app_dart/lib/src/service/scheduler.dart - mirrors/cocoon - Git at Google

 // Copyright 2021 The Flutter Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.

 import 'dart:math';
 import 'dart:typed_data';

 import 'package:cocoon_service/src/service/NoBuildFoundException.dart';
 import 'package:cocoon_service/src/service/build_status_provider.dart';
 import 'package:cocoon_service/src/service/scheduler/policy.dart';
 import 'package:gcloud/db.dart';
 import 'package:github/github.dart' as github;
 import 'package:github/github.dart';
 import 'package:github/hooks.dart';
 import 'package:googleapis/bigquery/v2.dart';
 import 'package:retry/retry.dart';
 import 'package:truncate/truncate.dart';
 import 'package:yaml/yaml.dart';

 import '../foundation/providers.dart';
 import '../foundation/typedefs.dart';
 import '../foundation/utils.dart';
 import '../model/appengine/commit.dart';
 import '../model/appengine/task.dart';
 import '../model/ci_yaml/ci_yaml.dart';
 import '../model/ci_yaml/target.dart';
 import '../model/github/checks.dart' as cocoon_checks;
 import '../model/luci/buildbucket.dart';
 import '../model/proto/internal/scheduler.pb.dart' as pb;
 import '../service/logging.dart';
 import 'cache_service.dart';
 import 'config.dart';
 import 'datastore.dart';
 import 'github_checks_service.dart';
 import 'github_service.dart';
 import 'luci_build_service.dart';

 /// Scheduler service to validate all commits to supported Flutter repositories.
 ///
 /// Scheduler responsibilties include:
 ///   1. Tracking commits in Cocoon
 ///   2. Ensuring commits are validated (via scheduling tasks against commits)
 ///   3. Retry mechanisms for tasks
 class Scheduler {
   Scheduler({
     required this.cache,
     required this.config,
     required this.githubChecksService,
     required this.luciBuildService,
     this.datastoreProvider = DatastoreService.defaultProvider,
     this.httpClientProvider = Providers.freshHttpClient,
     this.buildStatusProvider = BuildStatusService.defaultProvider,
   });

   final BuildStatusServiceProvider buildStatusProvider;
   final CacheService cache;
   final Config config;
   final DatastoreServiceProvider datastoreProvider;
   final GithubChecksService githubChecksService;
   final HttpClientProvider httpClientProvider;

   late DatastoreService datastore;
   LuciBuildService luciBuildService;

   /// Name of the subcache to store scheduler related values in redis.
   static const String subcacheName = 'scheduler';

   static const String kCiYamlCheckName = 'ci.yaml validation';

   /// Ensure [commits] exist in Cocoon.
   ///
   /// If [Commit] does not exist in Datastore:
   ///   * Write it to datastore
   ///   * Schedule tasks listed in its scheduler config
   /// Otherwise, ignore it.
   Future<void> addCommits(List<Commit> commits) async {
     datastore = datastoreProvider(config.db);
     final List<Commit> newCommits = await _getMissingCommits(commits);
     log.fine('Found ${newCommits.length} new commits on GitHub');
     for (Commit commit in newCommits) {
       await _addCommit(commit);
     }
   }

   /// Schedule tasks against [PullRequest].
   ///
   /// If [PullRequest] was merged, schedule prod tasks against it.
   /// Otherwise if it is presubmit, schedule try tasks against it.
   Future<void> addPullRequest(github.PullRequest pr) async {
     datastore = datastoreProvider(config.db);
     // TODO(chillers): Support triggering on presubmit. https://github.com/flutter/flutter/issues/77858
     if (!pr.merged!) {
       log.warning('Only pull requests that were closed and merged should have tasks scheduled');
       return;
     }

     final String fullRepo = pr.base!.repo!.fullName;
     final String? branch = pr.base!.ref;
     final String sha = pr.mergeCommitSha!;

     final String id = '$fullRepo/$branch/$sha';
     final Key<String> key = datastore.db.emptyKey.append<String>(Commit, id: id);
     final Commit mergedCommit = Commit(
       author: pr.user!.login!,
       authorAvatarUrl: pr.user!.avatarUrl!,
       branch: branch,
       key: key,
       // The field has a max length of 1500 so ensure the commit message is not longer.
       message: truncate(pr.title!, 1490, omission: '...'),
       repository: fullRepo,
       sha: sha,
       timestamp: pr.mergedAt!.millisecondsSinceEpoch,
     );

     if (await _commitExistsInDatastore(mergedCommit)) {
       log.fine('$sha already exists in datastore. Scheduling skipped.');
       return;
     }

     log.fine('Scheduling $sha via GitHub webhook');
     await _addCommit(mergedCommit);
   }

   Future<void> _addCommit(Commit commit) async {
     if (!config.supportedRepos.contains(commit.slug)) {
       log.fine('Skipping ${commit.id} as repo is not supported');
       return;
     }

     final CiYaml ciYaml = await getCiYaml(commit);
     final List<Target> initialTargets = ciYaml.getInitialTargets(ciYaml.postsubmitTargets);
     final List<Task> tasks = targetsToTask(commit, initialTargets).toList();

     final List<Tuple<Target, Task, int>> toBeScheduled = <Tuple<Target, Task, int>>[];
     for (Target target in initialTargets) {
       final Task task = tasks.singleWhere((Task task) => task.name == target.value.name);
       SchedulerPolicy policy = target.schedulerPolicy;
       // Engine repo and release branches should run every task
       if (commit.slug == Config.engineSlug || Config.defaultBranch(commit.slug) != commit.branch) {
         policy = GuaranteedPolicy();
       }
       final int? priority = await policy.triggerPriority(task: task, datastore: datastore);
       if (priority != null) {
         // Mark task as in progress to ensure it isn't scheduled over
         task.status = Task.statusInProgress;
         toBeScheduled.add(Tuple<Target, Task, int>(target, task, priority));
       }
     }

     // Datastore must be written to generate task keys
     try {
       await datastore.withTransaction<void>((Transaction transaction) async {
         transaction.queueMutations(inserts: <Commit>[commit]);
         transaction.queueMutations(inserts: tasks);
         await transaction.commit();
         log.fine('Committed ${tasks.length} new tasks for commit ${commit.sha!}');
       });
     } catch (error) {
       log.severe('Failed to add commit ${commit.sha!}: $error');
     }

     await _batchScheduleBuilds(commit, toBeScheduled);
     await _uploadToBigQuery(commit);
   }

   /// Schedule all builds in batch requests instead of a single request.
   ///
   /// Each batch request contains [Config.batchSize] builds to be scheduled.
   Future<void> _batchScheduleBuilds(Commit commit, List<Tuple<Target, Task, int>> toBeScheduled) async {
     final List<Future<void>> futures = <Future<void>>[];
     for (int i = 0; i < toBeScheduled.length; i += config.batchSize) {
       futures.add(
         luciBuildService.schedulePostsubmitBuilds(
           commit: commit,
           toBeScheduled: toBeScheduled.sublist(i, min(i + config.batchSize, toBeScheduled.length)),
         ),
       );
     }
     await Future.wait<void>(futures);
   }

   /// Return subset of [commits] not stored in Datastore.
   Future<List<Commit>> _getMissingCommits(List<Commit> commits) async {
     final List<Commit> newCommits = <Commit>[];
     // Ensure commits are sorted from newest to oldest (descending order)
     commits.sort((Commit a, Commit b) => b.timestamp!.compareTo(a.timestamp!));
     for (Commit commit in commits) {
       // Cocoon may randomly drop commits, so check the entire list.
       if (!await _commitExistsInDatastore(commit)) {
         newCommits.add(commit);
       }
     }

     // Reverses commits to be in order of oldest to newest.
     return newCommits;
   }

   /// Whether [Commit] already exists in [datastore].
   ///
   /// Datastore is Cocoon's source of truth for what commits have been scheduled.
   /// Since webhooks or cron jobs can schedule commits, we must verify a commit
   /// has not already been scheduled.
   Future<bool> _commitExistsInDatastore(Commit commit) async {
     try {
       await datastore.db.lookupValue<Commit>(commit.key);
     } on KeyNotFoundException {
       return false;
     }
     return true;
   }

   /// Load in memory the `.ci.yaml`.
   Future<CiYaml> getCiYaml(
     Commit commit, {
     CiYaml? totCiYaml,
     RetryOptions retryOptions = const RetryOptions(maxAttempts: 3),
   }) async {
     String ciPath;
     ciPath = '${commit.repository}/${commit.sha!}/$kCiYamlPath';
     final Uint8List ciYamlBytes = (await cache.getOrCreate(
       subcacheName,
       ciPath,
       createFn: () => _downloadCiYaml(
         commit,
         ciPath,
         retryOptions: retryOptions,
       ),
       ttl: const Duration(hours: 1),
     ))!;
     final pb.SchedulerConfig schedulerConfig = pb.SchedulerConfig.fromBuffer(ciYamlBytes);
     log.fine('Retrieved .ci.yaml for $ciPath');
     // If totCiYaml is not null, we assume upper level function has verified that current branch is not a release branch.
     return CiYaml(
       config: schedulerConfig,
       slug: commit.slug,
       branch: commit.branch!,
       totConfig: totCiYaml,
     );
   }

   /// Get `.ci.yaml` from GitHub, and store the bytes in redis for future retrieval.
   ///
   /// If GitHub returns [HttpStatus.notFound], an empty config will be inserted assuming
   /// that commit does not support the scheduler config file.
   Future<Uint8List> _downloadCiYaml(
     Commit commit,
     String ciPath, {
     RetryOptions retryOptions = const RetryOptions(maxAttempts: 3),
   }) async {
     final String configContent = await githubFileContent(
       commit.slug,
       '.ci.yaml',
       httpClientProvider: httpClientProvider,
       ref: commit.sha!,
       retryOptions: retryOptions,
     );
     final YamlMap configYaml = loadYaml(configContent) as YamlMap;
     final pb.SchedulerConfig schedulerConfig = pb.SchedulerConfig()..mergeFromProto3Json(configYaml);
     return schedulerConfig.writeToBuffer();
   }

   /// Cancel all incomplete targets against a pull request.
   Future<void> cancelPreSubmitTargets({
     required github.PullRequest pullRequest,
     String reason = 'Newer commit available',
   }) async {
     await luciBuildService.cancelBuilds(pullRequest, reason);
   }

   /// Schedule presubmit targets against a pull request.
   ///
   /// Cancels all existing targets then schedules the targets.
   ///
   /// Schedules a [kCiYamlCheckName] to validate [CiYaml] is valid and all builds were able to be triggered.
   /// If [builderTriggerList] is specified, then trigger only those targets.
   Future<void> triggerPresubmitTargets({
     required github.PullRequest pullRequest,
     String reason = 'Newer commit available',
     List<String>? builderTriggerList,
   }) async {
     // Always cancel running builds so we don't ever schedule duplicates.
     log.fine('Attempting to cancel existing presubmit targets for ${pullRequest.number}');
     await cancelPreSubmitTargets(
       pullRequest: pullRequest,
       reason: reason,
     );

     log.info('Creating ciYaml validation check run for ${pullRequest.number}');
     final github.CheckRun ciValidationCheckRun = await githubChecksService.githubChecksUtil.createCheckRun(
       config,
       pullRequest.base!.repo!.slug(),
       pullRequest.head!.sha!,
       kCiYamlCheckName,
       output: const github.CheckRunOutput(
         title: kCiYamlCheckName,
         summary: 'If this check is stuck pending, push an empty commit to retrigger the checks',
       ),
     );

     log.info('Creating presubmit targets for ${pullRequest.number}');
     final github.RepositorySlug slug = pullRequest.base!.repo!.slug();
     dynamic exception;
     try {
       final List<Target> presubmitTargets = await getPresubmitTargets(pullRequest);
       final List<Target> presubmitTriggerTargets = getTriggerList(presubmitTargets, builderTriggerList);
       await luciBuildService.scheduleTryBuilds(
         targets: presubmitTriggerTargets,
         pullRequest: pullRequest,
       );
     } on FormatException catch (error, backtrace) {
       log.warning('FormatException encountered when scheduling presubmit targets for ${pullRequest.number}');
       log.warning(backtrace.toString());
       exception = error;
     } catch (error, backtrace) {
       log.warning('Exception encountered when scheduling presubmit targets for ${pullRequest.number}');
       log.warning(backtrace.toString());
       exception = error;
     }

     // Update validate ci.yaml check
     log.info('Updating ci.yaml validation check for ${pullRequest.number}');
     if (exception == null) {
       // Success in validating ci.yaml
       log.info('ci.yaml validation check was successful for ${pullRequest.number}');
       await githubChecksService.githubChecksUtil.updateCheckRun(
         config,
         slug,
         ciValidationCheckRun,
         status: github.CheckRunStatus.completed,
         conclusion: github.CheckRunConclusion.success,
       );
     } else {
       log.warning('Marking PR #${pullRequest.number} $kCiYamlCheckName as failed');
       log.warning(exception.toString());
       // Failure when validating ci.yaml
       await githubChecksService.githubChecksUtil.updateCheckRun(
         config,
         slug,
         ciValidationCheckRun,
         status: github.CheckRunStatus.completed,
         conclusion: github.CheckRunConclusion.failure,
         output: github.CheckRunOutput(
           title: kCiYamlCheckName,
           summary: '.ci.yaml has failures',
           text: exception.toString(),
         ),
       );
     }
     log.info(
       'Finished triggering builds for: pr ${pullRequest.number}, commit ${pullRequest.base!.sha}, branch ${pullRequest.head!.ref} and slug ${pullRequest.base!.repo!.slug()}}',
     );
   }

   /// If [builderTriggerList] is specificed, return only builders that are contained in [presubmitTarget].
   /// Otherwise, return [presubmitTarget].
   List<Target> getTriggerList(List<Target> presubmitTarget, List<String>? builderTriggerList) {
     if (builderTriggerList != null && builderTriggerList.isNotEmpty) {
       return presubmitTarget.where((Target target) => builderTriggerList.contains(target.value.name)).toList();
     }
     return presubmitTarget;
   }

   /// Given a pull request event, retry all failed LUCI checks.
   ///
   /// 1. Aggregate .ci.yaml and try_builders.json presubmit builds.
   /// 2. Get failed LUCI builds for this pull request at [commitSha].
   /// 3. Rerun the failed builds that also have a failed check status.
   Future<void> retryPresubmitTargets({
     required github.PullRequest pullRequest,
     required CheckSuiteEvent checkSuiteEvent,
   }) async {
     final github.GitHub githubClient = await config.createGitHubClient(pullRequest: pullRequest);
     final Map<String, github.CheckRun> checkRuns = await githubChecksService.githubChecksUtil.allCheckRuns(
       githubClient,
       checkSuiteEvent,
     );
     final List<Target> presubmitTargets = await getPresubmitTargets(pullRequest);
     final List<Build?> failedBuilds = await luciBuildService.failedBuilds(pullRequest, presubmitTargets);
     for (Build? build in failedBuilds) {
       final github.CheckRun checkRun = checkRuns[build!.builderId.builder!]!;

       if (checkRun.status != github.CheckRunStatus.completed) {
         // Check run is still in progress, do not retry.
         continue;
       }

       await luciBuildService.scheduleTryBuilds(
         targets: presubmitTargets.where((Target target) => build.builderId.builder == target.value.name).toList(),
         pullRequest: pullRequest,
         checkSuiteEvent: checkSuiteEvent,
       );
     }
   }

   /// Get LUCI presubmit builders from .ci.yaml.
   ///
   /// Filters targets with runIf, matching them to the diff of [pullRequest].
   ///
   /// In the case there is an issue getting the diff from GitHub, all targets are returned.
   Future<List<Target>> getPresubmitTargets(github.PullRequest pullRequest) async {
     final Commit commit = Commit(
       branch: pullRequest.base!.ref,
       repository: pullRequest.base!.repo!.fullName,
       sha: pullRequest.head!.sha,
     );
     late CiYaml ciYaml;
     log.info('Attempting to read presubmit targets from ci.yaml for ${pullRequest.number}');
     if (commit.branch == Config.defaultBranch(commit.slug)) {
       final Commit totCommit = await generateTotCommit(slug: commit.slug, branch: Config.defaultBranch(commit.slug));
       final CiYaml totYaml = await getCiYaml(totCommit);
       ciYaml = await getCiYaml(commit, totCiYaml: totYaml);
     } else {
       ciYaml = await getCiYaml(commit);
     }
     log.info('ci.yaml loaded successfully.');

     log.info('Collecting presubmit targets for ${pullRequest.number}');
     final Iterable<Target> presubmitTargets = ciYaml.presubmitTargets.where(
       (Target target) =>
           target.value.scheduler == pb.SchedulerSystem.luci || target.value.scheduler == pb.SchedulerSystem.cocoon,
     );
     // Release branches should run every test.
     if (pullRequest.base!.ref != Config.defaultBranch(pullRequest.base!.repo!.slug())) {
       log.info('Release branch found, scheduling all targets for ${pullRequest.number}');
       return presubmitTargets.toList();
     }

     // Filter builders based on the PR diff
     final GithubService githubService = await config.createGithubService(commit.slug);
     List<String> files = <String>[];
     try {
       files = await githubService.listFiles(pullRequest);
     } on github.GitHubError catch (error) {
       log.warning(error);
       log.warning('Unable to get diff for pullRequest=$pullRequest');
       log.warning('Running all targets');
       return presubmitTargets.toList();
     }
     return await getTargetsToRun(presubmitTargets, files);
   }

   /// Reschedules a failed build using a [CheckRunEvent]. The CheckRunEvent is
   /// generated when someone clicks the re-run button from a failed build from
   /// the Github UI.
   ///
   /// If the rerequested check is for [kCiYamlCheckName], all presubmit jobs are retried.
   /// Otherwise, the specific check will be retried.
   ///
   /// Relevant APIs:
   ///   https://developer.github.com/v3/checks/runs/#check-runs-and-requested-actions
   Future<bool> processCheckRun(cocoon_checks.CheckRunEvent checkRunEvent) async {
     switch (checkRunEvent.action) {
       case 'rerequested':
         log.fine('Rerun requested by GitHub user: ${checkRunEvent.sender?.login}');
         final String? name = checkRunEvent.checkRun!.name;
         bool success = false;
         if (name == kCiYamlCheckName) {
           // The [CheckRunEvent.checkRun.pullRequests] array is empty for this
           // event, so we need to find the matching pull request.
           final RepositorySlug slug = checkRunEvent.repository!.slug();
           final String headSha = checkRunEvent.checkRun!.headSha!;
           final int checkSuiteId = checkRunEvent.checkRun!.checkSuite!.id!;
           final PullRequest? pullRequest =
               await githubChecksService.findMatchingPullRequest(slug, headSha, checkSuiteId);
           if (pullRequest != null) {
             log.fine('Matched PR: ${pullRequest.number} Repo: ${slug.fullName}');
             await triggerPresubmitTargets(pullRequest: pullRequest);
             success = true;
           } else {
             log.warning('No matching PR found for head_sha in check run event.');
           }
         } else {
           try {
             await luciBuildService.rescheduleUsingCheckRunEvent(checkRunEvent);
             success = true;
           } on NoBuildFoundException {
             log.warning('No build found to reschedule.');
           }
         }

         log.fine('CheckName: $name State: $success');
         return success;
     }

     return true;
   }

   /// Push [Commit] to BigQuery as part of the infra metrics dashboards.
   Future<void> _uploadToBigQuery(Commit commit) async {
     const String projectId = 'flutter-dashboard';
     const String dataset = 'cocoon';
     const String table = 'Checklist';

     final TabledataResource tabledataResource = await config.createTabledataResourceApi();
     final List<Map<String, Object>> tableDataInsertAllRequestRows = <Map<String, Object>>[];

     /// Consolidate [commits] together
     ///
     /// Prepare for bigquery [insertAll]
     tableDataInsertAllRequestRows.add(<String, Object>{
       'json': <String, Object?>{
         'ID': commit.id,
         'CreateTimestamp': commit.timestamp,
         'FlutterRepositoryPath': commit.repository,
         'CommitSha': commit.sha!,
         'CommitAuthorLogin': commit.author,
         'CommitAuthorAvatarURL': commit.authorAvatarUrl,
         'CommitMessage': commit.message,
         'Branch': commit.branch,
       },
     });

     /// Final [rows] to be inserted to [BigQuery]
     final TableDataInsertAllRequest rows =
         TableDataInsertAllRequest.fromJson(<String, Object>{'rows': tableDataInsertAllRequestRows});

     /// Insert [commits] to [BigQuery]
     try {
       await tabledataResource.insertAll(rows, projectId, dataset, table);
     } on ApiRequestError {
       log.warning('Failed to add commits to BigQuery: $ApiRequestError');
     }
   }

   /// Returns the tip of tree [Commit] using specified [branch] and [RepositorySlug].
   ///
   /// A tip of tree [Commit] is used to help generate the tip of tree [CiYaml].
   /// The generated tip of tree [CiYaml] will be compared against Presubmit Targets in current [CiYaml],
   /// to ensure new targets without `bringup: true` label are not added into the build.
   Future<Commit> generateTotCommit({required String branch, required RepositorySlug slug}) async {
     datastore = datastoreProvider(config.db);
     final BuildStatusService buildStatusService = buildStatusProvider(datastore);
     final Commit totCommit = (await buildStatusService
             .retrieveCommitStatus(
               limit: 1,
               branch: branch,
               slug: slug,
             )
             .map<Commit>((CommitStatus status) => status.commit)
             .toList())
         .single;

     return totCommit;
   }
 }
	// Copyright 2021 The Flutter Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style license that can be
	// found in the LICENSE file.

	import 'dart:math';
	import 'dart:typed_data';

	import 'package:cocoon_service/src/service/NoBuildFoundException.dart';
	import 'package:cocoon_service/src/service/build_status_provider.dart';
	import 'package:cocoon_service/src/service/scheduler/policy.dart';
	import 'package:gcloud/db.dart';
	import 'package:github/github.dart' as github;
	import 'package:github/github.dart';
	import 'package:github/hooks.dart';
	import 'package:googleapis/bigquery/v2.dart';
	import 'package:retry/retry.dart';
	import 'package:truncate/truncate.dart';
	import 'package:yaml/yaml.dart';

	import '../foundation/providers.dart';
	import '../foundation/typedefs.dart';
	import '../foundation/utils.dart';
	import '../model/appengine/commit.dart';
	import '../model/appengine/task.dart';
	import '../model/ci_yaml/ci_yaml.dart';
	import '../model/ci_yaml/target.dart';
	import '../model/github/checks.dart' as cocoon_checks;
	import '../model/luci/buildbucket.dart';
	import '../model/proto/internal/scheduler.pb.dart' as pb;
	import '../service/logging.dart';
	import 'cache_service.dart';
	import 'config.dart';
	import 'datastore.dart';
	import 'github_checks_service.dart';
	import 'github_service.dart';
	import 'luci_build_service.dart';

	/// Scheduler service to validate all commits to supported Flutter repositories.
	///
	/// Scheduler responsibilties include:
	/// 1. Tracking commits in Cocoon
	/// 2. Ensuring commits are validated (via scheduling tasks against commits)
	/// 3. Retry mechanisms for tasks
	class Scheduler {
	Scheduler({
	required this.cache,
	required this.config,
	required this.githubChecksService,
	required this.luciBuildService,
	this.datastoreProvider = DatastoreService.defaultProvider,
	this.httpClientProvider = Providers.freshHttpClient,
	this.buildStatusProvider = BuildStatusService.defaultProvider,
	});

	final BuildStatusServiceProvider buildStatusProvider;
	final CacheService cache;
	final Config config;
	final DatastoreServiceProvider datastoreProvider;
	final GithubChecksService githubChecksService;
	final HttpClientProvider httpClientProvider;

	late DatastoreService datastore;
	LuciBuildService luciBuildService;

	/// Name of the subcache to store scheduler related values in redis.
	static const String subcacheName = 'scheduler';

	static const String kCiYamlCheckName = 'ci.yaml validation';

	/// Ensure [commits] exist in Cocoon.
	///
	/// If [Commit] does not exist in Datastore:
	/// * Write it to datastore
	/// * Schedule tasks listed in its scheduler config
	/// Otherwise, ignore it.
	Future<void> addCommits(List<Commit> commits) async {
	datastore = datastoreProvider(config.db);
	final List<Commit> newCommits = await _getMissingCommits(commits);
	log.fine('Found ${newCommits.length} new commits on GitHub');
	for (Commit commit in newCommits) {
	await _addCommit(commit);
	}
	}

	/// Schedule tasks against [PullRequest].
	///
	/// If [PullRequest] was merged, schedule prod tasks against it.
	/// Otherwise if it is presubmit, schedule try tasks against it.
	Future<void> addPullRequest(github.PullRequest pr) async {
	datastore = datastoreProvider(config.db);
	// TODO(chillers): Support triggering on presubmit. https://github.com/flutter/flutter/issues/77858
	if (!pr.merged!) {
	log.warning('Only pull requests that were closed and merged should have tasks scheduled');
	return;
	}

	final String fullRepo = pr.base!.repo!.fullName;
	final String? branch = pr.base!.ref;
	final String sha = pr.mergeCommitSha!;

	final String id = '$fullRepo/$branch/$sha';
	final Key<String> key = datastore.db.emptyKey.append<String>(Commit, id: id);
	final Commit mergedCommit = Commit(
	author: pr.user!.login!,
	authorAvatarUrl: pr.user!.avatarUrl!,
	branch: branch,
	key: key,
	// The field has a max length of 1500 so ensure the commit message is not longer.
	message: truncate(pr.title!, 1490, omission: '...'),
	repository: fullRepo,
	sha: sha,
	timestamp: pr.mergedAt!.millisecondsSinceEpoch,
	);

	if (await _commitExistsInDatastore(mergedCommit)) {
	log.fine('$sha already exists in datastore. Scheduling skipped.');
	return;
	}

	log.fine('Scheduling $sha via GitHub webhook');
	await _addCommit(mergedCommit);
	}

	Future<void> _addCommit(Commit commit) async {
	if (!config.supportedRepos.contains(commit.slug)) {
	log.fine('Skipping ${commit.id} as repo is not supported');
	return;
	}

	final CiYaml ciYaml = await getCiYaml(commit);
	final List<Target> initialTargets = ciYaml.getInitialTargets(ciYaml.postsubmitTargets);
	final List<Task> tasks = targetsToTask(commit, initialTargets).toList();

	final List<Tuple<Target, Task, int>> toBeScheduled = <Tuple<Target, Task, int>>[];
	for (Target target in initialTargets) {
	final Task task = tasks.singleWhere((Task task) => task.name == target.value.name);
	SchedulerPolicy policy = target.schedulerPolicy;
	// Engine repo and release branches should run every task
	if (commit.slug == Config.engineSlug \|\| Config.defaultBranch(commit.slug) != commit.branch) {
	policy = GuaranteedPolicy();
	}
	final int? priority = await policy.triggerPriority(task: task, datastore: datastore);
	if (priority != null) {
	// Mark task as in progress to ensure it isn't scheduled over
	task.status = Task.statusInProgress;
	toBeScheduled.add(Tuple<Target, Task, int>(target, task, priority));
	}
	}

	// Datastore must be written to generate task keys
	try {
	await datastore.withTransaction<void>((Transaction transaction) async {
	transaction.queueMutations(inserts: <Commit>[commit]);
	transaction.queueMutations(inserts: tasks);
	await transaction.commit();
	log.fine('Committed ${tasks.length} new tasks for commit ${commit.sha!}');
	});
	} catch (error) {
	log.severe('Failed to add commit ${commit.sha!}: $error');
	}

	await _batchScheduleBuilds(commit, toBeScheduled);
	await _uploadToBigQuery(commit);
	}

	/// Schedule all builds in batch requests instead of a single request.
	///
	/// Each batch request contains [Config.batchSize] builds to be scheduled.
	Future<void> _batchScheduleBuilds(Commit commit, List<Tuple<Target, Task, int>> toBeScheduled) async {
	final List<Future<void>> futures = <Future<void>>[];
	for (int i = 0; i < toBeScheduled.length; i += config.batchSize) {
	futures.add(
	luciBuildService.schedulePostsubmitBuilds(
	commit: commit,
	toBeScheduled: toBeScheduled.sublist(i, min(i + config.batchSize, toBeScheduled.length)),
	),
	);
	}
	await Future.wait<void>(futures);
	}

	/// Return subset of [commits] not stored in Datastore.
	Future<List<Commit>> _getMissingCommits(List<Commit> commits) async {
	final List<Commit> newCommits = <Commit>[];
	// Ensure commits are sorted from newest to oldest (descending order)
	commits.sort((Commit a, Commit b) => b.timestamp!.compareTo(a.timestamp!));
	for (Commit commit in commits) {
	// Cocoon may randomly drop commits, so check the entire list.
	if (!await _commitExistsInDatastore(commit)) {
	newCommits.add(commit);
	}
	}

	// Reverses commits to be in order of oldest to newest.
	return newCommits;
	}

	/// Whether [Commit] already exists in [datastore].
	///
	/// Datastore is Cocoon's source of truth for what commits have been scheduled.
	/// Since webhooks or cron jobs can schedule commits, we must verify a commit
	/// has not already been scheduled.
	Future<bool> _commitExistsInDatastore(Commit commit) async {
	try {
	await datastore.db.lookupValue<Commit>(commit.key);
	} on KeyNotFoundException {
	return false;
	}
	return true;
	}

	/// Load in memory the `.ci.yaml`.
	Future<CiYaml> getCiYaml(
	Commit commit, {
	CiYaml? totCiYaml,
	RetryOptions retryOptions = const RetryOptions(maxAttempts: 3),
	}) async {
	String ciPath;
	ciPath = '${commit.repository}/${commit.sha!}/$kCiYamlPath';
	final Uint8List ciYamlBytes = (await cache.getOrCreate(
	subcacheName,
	ciPath,
	createFn: () => _downloadCiYaml(
	commit,
	ciPath,
	retryOptions: retryOptions,
	),
	ttl: const Duration(hours: 1),
	))!;
	final pb.SchedulerConfig schedulerConfig = pb.SchedulerConfig.fromBuffer(ciYamlBytes);
	log.fine('Retrieved .ci.yaml for $ciPath');
	// If totCiYaml is not null, we assume upper level function has verified that current branch is not a release branch.
	return CiYaml(
	config: schedulerConfig,
	slug: commit.slug,
	branch: commit.branch!,
	totConfig: totCiYaml,
	);
	}

	/// Get `.ci.yaml` from GitHub, and store the bytes in redis for future retrieval.
	///
	/// If GitHub returns [HttpStatus.notFound], an empty config will be inserted assuming
	/// that commit does not support the scheduler config file.
	Future<Uint8List> _downloadCiYaml(
	Commit commit,
	String ciPath, {
	RetryOptions retryOptions = const RetryOptions(maxAttempts: 3),
	}) async {
	final String configContent = await githubFileContent(
	commit.slug,
	'.ci.yaml',
	httpClientProvider: httpClientProvider,
	ref: commit.sha!,
	retryOptions: retryOptions,
	);
	final YamlMap configYaml = loadYaml(configContent) as YamlMap;
	final pb.SchedulerConfig schedulerConfig = pb.SchedulerConfig()..mergeFromProto3Json(configYaml);
	return schedulerConfig.writeToBuffer();
	}

	/// Cancel all incomplete targets against a pull request.
	Future<void> cancelPreSubmitTargets({
	required github.PullRequest pullRequest,
	String reason = 'Newer commit available',
	}) async {
	await luciBuildService.cancelBuilds(pullRequest, reason);
	}

	/// Schedule presubmit targets against a pull request.
	///
	/// Cancels all existing targets then schedules the targets.
	///
	/// Schedules a [kCiYamlCheckName] to validate [CiYaml] is valid and all builds were able to be triggered.
	/// If [builderTriggerList] is specified, then trigger only those targets.
	Future<void> triggerPresubmitTargets({
	required github.PullRequest pullRequest,
	String reason = 'Newer commit available',
	List<String>? builderTriggerList,
	}) async {
	// Always cancel running builds so we don't ever schedule duplicates.
	log.fine('Attempting to cancel existing presubmit targets for ${pullRequest.number}');
	await cancelPreSubmitTargets(
	pullRequest: pullRequest,
	reason: reason,
	);

	log.info('Creating ciYaml validation check run for ${pullRequest.number}');
	final github.CheckRun ciValidationCheckRun = await githubChecksService.githubChecksUtil.createCheckRun(
	config,
	pullRequest.base!.repo!.slug(),
	pullRequest.head!.sha!,
	kCiYamlCheckName,
	output: const github.CheckRunOutput(
	title: kCiYamlCheckName,
	summary: 'If this check is stuck pending, push an empty commit to retrigger the checks',
	),
	);

	log.info('Creating presubmit targets for ${pullRequest.number}');
	final github.RepositorySlug slug = pullRequest.base!.repo!.slug();
	dynamic exception;
	try {
	final List<Target> presubmitTargets = await getPresubmitTargets(pullRequest);
	final List<Target> presubmitTriggerTargets = getTriggerList(presubmitTargets, builderTriggerList);
	await luciBuildService.scheduleTryBuilds(
	targets: presubmitTriggerTargets,
	pullRequest: pullRequest,
	);
	} on FormatException catch (error, backtrace) {
	log.warning('FormatException encountered when scheduling presubmit targets for ${pullRequest.number}');
	log.warning(backtrace.toString());
	exception = error;
	} catch (error, backtrace) {
	log.warning('Exception encountered when scheduling presubmit targets for ${pullRequest.number}');
	log.warning(backtrace.toString());
	exception = error;
	}

	// Update validate ci.yaml check
	log.info('Updating ci.yaml validation check for ${pullRequest.number}');
	if (exception == null) {
	// Success in validating ci.yaml
	log.info('ci.yaml validation check was successful for ${pullRequest.number}');
	await githubChecksService.githubChecksUtil.updateCheckRun(
	config,
	slug,
	ciValidationCheckRun,
	status: github.CheckRunStatus.completed,
	conclusion: github.CheckRunConclusion.success,
	);
	} else {
	log.warning('Marking PR #${pullRequest.number} $kCiYamlCheckName as failed');
	log.warning(exception.toString());
	// Failure when validating ci.yaml
	await githubChecksService.githubChecksUtil.updateCheckRun(
	config,
	slug,
	ciValidationCheckRun,
	status: github.CheckRunStatus.completed,
	conclusion: github.CheckRunConclusion.failure,
	output: github.CheckRunOutput(
	title: kCiYamlCheckName,
	summary: '.ci.yaml has failures',
	text: exception.toString(),
	),
	);
	}
	log.info(
	'Finished triggering builds for: pr ${pullRequest.number}, commit ${pullRequest.base!.sha}, branch ${pullRequest.head!.ref} and slug ${pullRequest.base!.repo!.slug()}}',
	);
	}

	/// If [builderTriggerList] is specificed, return only builders that are contained in [presubmitTarget].
	/// Otherwise, return [presubmitTarget].
	List<Target> getTriggerList(List<Target> presubmitTarget, List<String>? builderTriggerList) {
	if (builderTriggerList != null && builderTriggerList.isNotEmpty) {
	return presubmitTarget.where((Target target) => builderTriggerList.contains(target.value.name)).toList();
	}
	return presubmitTarget;
	}

	/// Given a pull request event, retry all failed LUCI checks.
	///
	/// 1. Aggregate .ci.yaml and try_builders.json presubmit builds.
	/// 2. Get failed LUCI builds for this pull request at [commitSha].
	/// 3. Rerun the failed builds that also have a failed check status.
	Future<void> retryPresubmitTargets({
	required github.PullRequest pullRequest,
	required CheckSuiteEvent checkSuiteEvent,
	}) async {
	final github.GitHub githubClient = await config.createGitHubClient(pullRequest: pullRequest);
	final Map<String, github.CheckRun> checkRuns = await githubChecksService.githubChecksUtil.allCheckRuns(
	githubClient,
	checkSuiteEvent,
	);
	final List<Target> presubmitTargets = await getPresubmitTargets(pullRequest);
	final List<Build?> failedBuilds = await luciBuildService.failedBuilds(pullRequest, presubmitTargets);
	for (Build? build in failedBuilds) {
	final github.CheckRun checkRun = checkRuns[build!.builderId.builder!]!;

	if (checkRun.status != github.CheckRunStatus.completed) {
	// Check run is still in progress, do not retry.
	continue;
	}

	await luciBuildService.scheduleTryBuilds(
	targets: presubmitTargets.where((Target target) => build.builderId.builder == target.value.name).toList(),
	pullRequest: pullRequest,
	checkSuiteEvent: checkSuiteEvent,
	);
	}
	}

	/// Get LUCI presubmit builders from .ci.yaml.
	///
	/// Filters targets with runIf, matching them to the diff of [pullRequest].
	///
	/// In the case there is an issue getting the diff from GitHub, all targets are returned.
	Future<List<Target>> getPresubmitTargets(github.PullRequest pullRequest) async {
	final Commit commit = Commit(
	branch: pullRequest.base!.ref,
	repository: pullRequest.base!.repo!.fullName,
	sha: pullRequest.head!.sha,
	);
	late CiYaml ciYaml;
	log.info('Attempting to read presubmit targets from ci.yaml for ${pullRequest.number}');
	if (commit.branch == Config.defaultBranch(commit.slug)) {
	final Commit totCommit = await generateTotCommit(slug: commit.slug, branch: Config.defaultBranch(commit.slug));
	final CiYaml totYaml = await getCiYaml(totCommit);
	ciYaml = await getCiYaml(commit, totCiYaml: totYaml);
	} else {
	ciYaml = await getCiYaml(commit);
	}
	log.info('ci.yaml loaded successfully.');

	log.info('Collecting presubmit targets for ${pullRequest.number}');
	final Iterable<Target> presubmitTargets = ciYaml.presubmitTargets.where(
	(Target target) =>
	target.value.scheduler == pb.SchedulerSystem.luci \|\| target.value.scheduler == pb.SchedulerSystem.cocoon,
	);
	// Release branches should run every test.
	if (pullRequest.base!.ref != Config.defaultBranch(pullRequest.base!.repo!.slug())) {
	log.info('Release branch found, scheduling all targets for ${pullRequest.number}');
	return presubmitTargets.toList();
	}

	// Filter builders based on the PR diff
	final GithubService githubService = await config.createGithubService(commit.slug);
	List<String> files = <String>[];
	try {
	files = await githubService.listFiles(pullRequest);
	} on github.GitHubError catch (error) {
	log.warning(error);
	log.warning('Unable to get diff for pullRequest=$pullRequest');
	log.warning('Running all targets');
	return presubmitTargets.toList();
	}
	return await getTargetsToRun(presubmitTargets, files);
	}

	/// Reschedules a failed build using a [CheckRunEvent]. The CheckRunEvent is
	/// generated when someone clicks the re-run button from a failed build from
	/// the Github UI.
	///
	/// If the rerequested check is for [kCiYamlCheckName], all presubmit jobs are retried.
	/// Otherwise, the specific check will be retried.
	///
	/// Relevant APIs:
	/// https://developer.github.com/v3/checks/runs/#check-runs-and-requested-actions
	Future<bool> processCheckRun(cocoon_checks.CheckRunEvent checkRunEvent) async {
	switch (checkRunEvent.action) {
	case 'rerequested':
	log.fine('Rerun requested by GitHub user: ${checkRunEvent.sender?.login}');
	final String? name = checkRunEvent.checkRun!.name;
	bool success = false;
	if (name == kCiYamlCheckName) {
	// The [CheckRunEvent.checkRun.pullRequests] array is empty for this
	// event, so we need to find the matching pull request.
	final RepositorySlug slug = checkRunEvent.repository!.slug();
	final String headSha = checkRunEvent.checkRun!.headSha!;
	final int checkSuiteId = checkRunEvent.checkRun!.checkSuite!.id!;
	final PullRequest? pullRequest =
	await githubChecksService.findMatchingPullRequest(slug, headSha, checkSuiteId);
	if (pullRequest != null) {
	log.fine('Matched PR: ${pullRequest.number} Repo: ${slug.fullName}');
	await triggerPresubmitTargets(pullRequest: pullRequest);
	success = true;
	} else {
	log.warning('No matching PR found for head_sha in check run event.');
	}
	} else {
	try {
	await luciBuildService.rescheduleUsingCheckRunEvent(checkRunEvent);
	success = true;
	} on NoBuildFoundException {
	log.warning('No build found to reschedule.');
	}
	}

	log.fine('CheckName: $name State: $success');
	return success;
	}

	return true;
	}

	/// Push [Commit] to BigQuery as part of the infra metrics dashboards.
	Future<void> _uploadToBigQuery(Commit commit) async {
	const String projectId = 'flutter-dashboard';
	const String dataset = 'cocoon';
	const String table = 'Checklist';

	final TabledataResource tabledataResource = await config.createTabledataResourceApi();
	final List<Map<String, Object>> tableDataInsertAllRequestRows = <Map<String, Object>>[];

	/// Consolidate [commits] together
	///
	/// Prepare for bigquery [insertAll]
	tableDataInsertAllRequestRows.add(<String, Object>{
	'json': <String, Object?>{
	'ID': commit.id,
	'CreateTimestamp': commit.timestamp,
	'FlutterRepositoryPath': commit.repository,
	'CommitSha': commit.sha!,
	'CommitAuthorLogin': commit.author,
	'CommitAuthorAvatarURL': commit.authorAvatarUrl,
	'CommitMessage': commit.message,
	'Branch': commit.branch,
	},
	});

	/// Final [rows] to be inserted to [BigQuery]
	final TableDataInsertAllRequest rows =
	TableDataInsertAllRequest.fromJson(<String, Object>{'rows': tableDataInsertAllRequestRows});

	/// Insert [commits] to [BigQuery]
	try {
	await tabledataResource.insertAll(rows, projectId, dataset, table);
	} on ApiRequestError {
	log.warning('Failed to add commits to BigQuery: $ApiRequestError');
	}
	}

	/// Returns the tip of tree [Commit] using specified [branch] and [RepositorySlug].
	///
	/// A tip of tree [Commit] is used to help generate the tip of tree [CiYaml].
	/// The generated tip of tree [CiYaml] will be compared against Presubmit Targets in current [CiYaml],
	/// to ensure new targets without `bringup: true` label are not added into the build.
	Future<Commit> generateTotCommit({required String branch, required RepositorySlug slug}) async {
	datastore = datastoreProvider(config.db);
	final BuildStatusService buildStatusService = buildStatusProvider(datastore);
	final Commit totCommit = (await buildStatusService
	.retrieveCommitStatus(
	limit: 1,
	branch: branch,
	slug: slug,
	)
	.map<Commit>((CommitStatus status) => status.commit)
	.toList())
	.single;

	return totCommit;
	}
	}