4 files changed, 65 insertions, 0 deletions
diff --git a/js/deno.ts b/js/deno.ts
index a7350e03e..212544541 100644
--- a/js/deno.ts
+++ b/js/deno.ts
@@ -35,6 +35,7 @@ export { trace } from "./trace";
 export { truncateSync, truncate } from "./truncate";
 export { FileInfo } from "./file_info";
 export { connect, dial, listen, Listener, Conn } from "./net";
+export { metrics } from "./metrics";
 export const args: string[] = [];
 
 // Provide the compiler API in an obfuscated way
diff --git a/js/metrics.ts b/js/metrics.ts
new file mode 100644
index 000000000..d76b781db
--- /dev/null
+++ b/js/metrics.ts
@@ -0,0 +1,39 @@
+// Copyright 2018 the Deno authors. All rights reserved. MIT license.
+import * as msg from "gen/msg_generated";
+import { flatbuffers } from "flatbuffers";
+import { assert } from "./util";
+import * as dispatch from "./dispatch";
+
+interface Metrics {
+  opsDispatched: number;
+  opsCompleted: number;
+  bytesSentControl: number;
+  bytesSentData: number;
+  bytesReceived: number;
+}
+
+export function metrics(): Metrics {
+  return res(dispatch.sendSync(...req()));
+}
+
+function req(): [flatbuffers.Builder, msg.Any, flatbuffers.Offset] {
+  const builder = new flatbuffers.Builder();
+  msg.Metrics.startMetrics(builder);
+  const inner = msg.Metrics.endMetrics(builder);
+  return [builder, msg.Any.Metrics, inner];
+}
+
+function res(baseRes: null | msg.Base): Metrics {
+  assert(baseRes !== null);
+  assert(msg.Any.MetricsRes === baseRes!.innerType());
+  const res = new msg.MetricsRes();
+  assert(baseRes!.inner(res) !== null);
+
+  return {
+    opsDispatched: res.opsDispatched().toFloat64(),
+    opsCompleted: res.opsCompleted().toFloat64(),
+    bytesSentControl: res.bytesSentControl().toFloat64(),
+    bytesSentData: res.bytesSentData().toFloat64(),
+    bytesReceived: res.bytesReceived().toFloat64()
+  };
+}
diff --git a/js/metrics_test.ts b/js/metrics_test.ts
new file mode 100644
index 000000000..6954ae2ce
--- /dev/null
+++ b/js/metrics_test.ts
@@ -0,0 +1,24 @@
+// Copyright 2018 the Deno authors. All rights reserved. MIT license.
+import { test, assert } from "./test_util.ts";
+import * as deno from "deno";
+
+test(function metrics() {
+  const m1 = deno.metrics();
+  assert(m1.opsDispatched > 0);
+  assert(m1.opsCompleted > 0);
+  assert(m1.bytesSentControl > 0);
+  assert(m1.bytesSentData >= 0);
+  assert(m1.bytesReceived > 0);
+
+  // Write to stdout to ensure a "data" message gets sent instead of just
+  // control messages.
+  const dataMsg = new Uint8Array([41, 42, 43]);
+  deno.stdout.write(dataMsg);
+
+  const m2 = deno.metrics();
+  assert(m2.opsDispatched > m1.opsDispatched);
+  assert(m2.opsCompleted > m1.opsCompleted);
+  assert(m2.bytesSentControl > m1.bytesSentControl);
+  assert(m2.bytesSentData >= m1.bytesSentData + dataMsg.byteLength);
+  assert(m2.bytesReceived > m1.bytesReceived);
+});
diff --git a/js/unit_tests.ts b/js/unit_tests.ts
index ca152ad39..24fdac823 100644
--- a/js/unit_tests.ts
+++ b/js/unit_tests.ts
@@ -25,3 +25,4 @@ import "./trace_test.ts";
 import "./truncate_test.ts";
 import "./v8_source_maps_test.ts";
 import "../website/app_test.js";
+import "./metrics_test.ts";