build: shard integration tests on circleci (#27937)

PR Close #27937

integration/get-sharded-tests.js

@@ -0,0 +1,100 @@
+/**
+ * @license
+ * Copyright Google Inc. All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+
+/*
+ * Script that determines the sharded tests for the current CircleCI container. CircleCI starts
+ * multiple containers if the "parallelism" option has been specified and this script splits up
+ * the integration tests into shards based on the amount of parallelism.
+ *
+ * It's also possible to manually specify tests which should run on a container because some
+ * integration tests are more complex and take up more time. In order to properly balance the
+ * duration of each container, we allow manual test shards to be specified.
+ *
+ * The output of this script can then be used to only run the tests which are assigned to the
+ * current CircleCI container.
+ */
+
+const fs = require('fs');
+const path = require('path');
+const minimist = require('minimist');
+
+// Parsed command line arguments.
+const {shardIndex, maxShards} = minimist(process.argv.slice(2));
+
+// Ensure that all CLI options are set properly.
+if (shardIndex == null) {
+  throw new Error('The "--shardIndex" option has not been specified.')
+} else if (maxShards == null) {
+  throw new Error('The "--maxShards" option has not been specified.');
+}
+
+// List of all integration tests that are available.
+const integrationTests = fs.readdirSync(__dirname).filter(
+    testName => fs.statSync(path.join(__dirname, testName)).isDirectory());
+
+// Manual test shards which aren't computed automatically. This is helpful when a specific
+// set of integration test takes up *way* more time than all other tests, and we want to
+// balance out the duration for all specific shards.
+const manualTestShards = [
+  // The first shard should only run the bazel integration tests because these take up
+  // a lot of time and shouldn't be split up automatically.
+  ['bazel', 'bazel-schematics']
+];
+
+// Tests which haven't been assigned manually to a shard. These tests will be automatically
+// split across the remaining available shards.
+const unassignedTests = stripManualOverrides(integrationTests, manualTestShards);
+
+if (manualTestShards.length === maxShards && unassignedTests.length) {
+  throw new Error(
+      `Tests have been specified manually for all available shards, but there were ` +
+      `integration tests which haven't been specified and won't run right now. Missing ` +
+      `tests: ${unassignedTests.join(', ')}`)
+} else if (manualTestShards.length > maxShards) {
+  throw new Error(
+      `Too many manual shards have been specified. Increase the amount of maximum shards.`);
+}
+
+// In case the shard for the current index has been specified manually, we just output
+// the tests for the manual shard.
+if (manualTestShards[shardIndex]) {
+  printTestNames(manualTestShards[shardIndex]);
+} else {
+  const amountManualShards = manualTestShards.length;
+  // In case there isn't a manual shard specified for this shard index, we just compute the
+  // tests for this shard. Note that we need to subtract the amount of manual shards because
+  // we need to split up the unassigned tests across the remaining available shards.
+  printTestNames(getTestsForShardIndex(
+      unassignedTests, shardIndex - amountManualShards, maxShards - amountManualShards));
+}
+
+/**
+ * Splits the specified tests into a limited amount of shards and returns the tests that should
+ * run on the given shard. The shards of tests are being created deterministically and therefore
+ * we get reproducible tests when executing the same script multiple times.
+ */
+function getTestsForShardIndex(tests, shardIndex, maxShards) {
+  return tests.filter((n, index) => index % maxShards === shardIndex);
+}
+
+/**
+ * Strips all manual tests from the list of integration tests. This is necessary because
+ * when computing the shards automatically we don't want to include manual tests again. This
+ * would mean that CircleCI runs some integration tests multiple times.
+ */
+function stripManualOverrides(integrationTests, manualShards) {
+  const allManualTests = manualShards.reduce((res, manualTests) => res.concat(manualTests), []);
+  return integrationTests.filter(testName => !allManualTests.includes(testName))
+}
+
+/** Prints the specified test names to the stdout. */
+function printTestNames(testNames) {
+  // Print the test names joined with spaces because this allows Bash to easily convert the output
+  // of this script into an array.
+  process.stdout.write(testNames.join(' '));
+}