}`,
+        flattenVoipEvent(event)
       );
-
-      setNestedAttributesFromEvent(span, event);
-      span.end();
     }
   }
 }