Include unended spans in rageshakes

By turning the RageshakeSpanExporter into a SpanProcessor, it can now be notified of spans as soon as they're started.

src/analytics/RageshakeSpanProcessor.ts

@@ -0,0 +1,110 @@
+import { Attributes } from "@opentelemetry/api";
+import { hrTimeToMilliseconds } from "@opentelemetry/core";
+import {
+  SpanProcessor,
+  ReadableSpan,
+  Span,
+} from "@opentelemetry/sdk-trace-base";
+
+const dumpAttributes = (attr: Attributes) =>
+  Object.entries(attr).map(([key, value]) => ({
+    key,
+    type: typeof value,
+    value,
+  }));
+
+/**
+ * Exports spans on demand to the Jaeger JSON format, which can be attached to
+ * rageshakes and loaded into analysis tools like Jaeger and Stalk.
+ */
+export class RageshakeSpanProcessor implements SpanProcessor {
+  private readonly spans: ReadableSpan[] = [];
+
+  async forceFlush(): Promise<void> {}
+
+  onStart(span: Span): void {
+    this.spans.push(span);
+  }
+
+  onEnd(): void {}
+
+  /**
+   * Dumps the spans collected so far as Jaeger-compatible JSON.
+   */
+  public dump(): string {
+    const now = Date.now();
+    const traces = new Map<string, ReadableSpan[]>();
+
+    // Organize spans by their trace IDs
+    for (const span of this.spans) {
+      const traceId = span.spanContext().traceId;
+      let trace = traces.get(traceId);
+
+      if (trace === undefined) {
+        trace = [];
+        traces.set(traceId, trace);
+      }
+
+      trace.push(span);
+    }
+
+    const processId = "p1";
+    const processes = {
+      [processId]: {
+        serviceName: "element-call",
+        tags: [],
+      },
+      warnings: null,
+    };
+
+    return JSON.stringify({
+      // Honestly not sure what some of these fields mean, I just know that
+      // they're present in Jaeger JSON exports
+      total: 0,
+      limit: 0,
+      offset: 0,
+      errors: null,
+      data: [...traces.entries()].map(([traceId, spans]) => ({
+        traceID: traceId,
+        warnings: null,
+        processes,
+        spans: spans.map((span) => {
+          const ctx = span.spanContext();
+          const startTime = hrTimeToMilliseconds(span.startTime);
+          // If the span has not yet ended, pretend that it ends now
+          const duration =
+            span.duration[0] === -1
+              ? now - startTime
+              : hrTimeToMilliseconds(span.duration);
+
+          return {
+            traceID: traceId,
+            spanID: ctx.spanId,
+            operationName: span.name,
+            processID: processId,
+            warnings: null,
+            startTime,
+            duration,
+            references:
+              span.parentSpanId === undefined
+                ? []
+                : [
+                    {
+                      refType: "CHILD_OF",
+                      traceID: traceId,
+                      spanID: span.parentSpanId,
+                    },
+                  ],
+            tags: dumpAttributes(span.attributes),
+            logs: span.events.map((event) => ({
+              timestamp: hrTimeToMilliseconds(event.time),
+              fields: dumpAttributes(event.attributes ?? {}),
+            })),
+          };
+        }),
+      })),
+    });
+  }
+
+  async shutdown(): Promise<void> {}
+}