ci: upload build effective cache hit rate stats to Datadog (#48529)

* ci: upload build effective cache hit rate stats to Datadog

Co-authored-by: David Sanders <dsanders11@ucsbalum.com>

* ci: fix release branch name in build stats script

Update branch tag logic to handle release branches.

---------

Co-authored-by: trop[bot] <37223003+trop[bot]@users.noreply.github.com>
Co-authored-by: David Sanders <dsanders11@ucsbalum.com>

script/build-stats.mjs

@@ -0,0 +1,96 @@
+import * as fs from 'node:fs/promises';
+import { fileURLToPath } from 'node:url';
+import { parseArgs } from 'node:util';
+
+async function main () {
+  const { positionals: [filename], values: { 'upload-stats': uploadStats } } = parseArgs({
+    allowPositionals: true,
+    options: {
+      'upload-stats': {
+        type: 'boolean',
+        default: false
+      }
+    }
+  });
+
+  if (!filename) {
+    throw new Error('filename is required (should be a siso.INFO file)');
+  }
+
+  const log = await fs.readFile(filename, 'utf-8');
+
+  // We expect to find a line which looks like stats=build.Stats{..., CacheHit:39008, Local:4778, Remote:0, LocalFallback:0, ...}
+  const match = log.match(/stats=build\.Stats{(.*)}/);
+
+  if (!match) {
+    throw new Error('could not find stats=build.Stats in log');
+  }
+
+  const stats = Object.fromEntries(match[1].split(',').map(part => {
+    const [key, value] = part.trim().split(':');
+    return [key, parseInt(value)];
+  }));
+  const hitRate = stats.CacheHit / (stats.Remote + stats.CacheHit + stats.LocalFallback);
+
+  console.log(`Effective cache hit rate: ${(hitRate * 100).toFixed(2)}%`);
+
+  if (uploadStats) {
+    if (!process.env.DD_API_KEY) {
+      throw new Error('DD_API_KEY is not set');
+    }
+
+    const timestamp = Math.round(new Date().getTime() / 1000);
+
+    const tags = [];
+
+    if (process.env.TARGET_ARCH) tags.push(`target-arch:${process.env.TARGET_ARCH}`);
+    if (process.env.TARGET_PLATFORM) tags.push(`target-platform:${process.env.TARGET_PLATFORM}`);
+    if (process.env.GITHUB_HEAD_REF) {
+      // Will be set in pull requests
+      tags.push(`branch:${process.env.GITHUB_HEAD_REF}`);
+    } else if (process.env.GITHUB_REF_NAME) {
+      // Will be set for release branches
+      tags.push(`branch:${process.env.GITHUB_REF_NAME}`);
+    }
+
+    const series = [
+      {
+        metric: 'electron.build.effective-cache-hit-rate',
+        points: [{ timestamp, value: (hitRate * 100).toFixed(2) }],
+        type: 3, // GAUGE
+        unit: 'percent',
+        tags
+      }
+    ];
+
+    // Add all raw stats as individual metrics
+    for (const [key, value] of Object.entries(stats)) {
+      series.push({
+        metric: `electron.build.stats.${key.toLowerCase()}`,
+        points: [{ timestamp, value }],
+        type: 1, // COUNT
+        tags
+      });
+    }
+
+    await fetch('https://api.datadoghq.com/api/v2/series', {
+      method: 'POST',
+      headers: {
+        'Content-Type': 'application/json',
+        'DD-API-KEY': process.env.DD_API_KEY
+      },
+      body: JSON.stringify({ series })
+    });
+  }
+}
+
+if ((await fs.realpath(process.argv[1])) === fileURLToPath(import.meta.url)) {
+  main()
+    .then(() => {
+      process.exit(0);
+    })
+    .catch((err) => {
+      console.error(`ERROR: ${err.message}`);
+      process.exit(1);
+    });
+}