Merge pull request #48 from DataDog/stephenf/fix-async-metric-timestamps

Fix timestamps for async metrics

Author: sfirrin

package.json

@@ -1,6 +1,6 @@
 {
   "name": "datadog-lambda-js",
-  "version": "0.13.0",
+  "version": "0.14.0",
   "description": "Lambda client library that supports hybrid tracing in node js",
   "main": "dist/index.js",
   "types": "dist/index.d.ts",

src/metrics/build-metric-log.spec.ts

@@ -0,0 +1,15 @@
+import { buildMetricLog } from "./build-metric-log";
+
+describe("buildMetricLog", () => {
+  jest.spyOn(Date, "now").mockImplementation(() => 1487076708123);
+  it("handles empty tag list", () => {
+    expect(buildMetricLog("my.test.metric", 1337, [])).toStrictEqual(
+      '{"e":1487076708.123,"m":"my.test.metric","t":[],"v":1337}\n',
+    );
+  });
+  it("writes timestamp in Unix seconds", () => {
+    expect(buildMetricLog("my.test.metric", 1337, ["region:us", "account:dev", "team:serverless"])).toStrictEqual(
+      '{"e":1487076708.123,"m":"my.test.metric","t":["region:us","account:dev","team:serverless"],"v":1337}\n',
+    );
+  });
+});

src/metrics/build-metric-log.ts

@@ -0,0 +1,10 @@
+// Builds the string representation of the metric that will be written to logs
+export function buildMetricLog(name: string, value: number, tags: string[]) {
+  return `${JSON.stringify({
+    // Date.now() returns Unix time in milliseconds, we convert to seconds for DD API submission
+    e: Date.now() / 1000,
+    m: name,
+    t: tags,
+    v: value,
+  })}\n`;
+}

src/metrics/listener.spec.ts

@@ -98,6 +98,6 @@ describe("MetricsListener", () => {
     listener.sendDistributionMetric("my-metric", 10, "tag:a", "tag:b");
     await listener.onCompleteInvocation();
 
-    expect(spy).toHaveBeenCalledWith(`{"e":1487076708000,"m":"my-metric","t":["tag:a","tag:b"],"v":10}\n`);
+    expect(spy).toHaveBeenCalledWith(`{"e":1487076708,"m":"my-metric","t":["tag:a","tag:b"],"v":10}\n`);
   });
 });

src/metrics/listener.ts

@@ -2,6 +2,7 @@ import { promisify } from "util";
 
 import { logDebug, logError } from "../utils";
 import { APIClient } from "./api";
+import { buildMetricLog } from "./build-metric-log";
 import { KMSService } from "./kms-service";
 import { Distribution } from "./model";
 import { Processor } from "./processor";
@@ -86,14 +87,7 @@ export class MetricsListener {
     if (this.config.logForwarding) {
       // We use process.stdout.write, because console.log will prepend metadata to the start
       // of the log that log forwarder doesn't know how to read.
-      process.stdout.write(
-        `${JSON.stringify({
-          e: Date.now(),
-          m: name,
-          t: tags,
-          v: value,
-        })}\n`,
-      );
+      process.stdout.write(buildMetricLog(name, value, tags));
       return;
     }
     const dist = new Distribution(name, [{ timestamp: new Date(), value }], ...tags);