feat: OTLP trace export via observability.otlp frontmatter config

actions/setup/action.yml

@@ -10,10 +10,20 @@ inputs:
     description: 'Install @actions/github for handlers that use a per-handler github-token (creates Octokit via getOctokit)'
     required: false
     default: 'false'
+  job-name:
+    description: 'Name of the job being set up. When OTEL_EXPORTER_OTLP_ENDPOINT is configured, a gh-aw.job.setup span is pushed to the OTLP endpoint.'
+    required: false
+    default: ''
+  trace-id:
+    description: 'OTLP trace ID (32-character hexadecimal string) to reuse for cross-job span correlation. Pass the trace-id output of the activation job setup step to correlate all job spans under the same trace. When omitted a new trace ID is generated.'
+    required: false
+    default: ''
 
 outputs:
   files_copied:
     description: 'Number of files copied'
+  trace-id:
+    description: 'The OTLP trace ID used for the gh-aw.job.setup span. Pass this to subsequent job setup steps via the trace-id input to correlate all job spans under a single trace.'
 
 runs:
   using: 'node24'

actions/setup/js/send_otlp_span.cjs

@@ -0,0 +1,251 @@
+// @ts-check
+/// <reference types="@actions/github-script" />
+
+const { randomBytes } = require("crypto");
+
+/**
+ * send_otlp_span.cjs
+ *
+ * Sends a single OTLP (OpenTelemetry Protocol) trace span to the configured
+ * HTTP/JSON endpoint.  Used by actions/setup to instrument each job execution
+ * with basic telemetry.
+ *
+ * Design constraints:
+ * - No-op when OTEL_EXPORTER_OTLP_ENDPOINT is not set (zero overhead).
+ * - Errors are non-fatal: export failures must never break the workflow.
+ * - No third-party dependencies: uses only Node built-ins + native fetch.
+ */
+
+// ---------------------------------------------------------------------------
+// Low-level helpers
+// ---------------------------------------------------------------------------
+
+/**
+ * Generate a random 16-byte trace ID encoded as a 32-character hex string.
+ * @returns {string}
+ */
+function generateTraceId() {
+  return randomBytes(16).toString("hex");
+}
+
+/**
+ * Generate a random 8-byte span ID encoded as a 16-character hex string.
+ * @returns {string}
+ */
+function generateSpanId() {
+  return randomBytes(8).toString("hex");
+}
+
+/**
+ * Convert a Unix timestamp in milliseconds to a nanosecond string suitable for
+ * OTLP's `startTimeUnixNano` / `endTimeUnixNano` fields.
+ *
+ * BigInt arithmetic avoids floating-point precision loss for large timestamps.
+ *
+ * @param {number} ms - milliseconds since Unix epoch
+ * @returns {string} nanoseconds since Unix epoch as a decimal string
+ */
+function toNanoString(ms) {
+  return (BigInt(Math.floor(ms)) * 1_000_000n).toString();
+}
+
+/**
+ * Build a single OTLP attribute object in the key-value format expected by the
+ * OTLP/HTTP JSON wire format.
+ *
+ * @param {string} key
+ * @param {string | number | boolean} value
+ * @returns {{ key: string, value: object }}
+ */
+function buildAttr(key, value) {
+  if (typeof value === "boolean") {
+    return { key, value: { boolValue: value } };
+  }
+  if (typeof value === "number") {
+    return { key, value: { intValue: value } };
+  }
+  return { key, value: { stringValue: String(value) } };
+}
+
+// ---------------------------------------------------------------------------
+// OTLP payload builder
+// ---------------------------------------------------------------------------
+
+/**
+ * @typedef {Object} OTLPSpanOptions
+ * @property {string} traceId       - 32-char hex trace ID
+ * @property {string} spanId        - 16-char hex span ID
+ * @property {string} spanName      - Human-readable span name
+ * @property {number} startMs       - Span start time (ms since epoch)
+ * @property {number} endMs         - Span end time (ms since epoch)
+ * @property {string} serviceName   - Value for the service.name resource attribute
+ * @property {Array<{key: string, value: object}>} attributes - Span attributes
+ */
+
+/**
+ * Build an OTLP/HTTP JSON traces payload wrapping a single span.
+ *
+ * @param {OTLPSpanOptions} opts
+ * @returns {object} - Ready to be serialised as JSON and POSTed to `/v1/traces`
+ */
+function buildOTLPPayload({ traceId, spanId, spanName, startMs, endMs, serviceName, attributes }) {
+  return {
+    resourceSpans: [
+      {
+        resource: {
+          attributes: [buildAttr("service.name", serviceName)],
+        },
+        scopeSpans: [
+          {
+            scope: { name: "gh-aw.setup", version: "1.0.0" },
+            spans: [
+              {
+                traceId,
+                spanId,
+                name: spanName,
+                kind: 2, // SPAN_KIND_SERVER
+                startTimeUnixNano: toNanoString(startMs),
+                endTimeUnixNano: toNanoString(endMs),
+                status: { code: 1 }, // STATUS_CODE_OK
+                attributes,
+              },
+            ],
+          },
+        ],
+      },
+    ],
+  };
+}
+
+// ---------------------------------------------------------------------------
+// HTTP transport
+// ---------------------------------------------------------------------------
+
+/**
+ * POST an OTLP traces payload to `{endpoint}/v1/traces`.
+ *
+ * @param {string} endpoint - OTLP base URL (e.g. https://traces.example.com:4317)
+ * @param {object} payload  - Serialisable OTLP JSON object
+ * @returns {Promise<void>}
+ * @throws {Error} when the server returns a non-2xx status
+ */
+async function sendOTLPSpan(endpoint, payload) {
+  const url = endpoint.replace(/\/$/, "") + "/v1/traces";
+  const response = await fetch(url, {
+    method: "POST",
+    headers: { "Content-Type": "application/json" },
+    body: JSON.stringify(payload),
+  });
+  if (!response.ok) {
+    throw new Error(`OTLP export failed: HTTP ${response.status} ${response.statusText}`);
+  }
+}
+
+// ---------------------------------------------------------------------------
+// High-level: job setup span
+// ---------------------------------------------------------------------------
+
+/**
+ * Regular expression that matches a valid OTLP trace ID: 32 lowercase hex characters.
+ * @type {RegExp}
+ */
+const TRACE_ID_RE = /^[0-9a-f]{32}$/;
+
+/**
+ * Validate that a string is a well-formed OTLP trace ID (32 lowercase hex chars).
+ * @param {string} id
+ * @returns {boolean}
+ */
+function isValidTraceId(id) {
+  return TRACE_ID_RE.test(id);
+}
+
+/**
+ * @typedef {Object} SendJobSetupSpanOptions
+ * @property {number} [startMs]  - Override for the span start time (ms).  Defaults to `Date.now()`.
+ * @property {string} [traceId] - Existing trace ID to reuse for cross-job correlation.
+ *   When omitted the value is taken from the `INPUT_TRACE_ID` environment variable (the
+ *   `trace-id` action input); if that is also absent a new random trace ID is generated.
+ *   Pass the `trace-id` output of the activation job setup step to correlate all
+ *   subsequent job spans under the same trace.
+ */
+
+/**
+ * Send a `gh-aw.job.setup` span to the configured OTLP endpoint.
+ *
+ * This is designed to be called from `actions/setup/index.js` immediately after
+ * the setup script completes.  It always returns the trace ID so callers can
+ * expose it as an action output for cross-job correlation — even when
+ * `OTEL_EXPORTER_OTLP_ENDPOINT` is not set (no span is sent in that case).
+ * Errors are swallowed so the workflow is never broken by tracing failures.
+ *
+ * Environment variables consumed:
+ * - `OTEL_EXPORTER_OTLP_ENDPOINT` – collector endpoint (required to send anything)
+ * - `OTEL_SERVICE_NAME`            – service name (defaults to "gh-aw")
+ * - `INPUT_JOB_NAME`               – job name passed via the `job-name` action input
+ * - `INPUT_TRACE_ID`               – optional trace ID passed via the `trace-id` action input
+ * - `GH_AW_INFO_WORKFLOW_NAME`     – workflow name injected by the gh-aw compiler
+ * - `GH_AW_INFO_ENGINE_ID`         – engine ID injected by the gh-aw compiler
+ * - `GITHUB_RUN_ID`                – GitHub Actions run ID
+ * - `GITHUB_ACTOR`                 – GitHub Actions actor (user / bot)
+ * - `GITHUB_REPOSITORY`            – `owner/repo` string
+ *
+ * @param {SendJobSetupSpanOptions} [options]
+ * @returns {Promise<string>} The trace ID used for the span (generated or passed in).
+ */
+async function sendJobSetupSpan(options = {}) {
+  // Resolve the trace ID before the early-return so it is always available as
+  // an action output regardless of whether OTLP is configured.
+  // Priority: options.traceId > INPUT_TRACE_ID env var > newly generated ID.
+  // Invalid (non-hex, wrong-length) values are silently discarded in favour of a new ID.
+  const rawInputTraceId = (process.env.INPUT_TRACE_ID || "").trim().toLowerCase();
+  const inputTraceId = isValidTraceId(rawInputTraceId) ? rawInputTraceId : "";
+  const candidateTraceId = options.traceId || inputTraceId;
+  const traceId = candidateTraceId && isValidTraceId(candidateTraceId) ? candidateTraceId : generateTraceId();
+
+  const endpoint = process.env.OTEL_EXPORTER_OTLP_ENDPOINT || "";
+  if (!endpoint) {
+    return traceId;
+  }
+
+  const startMs = options.startMs ?? Date.now();
+  const endMs = Date.now();
+
+  const serviceName = process.env.OTEL_SERVICE_NAME || "gh-aw";
+  const jobName = process.env.INPUT_JOB_NAME || "";
+  const workflowName = process.env.GH_AW_INFO_WORKFLOW_NAME || process.env.GITHUB_WORKFLOW || "";
+  const engineId = process.env.GH_AW_INFO_ENGINE_ID || "";
+  const runId = process.env.GITHUB_RUN_ID || "";
+  const actor = process.env.GITHUB_ACTOR || "";
+  const repository = process.env.GITHUB_REPOSITORY || "";
+
+  const attributes = [buildAttr("gh-aw.job.name", jobName), buildAttr("gh-aw.workflow.name", workflowName), buildAttr("gh-aw.run.id", runId), buildAttr("gh-aw.run.actor", actor), buildAttr("gh-aw.repository", repository)];
+
+  if (engineId) {
+    attributes.push(buildAttr("gh-aw.engine.id", engineId));
+  }
+
+  const payload = buildOTLPPayload({
+    traceId,
+    spanId: generateSpanId(),
+    spanName: "gh-aw.job.setup",
+    startMs,
+    endMs,
+    serviceName,
+    attributes,
+  });
+
+  await sendOTLPSpan(endpoint, payload);
+  return traceId;
+}
+
+module.exports = {
+  isValidTraceId,
+  generateTraceId,
+  generateSpanId,
+  toNanoString,
+  buildAttr,
+  buildOTLPPayload,
+  sendOTLPSpan,
+  sendJobSetupSpan,
+};